Uwe Bergmann

Phillips:

All right, this is Jon Phillips, the oral historian at the American Institute of Physics. Today is January 29th, 2024. And I'm speaking today with Dr. Uwe Bergmann at the University of Wisconsin-Madison as part of our oral history of the SLAC national accelerator lab. Thank you so much for talking with me today.

Bergmann:

Thank you.

Phillips:

So as I was sort of mentioning a moment ago, we like to start off with discussions about where you came from, your early life. So can you tell me a bit about what your parents did when you were young, where you're from, and what it was like growing up?

Bergmann:

Yeah, so I grew up in a town called Karlsruhe, which is in the southwest of Germany. It's a mid-sized town. It has about 300,000 inhabitants. It's a beautiful location close to the Rhine River, and it's on the basically to the southeast, you have the Black Forest, and to the west you have the extension of the Vosges, which is a big chain which goes from across the French-German border. And Karlsruhe is right at the kink where France and Germany, where the Rhine is no longer the border between France and Germany.

And my parents, none of my parents were in science. In fact, I remember when I told my dad when I was in high school, and I said—So he said, "So what do you think you want to do as your major, right?" For the last two years in Germany, you have to take a major. And I said, "I think I'll take math and physics." And then he was just replying "Are you sure?" I still sometimes wonder, I don't think it meant that he thought I wouldn't be able to do it or that he thought it was useless, but I think he, in a sense, he thought, "Okay, so that is kind of interesting, because that's really... I don't have much of a relationship to it." Or something along those lines. I might have said, "Yeah, I think that's easier." Or something like that. And maybe he was also put off by this comment, that I thought that that was easier.

But no, I had, I remember it as a wonderful childhood. I have an older brother, a younger sister, and my parents had a little cabin actually not in the Black Forest. That was later on. But when I was really young, we had a little cabin in the woods left of the Rhine, very, very basic, no electricity, not even flowing water. So we usually came up on a Friday night. Sometimes my grandparents also came with us like a large family. It was off-road. You had to drive on a, not even a dirt road, but like a path through the forest to get there. And I think that was kind of the time when I started to develop really my deep appreciation and also love for nature. And in a sense, I know that physics is the kind of study of nature, but usually we don't mean nature in the sense of biology, right? We usual refer to physics as nature in the sense of like the laws of gravity and motion etc. And I always, you know, I always felt that that distinction shouldn’t be so strict. And I think if I look now back, I mean I'm 60 years old, so if I look now back 55 years or 53 years or so, I think I have, even though I have become a physicist and I'm in a physics department, I have kind of stuck to this idea, which, I think already at that time, I developed by just being in this beautiful place with birds around and no cars, no noises. In the evening, the forest has beautiful sounds to it, and the simplicity of taking care of the basic needs. I think that's one of the things which attract a lot of people to camping also, obviously, right?

Phillips:

Yes.

Bergmann:

And I think even though I was in the more kind of protected, small, midtown, safe town environment, that was kind of instilled very early on. The other thing I wanted to say about my parents, both of my parents came from, they were from this area of Bohemia, where before WWII a lot of Germans lived. It is now part of the Czech Republic. And there were actually, in total, there were I think 2.5 million Germans who lived not only in the Czech part, but also in Russian parts, Polish parts, etc. These were ethnically German populations. They typically had two passports. They had a Czech and a German passport. And then of course afterwards, after all the atrocities Germany had done to all their neighbors, all these Germans were basically forced out and had to resettle in what then became West Germany and East Germany. It didn't matter. And both of my parents independently, even though they didn't know each other at that time, came from that area. And they lost everything. My father came from a reasonably wealthy family and basically at the end of WWII, everything was gone except for a suitcase of 50kg which they were allowed to take.

And on my mom's side was basically the same situation. Her family was, you know, they were not a very wealthy family, but they were a proud craftsman, working-class family. And so in a sense, then after the war, thanks largely also to obviously the politics of the United States, etc. and the West, my parents ended up in West Germany, and West Germany started to get back on their feet, and so did my father and his part of his family who also came, and they actually started a new life and I would say they made it. They were successful, they were working hard, and they had a small business. A small family business, and they continued to do that without too much looking back. I tell this, because that was really one of the main reasons after I was a student, first in Karlsruhe, and then at the University of Hamburg to do a diploma in physics, which is similar to a masters, and I had expressed the desire to maybe do a PhD in the United States or somewhere abroad, my father was very encouraging to that idea. And my mother too, both of my parents. They never wanted to keep me. They said, "Look, there comes a time when you might lose everything you have accept what you learn and what you can do, so this is a great education. Whatever comes out of it, you will learn. You will learn a lot doing that." And I think that actually gave me a lot of the freedom and a lot of courage also to step into a completely different culture, and I think it has to do a little bit with this upbringing, which I got from my parents, who both had experienced much, much, tougher conditions, obviously. But they both had to go through this, and they both felt how it, you know, how it feels to make a new home.

And now, looking back, I made my home. We are living in California. I'm working in Madison. I'm teaching half of the year, I'm there fully employed, but I spend a lot of time still close to SLAC, where we live, and we consider California our home. Our daughter was born in California (she now lives in Berlin) and my wife is from Italy. We have lived in California for 28 years, but I have lived in the US more than 30 years. And you know, I know what it feels like to make your home. That doesn't mean that I don't have strong roots to my home country and so does my wife. She has very strong roots in Italy. I love to see my mother and my brother, who still live , in Germany. I love to spend time there. But I also know what my home is, and I think I have to thank my parents for instilling that philosophy into me at a very young age.

Phillips:

Yeah. I'm curious, just sort of talking about resettling and establishing a home. Did your parents manage to stay in contact with any friends or family who had resettled into East Germany instead of West with them?

Bergmann:

Yeah, that's a very interesting point. In fact, my father has one sister, his older sister. She just passed away at age 100.

Phillips:

Oh wow.

Bergmann:

Yeah. My dad passed away 12 years ago, but I still was seeing her in December, and we had a lovely time. She was a wonderfully remarkable woman. Sharp to the last minute. And they had... so the family was kind of split up. Of their cousins, two had settled in West Germany. One fled, actually, in I don't know whether it was '61 or... In the early 60s, he basically took to his motorcycle when it was clear that the border would be—I mean, there's the Berlin Wall, but there was also this wall between West and East Germany, this long one. When it became clear to him that this is not going to be a normal relationship, he basically said, "Okay, I move." So, we had three in West Germany and four in East Germany, and we went several times to see them in East Germany before the wall came down, and one of them was also allowed to visit us. They were sometimes allowed if the rest of the family stayed in the East. It was very difficult for East Germans to come to visit West Germany. It was only possible if they had a family and the children and the husband and then the wife and children stay and then they could sometimes visit. So, one of my uncles was actually allowed to come. And it was, for us, it was a wonderful time, actually. We still have a great relationship, but we also noticed the vast difference of in the time when I was young, it had only been maybe 15 years or so, but we realized how two different worlds in a 30-year separation of how the same country, same population, same genetics, same background, same ethnicity, just from a political system, how it could be changing to such different worlds.

Phillips:

Absolutely.

Bergmann:

Absolutely remarkable. I still sometimes cannot fathom it today, how big that difference was, and it's now almost homogeneous, but still there are still some lingering small differences, and it was a peaceful unification, which is extremely rare also in the history. 

Phillips:

(laughs) Yes. So going back to, you mentioned this appreciation for nature that you developed and that sort of leading into maybe an interest in science more broadly. Was it expected in your family as you were growing up that you would be going on to university after Gymnasium or after your high school education?

Bergmann:

No, there was no expectation. There wasn't even... it wasn't even clear—you know, in Germany, not everyone goes to Gymnasium, so we have three different levels of school education. And when we went to school, there was no expectation, and then as we went along, it kind of crystallized out. And I went actually right after high school. So, I was relatively young in my class because I'm born in August. When you're born in August, you can either still go into school when it starts in basically early September or late August, or often you would start like a year later, right? In my case, they already had missed, my parents had already missed the application. They thought that, oh yeah, we will send him a year later, and then for whatever reason, I don't know the exact story, but someone chatted with me and then said to my parents, "No, no, you need to get this guy to school." (both laugh)

So they changed their minds, and I'm not sure I was happy, but I ended up being one of the younger ones, so I got my Abitur, which is after 13 years of school, at age 18, and then I went straight to the army, which at the time was still a compulsory military system in Germany. And that was a very good... I found that was very good experience for me. It was good not in the sense that I felt I learned how to shoot or to do these things, but what I did learn and what you did learn there in a basically 15 months period, was how to make yourself...I mean, to survive, for lack of a better word, in a very different environment than what you had grown up. I mean, I would say that I was kind of a little bit spoiled, and my friends had similar backgrounds and you have the same interests, same education level, and then you go to the army. And there we were all together, and you come from reasonably different backgrounds, you're like in a small room, probably just a little bit bigger than my office. Nine bunk beds, 3x3. It's like three levels, nine guys from totally different backgrounds, from across Germany, and we only had two in our room who had a high school Gymnasium degree, and the others were already working. And it was tough. I mean, it was tough, you needed to watch what you said, you needed to watch how you behaved. If not, they would stick it to you.

And I have witnessed many, many things. I was kind of lucky. One of my bosses there, he was one of the sergeant majors, he didn't like me. So, he gave me a hard time, and I had to spend some of weekends there, after he penalized me with something random. But all in all I got around well (laughs). But some of my colleagues were not as lucky, because they didn't get the idea of when it's time to shut your mouth, and when it's time not to make a comment on something. So that was an interesting 15 months, and it was also great, because when it was done, I was ready, you know, I was drooling to go to university. It was like, okay, let's not get up at five in the morning. Let's do something different. So it was, in a sense, retrospectively, even though I'm not saying that I enjoyed the whole time, but it was a very good learning experience.

Phillips:

And your 15 months in the military, were you just infantry, an enlisted person?

Bergmann:

I was in the rocket artillery battalion 121, in the fourth battery. And I was the driver for the second highest battalion commander, I'm trying to get the US rank, he was a major.

Phillips:

Okay.

Bergmann:

So my boss was a major was my boss. And I'm not sure what the name was, but— (P.S. now I remember: Major Langelüddecke)

Phillips:

(laughs) That's fine.

Bergmann:

But he was a great guy. We had a few little things but generally speaking, I would say he was a great guy. And I was basically his driver. I drove like a small Volkswagen Kübel. They are still very popular in California. Two-wheel drive, not four-wheel drive. He expected me to get to all the dirt roads where only the four-wheel drives work. I was driving like a maniac, and I sometimes I got stuck. But yeah, so that was my job. I was mainly in the office, but every once in a while, when we did have an exercise, I was with this guy driving in the vehicle.

Phillips:

Right, yeah. So you ended up, then, very excited (laughs) to move on to university. You went in already thinking math and physics. What were the course offerings available to you when you started? Were you able to jump in right away?

Bergmann:

Yeah, I studied physics basically. So, I enrolled, I was accepted at Karlsruhe and Freiburg. So those are the only two universities I applied. I wasn't eager to leave the house. It wasn't that I was one of those who needs to run away right away. And so basically, I should mention that we had a small group in my high school. And I'm still very good friends with one of my friends, (Patrick), and another friend of ours, Martin. Unfortunately, he died very young of cancer.

Phillips:

I'm sorry.

Bergmann:

He was a great guy. And we met—that's why I also enjoyed physics so much in high school already, because we had this friendship and then we met in the afternoons and we were making maybe some French fries or we were doing some other things, fun activities, and then we all got together and we started to solve problems together, right? And we actually made the whole thing fun—it was like a fun event. It was like, "Oh, gee, now I have to solve the problems again." So we said, "No, no, let's meet and then see." And we enjoyed it, and we discussed the physics in a way of going beyond just getting the numerical solution of that problem. But kind of trying to understand what it means. Right? I also had a very, very good high school teacher in physics. He was extremely good. Patrick didn't like him so much, they didn’t get along, but I thought he was good. My math teacher was very good as well. So I remember we started to learn early about even the uncertainty principle and the wave particle dualism. So you get the first taste already in high school. And I remember how thoroughly we enjoyed these concepts and how we sometimes would replay them in a funny way, and how we understood them. And we were good. I was a good student, but in my overall grades, there were better students. But our little group, we were maybe a little bit lazier than the others, right? So, some of the others, maybe they made up for it because they were working harder, right?

Phillips:

Right.

Bergmann:

But every time there was an unannounced test, where you couldn’t know that you had to learn for it, we actually did very well, because we understood this stuff. 

Phillips:

Right.

Bergmann:

Right? But we didn't need to kind of go in the books and then learn everything by heart, but we understood things. I put a lot of credit to my friend Martin and also Patrick during that time, who kind of helped me to pick it up. It's really this joy, pure joy, of physics. And I still have it today. I'm teaching right now. I'm teaching ‘Ideas of modern physics’ to undergraduate students, and I put everything into it. I'm doing 'Relativity’ tomorrow. I have my second relativity lecture tomorrow, and I'm doing everything internal. I'm trying to see my students like I was when I was kind of a similar age. And what it takes to understand these crazy concepts. So, a lot of credit to my friends at that time. And so yeah, I studied physics and it's a basic curriculum in Karlsruhe. We have a pre-diploma, which is a kind of you need to pass that after two years. And that was the time when I also switched. I had kind of outgrown living at home. I realized I was like, at the time I was maybe 21, yeah, 21 going on 22. And I realized that it's time for me to move out of the house. I mean, I had my own little apartment, but it wasn't a healthy relationship, because I was taking advantage of getting food, but I wasn't giving anything back, because I had my own life. And so that was the time to move, and I decided after considering a few options to move to Hamburg.

Also, because you know Hamburg, I mean obviously you look at which are good universities, but you know in Germany, it's a little bit more homogeneous. It's not that you have... I mean, now you have a few of those so-called "elite" universities, but generally speaking, it's a little more homogeneous, so I liked the idea of being far away. I liked the idea of being in the north. I like ships, and Hamburg, although it is not right at the ocean, but it was relatively close, and we were in the middle of an amazing city where you have these huge, gigantic container ships coming in. You felt the pulse of the world was beating there, and it was a great time for me.

And yeah, I passed all my pre-diplomas. At that point, you don't specialize yet, and then in Hamburg, I was really lucky again. I got into a wonderful group for my PhD—sorry, for my ‘Diplom’ research. So in Germany, you first do a ‘Diplom’, it's like a small thesis, similar to a PhD, just at a bit lower level. And the group I worked with was led by Professor Erich Gerdau. And I had a wonderful mentor, Ralf Röhlsberger, and it was a fantastic group. We had a great atmosphere. There was tea every afternoon at 4:30 pm, where the group met to chat. We worked hard. I had built my own first X-ray experiment all by myself. I had to get tables, I had to get an X-ray tube, I had to unpack it. I had to get all the components. I got a lot of help from many people, but at the end, I was able to build my own first experiment. And it kind of worked. So, I still remember the joy when you do an experiment and you were looking with this monochromator where the molybdenum K alpha line is, because that was the X-ray tube we are using. And I remember when we first found it, the first time it comes up, and then it comes down again. And then whoa, it was like this is like a miracle. It was a wonderful experience, and I was lucky to be in such a great group for this period.

Phillips:

Did the group as a whole focus on X-ray research? Were they doing spectroscopy?

Bergmann:

Yes, so the group was actually focusing on a phenomenon called Mössbauer spectroscopy. It's a nuclear resonance effect, which allows you to make very, very precise measurements of very small changes, and it is used as a tool for mearing chemical states. Nowadays, you can get commercial spectrometers everywhere. It was even, I think that even one of the mars landers had a spectrometer. It's a very straightforward way to study materials. If you have iron, and iron is everywhere, you can study the oxidation state. You can study the chemical state of iron in a very easy way with this technique. But my group was more interested in the physics and in they used the synchrotron as an excitation. So not a radioactive isotope, which is the normal source when you buy a commercial setup. My ‘Diplom’ research was to come up with a new idea of mirrors, which have an anti-reflective coating that would filter out everything but the exact resonance. Then for my PhD, I realized that I wanted to stay in that field, and I ended up joining a group at Brookhaven Lab in New York, and I was enrolled then at Stony Brook University, which kind of came with it, and my group was in that same field. In a sense that they were kind of a little bit of a competitor to the group in Hamburg. Retrospectively, I might have ruffled some feathers by doing that. I wasn't aware of it at that time. I also don't think that there was any intention or anything. I liked Hamburg, it was a wonderful time, and I still have some of my best friends today from the time in Hamburg. But I think for me, I think it was my inner...something in me was saying, "Okay, you need to move on." And in fact, there were two options. I could have gone to Grenoble. I had an offer there as well for a PhD project, and then I got this other one from Brookhaven, and I decided let's go to New York, why not? And by the way, later, four years after my PhD, I ended up going to Grenoble, and I spent two years there as well. But so yeah, so that was the big step actually. I think the really big step was to go to get the PhD in the United States.

Phillips:

Yeah. Before moving onto your PhD, with your diploma work, you said your diploma project was on developing this mirror, the coating on the mirror, for the X-ray apparatus. Did you have any sort of engineering or machining experience prior to this, or was this something that you had to learn over the course of doing this?

Bergmann:

No, you needed to have to learn it.

Phillips:

Yeah.

Bergmann:

Yeah. In fact, also during my PhD project that part was great. So my boss came on the first day, he had this hunk of silicon. He put it on my desk, and he said, "Okay, build a four-bounce, asymmetric-symmetric, pre-bent, polarizing monochromator for synchrotron-based Mössbauer spectroscopy."

Phillips:

(laughs)

Bergmann:

"Off you go." We had a lot of... I mean, I can do some basic machining, but for most of the things we were kind of designing it, and then we had a machine shop, and we would talk to the people in the machine shop, and they would do it for us. I mean, over the years, I've done a lot of small machining myself, but nothing kind of serious. But the idea, I think I did learn over the years the idea of what works and what doesn't work. So, I can see what is a good design or more likely to be a good design effort. I would say that I have a sense of it, and I learned that starting in Hamburg. We had a great machine shop but obviously at the end, if you run the experiment, if you do the alignment etc., it's up to you to do it all correctly.

Phillips:

Right, yeah.

Bergmann:

I explained a lot of my passion for building instruments to growing up playing with Legos. I loved it, I could spend hours and hours, and my mum, she had to drag me to dinner. And I liked to build airplanes. I love airplanes. I have always loved airplanes. Early on, I actually wanted to become a pilot, but with my glasses, I couldn't do it. But I think this playing with Lego and building stuff has helped me in my whole career in physics, there is no question about it. 

Phillips:

Yeah, absolutely.

Bergmann:

So it's kind of this combination, the love of nature on the one hand, right?

Phillips:

(laughs) Yeah.

Bergmann:

The cool things with my friends, like doing these physics experiments, and then also playing with Legos. So that was the school— (both laugh)

Phillips:

A perfect environment to nurture a young scientist.

Bergmann:

That were kind of the ingredients that drove me into that.

Phillips:

So when you arrived at Brookhaven, did you have someone there that you already wanted to work with, or did you have to—?

Bergmann:

Yeah. So there was a group, and so my thesis advisor was one of two guys, Jerry Hastings. He's still at SLAC, and he was at the time a scientist, a senior scientist, at Brookhaven Lab, and he and his colleague Peter Siddons had just done some really beautiful and successful experiments in this field. And basically, he said, "Oh, well you'll just come. And don't worry about it, I'll get you into Stony Brook." And I had an official thesis advisor at Stony Brook, Peter Stevens. He was very kind. I really didn't do any work with him, but he was willing to give his administrative title for me so that I could do it. And then I had to do classwork also and qualifiers and I struggled with my qualifier because I didn't pay attention to properly learn for it, because I was already excited doing experiments.

But yeah, I spent basically most of my time at NSLS, the National Synchrotron Light Source. It was this, I think, 2.5 GeV synchrotron ring, and I had an enormous amount of freedom. I basically had, for some part, I had a beamline all by myself, an R&D beamline, which is very unusual, because Jerry had a really large group. He was running the whole R&D effort. So he ran I think at least five or six beamlines. And it was a really wonderful learning experience, with good supervision. On a daily basis, lots of time learning how to do experiments, how to watch first how they are done and then doing it yourself. I remember there was this new and crazy spaghetti garden of cables and these two guys, they understood where everything went. And so eventually I unplugged them all and I wrote down and I made a diagram and wrote down everything and tried to understand every single part of it. And eventually I was able to do it myself. It was a great place to learn how to do experimental designs. I would say my two advisors knew silicon crystals, but also the detector side and the electronics, and also on the mechanical stability and of course synchrotron radiation extremely well. I would say they were amongst the best in the world. I mean, incredible. Absolutely incredible. Knowing how to successfully do a synchrotron experiment, I couldn't have had better teachers than that. They were absolutely incredible. And also, for my postdoc, by the way. But then I did my first postdoc also very, very quickly, yeah.

Phillips:

So during—

Bergmann:

A lot of credit to those guys.

Phillips:

Yeah. Absolutely. So, during your PhD, you're primarily at Brookhaven, at NSLS. How were you funded?

Bergmann:

I was funded through the funding from this R&D group. Which was a large group—so I hope I'm not saying anything wrong, but I'm pretty sure I was funded through the core funding of NSLS from DOE.

Phillips:

Okay.

Bergmann:

When I was running LCLS for some years as deputy director and also acting director, I remembered my PhD funding. Each big user facility in the DOE has a budget, where internal R&D can be funded, which is mostly focused on user support. But R&D is also moving the facility forward, and I had been a beneficiary of that kind of funding for my PhD research.

Phillips:

Okay. And so can you tell me a bit about what your sort of experiments that ended up leading towards your dissertation project, what went into that and how that project developed?

Bergmann:

Yeah, I have already mentioned this Mössbauer effect. The reason why it is so powerful is because you have this nuclear resonance, which is incredibly narrow in frequency, and that means you can observe the smallest shift in energy. And the way how a conventional Mössbauer experiment is done is that you have the source and you have an absorber, which is your sample, and you have a detector. And the source and the absorber move relative to each other. Usually they put the source on a drive or sometimes the absorber, but it doesn't matter. And just by a few millimeters per second of speed, you can Doppler shift the gamma rays at the 14.4 keV resonance enough to get out of the resonance. That just shows you how narrow this resonance is. And you could see features because through the chemical environment around the nucleus has very small forces, which changes the absorption. You can then map out different absorption lines as the resonance would have so-called hyper-fine splittings. So normally you would think of it as one line, but when you look in detail—and you could do that with a normal gamma ray source, you could measure in what environment the nucleus is.

That was the conventional way of Mössbauer spectroscopy, and still is. Our group and the group of my advisor in Hamburg had a different idea. They said, "Why don't we do the whole thing in the time domain instead of the frequency domain? We'll use a short pulse, a synchrotron pulse, it's just short. Not a short as like an FEL pulse, but short compared to the Mössbauer resonance. 100 picoseconds or so. Mössbauer resonance of iron 140 nanoseconds. An order of magnitude slower. And we excite that when excite this resonance, instead of seeing a change in frequency of the scattering, we look at the time changes, because a frequency change also corresponds to a time change. And so, for example, if you have two frequencies, you see a ringing, and if you have four frequencies, you see a more complicated ringing. And if you have one line but the sample is getting thicker, your exponential decay time changes and then you get other time features. There is a direct, a 1:1 relation via a Fourier transform between the frequency domain of this absorption and the time domain. And so they basically said, "Let's do Mössbauer spectroscopy in the time domain."

So, my whole PhD was about doing resonant nuclear scattering with synchrotron radiation. That's also the title of my thesis. And by doing it in the time domain. And we were able, in my first experiment, which I did as a PhD student, to observe that it was possible with a very good monochromator to do this directly in the forward direction. I basically then started to go deeper into this and studied this forward scattering on different systems, for example, as a function of temperature. How does the magnetism break down when you start to heat up iron? And we even made one measurement where we estimated how this so-called Lamb-Mössbauer factor, which describes how stiff an iron is bonded in the lattice, changes with temperature. And we also showed how these different hyperfine lines of the Mössbauer resonance had different polarization properties. And we use kind of a trick of crossing polarizers to show how this polarization can change in nuclear resonance scattering. So that was what we did. Different aspects of nuclear resonance scattering with synchrotron radiation. Aspects, which would have been much harder, some of them impossible, to study with a conventional Mössbauer spectrometer.

Phillips:

Right. 

Bergmann:

And when I was done with it, my boss told me, he said, “Okay now, off you go. Now you need to do something different.”

Phillips:

(laughs)

Bergmann:

It was very good. Yeah and I did, and I did.

Phillips:

So, before we move onto the work you were doing in your postdoc, I’m curious. Moving from Hamburg to Long Island, what was the sort of cultural transition like in the 80s going from West Germany to New York?

Bergmann:

Yeah, well, first of all, it was in exactly 1990.

Phillips:

Oh, 1990, excuse me.

Bergmann:

It was like very late 80s, yeah. It was so interesting. Exactly when the Wall, when the Berlin Wall came down, I left to the US. And I left for New York. And I can tell you what, it was very difficult. It was, I was lonely, I felt lonely. It was a very difficult time. The first year, it was so, it was tough. And at some point, I wasn't sure I could do it. And it wasn't the fault of anyone. It was just the cultural change was larger than I thought, and also the situation was, I was in a National lab. I mean, I was in a university on the one hand, but I was kind of spending all of my time in the National lab. So, the social environment in the National lab wasn't like in a campus environment. And so, the combination of those things made it kind of, for me, mentally challenging. It was also a great period of kind of learning a little bit of who I am. I'll give you one example: I didn't have a TV. I had a small apartment which was part of a house, but my family, they were wonderful, they were actually two doctors. They had young children also. And they sometimes, the husband was from Pakistan and the wife was from India. In fact, she was from Nepal, but she was Indian national. And they sometimes brought me food, like when I came home there was sometimes food on the table. I had a great relationship with this family.

But I also spent a lot of time by myself, and I started, for example, my deeper interest in classical music. I had always liked classical music. I have already liked it when I was in high school or even earlier, but I never really got much into it. But then these four years when I lived on Long Island, I really got into it and I listened, there was a fantastic classical music radio station from Connecticut. I forgot the name of it. And I listened every evening and I learned so much. And I bought CDs. I bought every weekend one or two CDs and I started to get all the symphonies of Brahms, all the symphonies of Beethoven. Even all the symphonies of Mahler, which is tough, because those are like big ones, ten of them. And I used that time to read a lot. I used that time to develop some of the passions, which I still have today. I always liked sport. My boss was a fantastic runner, so we had a running group every day at lunch. We were going running sometimes eight miles, sometimes five miles. Like, long distance, fast. So yeah, but it got better. Year one was difficult. Year two, I started to make some friends, and then by year four, I finished my PhD in four years, by year four, I actually had quite a nice social network. And it was kind of time to move on.

I also have to say, I became friends with two families. One family, which I met through a student of mine in Vermont, and another family in Connecticut. And both of them were incredible for me, and I spent a lot of time with them, lots of weekends. In one of them the parents were the generation of my parents, and they had children similar to my age. The other ones were kind of halfway in-between, so their children were a little bit younger than me, and the parents were a little bit older. But somehow, I kind of fit into them and we spent many, many hours and many weekends together. And I think without these two families, my time at Brookhaven would have been more difficult, but with these families, I developed, also, this love of New England in general. I can tell you when I think of Long Island, when I think of New England, like Massachusetts, Connecticut, Vermont, Maine, I get like a warm feeling to my heart. (both laugh) It's an incredible area and I have a very, very strong love of that area, thanks to those families and thanks to those four years I spent there. 

Phillips:

Yeah, yeah. And so, I know you've already mentioned briefly, but after this, you went on to Grenoble to do a postdoc.

Bergmann:

Yes. 

Phillips:

Before you started that, I'm curious, were you at all considering either going into either an academic or an industrial route as opposed to staying with the sort of the large national laboratories?

Bergmann:

Yes, it's an interesting point. I mean, in a sense, maybe partly also from my family background, it wasn't that there was any job for me in my family, but from this non-academic background, I actually never thought about one way or the other. I kind of tried to stay true to myself, and then let's see how much fun it is. And I think that's even true to that most recent change of job, which only happened three years and two months ago. This wasn't planned. I can't say that with a straight face. I am generally not a believer in these kind of five-year planning things. Because first of all, often they don't come as you planned anyway, and then if they don't, what does that mean? Does that mean you should be disappointed, or you should be happy or whatever? So my philosophy has been, and I have held true to that, with very, very few exceptions, as long as you enjoy what you're doing and you feel like you can give it your all and you wake up in the morning and say, "Okay, I want to go into work.", you are in the right place. And as soon as you don't do that anymore, you need to be very seriously thinking about some changes.

And that has been the guiding principle, and I tell you, there have been times where I was almost... At one point, when I was a postdoc in my second postdoc in Berkeley, there was a guy from... what company was it? I think it was IBM or something. He said, "Oh yeah, do you want to come?" And I said, "Sure, yeah. Let's do it." Because I had this second postdoc, it was not well-paid, etc. I was ready to go. I said, "Yeah, let's go. Let's do it. I'll send you my CV." And he said oh yeah, it's great. And then he said, "Oh but, do you have a green card?" I said, "No, I don't have a green card." So he said, "Oh, sorry, that we cannot do." (laughs) So I had this whole thing, as fast as it came, it fell apart. (both laugh) I was always open-minded, but in a sense, it was almost true for every step in my career, that it kind of came... it doesn't mean that I didn't apply for a job. But it kind of came as what I felt as like a logical next step. And if at any time between the logical next step would have been, let's say, a startup company or something else, I would have probably done it. And even today, if someone says, "Hey Uwe, we are going to do a startup company and we need you and no one else can do it." I mean, why not, right? No problem, right? So anyway, that's kind of the answer, I don't know whether that's a good answer...

Phillips:

No, no, that's fantastic. So, but you did stick around these national labs, and you said you did the postdoc at Grenoble. Can you tell me a bit about working there?

Bergmann:

Yeah. So, in a sense, at the time, there were two opportunities. One was to...actually do a postdoc in Berkeley. I already had contact with the person to whom I would then later go. And then there was the postdoc position in Grenoble, and I knew the person a little bit. Not very well at the time. The person was Francesco Sette and he ended up also being the lab director of the ESRF for many, many years. And he was a good friend and colleague of my boss, Hastings, and so Jerry said, "Hey, what do you think of going to the ESRF to join Francesco, they are starting a brand-new beamline. It's inelastic scattering. It's a slightly different technique. It's still synchrotron radiation, it's still X-rays. You will learn something new. It's a good, it's a very strong group. What do you think?" And I said, "I think that sounds great." So, I ended up doing it. And I also felt, I mean I had four years of New York. There was a little bit Europe...not that I missed it too much, but I was kind of, "Oh yeah, spending some time in Europe sounds good too." And so, I basically, with not much thinking, I followed that plan and that idea, and I ended up in Grenoble and at kind of a brand-new synchrotron at the time, this was 1994. It was just starting up. I mean, there were the first beamlines that were running, and the main building had just been finished. The groups were all new, lots of young people. A lot of energy. And I ended up in this extremely driven, energetic group. And I learned, again, a new aspect of X-rays, a new aspect of X-ray optics and X-ray experiments in a group with some extremely, very, very hardworking, talented scientists. And I felt very privileged to be part of that group, yeah. So, I also met my wife, Elisabetta, at the time. We started to become friends and it took some time, but we were friends for like a year or so, and we started to get closer. And it was a great time. It was the first time that I lived with a roommate. (Claudio Masciovecchio, he's from L’Aquila and lives now in Trieste). We rented an apartment together. It was in a big, old house, like you think about when you think of France. It was this 200, 300 year-old house, and we had a whole floor of it with a gigantic kitchen. Big, really big parties there. Big, monster parties. Like a total mess, we turned the whole thing into a total mess. And we had an extra room, which we kept as a kind of a spare room, and it was always (laughs) always occupied—not a single time that room was empty. Always someone was staying, living in there. And lots of adventures during that time. It was a very interesting time, yeah.

Phillips:

And your now-wife, was she working at the lab there?

Bergmann:

She was working at the lab and I met her basically on the first day. She was in charge of the travel. She was the head of the travel group and yeah, so that's how we started...she also knew everyone in the lab, which was of course because if you had to travel, you pretty much needed to... so you don't know everyone, but you know most of the people. And yeah, I used these two years to really learn an enormous amount of experimental work. And other things as well, right, but for me, it was a really great time of learning. And I could have stayed longer. There was an opening to stay longer. We had funding for another postdoc for another extra two years, but there were a series of circumstances where I felt, and then also together with the decision was made with Elisabetta, where we said, "Okay, this is a good time to start our own life now." And because you know it was good to start in a new place, in a neutral place, where we didn't already have pre-existing conditions, if you want to call it that. (both laugh)

Phillips:

Right.

Bergmann:

And so that was one of the reasons where we said, "Okay, let's jump into this big adventure and move to the West Coast. And it was so easy to get this first job. And it was so difficult then to get another one. But this first one was very easy. So, there was this colleague of mine, Steve Cramer, he had been at Brookhaven, and I knew him from when I was at Brookhaven. We had met at a Gordon Conference, where we played soccer together, and at the time he had offered me the job but I had told him that I was going to Grenoble. He had said, "Never mind, right, that's all good." And so, then two years later, I sent him an email and I said, "Hey, remember you wanted to hire me as a postdoc two years ago, is that still an offer?" (both laugh) I think he answered within five minutes and replied, "Sure, when can you come? When can you start?" And I said, "Wow, this (laughs)." So, at the time, yeah, basically that job opened up. There was also some pressure, and I don't want to go too much into detail. There was some pressure from some people not to take this job. And it made it more difficult, but at the end, it was one of those things which I learned over the years, that sometimes you have to make your own decision. And advice is great, right, and you usually follow it, but sometimes, even if the advice goes a different direction, you should just follow your own direction. And that's fine. There's nothing wrong with that. And it doesn't mean that the advice is wrong or even bad or anything. It just means that in that situation, you need to make up your own mind. And that's what I did and we ended up going to Berkeley. I stayed in that group for seven years. I was starting as a so-called postdoctoral fellow, so it was kind of a second postdoc, and they turned it into a scientist position. And then came the time when I started to do more and more...became more and more independent in my research. But of course, I was funded through that group and through the soft money of that group, and so it was clear that sooner or later, either I stay there and stop doing my, following my own collaborations, or I need to move on and get kind of my own so-called "real job," right?

Phillips:

(laughs) Yeah.

Bergmann:

And there was also a person at Lawrence Berkeley Lab who asked me to sit down with him, and he told me, "You know what, we very much appreciate your research, but we don’t see that you have the support from your PI, and we cannot hire you around him. So we feel, it would be best for your career to leave this group and for you to move on." And retrospectively, it was the best thing that happened for my career. I think it was, for me, a kick in the butt, which was what I needed. And that's when I basically did my first really serious application. (laughs) Which was to SSRL, to SLAC.

Phillips:

Right. A very minor thing that I'm curious about. You mentioned the IBM job fell apart because you didn't have the green card. So, going from a postdoc to a staff scientist position, did you have to navigate the whole immigration system?

Bergmann:

Oh no, yeah, I didn't tell you this. When this IBM thing happened, I said to myself, "You know what, I need to get a green card." And so, at the I-House, the International House, in Berkeley, was a great guy, I forgot his name. I wish I had remembered his name. He was just about to retire, and so I called him up and I said, "How can I get a green card?" And he said, "Well, do you have a permanent position?" And I said, "No, I don't have a permanent position, but I still want to get one, because if I don't have a green card, I cannot get a permanent position." And he said, "Yes, I know, I get it, I get it.” Here was someone who had been there for many years, and he said, "I'll help you. You'll need to get a letter from your boss that he intends to hire you into a permanent position. And that doesn't mean he has to hire you, he just has to write you this letter that he intends to hire you. Then we can get a lawyer and Lawrence Berkeley Lab will pay for it and we get you a lawyer and we start your green card process." So, I went to my boss who was a great guy, Steve Cramer. I said, "Steve, I have something for you to sign." He said, "What is it?" "Well, you have to sign that you have the intent to hire me." And he looked at me and he said, "What does it mean?" I said, "It means that you intend to hire me." He said, "Does it mean that I have to hire you?" I said, "No! It means you intend to hire me." He said, "Okay. Does it cost me anything?" "No, no, no, you don't have to pay anything." And so he signed it and at the time, my wife and I—well, at the time, we still were not married, and then we basically decided to do an ad hoc wedding, not in Las Vegas, but in Lake Tahoe, on the Nevada side of Lake Tahoe. Which is still Nevada, but not Las Vegas. So we ended up getting married very quickly because then she could qualify first for the J-2 on my J-1 visa, and then also the green card. Yeah and so we co-applied then, and it was one of those things where I felt that having a green card was more valuable than having a permanent position at LBL, because with a green card now, all of a sudden, you can get a position. And it was correct. It was correct and yeah, and so I started to be interested in work on water.

I had a great collaboration with Anders Nilsson, and he and I, as well as of some of his old postdocs, are still very good friends. I also started to work more with the group from Berkeley. Vittal Yachandra and a bit later Junko Yano, and later Jan Kern joined that group. At the time, there was still Mel Klein and Ken Sauer, they were the PIs, and Vittal was a staff scientist. And we started work on photosystem II together. And they realized that I'm actually a great collaborator because I can get experiments—my experiments to work, right? (laughs) And I had ideas like how to change things, how to do different things. It was a good time. During the seven years at LBL, we had lots and lots of publications together, we did a lot of good work, I'm very thankful to my boss, Steve Cramer. But then came the time, when I had to make up my mind: either do I stay in this secondary role for the rest of my career or do I move on? And after getting this kick in the butt, I moved on. SSRL had new leadership at that time. Jo Stöhr was the new deputy director at SSRL, Keith Hodgson was the new director. Anders Nilsson had also moved at SSRL. He became a SLAC faculty at the time. And he said, "Uwe, why don't you come to SLAC, because we are already doing experiments together anyway?" And so, I had an opening.

At the same time there was also an opening in Hamburg. And I was strongly encouraged to apply for that. That was a more senior position, and I didn't kind of like the idea of moving away from California, but I applied anyway and at the end of the day, I ended up second in this other search. But even before I knew whether the other candidate would accept or not, we had decided to move across the bay to SLAC. And at the time, our daughter was four years old. We had just purchased a house in the East Bay, and it was a little bit inconvenient, but we ended up, even though it was after the 2001 dotcom crash, being able to sell the house actually quite well, and that helped us to get our foot into the door into the even more expensive area of real estate around Stanford. And so in 2003, I join SLAC and started at the SSRL, at the Stanford Synchrotron Radiation Lightsource, as a staff scientist.

Phillips:

So, when you started on at SSRL as a staff scientist, did that also come with an appointment at Stanford, or was it just at the lab?

Bergmann:

Most appointments at SLAC don't have a faculty appointment at Stanford. And there are some which do, but most don't. But as a SLAC employee, you're automatically a Stanford employee, because Stanford runs SLAC. And so, in that sense, you had access to certain nice things on the campus, but you were actually at SLAC. And my position was that of a staff scientist, which was kind of what I always had aimed for anyway. And in Berkeley, I had never made it to staff scientist. I made it to scientist, but staff scientist is one level further. And the other good thing about the SSRL position was that it was funded through the core of the facility.

Phillips:

Right.

Bergmann:

Being core-funded through the facility is still kind of soft money, but not as soft as the funding from an individual PI. And I started to build my own instrument for which I got seed funding from SSRL, and my research was going quite well. And then there was also this Archimedes project…

Phillips:

Yes!

Bergmann:

…which maybe we should talk about in a little bit as well, that kind of came out of nowhere. And that's why I'm saying these five-year plans don't always work. While I was doing all my research on water, on photosynthesis, building new spectrometers, I'm in Germany for a conference and I'm reading... actually, it was a conference on photosynthesis, I'm reading this, you know, this German type of National Geographic magazine, which my mom had given me to read. The German magazine is called GEO, and I find this article about the Archimedes project, where scientists are trying to read covered pages of the oldest surviving copy of work by Archimedes. Writings that no one had seen before. And I was thinking, to bring it to the point, I found it remarkable, that no one else would have had the idea to use X-ray fluorescence to better-image these obscured parchment pages.

I should point out, some other person actually had the idea. He was one of my colleagues of the Archimedes project, but he hadn't suggested to using synchrotron radiation. My colleague had suggested to use a commercial system, which would have ended up not being practical for imaging a large enough area. Nowadays such commercial systems are actually getting better and better, and in some cases one can actually use one of these new systems to do such x-ray imaging work. But at the time when I contacted the Archimedes team, I was kind of shocked that no one had proposed the use of synchrotron radiation. And then later over the years, I kept thinking about, "Why is that?" And I realized that scientists generally are very stove piped in their thinking. You become an expert and you get so deep into this expertise that you, kind of...all your energy is sucked into it, right? In particular also if you do good work. I mean, of course, you get known for it and it just pulls you deeper and deeper. I have always thought, and that comes back to my nature and the way I grew up, that the bigger view is more interesting to me. I like to build a good instrument, but I never get that obsessed that I don't think other stuff is also very cool. And I think that in this particular case of the Archimedes project, that thinking made a difference. Because I could have given you five other people who I know, they would have proposed probably something entirely different, because what I proposed to use was not exactly what I had done before. It was related to the techniques I had been familiar with, but it was slightly different. But I understood enough about the difference of what is needed and what you can do that I was able to make that kind of connection. And someone else would have just looked through it and said, "Okay, so what?" Right? And I'm very grateful for that, and, by the way, in a sense, my idol as a scientist is actually Alexander von Humboldt.

Phillips:

Oh yes.

Bergmann:

And I recently read his biography from, there's a fantastic biographer from a German woman, I'm trying to remember her name. [Andrea Wulf] She wrote it originally in the English. It's called The Invention of Nature, and there's a German translation which I happened to read. And this guy was, he was all about making these connections. This guy was an incredible scientist, like unbelievable. And he was even very famous when he died, but then he kind of slowly more and more he got forgotten, and nowadays, if you ask people about him, lots of things are named after him, but if you really ask people, what did he do, a lot of people cannot tell you, because his research was just so broad. And to me, it's kind of sad, because as a scientist, you need to have this one thing, what are you known for, right? What's the one thing you're known for? Our society doesn't lend itself to these universal geniuses. But if you look in this history, all the great ones, whether it was Galileo, Archimedes, Leonardo da Vinci, they were universal. They were people, who were universally interested. They didn't just focus on one thing. And I'm inspired by that. It's more difficult to get funding, it's more difficult to find a department where you can fit in and all this, but if you can somehow manage it, and you have somebody to fund it, I think it's very rewarding. And the Archimedes project and everything which followed from it, the enormous amount of research, which came out of it afterwards for me and for many of my colleagues, is an example of that philosophy.

Phillips:

So, I'm curious, if I remember correctly, the Archimedes Palimpsest was at the Walters Museum in Baltimore.

Bergmann:

Right.

Phillips:

So did you just reach out to the conservation staff there and...?

Bergmann:

I sent them an email. Abigail Quandt was the first one and then Will Noel, who was director of the project, he contacted me right away. They invited me to a workshop. I proposed my idea, then they said “okay,” but they were very skeptical about synchrotron radiation. My colleague who had proposed the commercial X-ray system, he was also very skeptical. He said, "Oh, it may be too strong and blah blah." And so, for one year, I had great colleagues at SLAC, Martin George from SSRL and others, and we built a prototype system. They gave us a little piece of parchment with text written with iron gall ink, and we showed them how quickly we can image it. And I said, "Guys, look, we did that one in ten minutes." And it had taken the other person eight hours just to get one letter. We did like a whole word in ten minutes. And once they realized, "Oh, this could work," they came, they took the risk. We made it safe, we put in shutters that automatically closed the beam when the parchment was not scanning. We had two beam times. First, we were able to read text, and then during the second beam time, it was incredible what we were able to read, and of course, it went all around the world. I made a mistake. I should have published like one definite publication on it. But I kind of scattered them a little bit. It was published in a book. I have the book right here. I published the original idea in a SLAC memo. So, I kind of never got many citations on this work, but it doesn't matter because it got so much attention and it catalyzed so many things, so that's fine. And yeah, that was pretty awesome.

Phillips:

Yeah, and I'm curious, and you may not know anything about this, or you may not be able to speak to it, but I also know that the history of the Archimedes Palimpsest is such that there's been some contention over ownership of it. 

Bergmann:

Yes.

Phillips:

Did you interact with the owner at all? Or was it just with the curatorial and conservation staff?

Bergmann:

No, I have, by now, not at the time, but by now, yes, we have interacted personally, also because we've done another project together, which is not published yet but it was already in the news, but we are waiting for the publication coming out anytime. And I know the controversy about the Greek government and the owner, and why the Greek government didn't want to go higher in their bid. I mean, it was… Christie's is an auction house. They auctioned it. And why the owner ended up getting it and the Greek government said, "Okay, that's as much as we can go." I don't understand, to be honest. And I don't know where the owner would have said "stop" right? At what price, I have no idea. But I can tell you one thing, okay? In my mind, there's no question that the access to doing this work at SSRL, or no matter where, and also the conservation effort, which has been done, and the other multispectral imaging efforts, which my colleagues have done (which was actually much larger, as we had just specialized on some of the most difficult pages) would have probably not been possible. To go through the bureaucracy of a government kind of library would have probably made that conservation effort and then also that scholarship and what we've learned about it probably much more difficult. So as much as I understand and also feel that certain things should be publicly owned, as a scientist who has now worked with lots of publicly- and privately-owned artifacts, a good owner who encourages and supports scholarship can also be very, very good. And it turned out to be that that owner is a good owner who actually has encouraged, has enabled the generation of wonderful results for the whole world. Now, should the Palimpsest be on display somewhere in Athens or in Syracuse, where Archimedes is from? Possibly one can argue that. But do we know more about Archimedes because of this private owner? I am convinced we do.

Phillips:

Yeah. So the other thing that I'm curious about with this is obviously this kind of imaging has proven to be extremely successful, and you were able to demonstrate to the conservation scientists at Stanford and at the Walters that this worked, but when you first started publishing these results, was there skepticism or pushback from the broader conservation science community about using something as powerful as the light source at SSRL on these documents? 

Bergmann:

No, there wasn't, and the reason there wasn't, was because we did a damage test. We worked with a conservation scientist from Ottawa, who was consulting also with the Archimedes Palimpsest, and he sent us some parchment, and we went to Argonne, which still has one of the brightest beams of synchrotron radiation. And we basically exposed it and measured what happens if you expose it for certain amounts of time. And by doing that, we established a dose, which is very safe. In fact, I keep making the argument to my colleagues who don't use synchrotron radiation but commercial systems that the signal-to-noise, the image quality you get for the same dose at the synchrotron is always superior to that from a commercial system.

Phillips:

Right.

Bergmann:

Because in a synchrotron, you can tune the frequency to exactly what you want. You don't have all this other stuff which gives you more background. If you do the experiment correctly, there is no advantage from a commercial system other than the practical advantage of not having to move the object and not having to apply for beam time. But in terms of technical advantages, there is no real advantage of not doing it at the synchrotron. So, I never got pushback on that. And we were—ever since we have been contacted, not at a very high rate, but at a reasonable rate, as recently as two weeks ago, I was contacted from a guy who wants to read an old text and he called me, and I sent him information and we might follow up on this one. And we started all the fossil imaging for which I have to give a lot of credit to my colleagues from Manchester, Roy Wogelius, Phil Manning, and then also to Pete Larson, who contacted us originally. Pete Larson is this famous guy. I don't know whether you have seen it, but the CNN document Dinosaur 13 is about Pete Larson. He discovered the T-rex Sue. And they brought an Archaeopteryx fossil from Thermopolis, Wyoming and another early dino-bird, Confucius ornis from Liaoning, China. I mean, these are some of the most iconic fossils you can find, and we were able to use that same x-ray fluorescence technique. We had perfected it by then, and we were able to use the technique and to actually find new information about these chemical composition of these fossils. And we imaged other books, right, other texts, like a section of the opera Medea by Luigi Cherubini, another palimpsest, and other writings. So I think this whole X-ray fluorescence imaging of large objects got a big boost. And now museums are buying these commercial scanners they apply to analyze their large painting. Would all of it have happened without the Archimedes Palimpsest? Probably. But I think we can take some credit of being some of the early ones who did it and got good results, yeah.

Phillips:

I'm also curious with the fossils like Archaeopteryx, were there any technical difficulties or considerations in moving from imaging this iron gall ink on parchment essentially to calcified stone?

Bergmann:

Yeah, in the following sense: I mean, first of all, the fossil is heavy, right, and it's big and if you drop it, it's broken. It breaks. The parchment if you drop it, it's terrible, but it's not the end of the world. If you break the fossil, it's kind of the end of the world. But these were on the practical side. And then we also realized that the lighter elements are much more important to these fossils. In the Archimedes Palimpsest iron was the important element. One image we actually saw in calcium, which was interesting. It was one of the drawings of Archimedes, and that was published in Science as a news article. This came out better in calcium, but most of the images were from the iron in the ink, so that was straightforward. But with the fossils we realized that phosphorus and sulfur is are very important. So we needed to excite at an x-ray energy below the calcium absorption edge, because the calcium signal in the limestone was so overwhelming. So, we imaged most of the fossils in two runs. One was this so-called, we called it the High-Z run, where we looked at elements with high Z, especially all the transition metals: nickel, zinc, iron and also the other transition metals, and sometimes also lead. And then for the light elements, the low-Z run, we went to the excitation energy below the calcium edge, so that we wouldn't get that big calcium signal. For this, we also put the fossil inside a helium environment. We had a very thin cellophane film, and there was a little bit of room in-between that was filled with helium, because the lower energy X-rays don't make it in and out through air. And we put the detector directly to touch the cellophane film, so there was no air absorption. So there were really two setups: The high-Z XRF setup and the low-Z XRF setup where the geometry was changed.

Phillips:

Yeah. So now also, when you started working on imaging. The Palimpsest and then the fossils and such, this was mid-2000s, right? 2005-6ish?

Bergmann:

Yeah, 2005 was the start.

Phillips:

Was this also around the same time that you started—oh, excuse me, sorry, I've got a cat showing up. Excuse me.

Bergmann:

Yeah, don't worry. Please let’s take a tiny break, I'll just get a little more water.

Phillips:

Of course. (break) Okay. And we're back. So, I was just curious, is this around the same time when you also started looking more into water and aqueous systems?

Bergmann:

Yes. This work started a little earlier. The first big water paper was in 2004, but we had already done the experiments. Basically, there was another technique called X-ray Raman scattering, and we had developed the instrumentation that is similar to what is needed for this technique. By the way, this X-ray fluorescence technique was never part of my main research. It is a big part now, but in terms of what I was hired for at SSRL, and what I was kind of specialized on and what I was kind of a little bit more known for, wasn't that. That just came as kind of this accident, but is has now got a life of its own. Even today, I have two of my graduate students and one postdoc is working in this cultural heritage work. Which are not all of them XRF, but related. And X-ray Raman was another technique, which at one point my boss at LBL had pointed out that that should be possible. So we did some initial experiments on carbon systems. And then we had this idea of, oh, why not look at water? And then I met up with Anders, and we did some really important contributions to the water research, because we were able for the first time to measure, to get x-ray absorption spectroscopy data of water under different conditions, not just room temperature, but from 4 degrees Celsius to 90 degrees Celsius, and X-ray Raman was critical for that work. So that was happening at the same time. And yeah, there was some really important and nice papers on water. And, by the way, I'm now back in the water game.

Phillips:

Oh, excellent.

Bergmann:

We are doing, I have one student who is working on it. We are looking at argon dissolved in water, and we are now considering doing, with my colleagues in Berkeley and others, more water work. Water is a fascinating topic. It's not solved, right? And it's also nature. (both laugh)

Phillips:

Yes, exactly.

Bergmann:

It is like the quintessential elixir of nature, right? And life. So yeah, so that happened at the same time.

Phillips:

And so, what was—

Bergmann:

And photosynthesis, by the way, photosynthesis has been ongoing, I mean ever since I came to Berkeley, I've been working on photosynthesis. And in the last ten years with X-ray lasers, at LCLS, all the big impact, the major impact papers, are one way or another have been related to photosynthesis. More recently, we have done some, maybe in the last six, seven years, we have also developed some non-linear X-ray spectroscopy and I am very excited about that work as well. And that's the most recent work which I am doing, some work with Claudio Pellegrini and some others, Nina Rohringer and others. If you think about the three science topics, the photosynthesis has been there always, and then water and then cultural heritage. And then in between lots of other things, not to the same level, and R&D work. And recently I have also started materials science work as well.

Phillips:

So, you said when you were brought into SSRL, the XRF work that went onto the cultural heritage stuff was sort of almost a side project. What was it that you were hired specifically then to focus on?

Bergmann:

Yeah, X-ray emission spectroscopy was something, which I had developed with Steve Cramer, and he had some of the original papers also. Working in his group, I had shown that we could build a much, much better instrument than anything that had existed until then. SSRL was interested to have such an instrument and to develop a program with it. And so, we ended up doing a lot of work after I left Steve's group. We ended up continuing to do a lot of work, some of it on photosynthesis too. Actually, quite a few papers. But I started to do other work with other collaborators. That was what I was brought in for to do. I should point out that I'm really grateful to SSRL that when the Archimedes project came up, and I remember Keith Hodgson was one of the people who was important in this regard (he was the SSRL director), because I went up to his office and I told him what's happening, and I just wanted to let him know. And he could have said, you know, no, you cannot do that. We hired you to do this and you need to do this. But he didn't. And the same with Jo Stöhr. So, I want to give credit to the leadership at SLAC, that the staff scientists have freedom to do their own research as well. I still think they still have that freedom. If your bandwidth is such that you can do the work which you're hired for, no one stops you from doing other work. I was very grateful for that. 

Phillips:

I guess, speaking of the leadership at SLAC, you were at SSRL for a few years and then moved to LCLS, where you, as you mentioned earlier, you were director for a couple of years. So how did that come about, and I guess can you tell me a bit about your tenure running LCLS?

Bergmann:

At SSRL, I was a staff scientist, and shortly after I joined SLAC, Jo Stöhr became the director of SSRL. We had a good relationship, and at one point, he created a Chemical & Materials Science & User Support Department at SSRL. Shortly after that he said, "Why don't you become the director?" to me. (both laugh). I said okay, let's do it. And he tasked me to do a project. He said, "We want to get a career structure into the SSRL scientists. He said, "You know, faculty is out of reach for most, and for staff scientists there was only one level." He tasked me with this job, and we put together a committee. And we did, and we ended up suggesting the structure, which is kind of the same structure still used today. And it was taken over from SLAC. Maybe they changed it slightly, but at the time, and we created this position of associate staff scientist, staff scientist, senior staff scientist, and then distinguished staff scientist.

And I think Jo was happy with my administrative duties. And we also kind of liked each other from our research. He does a lot of soft x-ray spectroscopy and also looks very deep into the details of the theory of magnetism and also spectroscopy and photons. And my research was mainly on hard x-rays. We always had very interesting discussions—still have, he's a very good friend of mine, and we are collaborating even now as we speak. When he was asked to become LCLS director, kind of the first LCLS director, I remember he came to me and said, "Uwe, if you know anyone just let me know." And I said, "Sure." And I gave him a name or two names. And he said, "Thank you, that's okay, thank you, that's good." And I don't remember exactly how long, but it was very shortly after that when he came to me and said, "How about you? How about you for it?" And it was a shock. I had just gotten a million dollars of funding to build this big X-ray Raman spectrometer. It was a monster. I was happy. You know, I had my Archimedes fame, I had all these different things. I had no intention to switch to x-ray lasers, and I didn't really know much about them. I obviously had followed the field, I was on several workshops, already starting in 2003 or so, even wrote a paper on doing x-ray Raman spectroscopy with XFELs. But I didn't know whether my science would fit, how to shift my science.

But anyway, it was just too great of an honor and too great of a challenge to say no, and so it didn't take me long, it took me like a week or so, and I said yeah, I'll do it. And then a whole new life started. And very interesting, incredible, and I'm very thankful for, first of all the time as the deputy director, and also for serving as an acting director. I learned enormously about management and leadership. Retrospectively now looking back at the time, it was all a bit too fast. I didn't learn enough, fast enough. In hindsight, I think I could do a much better job now. But it was like drinking from a fire hose. You jump in, and we had an important job to do. We needed to come up with a proposal review panel, a big one, to provide the ranking for who was approved to do experiments at LCLS. How could we do it in a fair way? It was a lot of work, and he put me in charge of that. That was one of my jobs as a deputy director. And I think the system we came up with, Jerry Hastings had some really good suggestions early on, is good, and it is still pretty much the one they use today. I thought that was good. There was also enormous amount of pressure in terms of the amount of funding from DOE that goes to LCLS. A lot of that funding goes to the machine, how do you manage it well, etc., etc. It was an extremely busy time. Very, very busy.

We also started the research, I proposed together with my colleagues Vittal Yachandra and Junko Yano from Berkeley. It started when I met Vittal at the Frankfurt airport by chance, we were on the same flight back to San Francisco. It was one of those events. I met him at the airport. I had just come from a conference. And I kind of almost shouted at him, "Vittal, we need to study photosystem II with X-ray lasers. We need to get into the game. But beyond just what we are doing ,spectroscopy, we need to do all, also x-ray diffraction." Even though it was completely new, and we didn't know quite yet how to do it.. We combine x-ray diffraction and x-ray spectroscopy, and we will do it. And then Vittal and Junko were really excited and the whole thing started. They brought in people from Berkeley who knew diffraction. And this was the start to how this whole team was built together. It's very striking now, it's an incredibly strong team. It's led out of Berkeley right now. I'm obviously still one of the senior guys, but I don't spend as much time with it. They have taken it and really run with it incredibly well. And it was at the birth of LCLS that our science took a turn. I think some of the most important work—I stand by this—some of the most important work to date on photosystem II is done at X-ray lasers, like LCLS and SACLA. This work done by our collaboration and also by the collaboration from Japan. They have done some of the ground-breaking research first at the synchrotron, and then they used a slightly different approach at SACLA. And there are others who I can name, but they haven't done major contributions. But these two groups (ours and the one from Japan) have done major, major contributions to understanding the mechanism of photosystem II and to using this x-ray laser approach to study biological systems in real time. Even with such a destructive beam.

Phillips:

Right.

Bergmann:

Because you don't care that you destroy the sample because it takes too long for the sample to blow up. The x-ray photons start out towards the detector before the sample has been damaged. That was thanks to being able to work at LCLS. It just showed you again, this planning, this five-year plan, doesn’t work. If I would have said, "Oh, I make my career is at SSRL”, what then? You just don't know.

Phillips:

Right. You mentioned sort of this stiff competition or fighting over access to LCLS at first. And you developed the system to evaluate and prioritize access. Can you tell me a little bit about how you evaluated these projects?

Bergmann:

Yes, it was not a new idea, because you know proposal reviews have been around for a long time. We basically divided into five or six different research areas with a roughly similar number of proposals. Suppose you get 120 proposals and you have six research areas, then you get roughly 20 in each area. And then we did what is called pro rata, where we said let's take the best five of each area and give those beam time, even though we don't know whether the best five from group A are better than the best, or second best five of group B. We don't know that because it's very hard to compare different fields. But we know, within their peers, they are the best. And that's how we assigned proposals. We had an independent panel. We gave them a lot of freedom. We selected the panel members and each had to serve two years. We had a chair for each panel. We had staff scientists from LCLS who led the discussions and who were keeping notes. They were what we called the secretaries. They also kept an eye on what’s happening during the review meetings. Is one person dominating the whole discussion? Is there favoritism going on here? I got heavily criticized by the users. We did some decisions that they didn't like. They called me all kinds of things, but we stood by our decisions, because we had a good system. We had a system, which we could defend with a straight face. We could say, "This is the best we could do." And here is the result, and it's not perfect, but this is the best we could do. And I'm actually proud of that. That part of my work as an LCLS deputy director I'm kind of very proud of. We did have some issues with DOE regarding budget control, and then I had to also step in when users were fighting with each other. 

Phillips:

(laughs) Oh no.

Bergmann:

They were coming to me to complain about each other, and then I had to step in. Sometime, in one of those disputes, it took me several months to actually get to the bottom of it. Because the first impression was wrong. I thought okay, this is a clear cut—and then the more I dug into the issue I found, "Wait a second, this doesn't make any sense." And then finally I figured out that it was more complicated than I had thought. Those things very tough. But I benefited from what I had learned at two separate leadership classes at Stanford with my wonderful coach Brian McDonald. I also met a lot of cohorts from Stanford, some of them, I'm still friends with. I was able to listen to talks from the president of Stanford at the time, John Hennessy, and the provost John Etchemendy, and also John Morgridge. He's actually a big donor also to UW-Madison. He's from Madison, I think, or at least from Wisconsin. You meet these really, really interesting people, we even met the Stanford Women’s Basketball coach, what's the name, Tara VanDerveer? She's now the winningest coach in the history of women's college basketball, of any college basketball, I think. She gave a talk and it was wonderful. That was wonderful. All these DOE meetings, directors’ meetings, talks, reports. All this lots and lots of work. A lot of work, but a lot of fond memories.

Phillips:

Yeah. So, one other thing I'm curious about with your administrative tenure there is can you give me a sense of how you felt the relationship between LCLS as a sort of sub-institution with the leadership of SLAC more broadly, during your time as a deputy director and then as an acting director?

Bergmann:

Persis was at the helm of SLAC when Jo became LCLS director, and when I became deputy director. She was incredibly supportive of LCLS. Of course, it was the big new kid on the block. I can remember when she asked me to come see her in her office and I was a little scared to have this one-on-one with such an impressive person. And she looked me straight in the eye and she said, "You are going to be great." And I felt, oh that is what I wanted to hear. Like a good coach. At the time there were lots of challenges at SLAC because the lab had made such a rapid change. It used to be a high-energy physics lab and now it had become a multipurpose lab with LCLS being the new big thing. The accelerator had been shut down for particle physics. She did that, Persis did that. I'm sure there was a lot of people in the high-energy physics community of SLAC who looked at LCLS with kind of a skepticism and maybe a little bit of jealousy that, all of a sudden, they were no longer the superstars. But we didn't feel that so much I have to say. The leadership with Persis being our boss, I think that was straightforward. Because of the way how the funding was set up within DOE, there was a little bit of skepticism sometimes whether all the money went to the right place. When I was acting director, some at DOE kind of put their guns on my head and they wanted to know where every cent of the $125 or $130 million we got ended up. We had our team, and we knew it, but the DOE sometimes wasn't quite happy with the answer and they tried to dig deeper and deeper.

But I can say retrospectively, I can say that I possibly could have been a more kind of bean- counting head. And that is true. I take that. But I also know that with the things we funded, and the review committee came to the same conclusion by the way when they saw all the number, we did not waste tons of money. We did not siphon off money to other things. No, whatever they might have thought we did, I think there was no evidence for that. This review happened after Jo had left and I was LCLS interim director, and I am proud of my team how we handled it. It became also clear to me that I will not become the new LCLS director. And I sometimes felt I didn't have the full support from the SLAC senior management.

Phillips:

Was Persis still director at that point, or was it Chi-Chang?

Bergmann:

No, she had already stepped down, Chi-Chang had already started, and Norbert Holtkamp was the SLAC deputy director. During my time as LCLS interim director, sometimes I felt that I did not have the full support for whatever reason, although I don't want to speculate too much.

Phillips:

Absolutely.

Bergmann:

I think they had kind of made up their mind that they wanted to get a fresh new leadership, and so in a sense, the support wasn't at the same level as it had been with Persis. This is completely understandable. They had no ill will or something like that. But I was very happy with my team and proud of how they handled all the uncertainty and pressure. With some exception, the team I put together was very supportive. Interestingly, one would not have thought the person who tried to undermine us would do that, but it happened. I'm not crying or anything, with leadership you are in thin air. And once you work in this very, very thin air, I mean all guns are pointed at your head and you have to just understand the people. That was fine. What was tough for me was only the fact that there was this big uncertainty for quite some time, because I could have ended up getting the job at the end after all. It got very close, and it wasn't clear for a long time who will get this LCLS job. Working with this uncertainty for more than year without the full support was tough. As soon as it was clear that Mike Dunne was the new director, we tried to make the transition as smooth as possible. Bill White from my team had this great idea to invite him to a pub, and I introduced him to all the senior leadership. And we have been good colleagues ever since. And I'm still very good friends with Mike. And he has been supportive of our research and hopefully I have been supportive of his work and accomplishments. At the end of the day, even though it was personally a tough time for me, and a time with a lot of uncertainty, I'm really glad that I had this experience and it was a privilege to be in this role. 

Phillips:

So, despite that uncertainty, would you have wanted to stay on as director, or was it kind of a relief to go back to a staff scientist position?

Bergmann:

No, I had applied for it, and the interview didn't go well. I knew it right after the interview. In my retrospective opinion, the interview was done in a way that showed there was no interest in me for this role, although I tried my best. Who knows, maybe every candidate was feeling the same way. I don't know that. But it was what it was, and although I would have been very happy to stay on as director I was also very happy to go back to research. And I was able to do some really nice research for the subsequent years. It was also clear that after that I wouldn't go back to LCLS, after some back and forth I ended up in the Stanford PULSE Institute at SLAC. My standing in the lab, even though I was promoted to distinguished scientist, was now more uncertain. At the end of the day, that title doesn't really mean much. But my research was going well. I started to bring in funding, and I could have maybe brought in even more funding, but my research was going well and I could have kind of slowly let it run to the end of my career. But then all of a sudden this opportunity with Wisconsin came. This came really out of the blue. If you want, we can chat a few more minutes, or maybe you want to know about other things.

Phillips:

Oh well yeah, I want to just at least briefly just go over some of the work that you did do at PULSE. Just—

Bergmann:

I started to get into materials science, which was interesting. Which I basically hadn't done hardly ever before. Just a little bit. And we did some really nice papers with, we got DOE funding for a center called MAGICS, it was led by my colleague Priya Vashishta out of the University of Southern California. We ended up getting funding for five years total. We used UED, Ultrafast Electron Diffraction, and we also ended up doing some XUV femtosecond transient absorption spectroscopy experiments, and some experiments at the x-ray laser in Pohang in Korea. And I have since then some very, very good friends and colleagues at USC. I thought that was very successful.

I also started to be interested in stimulated x-ray emission, which is a phenomenon of inner-shell X-ray lasing. This requires very intense X-ray laser pulses. In the case of the Archimedes work with the synchrotron, for example, the x-ray fluorescence is emitted in all directions. But if you have a very strong x-ray pulses, there can be a population inversion, and the fluorescence emission can get stimulated into the forward direction. And you can have a very strong signal in that forward direction. And we started to get interested in this phenomenon. Can you use it for spectroscopy? Can you use it as a new source for other work? And I now have DOE funding for this research. This is one of my main research areas now. So that was one of the things that started while I was at the PULSE Institute.

I also spent more time in developing more ideas in the application of how we do the photosystem II work at LCLS, and I also started to continue my work on fossils and ancient books. But I have to say that when being outside the core funding of LCLS or SSRL was kind of a little bit strange. Because after all these years, I'm back to being on soft money like in the beginning of my years at Berkeley. And you depend on the good will of someone to fund you, and you are not part of this facility. And this was a little uneasy for me, despite the fact I had my name and everything. Deep down I knew that I was kind of in a strange situation, because I wasn't part of a very large facility or team. As an individual PI at a National Lab you can be very vulnerable. One or two bad periods of funding, all of a sudden you can go down. I was aware of that vulnerability at the time when I was approached by Wisconsin, but I was also very much enjoying my life and my work. I was also able to do a three-month’s visiting professorship in France at IPANEMA, an institute for cultural heritage research at Synchrotron SOLEIL. And we developed some new ideas there, which we are now pursuing. All in all, the time after LCLS before my new job in Wisconsin was actually a very good time, yeah.

Phillips:

So then, I mean you've alluded to it a few times now, but how did the Wisconsin job end up sort of...?

Bergmann:

One of our colleagues, Franz Himpsel, was the chair of the user organization at SSRL, I believe, and he is an eminent materials scientist. Photoemission was one his specialties, and I had known him from meetings, and Jo Stöhr knows him very well. And one day I get an email from him about a new senior faculty position at UW-Madison, an endowed chair named after Martin Perl from SLAC and it's in ultrafast X-ray science. And this could be used to build on the strong connection between SLAC and Madison, which goes back to their connections in high energy physics. He asked me if I want to visit and give a seminar. Even though this sounded great, I replied to the email, "No, I'm not really looking for a job. I'm not really interested. But if you want, I can come to give a seminar, if that's of interest." And he said, "Yeah, why don't you come to give a seminar anyway?" I gave the seminar about LCLS and about X-ray lasers and all these things. I had done some really nice public lecture talks, which I had prepared over the years, which makes it exciting and even for a broad audience that does not have that same background.

And so then after my talk they took me for dinner, and one of the faculty, Pupa Gilbert, asked me, "So I don't understand, why would you not be interested to join Madison?" And I said, "Yeah, you know, my wife doesn’t want to leave California." At the time, our daughter was still living with us although she was in college. But then basically Pupa made clear to me that this wasn't a problem, because she said, "My husband is at Berkeley. I spend a lot of time at Berkeley. And then the chair of the department, Sridhara Dasu said, "My wife works at Stanford. I work and breathe at SLAC. You don't have to spend every day in Madison to be on the faulty to do your research." And I said, "Hmm, that sounds very interesting. And kind of much better." That's how it started, and then they started to get serious and say, "But we are already closing the application, and if you want us to keep it open, you need to do a real application and come back, because otherwise we're wrapping it up." And Pupa said that I need to let her know a few days later. It took me a week and a lot of back and forth with Elisabetta, and she said, "Just do it." And so I applied. The first seminar was in May and then I went back for the application seminar and interview in October 2019.

Phillips:

Yeah, that's not a problem.

Bergmann:

After I gave my second talk, which was my application, they were still very positive and we started to actually negotiate, and then Sridhara said they were going to make me an offer. Around Thanksgiving 2019, I got an offer for this job. By the way, I think there is nothing wrong with having that in this historical record, and I signed in January 2020. But before that, even though I had kind of made up my mind, I had a meeting with Persis during the Christmas holidays. I have always been a big fan of Persis, but I also know that she is a very wise person. We met at a small coffee place at the Woodside Bakery (used to be called Martha’s) at the Sharon Heights in Menlo Park. I go there all the time now also with Claudio Pellegrini and with other colleagues from SLAC. And I chatted with her about it. I said, "What do you think?" And she just looked at me and said, "You have to do it, you can't even twice to think about it. Absolutely, this is an incredible opportunity.” It's an endowed chair and it was basically almost like, "You’d be crazy not to take it." Although, I kind of had already made up my mind, this gave me this extra confidence about the decision. I signed it in January 2020, and for various practical reasons, I started on December 1st, 2020.

Phillips:

Had you had any experience at all with undergraduate teaching before this point?

Bergmann:

No.

Phillips:

No. So just—

Bergmann:

I had, I taught a few graduate classes, like at SOLEIL for example, and a lecture or two for Ed Solomon at Stanford for the graduate students. But you know what was the other great thing about the Archimedes project? For me, personally, other than the best part of it, which are the friendships of the team we made and still have. That will always be the same, like you know when you win kind of some championship or something. And you need a team, like they always stay together. Our team is like this, we're still good friends and a big part of each other. [Note: Tragically in April 2024, my good friend Will Noel, the head of the Archimedes team, passed away after being struck by a van while walking on a sidewalk in Edinburgh.] But I also learned how to give lectures to general audiences. Because I was kind of thrown into this. I have been invited to give maybe 350 talks or so in my life. And probably 100 of them on Archimedes…. 

Phillips:

(laughs) Okay.

Bergmann:

I'm not exaggerating. 1/3 probably, one in three talks ends up being given on Archimedes or what followed. I've given so many talks that I've now perfected it. And I used this same approach of making a complicated topic understandable and exciting without dwelling on the details. I don’t mean dumbing it down, I think this is such a terrible word, because you're not dumbing it down. You're just illuminating it from an angle where you don't show the math, because who cares about the math? No one can follow the math anyway. And so that has helped me, and I think it has helped me also with my teaching, since I came to Wisconsin. I use a kind of similar approach for my teaching. I think I got a pretty good result. I hope that I'm getting decent reviews, but yes, I have to thank the Archimedes project for that, because it has affected any topic I talk about, whether I talk about photosynthesis, whether I talk about water, whether I talk about stimulated X-ray emission, lasers, X-ray lasers and LCLS. All of it, I'm using this approach now, which I've kind of learned (laughs) through this. And for my current teaching of Physics 107, ‘The Ideas of Modern Physics’, I'm using the same approach.

Phillips:

So, I guess the other thing I wanted to ask about, and this is something that sort of inevitably comes up in just about every interview we've done over the last couple of years, but you started at Wisconsin, then, in December of 2020, you said. Or 2021. 

Bergmann:

No, December 2020.

Phillips:

December 2020, so what was your experience teaching during sort of the height of the pandemic?

Bergmann:

The first class I taught was in the Spring semester 2021, Physics 109 ‘Physics in the Arts’, and this one was during the pandemic, so we did it via Zoom. So that was fine. I cannot say any different, but I already enjoyed it, and then I taught it again in real person. More than 200 students, same lecture back to back with 100 students or so each. And what I learned is the following, and I'm so grateful for that. is When you become a scientist you are at the cutting edge of research, very deep in one topic. If you think of it as a rainforest, when you learn science you're starting at the bottom in that kind of swampy area. You climb up that tree and you're climbing to the canopy, to the very, very top. And then you spend the rest of your life dangling around in the top of that canopy. When you start to teach, you have to rope yourself back down to the bottom. Because now you have to teach these things which you had maybe once done and totally forgotten about. And you now need to understand them again. For example, all these equations, for relativity, or when you look at some of the things you haven’t seen in 30 years, you get humble. You say, "Oh, I realize this, only because I'm sitting up there on the canopy, I don't really know much about the swamp at the bottom anymore, I've forgotten all of this stuff."

Phillips:

(laughs) Yeah.

Bergmann:

And I'm now finding how much I enjoy to prepare for this class. I found myself reading the Feynman lectures again. I'm reading these books and some of the things, I realize how much I liked them at the time, and lots of these things, said, "Oh, I finally understand it for the first time, actually. I really understand it now." Because now you look back at it with all this knowledge. It is a journey. I think it's actually similar to what happened to me being in the Midwest now. I've lived in New York; I've lived in California. I don't know the Midwest. I don't know most of the United States. Through this opportunity now, I'm kind of thrown into this area, into a new area of the country, and I enjoy learning new things. I would have otherwise never, ever gotten a chance to learn about this area. And the same is true with teaching, like I've been sitting around there, hovering around in the canopy of the rainforest, and now all of a sudden, I'm stumbling back to the bottom and have to climb up (laughs). And this is fun! That may be the best way to say it.

Phillips:

Yeah, no that's fantastic. Well, and we've more or less made it up to the present now. So, was there anything that you wanted to talk about that we didn't get to, or anything that you want to make sure that we include?

Bergmann:

I just want to say, and since this will be recorded, etc. I have to say it. I know that maybe others have said that, it’s about being a scientist, whether it's a university professor or a staff scientist. Because now as a professor, I also enjoy again working with young people and might really be changing the trajectory of their careers. But also as a researcher with your colleagues, to be able to actually follow and discuss your ideas and then go to conferences around the world where you meet interesting people, and you go there not because you have to sell a product or you have to win something but because you just present something of what you like to do, and then you learn about it and other things. And being able to do that and being paid for that and seeing the whole world and meeting so many interesting people in the world. Your colleagues, but also other people. I think only once you stop doing it do you really appreciate what kind of a privilege that is. It's up to the person. You know there are people, who are paid more than we are, but we are well paid. We don't suffer or anything. And so it's just like a dream. Well maybe one day I'll wake up, but it feels like the whole thing seems like a dream. That's what I want to say.

Phillips:

Well, thank you, this has been truly a fantastic interview, and I really appreciate you taking the time.

Bergmann:

Yeah. Thank you so much for all of this, and I really appreciate it. I'm happy that I got the privilege to talk in this series.

Phillips:

Well thanks again.