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Interview of Joachim Stohr by Jon Phillips on April 28, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/48025
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Interview with Joachim Stöhr, Professor Emeritus of the Photon Science Department at Stanford and former Associate Laboratory Director at SLAC. Stöhr begins the interview recounting his childhood in Germany, his interest in sports, and his introduction to physics in high school. He discusses his undergraduate studies at Bonn University and his Fulbright scholarship to Washington State University where he studied optical spectroscopy. Stöhr then describes his doctoral studies with Rudolf Mossbauer in Munich, and his subsequent postdoctoral position at Lawrence Berkeley National Laboratory. He recounts his time as a staff scientist at the Stanford Synchrotron Radiation Lightsource (SSRL) before transitioning into a position at Exxon and then IBM. Stöhr describes his return to Stanford and SSRL, working as Deputy Director and then Director. He then talks about accepting the opportunity to become the first director of the Linac Coherent Light Source (LCLS) and the challenges that came with building up a new program. The interview concludes with Stöhr’s reflections on his return to the science after his directorship and his work on a forthcoming book.
[Editor's note: After the interview, Prof. Stöhr generously took the time to provide extensive written edits to this interview transcript to clarify and expand on points discussed in the spoken interview.]
This is Jon Phillips, the assistant oral historian at the American Institute of Physics. Today is April 28, 2021, and I am speaking with Dr. Joachim Stöhr from SLAC/Stanford. Jo, thank you very much for speaking with me today.
All right. It’s a pleasure.
So before we get started, can you just give me your current full title and affiliation with SLAC?
Okay. SLAC is an interesting institution because it’s very much interwoven with Stanford University. As a National Laboratory it has its own staff. Some of the scientists and top managers of the science areas are also professors within the University. It is almost as if SLAC were an eighth school of Stanford University. This is not formally put in place, but effectively the SLAC director typically acts as a Dean of Stanford. It’s a long answer to your question because it’s complicated.
My present title is Professor Emeritus (because I’m retired) of the Photon Science Department at Stanford. There are actually two faculties at SLAC, and so that’s why the SLAC director is like a Dean who has two departments under him or her. One is high energy physics (now called Particle and Particle Astrophysics) and the other one is called Photon Science. These are the two big directions of SLAC National Accelerator Laboratory, with the science of accelerators being the glue between the two. So formally, therefore, I am a member of the Photon Science Department and a Professor of Photon Science. As a member of the SLAC staff, my title is, I guess, ex LCLS director or ex Associated Laboratory Director. [Laughs]
Great. Thank you. I guess we’ll start out… I’d like to go sort of all the way back to the beginning. Where were you born?
I was born in Germany in a little town. I don’t think we have to go into details, do we? [Laughs]
As much detail as you like or not.
Oh, it’s a little town, Meinerzhagen, that is in a mountainous region that is pretty much in central Germany, about 50 miles from Cologne —a small town, 20,000 people. So I grew up there. My hometown didn’t even have a high school. I mean, high schools in Germany are a little different because they used to be sort of elitist. You had to actually get accepted to go to high school. Not everybody went to high school, and so my hometown didn’t have one. So I had to take the train every day to go, you know, ten miles or so to the next bigger town. Actually, high schools are called Gymnasiums, which is from the old Greek word of exercising, but it’s not exercising the body only; it’s also exercising the mind or learning, expressed by the Latin phase “Mens sana in corpore sano” or "a healthy mind in a healthy body”. Finishing Gymnasium enables you to then go to a university. The German school system has changed. It is much like the American system now, but when I grew up, at the age of ten there was a fork in the road. You either stayed in elementary school until you were 14 and then apprenticed for a job, went to a middle schools that took you a step further, or you were accepted into a Gymnasium which then opened the door for you to go to a university. Otherwise you couldn’t go.
Was your placement in Gymnasium… That was determined through testing?
It was… Yeah, when I was ten years old I had to take an entry test and had to pass it—or maybe it was graded on a curve; I don’t remember—and a certain fraction of students was accepted.
So what did your parents do when you were a child?
My father was an engineer. He did not have a formal university degree because he was drafted when he turned 18 under the Third Reich, so at 18 he was shipped off to the Russian front and fortunately he survived. He was a self-made man who basically missed his educational years of the late teens and the early twenties because of the war. So then he took courses at home and worked his way up. In his own right, I would say he became quite successful and was one of the top guys in a company later on. My mother was a homemaker. She really was there for the kids—a very conventional family. In retrospect, my father instilled in me the concept of integrity and my mother gave me, a very independent child, what I needed most, understanding and love.
What were your interests? If your father was an engineer, was that something that sort of appealed to you as a possible path forward?
No, no. My only interest when I was a kid and teenager was sports. [Laughter] We’ll come to it later how I got into physics, but yeah, no. My life revolved around sports in every way and form: I was playing soccer, did gymnastics and track and field, but was mostly into tennis and skiing, which I did competitively. Ironically, my father could not participate in what I loved since he contracted polio when I was 3 and had to walk on crutches the rest of his life. But he supported me and my brother, sending us to the Alps with our ski club every year over Christmas and Easter vacations … I also did ski jumping because my hometown had a big ski jump (70 m) where you could jump even in the summer. Skiing in all forms, Nordic and alpine was my real love and it is still part of my life. My wife Linda, who is from Colorado and also a big skier, and I have a place at Red Mountain Resort in British Columbia, Canada., where we spend the entire winter because of the fantastic powder snow. This winter we couldn’t get into Canada because of Covid.
Right!
It’s the first time ever, I think, since I was six years old that I missed a winter of skiing. So anyway, sports was my main interest. Coming back to education, I would argue, that although the German school system was rather elitist and I would not recommend it in today’s world, you nevertheless got a fantastic education. There was basically very little choice. Once you got into high school, there were very few electives. You were trained in all of the fundamental disciplines, a concept going back to Alexander von Humboldt, a polymath or “universal man”. Historically that included learning Greek and Latin. By the time I entered Gymnasium, Greek wasn’t required any more but I had to put up with Latin (my least favored subject). I liked learning English and one of my big regrets is that I did not learn French. This happened because I was in a branch that was geared toward the natural sciences, so I had biology, chemistry and physics and a lot of math in high school. This really prepared me well for my later career, although I wasn’t that interested at the time in the sciences.
I have to say, though, that physics actually came very easy for me. I don’t know why. I hated how chemistry was taught, kind of mixing things together and things bubbling up and exploding and stuff—that didn’t interest me. But the subtleties of physics I liked…and I had a very good physics teacher who also, in the end, contributed to me becoming a physicist. I could remember it without really having to study at home. I just felt, “Oh, yeah. Physics is interesting.” [Laughs]
There were nine grades in Gymnasium, and I was 18 when I graduated. Then I went to Bonn University. Like many seniors, I had to do some soul-searching of what am I going to do? I wasn’t going to make a career in sports. [Laughs] At least I didn’t think I could and so I had to figure out something else.
So there was this friend of mine who was a grade ahead of me, and he was the smartest kid I knew. I was always arguing with him because he, of course, knew things that I hadn’t learned yet. He decided to study physics in Bonn, and after one semester—I was still in high school—he told me that he had to work too hard to study physics, so he went into medicine and he became a medical doctor. So I said to myself, “Well, you kind of like physics. Wow, that would be a great challenge. I wonder whether you could do it!” [Laughs] So it’s the typical thing that drives humans—the challenge. I wonder whether I can do that!
So that’s how I got into physics, and my friend was right. The first year was hard. I didn’t study much physics but it was all math. I took all the courses with the mathematicians and there were some brilliant kids. I was okay, but I would also at times think, “God! They make me work so hard doing all these homework problems, and all my other friends who are in law or the humanities get to go see movies and have fun and do things. I just sit here and solve my damn homework problems!”
I was a little frustrated, but there’s one thing about the sciences - it’s always challenging. You cannot sit still. Your mind has to work, and not just work—you have to work hard at it. One of my recognitions in life has been that there are a lot of smart kids around and a lot of people who are capable, but the ones that really succeed will succeed more often than not, because they really put in the work. It’s the work ethic and the diligence, the effort that you put in that at some point will distinguish you from other people. I guess I was willing to work hard. At times I cursed it, of course, but I just stuck with it.
I would say that the interesting part of physics for me or when I really discovered that I loved physics, was not until most of my classes were actually done, and it was the research part where I got to choose a problem and work on it and try to figure out what I was observing. That to me was the beauty of science.
Do you remember what the research problem that you got to work on as an undergraduate was?
Yeah. We are jumping ahead a little bit.
Oh, sorry.
So at Bonn University, I was just doing courses, right, and homework problems. Then after my pre-diploma, which is I guess equivalent to a bachelor’s degree, I applied for a scholarship to go to the US because, growing up in Germany after the war, America was envisioned as the “land of unlimited opportunity”. That was the phrase that was floating around, and so I said, “Wow, I wonder! Interesting, I need to check this out.”
Of course by that time I also had realized that European physics, especially German physics—that had been really great with quantum mechanics was no longer at the forefront. After the war, the United States clearly became the superpower in physics, and this was where the biggest innovations occurred. To some degree, of course, they were driven by an influx of European physicists, a lot of them of Jewish origin that had to leave. Some of the most brilliant minds that Germany had, left during the Third Reich and went to the US! All of that contributed to me thinking, “I need to check this out.” So I applied and I got a Fulbright Scholarship to study in the US.
Skiing was very much on my mind too [laughs], so I got out the German “Atlas” map to check out the location of universities that offered a free ride. I ended up at Washington State University in Pullman, Washington - out in the boonies. On the German map – mountain regions were brownish and flatlands were green - it looked like Pullman had mountains close by. [Laughs] For lack of better knowledge I thought WSU was in the Rocky Mountains. But Pullman was in the wheat fields and it was at least a two hours’ drive to go skiing. But anyway, that was one of the motivations why I went there in 1969.
So I did two years at WSU and also did a research problem in optical spectroscopy with a professor, John Gruber. In his younger years, Gruber had been at Caltech and overlapped with Mössbauer there. So he wrote Mössbauer a letter and asked whether I could come to Munich and study with him, and Mössbauer said yes. So in ’71 I went to Munich after my master’s and did my doctorate there.
Mössbauer was famous. After the war, he was the first German to win the Nobel Prize in Physics - I think in ’61 - so he was very well-known. But of course he had a lot of obligations because once you’re famous, you get pulled into many different directions, and about two months after I got there, he became the director of the Institut Laue-Langevin in Grenoble, France and left. A new professor came who had been at Argonne National Laboratory for many years. His name was Michael Kalvius and he brought a little bit of an American flavor with him since he had been at Argonne for quite some time. I called him Mike, which was unusual because in Germany it was “Herr Professor,” right?
He was very easygoing and so I said, “You know, that problem Mössbauer gave me, I looked at it. I don’t like it. I will be here forever because first of all, we have to build an accelerator to do this and that will take at least three or four years, and I hope to be done with my doctorate around that time.” He said, “Oh, that’s okay. Pick your own problem.” [Laughs]
At the time, there was a guest scientist who was also from Argonne and later played another role in my life. His name was Gopal Shenoy. He came with Kalvius from Argonne to Munich. So Gopal and I became good friends and he encouraged me to work on a certain problem, which I did. We don’t need to go into details but it was looking at magnetic impurities in non-magnetic metals, a popular topic at the time. Anyway, that’s the problem I chose and finished, and I got my PhD three years later in ‘74. That was an important year because also my daughter Megan was born.
Earlier that year I had heard David Shirley, a professor of chemistry in Berkeley, give a talk in Uppsala, Sweden at a conference. The talk was mostly on photoelectron spectroscopy - which had been pioneered in the form of ESCA by Kai Siegbahn in the town of the conference, Uppsala. I was so impressed by Shirley’s talk that I said to myself, “Why am I wasting my time with Mössbauer spectroscopy? If you want to learn something about solids, you need to look at the electrons, not at the nucleus.”
So I wrote Dave Shirley a letter and said, “I want to come to Berkeley and work with you and learn photoelectron spectroscopy.” At the time, one of Mössbauer ‘s previous students in Munich, Günter Kaindl, who would become a Professor at Freie Universität, Berlin, was a post-doc in Berkeley with Dave and put in a good word for me. So Dave wrote back, “Okay, fine.” But he also added, “Can you bring some financial support?” [Laughs] So I applied for another scholarship and actually got it and then I went to Berkeley in `75. That was a very, very fortunate event. I always loved Berkeley and the intellectual atmosphere. Even to this day I’m very fond of Berkeley.
When I arrived, something very fortuitous happened. At Lawrence Berkeley Lab, Shirley’s group had done photoemission with a commercial instrument using one fixed photon energy. The use of synchrotron radiation allowed changing the photon energy, which was basically unheard of. So Shirley’s group had just started to do synchrotron radiation experiments at near-by SLAC/Stanford. After hearing about the disastrous earlier trials I said to myself, “This sounds really interesting and challenging. I want to get involved.”
At the time, there was one dedicated synchrotron radiation facility in the US called the Tantalus storage ring at the University of Wisconsin. That was a small ring and so it wasn’t super-expensive to build and operate, and was specifically built to produce synchrotron radiation in the extended ultraviolet region. This is where photoemission with synchrotron radiation was developed by people like Dean Eastman, Neville Smith and Jerry Lapeyre. Very many of the early experiments in photoemission were done there and I read those papers.
At SLAC, we used the SPEAR storage ring built for high energy physics. At the time it was used to study collisions between electrons and positrons that led to the discovery of the J/psi particle by Burton Richter in 1974 and won him the Nobel Prize in 1976. X-ray scientists, notably Ingolf Lindau and his student Piero Pianetta, were allowed to drill through one of the shielding walls and bring out the x-rays produced by the circling electrons. X-ray scientists were so-called “parasitic users”.
When I arrived there was already a real beam line with the so-called grasshopper monochromator, built by scientist from the Xerox Palo Alto Research Center. But the high energy physicists at SLAC were fiddling with the beam a lot and it was often useless to us. It felt like a love-hate relationship. At times when you got beam and it was stable, it was amazing and you could do the things you had dreamed of. But then, oh god, the beam was dumping again and you had to wait… You told the ring operator, “Call me when the beam comes back up,” so you got a call at three in the morning: “The beam is back up!” Okay, you get dressed and walked into the lab and boom, the beam dumps again. From that point of view, it was a frustrating time, but in all pioneering endeavors there is great excitement mixed with frustration.
This would have been around ’76, ’77, right?
This was ’75.
Oh, ’75. Okay.
Between ’74 and ’76 were the formative years at SPEAR. We had a little bit of an advantage over Wisconsin because we could go to higher energy -- Oh, I see on the screen that you’ve got a cat!
Yep. She gets curious when I’m talking to the computer.
Oh yeah, yeah. I have two. So anyway… Let me see. I lost my train of thought.
Sorry.
Remind me. What was I…?
We had just discussed this was a pioneering and frustrating time, ’74 to ’76.
Yes.
While you were at Berkeley.
Okay. So we had the advantage over Wisconsin that we could go up in energy and produce real x-rays - because the ring was bigger. Basically there’s a rule of thumb: the bigger the ring, the higher the energy. With the electron beam energy going up, the photon energy also goes up, so we could do experiments that they couldn’t do in Wisconsin. This was one of the good things for us.
By the way, the ring energy had an interesting consequence later on; I’ll just mention it here. Because high energy physicists explore the frontier of discovering new building blocks of matter by smashing particles together - eventually the energy needed to break them apart more and more, was limited by the size and cost of accelerators. That basically limited particle physics experiments at SLAC and in the new millennium the forefront shifted to CERN in Geneva, Switzerland, which had a ring of about 20 miles in circumference and was even crossing the border with France. The first step in that direction occurred in 1990 when the high energy physics program at SLAC shifted from the SPEAR ring to a bigger ring called PEP, and SPEAR became available as a dedicated x-ray source. The present Stanford Synchrotron Radiation Lightsource, SSRL, came out of that, which is a dedicated x-ray user facility. We finally were no longer parasites…
Oh, so after my post-doc time at Berkeley I decided I was sufficiently hooked on x-rays and in ’77 went to SSRL and became a staff scientist. Apart from the beam frustrations, it was scientifically an amazing time because SPEAR was one or maybe the premier x-ray facility in the world at that time. Scientists from Europe and other parts of the world came to do their experiments at SSRL—still in parasitic operation, but everybody was really keen to use this facility. There was a conglomeration of scientists that I experienced because I was on the floor all the time, so I got to know all these guys from everywhere. I got deeply immersed into every aspect of synchrotron radiation. Where can we go from here? What can we do? What new techniques can we develop? So I was fortunate to experience, what I would call the first revolution in x-ray science after the original discovery of x-rays in 1895 by Wilhelm Röntgen. It was a tremendous step up from x-ray tubes to synchrotron radiation facilities. If you look today at what is done in x-ray science, it’s all done at synchrotrons, right?
Yeah.
They’re actually not synchrotrons; they’re storage rings because in a synchrotron the electrons spiral out from the center and are then discarded. In a storage ring, the electrons circle for hours and hours on the same orbit, so you have very good stability and you lose intensity only very slowly.
Right.
The intensity goes to half the original value when the ring is filled over several hours. That is very important because you want stability in your photon intensity.
Can you maybe give me--
Maybe I’ll stop for a second and you ask a question.
[Chuckles] I was going to ask if you could maybe describe just a few of the major projects that were being pursued at SSRL in the mid- to late ’70s in that sort of first era of synchrotron research there.
Yeah. I mean, it was fascinating and 25, 30 years later I saw the same thing happen again when LCLS came about. That was the second revolution where you went from storage rings to x-ray free-electron lasers. The same philosophy basically dictated both periods. It was, we don’t know yet where the real winners are, the real scientific breakthroughs will occur. We need to explore everything. We need to explore how the radiation interacts with atoms, molecules in the gas phase. We have to figure out what new things we can learn about the atomic and electronic structure now that we have intense x-ray beams whose energy can be tuned.
Photoemission spectroscopy at SSRL was developed mostly by Dave Shirley’s group and Bill Spicer’s group at Stanford with Ingolf Lindau playing a key role. These groups produced a remarkable number of students who later became key users, proponents and leaders in the large field of photoemission with synchrotron radiation. Z. X. Shen from Spicer’s group comes to mind and Steve Kevan (now ALS Director) from Shirley’s group but there are many others…
At the time, much work at SSRL involved the development of EXAFS (extended x-ray absorption fine structure), pioneered by Farrel Lytle, Ed Stern and their student Dale Sayers who regularly came down from Seattle for experiments at SSRL. EXAFS allowed you to pick out an atom by tuning to its characteristic absorption edge and then determining its local bonding environment, the type and number of neighbors and their bond distances. I often spoke with Farrel Lytle from Boeing and Peter Eisenberger, at the time at Bell Labs, who seemed omnipresent on the experimental floor and played a role in the development of my own research.
As a staff scientist at SSRL, I also had to help outside users with their experiments. Of course, my real love was doing my own and I have to thank then SSRL Director Artie Bienenstock for protecting my strong independent steak. When at Berkeley, I had learned from Dave Shirley (who was a chemist) the importance of molecules containing C, N and O atoms. Their absorption edges were in the soft x-ray spectral region which at the time was not readily accessible due to limitations in beam line optics. The lack of good grating monochromators at the lower end of the spectrum (above 200 eV) and the presence of absorbing Be windows and suitable crystal monochromators at the upper end (below 3000 eV). So I made it one of my tasks to open up the soft x-ray region by optimizing the existing grasshopper grating monochromator beam line and building a new ultra-high vacuum compatible crystal monochromator, named Jumbo.
In the process I applied EXAFS to surfaces, coined SEXAFS by the Bell Labs group of Paul Citrin and Peter Eisenberger. My emphasis, however, was on the surface complexes formed by low-Z atoms, in particular oxygen. It so happened that my first SEXAFS study in 1978 of an oxidized aluminum surface above the O K-edge at 540 eV was also the first EXAFS spectrum taken in the soft x-ray region. I soon realized the importance of using the first part of the SEXAFS spectrum, which especially for molecules, is dominated by huge molecular resonances. This led to the cheeky name NEXAFS (near edge x-ray absorption fine structure). In retrospect, I consider the development of polarization dependent NEXAFS around 1980, my most important science contribution while at SSRL. It also first demonstrated the power of using the polarization of x-rays (dichroism).
Another area that was developed at SSRL, largely by Keith Hodgson’s group at Stanford, was protein crystallography because one could now put a small crystal in the beam and with the increased intensity record a diffraction pattern 100-1000 times faster than with the best rotating anode x-ray tube. Limited beam time also triggered the development of robotics to screen protein crystals. This helped in speeding up the crystal growth and evaluation process. Today whole experiments can be performed remotely from your laptop at home through robotics.
Because synchrotron beams were so intense, people also started to worry about whether the fragile protein crystals, if you kept them in the beam for an extended time to accumulate a pattern, would change in the beam so the pattern that you finally analyzed was partly that of defective crystals. Thus the important radiation damage problem began rearing its ugly head and led to the use of cryogenic freezing of samples.
If you think back now 50 years (or not quite 50), I would say that besides photoemission and x-ray absorption spectroscopy, protein crystallography emerged as one of the big winners. Also, with synchrotron radiation you could do protein crystallography experiments in a new way, namely record patterns of the same crystal at two x-ray energies rather than one. This is now called multi-wavelength anomalous diffraction, MAD.
The history of MAD is quite fascinating. I’ve been reading up on it lately and hadn’t really appreciated how complicated it is, going back to work by Mark and Szilard in 1925 that was picked up by Bijvoet in the early ‘50s and demonstrated in 1971 by Hoppe and Jakubowski. Jerome Karle, who won the 1985 Nobel Prize with Herbert Hauptmann for solving the phase problem by statistical computational methods, also worked on it, and one of the names that is often mentioned is Wayne Hendrickson, who was a post-doc of Karle. He took protein crystallography a step further and coined the name MAD in 1985. MAD is now routinely used for most crystal structure determinations. You go below an absorption edge then above it; something changes in the way the atoms respond and you can figure out the lost phase in the diffraction pattern that is required to link it to the atomic structure of your sample. So if you do two measurements, you have more information and can solve the phase problem more easily. So a Nobel Prize for MAD is complicated by its long history.
It always is!
Yeah. I’m writing a new book and love to dig into the history. In the process you realize that we modern scientists often think we invented something new and make a big deal out of it. The fact that people may already have had the same idea, may have remained hidden in the archives or is sometimes swept under the rug. Scientists may not want to admit that they got the idea from an old paper. It’s very fascinating. [Laughs]
Absolutely. I’m curious. This was, you said, ’75 to ’80.
Yeah.
And the crystallography was such a big component of what was going on. Did the work that SSRL was doing attract the attention of the biology department at Stanford? Did they try to get involved at all?
Oh. This is another interesting story. X-ray crystallographers who develop new techniques are often physicists not biologists or bio-chemists who are experts in the function of proteins, the worker molecules in our bodies, and why a problem is important. Biochemists may work on a single protein for years – may be their entire life - in their home labs. In the past, it has been these scientists who typically have won Nobel Prizes for solving the structure of particularly important proteins. They are not necessarily x-ray jocks. In fact, there are funny stories about people saying, “Well, you know, we used this facility” but they’ve never even been there because their students and postdocs did all the x-ray work. [Laughing] Also, the deciphering of diffraction pattern is done by sophisticated computer programs developed by physicists/mathematicians. Such “black box” computer programs can be used without truly understanding how they work. In the end, it is the molecular structure that counts. By solving it, you get insight about how the protein works, how one can enhance or inhibit its function by drugs. Where are the parts of the macromolecule that you can plug up or activate? This is where the Nobel Prizes – about ten of them - have been won.
Yeah, that’s actually something I’m going to have to look into more, that historical relationship between the biologists and the x-ray physicists.
At first there were a lot of naysayers who pooh-poohed the use of synchrotron radiation, mostly because they didn’t see the need to leave their own labs. I give Keith Hodgson a lot of credit. He’s a professor of chemistry at Stanford, one of my colleagues, a previous director of SSRL. He pushed x-ray crystallography with synchrotron radiation early on and stuck out his neck and probably took a lot of flak initially. By the way, Keith Hodgson is a good person that you should talk to.
I will. Keith Hodgson.
Add him to your list. He knows a lot about SLAC’s history. In fact, he was my boss for many years. When I first was recruited to Stanford, he was director of SSRL.
He is now officially on the list.
Yeah, yeah. He should be on the list.
So I guess following those first few years at SSRL, you went to Exxon after that.
Okay, so this is another story. You know, all these scientific stories are of course interwoven…
Of course.
… all the circumstances that enter into career paths. When I was a staff scientist at SSRL, I actually wanted to be a professor at some point, but there is a biblical saying that a prophet doesn’t count in his own country. I don’t know the exact phrase, but something like that.
Right.
So I realized that it would be very difficult for me to make the case to become a professor at Stanford – they already had me… I realized I had to go away to come back on my own terms.
And it worked!
This is often how it works. I wasn’t too thrilled moving away and tried to avoid it for a long time because I loved California. Once I’d come over from Germany to California, I just thought, wow, it’s such a beautiful climate here and Lake Tahoe has world class skiing close by.…well anyway, I loved California. So my end goal was to come back to California, but I realized I needed a stepping stone.
Exxon at the time was undergoing a transition. It had made a lot of money and at the time (1981) was the biggest company, I believe, in terms of annual revenues. So they, like a few other companies, had cornered the market. AT&T had the telephone monopoly, IBM had the mainframe computer monopoly. Exxon had the oil business monopoly.
It’s actually an interesting question why these companies had science laboratories. The science laboratories in those days were almost decoupled from the bread and butter business of the companies. They were think tanks most of all where people had tremendous freedom just like academia. You could pick your own research problem and they would support it. The companies wanted some out-of-the box thinking and to be famous for their research laboratories, which enhanced their reputation.
Another aspect is that they realized that the brightest guys that graduated from universities, might not be interested in the core engineering part of the business but you could attract them by saying, “Hey, we value you for your intellectual prowess. Come to us! We’ll give you opportunities to explore.” With time, they show you other opportunities like becoming valuable to the company as technical managers, for example. So the research labs were an important recruiting tool, right?
In those days, Exxon was really building up their science program, and so I caught that wave. The wave actually only lasted a little more than five years when management was starting to ask increasingly harder questions like “What have you done for the company’s bottom line lately?”
Sure. Yeah.
We saw that everywhere. We saw it at AT&T Bell Labs in the early ‘80s, Exxon in the mid ‘80s and IBM in the early ‘90s. At some point when the money stream gets tighter, if the competition increases, you need all your resources to focus on how you maintain or increase revenues. So the scientists were increasingly pulled into firefighting problems in development and manufacturing, catalysis at Exxon, networks at AT&T Bell Labs, computer chips and magnetic storage at IBM. So this is when the free spirited think tanks turned into more applied or directed research labs.
I actually did not experience the layoffs at Exxon, but luckily left earlier because I wanted to go back to California. I left four years after I joined and have to say that Exxon treated me very well. It was a great stop in my career and I learned a lot about catalysis and surface science while I was there. Then in `85 I went to IBM.
Right. That’s going to be a very big topic, but before we get… I’m just curious. There’s this cultural shift within Exxon that you saw there with the scientific community inside Exxon, but when you first started, this think tank feeling that it had, was it similar to or still somehow different than academic science? Did you feel a cultural shift moving from academic science into industry, even when it was more open?
No. About the same. There was very little difference. You could think of a wide range of scientific topics you wanted to do, and if you could sell it, make a pitch, there was a certain advantage. Big companies had deep pockets. You didn’t have to write a 50 page proposal to the National Science Foundation to compete for a relatively small amount of money. If you could convince your manager or your manager’s manager that you had a great idea, you got the money, right?
Right.
And it wasn’t just like dribbling in at tens of thousands per year. It could come in big chunks. I mean, I did that a few times. At Exxon, I built a beamline at Brookhaven National Lab and that was a $1 million project. At IBM I built two beamlines that were million-dollar projects, so you could get big money. It was just that you had to have a good idea and sell it. The main difference with academia was that you didn’t have graduate student. You may have had a postdoc or two but you did experiments hands on.
I’m also curious, then. Towards the end of your time at Exxon, when they were sort of more turning the screws, trying to get things more cost-effective, was there any particular application that they were interested in as far as your work in surface science was going?
Exxon had of course some scientists who made a lot of money for the company. One of them was John Sinfelt. He invented a bimetallic catalyst which made Exxon gobs of money. The scientists that really understood the bread and butter of catalysis were actually quite skeptical that basic research - surface science - was very important. Who cares whether in model systems this molecule bonds to this surface by standing up instead of lying down? They said, “In a real catalytic process, we have a big reactor. We throw all kinds of crap in there and go to high pressure, temperature and stuff like that to convert oil into gasoline.” The process is so complex that in most cases advances come from a trial-and-error engineering rather than a surface science approach.
Also, in surface science you have to work on a specific problem in great detail for some time. The work is then published and available to the whole scientific community. It’s known not just to your company but also the competitors. So why pay for it?
Right. I’m also curious. The beamline that you set up at Brookhaven—how closely integrated into the research community at Brookhaven were you when you did that?
Oh, I was. I was living on Long Island. That was another interesting thing. At first when I went to Exxon, I actually requested (because the Brookhaven light source wasn’t operational yet) that I wanted to be close to an x-ray facility, so I lived in California for two more years and just had a small apartment in Manhattan, from where I could take the train to Exxon in Linden, New Jersey. Then Exxon said, “Hey, Jo. It’s time to move to the East Coast. We want to see more of your face.” I said, “Fine. I’m going to move, but don’t forget. First of all, I’m an x-ray scientist. I need to be where the experiments are done.”
So I talked them into letting me live near Brookhaven National Lab on Long Island and I just drove my car once a week to Exxon’s new research Lab in Clinton, New Jersey. But I lived on Long Island and my office was at Brookhaven National Laboratory. At the time, Exxon was building several beamlines at Brookhaven that I was involved in.
Okay. Yeah, that’s great. So when you left Exxon then, you wanted to get back to California and IBM was your ticket back.
I’m sorry. At IBM?
IBM was your ticket back to California.
That’s correct.
Were you brought in--
IBM had several research Labs. The largest was in Yorktown Heights, north of New York City. Dean Eastman had tried earlier to recruit me to work there [laughs], but I didn’t want to go to Yorktown. I wanted to go back to California. It turns out that IBM had another research lab in San Jose, and that’s what I set my sights on…
I’m from the West Coast myself, so I am very familiar with that attitude!
[Laughs] Okay. Keep me on track, please.
No, no. This is wonderful so far. So you started off at IBM.
I believe I was mostly hired at IBM San Jose because of my expertise in synchrotron radiation and to a lesser degree surface science.
Had IBM and SSRL had any sort of collaborative working relationship prior to you starting with the x-rays?
Very little. I was hired specifically to make that connection. But there is another story how this came about. There was an important Government advisory committee appointed in ’84 by President Reagan’s Science Advisor George Keyworth, the so-called Seitz-Eastman committee, to make recommendations on large proposed national facilities. The key question was the order of priority of two proposed next generation synchrotron facilities and a new neutron facility – we are now talking hundreds of millions of dollars for each facility...
Right.
The motto for the third generation x-ray facilities was, “Let’s stick our heads together and figure out how to build the best storage ring, the best x-ray source.” The emphasis was entirely on the quality of the produced x-rays, called “brightness” which is a measure of x-ray density or coherence.
There were two x-ray proposals on the table: a larger higher energy (hard x-ray) facility which later became the Advanced Photon Source (APS) at Argonne and a lower energy (soft x-ray) ring which later became the Advanced Light Source (ALS) at Berkeley. The latter was pushed by then Berkeley Lab Director David Shirley. Of course, his knowledge came from the early experiments at Stanford. I fully supported the Berkeley proposal and I was invited to present the scientific case for soft x-rays to the Seitz-Eastman Committee.
So while the synchrotron community was fighting within itself which of the two x-ray facilities had priority, another question that the Seitz-Eastman committee was addressing was whether to first build one of the x-ray sources or a new neutron source? Rumor had it that the committee was divided. The x-ray facilities had the advantage that the community was strong and that the brightness could be increased by a whopping factor of 10,000 while the neutron flux could only be increased by a moderate factor of no more than 10 in a steady state neutron reactor source. Construction of a pulsed neutron source (the later Spallation Neutron Source (SNS) at Oak Ridge National Lab) was also on the table but the concept wasn’t sufficiently developed.
The outcome of the committee was the recommendation to build the higher-energy x-ray ring as the first priority and then the steady state neutron reactor and soft x-ray ring.
Right.
At that point, the hard x-ray ring had the edge and typically it would have been built first. However, the Berkeley plan for the lower energy source was fully developed and ready for construction. Berkeley also had outstanding political connections to Keyworth’s office in Washington. So the ALS snuck in through the back door and was built first. [Laughs]
That’s good administration!
And politics.
Absolutely.
So anyway, after my talk to the Seitz-Eastman Committee in early ‘84 I wrote up a paper for the committee. I had the manuscript with me when I went to IBM San Jose in the fall of `84 to give a talk about the possibilities of synchrotron radiation research. George Castro, who was the manager of the physical science laboratory at IBM San Jose, liked it very much and said, “I want to hire you and get involved in synchrotron radiation and build a beamline at SSRL so we can do science there. It’s a no-brainer for me because SSRL is so close. We need to get involved.” So that’s how I got my job at IBM. I always felt that George Castro had my back. He helped get the funds to build a beam line at SSRL. Ten years later, he and Paul Horn at Yorktown also helped Franz Himpsel from Yorktown and I to secure the funds to build another beam line at the ALS.
About a year after my arrival, IBM Research moved into a beautiful new building in the near-by Almaden Hills - the IBM Almaden Research Center. While planning the SSRL beamline I continued to do surface science at existing SSRL beamlines. I loved the Almaden environment and was surrounded by outstanding surface scientists in experiment and theory, Dick Brundle and Paul Bagus, for example. Over the next few years I had tremendous freedom and also collaborated with the university groups of Bob Madix at Stanford and Cynthia Friend at Harvard, and did experiments with Klaus Baberschke’s group in Berlin at the BESSY synchrotron facility. At IBM I benefitted from the intellectual environment and learned about polymer science from my colleagues Jerry Swalen and Tom Russell. At the end of my surface science period, I wrote my first book “NEXAFS Spectroscopy”, which was published in ’91.
In 1989, the Director of Physical Sciences Dan Auerbach had asked me to manage the Materials Science Department and in 1991 I became the manager of the Department of Magnetic Materials and Phenomena. I had about 30 people or so in my Department. What IBM San Jose was famous for was magnetic data storage. That’s where it was invented starting with the famous IBM RAMAC in the mid 1950s. In those days, foot high stacks of record-like recording disks were still required to store data equivalent to one song! IBM invented magnetic data storage and had remained at the forefront.
Was magnetic storage an entirely new field for you?
I wasn’t completely ignorant in magnetism since I had studied magnetic phenomena with Mössbauer effect in Munich and knew some fundamentals. But like computer chip technology, magnetic storage technology was developing at an incredible pace following Moore’s law - smaller and faster. Fortunately, I could learn fast from the scientists in my department who were working on developing new magnetic materials to be used in recording heads and disks.
Right.
Two unrelated events had happened by coincidence in 1987 that set my department and my own science on a new trajectory. Peter Grünberg, working in Jülich, Germany, and Albert Fert in Paris, France, discovered giant magnetoresistance - GMR. They went on to win the 2007 Nobel Prize in Physics. I remember meeting them at a workshop organized by IBM at the French Rivera where they told me, “Look. We have agreed that we did this independently – there is no rivalry.”
Grünberg in Germany was the one holding the key patent which is conceptually very simple. You send a current through a magnetic structure consisting of two magnetic layers separated by a thin non-magnetic layer. They discovered that there is a big change in resistance when the magnetic orientation in the two outer layers changes from the same to the opposite directions – the GMR effect. To make it useful, the key was to pin the direction of one layer and through the spacer layer decouple the two magnetic layers sufficiently so that the other one could be rotated.
Right.
So GMR was the big discovery. So we at IBM tried to get around Grünberg’s patent with all kinds of fancy ideas, but it turned out that the patent was extremely well-written and broad in what it covered. I believe, that in the end, IBM had to pay to utilize it.
After the Nobel Prize was given to Fert and Grünberg, some people asked me whether Stuart Parkin, who was in my department and is now a Max Planck Director in Dresden, should have been included. Stuart truly did beautiful work that followed the initial invention, like making it applicable for devices. The Physics Nobel Prize, however, is usually given for the original invention or idea, with the notion that once the idea is out, it’s easier to take it to the next level.
Right. That makes sense.
So GMR had a big technological impact because it is used in all of today’s magnetic recording heads. They actually fly, elevated aerodynamically like a plane, when the magnetic recording disk starts spinning underneath. The technological development is astounding! Computer hard drives are conceptually similar to an old record player, but the head does both writing and reading of the data bits on the disk spinning underneath. It has been miniaturized to the extent where you can’t see the magnetic bits anymore with the best optical microscope. That fact led me think about seeing them with x-rays instead.
X-rays for magnetism?
Before answering your question, let me just say that today we have of course different kinds of data storage besides magnetic, like flash drives. But in many computers, especially big computers, storage is still in the form of magnetic bits. Just think about all the information on the cloud that has to be stored. Magnetic bits are robust - since the magnetization direction, which defines a 0 or a 1 bit, basically stays put for a long time and you don’t need to have power. Magnetic bits don’t lose charge like electronic bits - once the bit is written, it doesn’t degrade. Archives still use magnetic data storage, so this has remained big business.
Right.
So to come back to x-rays. During my time as a manager I learned of course of the forefront problems in magnetism research. I also knew of a discovery made by Gisela Schütz, from my alma mater in Munich that opened the door for studying magnetic materials with x-rays. Before her pioneering work in 1987, neutron diffraction gave you the most important magnetic information on the atomic level. Neutrons are like tiny magnets that scatter off magnetic atoms. The scattering gives you information of the arrangement of the atomic spins in materials and also the size of magnetic moments. In 1994, Bertram Brockhouse at McMaster University in Canada and Cliff Shull at MIT had won the Nobel Prize for discovering how neutrons interact with magnetic materials. So they could tell for the first time, for example, that in so-called antiferromagnets, the atomic spins of neighboring atoms pointed in opposite directions. This had been proposed earlier by Louis Néel in France, but nobody could prove it before the neutron work.
The work by Gisela Schütz was rapidly further developed to show that by tuning x-rays to certain atomic resonances one could detect a signal from a relatively small number of atoms. For samples as small as magnetic bits, for example, neutrons are useless because the signal is way too small. In contrast, by use of circularly polarized x-rays in a technique called X-ray Magnetic Circular Dichroism, you are sensitive to very few atoms. So around 1993 I realized that I was sitting on a gold mine. I had around me people who understood magnetism to a degree of very few other people in the world, and I had SSRL close by. I said, “What am I waiting for, let’s go!” [Laughs] That’s when I changed my research program to magnetism.
I’m curious. You were at IBM for a lot longer than at Exxon. Do you think it was more that they--
I’m going to have to go and plug my phone in because my battery is up and talking a lot, so I’m going to go inside and sit inside and change locations. Just one second.
No problem. [Break]
So remind me where we’re at.
I was asking at IBM, the internal culture there, was it undergoing the same kind of shift that happened at Bell Labs and Exxon, or was your work just more in line with what they wanted, or did they stay more open to the basic research?
The true personal computer revolution from an IBM business point of view did not become apparent until the early ‘90s. I had joined IBM in the heydays when Research was still expanding, as shown by the construction of the new Almaden Lab.
Okay.
By the early `90s the desktop or personal computer revolution had evolved to a point where IBM’s cash cow of a mainframe computer was affected. Other companies were building mainframes and IBM didn’t have their pseudo-monopoly anymore. [Laughs] In fact, it was the monopoly issue that led to the split-up of AT&T Bell Labs, arguably the most famous US industrial research lab, in the early eighties. IBM didn’t split up but there was a severe belt tightening that started in the early nineties accompanied by layoffs.
Okay.
So I had a fantastic ride at IBM for my first seven or eight years.
If we need to take a break for you to get a glass of water or anything, that’s fine, too. Just let me know.
Let me just grab a little water. I’ll be right back.
Yeah, of course. I always have water on hand. [Break]
Okay, I’m back. All right, so IBM…
Yeah, you--
Go ahead.
So you were saying that they gave you a great deal of intellectual freedom for the first seven or eight years.
Yeah, ironically it was my move into management that made me think about using x-rays to study magnetism. [Laughing] I mean, companies all develop short lists of people they think can become good managers and then they groom them, right? So I was groomed by being sent to IBM courses in New York and “shadowing” the head of research for a week. [Laughs] But around `93 - ‘94 the difficult part of my management at IBM had started – downsizing. This gave me little pleasure. [Laughs]
Sure! Who likes it?
So I said to myself, “Nah. I need to go back to science,” and stepped down from management in ’94 . IBM Research had a remarkably mature philosophy and stepping down did not feel exceptional to me.
While managing the magnetic materials department I had started to collaborate with Stuart Parkin and Dieter Weller, who were experts in magnetic materials, and started to study them with the x-ray dichroism technique. Out of that came the first x-ray picture of magnetic recording bits. I had dreamed about it and remember coming into SSRL one morning and my collaborators showed me the picture they had taken over night. “You must be kidding – so that’s what they look like,” I said. X-ray imaging of magnetic nanostructures later became a major research theme and my postdocs and Stanford students actually made movies of how a magnetic memory device switches.
Our new IBM beamline at the ALS was also ready and there I explored something new for me. The group of Joseph Nordgren at Uppsala University, Sweden, had developed a compact x-ray emission spectrometer, and we installed an improved version on our beam line. The collaboration with several Uppsala scientists had developed over the years, after I had met Nils Mårtensson and Anders Nilsson in ’98 in Kaprun, Austria, at the International Symposium on Surface Science, held at a sports hotel high up on a glacier. We called it the 3S meeting for Surface Science and Skiing. Anyway, Anders Nilsson impressed me right away. He was still a graduate student but understood things at an amazingly deep level. We hit it off and over the next few years became really good friends. The work on our ALS beamline was driven by Anders who moved to Berkeley and made a name for himself by applying x-ray emission spectroscopy to surfaces. He later became a professor of Photon Science at Stanford and is now a professor at KTH Stockholm. Anders had this incredible intuition and was willing to stick out his neck. He has done some amazing work on the properties of water, the most important substance on earth, and he seemed to have already envisioned everything in his head, before proving it through experiments. Anders taught me the importance of imagination in science, famously touted by Einstein.
Around 1997, Tom Russell and Hugh Brown (one of my running buddies), who worked on polymers at Almaden, told me about a fascinating science problem – and it had to do with IBM’s business - yeah! It wasn’t in magnetism; it was in flat-panel displays.
Tell me about it…
At the time, the highest resolution flat-panel displays were so-called liquid crystal displays that depended on an interesting phenomenon. The liquid crystals (LCs) modulated whether a pixel of the screen was dark or lit up. The LCs where composed of tiny rod-like molecules that in each pixel formed a spiral staircase sandwiched between two polymer layers. The spiral twist enabled transmission of polarized light but you could straighten them out with a voltage and the pixels when dark.
The complete display was very complicated high technology, but it depended on an arcane low tech process to anchor the liquid crystals at right angles on the polymer layers to get the stair case twist. It consisted of rubbing a polymer surface – in practice done by large rolling brushes. When you put the liquid crystals on a rubbed surface their molecular rods aligned along the rubbing direction. So they first thought, “Oh, it’s simple, rubbing causes grooves like plowing a field and the rods just lie down in these grooves.”
The model seemed plausible but I had my doubts. We had earlier developed the NEXAFS technique which through its polarization dependence can detect the orientation of molecular bonds near surfaces. So we investigated a lot of different polymer films that had been rubbed. They showed preferred molecular orientations (e.g. in phenyl rings) that were in some cases perpendicular to the rubbing direction. When you put liquid crystals on these surfaces they did not align along the rubbing direction, but rather along the direction of molecular orientation at the polymer surface. So it wasn’t mechanical grooves. The alignment was rather caused on the atomic level through preferential molecular orientation at the polymer surface.
Liquid crystal alignment was actually worked on at IBM Yorktown together with IBM Japan which had a joint production facility with Toshiba. The rubbing process involved big rollers that had to get cleaned all the time due to debris buildup and they were keen to replace it. People at Yorktown were trying a lot of things – trial and error – and in the process had bombarded one of the typical polymers with a directional ion beam, and liquid crystal alignment occurred.
So my colleague Mahesh Samant and I looked at these surfaces with NEXAFS and found that the alignment had nothing to do with the polymer. It was completely destroyed by the ion bombardment and turned into a very thin amorphous carbon layer. The layer, surprisingly showed a small orientational ordering of carbon-carbon bonds – a very small effect. Larger orientational order is known to occur in so called nematic liquid crystals and the bombarded carbon surface had a similar property. So we suggested, “We don’t need to use polymer films at all. Just deposit a carbon film, run the ion beam over it, and the directional bond breaking will give you the needed alignment template - and - the process can readily be integrated into manufacturing”. They first didn’t believe us but checked it out right away, and it worked beautifully. [Laughs] This was a big thing and we got several patents on the process and it was used to build the highest resolution displays.
We were of course elated by our home run; and then an unexpected thing happened. Shortly thereafter IBM decided to get out of the flat panel business. The joint IBM-Toshiba flat panel business was sold to a Taiwanese company around 2000! We consoled ourselves by knowing that our patents had increased the sales price.
Right.
For many years, IBM was a Japanese style company where people had a job for life. In the early days there were even IBM corporate song books – can you believe it? Things changed in the ’90s, and people actually lost their jobs. Scientists were fired for the first time and in the late ‘90s I told myself, “It’s been a great ride, but I can only see myself here for another year or so - it’s time to leave.” By luck, Stanford approached me in late ‘98 for various reasons and I said, “Yeah. Perfect timing!”
One quick question.
…but overall IBM was a great experience!
Real quickly, with the flat screen displays, the liquid crystals, it’s not just that you made them a bunch of money by introducing this new method of producing a liquid crystal display with the carbon film, but the prior iteration of liquid crystal technology, which had been around for quite a while… The polymer rubbing, they didn’t understand the mechanism; it just worked. Is that right?
Yeah, yeah. I would argue that Mahesh Samant and I figured out the molecular mechanism of alignment. It was this scientific understanding that led to the new alignment technology. That actually doesn’t happen very often and this may be one of the reasons why the industrial science labs turned into more directed or applied research. Even if there is new scientific discovery or innovation there are many other factors, like manufacturing cost and profit margins, that determine whether it becomes used. To go from research to manufacturing is a really big step, and in our case it happened. We got lucky…
This was sort of ’99, 2000-ish and then Stanford offers you a position. The position was basically back at SSRL, right?
Mostly, but there was a twist. I also became a professor at Stanford that allowed me to have students – that was very important to me.
Okay, I forgot a key point about how I ended up at SLAC/Stanford. In the ’90s people started thinking about x-ray free-electron lasers (XFELs). The development story is quite complicated because there were different concepts of free-electron lasers. The first one was developed by John Madey in 1971 at Stanford, but it was based on a storage ring that had a long straight section. You would just make the emitted x-rays go back and forth with mirrors in this section and synchronize it with the circulating electron beam. Every time an electron bunch came by the previously emitted and reflected light would interact with it and create some ordering of the billion electrons in a bunch. The ordered electrons emit x-rays in sync (as in a choir) and the intensity gets higher and higher, similar to a conventional laser. This scheme was limited by the extremely low x-ray reflectivity of mirrors, so that the scheme could not be extended into the x-ray range.
Then in 1980, two Russian scientists, A. M. Kondratenko and E. L. Saldin at Novosibirsk and a little later three Italian scientists, R. Bonifacio, C. Pellegrini and L. Narducci came up with another concept, “Do away with the mirrors and just make an exquisite electron beam”. If you run that tiny compressed electron bunch through a long wiggly section called an undulator, then the radiation that is emitted from the back side of this electron bunch defines a wavelength and electrons in the front of the bunch get modulated by that wavelength, ordering essentially in sheets. The in-phase superposition of the radiation from electron sheets builds up from noise. Pellegrini coined the name for this process `self-amplified spontaneous emission’ or SASE, in analogy to the optical process known as amplified spontaneous emission.
SASE requires a very high-quality linear accelerator (linac), not a circular accelerator as used for making synchrotron radiation. In a linear accelerator the electrons rapidly get up to nearly the speed of light and then basically coast without emitting x-rays. This is good because emission of x-rays causes kickbacks on the electrons leading to blow up of the beam size. So you can avoid this in a linac and instead do all kinds of gymnastics with the relativistic electron bunches – you can squeeze them to a thousand times smaller size than in in ring. Only when you have made the smallest possible bunch is it sent through a long undulator to make x-rays. But you can’t use the electron bunch again and discard it.
This SASE concept was tested first by producing infrared and visible light. It worked. Claudio Pellegrini at UCLA then contacted Herman Winick at SLAC and they are the true fathers of LCLS. Claudio is retired from UCLA and living close to SLAC, where he stills interacts with the accelerator scientists. He’s in his mid-eighties and I’m always keeping my fingers crossed that he wins the Nobel Prize…
In the US, SLAC was a natural choice because of its existing 2 mile long linear accelerator that wasn’t used anymore! [Laughing] So the challenge was to get the project funded by the Department of Energy - DOE. In 1998 a committee was appointed by DOE to address the feasibility and capabilities of novel x-ray sources. The outcome was the so-called Leone Report. It specifically emphasized that the new machine, if built, should produce hard x-rays. This aided SLAC since it had the biggest linac and a facility could be built there much cheaper.
My own take - as a soft x-ray lover - is that around ’98 many laser scientists still believed that upconversion of conventional lasers was a better path of getting to soft x-ray energies. This turned out to be wrong - even today, the upconversion concept is limited and the intensity falls off a cliff around 100 eV – not the envisioned 1000 eV!
Right.
So it became clear what SLAC had to do, “We need to make the case to build this thing. From a financial point of view, this is a no-brainer, you can’t build it any cheaper anywhere else. The key is the scientific case. We need to tell the DOE why they should cough up a half a billion or a billion dollars”. We didn’t really know at the time how much it would cost, but it was hundreds of millions.
So in late 1998 Keith Hodgson from SLAC/Stanford approached me (I was still at IBM), “Well, Jo, would you be willing to put together the scientific case?” I said, “Wow, this is fascinating and allows me to learn a lot,” so I volunteered. Since DOE likes national laboratories to work together I asked Keith, “How about if we bring in Gopal Shenoy from Argonne to help? I’d love to work with Gopal”. In the meantime, Gopal had also left Munich and had gone back to Argonne to see the light [Laughs]. He had become one of the Directors at the Advanced Photon Source. So Keith agreed, “Fine.”
I said, “Let’s get rolling,” and we organized a lot of meetings and brought in scientists from the synchrotron and laser communities in the US and Europe. The x-ray community was still very ignorant about short intense pulses and so was I. I remember thinking, “What is a femtosecond? Why is this important?” So we x-ray scientists had to first learn a lot of things that the laser guys already knew. [Laughs] In the end, we all realized that we had to come up with x-ray experiments that could the give new information on the combined ultrasmall and ultrafast worlds.
Right.
So atoms move at the speed of sound, and it turns out that’s about a picosecond or so. But when you want to actually look how electron bonding changes you need to be faster by a factor of about 1000 – a femtosecond. Since electrons are lighter they can move faster. It’s just the old inertia thing: the smaller, the faster. So we finally got it into our heads – “Ah, we can now dream of seeing motions on the intrinsic time scale of the building blocks of matter, the atoms, and the “glue’’, the electron density, that holds them together.”
We wrote a report in 1999. Gopal and I were the editors, but it was the work of many scientists. We weaned the scientific case down to six experiments that we envisioned. This required six different experimental stations – three close to the undulator source, three far away – about 300 m. In the Near Hall the beam was very small and concentrated and it became larger in the Far Hall. So this committee came up with a conceptual plan what needed to be built.
The report clearly contributed to me accepting an offer from Stanford around the same time and I started at Stanford at the ominous Y2K date 1-1-2000. We then had to go to Washington and sell it to a committee called BESAC (for Basic Energy Sciences Advisory Committee) of DOE. I was actually a member of BESAC, so I had to recuse myself [Laughing] and sit in the audience. We had thoroughly practiced the presentations. They had to hit the right points, like how revolutionary this was, why SLAC was the right place to build it, and so on...
To make a long story short, the committee and DOE liked it. I give credit to Pat Dehmer, who was the Director of Basic Energy Sciences in DOE at the time. She supported the idea, cleared bureaucratic hurdles and made it happen. [Chuckles] She said, “We want this. We’re going to do this,” and that’s the beginning of LCLS.
What year was that? Was this while--
That was in October 2000.
Was it still the Clinton DOE or was it the Bush DOE?
It was towards the end of the Clinton DOE – but both Democratic and Republican administrations have supported science – it’s quite remarkable. It took some time to build LCLS. I was not involved in the nitty-gritties of the construction process. LCLS was built under the capable leadership of John Galayda, an accelerator scientist – and in early 2009 we had the first beam.
As SSRL Deputy Director I learned the ropes of dealing with users and the DOE. SSRL ran like a well-oiled machine and my management job was relatively easy and left me time to build up my research group. At IBM, I had still done experiments myself, but that changed into writing funding proposals, finding good postdocs and graduate students – they would do the time consuming experiments…
Building up my Stanford science program was facilitated by another lucky event. In October ’99, I had run into Hans Siegmann, a Professor at ETH in Zürich, Switzerland at a conference in Seattle. Hans was one of the pioneers of modern magnetism, he invented spin polarized photoemission for example, and I knew him from conferences and longer visits at IBM Almaden where he consulted. Over lunch he said “Jo, it’s sad, in Europe they discriminate against old people! I’m 65 and they are making me retire from ETH!” I said, “Hans, come to SLAC and we’ll work together (I had already accepted the Stanford position)! I know you like California and your wife has even kept her house in San Francisco.” He liked the idea, and that was the beginning of a close scientific collaboration that only ended when he passed away in 2009. We all loved and learned from Hans who was there every day. I still miss him and our scientific banter. I’m sure my students saw much more of him than his own students had at ETH. At some point I suggested “Hans you have all this magnetism stuff in your head and have taught it at ETH. Let’s write a book together, kind of like ‘magnetism meets x-rays’.” I feel it was meant to be, and I helped him putting it all down in the book “Magnetism: From Fundamentals to Nanoscale Dynamics” that was published in 2006.
By then I had become SSRL director in 2005 and that required more of my time. In 2008, the SLAC directorship changed from Jonathan Dorfan to Persis Drell who is now the Provost of Stanford. Over the next four to five years the lab structure evolved with emphasis on x-ray facilities and science. [laughs]
Right.
Under the new directorship, the seminal question was how SLAC could be steered in a new direction without too much turmoil? You can’t stop science programs cold and we had to figure out how to move it slowly into the new direction over a period of several years. As an Associate Lab Director I was very involved in the process of redirecting the Lab from its original mission, high energy physics (HEP). With the construction of LCLS, x-ray science funding had overtaken HEP funding and in 2009 was already about 2/3 of the total SLAC annual budget. As the new Director, Persis Drell was tasked with that transition and it was a great pleasure and experience for me to work with her.
In 2009 she asked me to become LCLS director. The LCLS budget was the biggest chunk of the SLAC budget. It was about three to four times that of SSRL which for historical reasons had remained a largely autonomous part of SLAC. LCLS required resources spread across the entire lab like the use of central services like machine shops and most importantly, the expertise of the accelerator division. After some hesitation - I liked my SSRL job since it ran like a well greased machine - I agreed to the challenge. So I told her “Yes, ok.” The downside was that the job required all of my time and I had to put my science on the backburner. At the time I had about 10 graduate students and they suffered through this period until Hermann Dürr was brought in to run the magnetism program in 2010.
With the advent of LCLS, SLAC also built up programs in materials science and energy science. Particle physics was extended to particle astrophysics to explore forefront subjects like dark energy and dark matter. Our sister lab DESY in Germany did exactly the same thing, and accelerators previously used for high energy physics were converted into world class x-ray facilities.
The LCLS directorship was one of the most challenging periods of my life. Although I knew a lot about running a national facility from SSRL, this was different since the operation and science program at LCLS had to be built up from scratch. Foremost on my mind was how to make LCLS successful as a user facility with fair and transparent access to the best scientists around the world.
Right.
Because scientists are very competitive, it was essential to ensure that the best scientific proposals got “beam time”… and the competition was fierce. Only one out of five proposals was accepted for beam time.
Wow.
We had to create a proposal review committee. It’s a job I delegated to my Deputy Director Uwe Bergmann who with the help of Ingolf Lindau, one of the SSRL pioneers, created a proposal review committee which had about 50 people in it, experts in every area of science from around the world. In the beginning, it was like in the early days of SSRL where we were asking ourselves, “What are going to be the killer experiments?” We had to explore the scientific landscape again from scratch. The early experience at SSRL helped and we decided, “Let’s not commit ourselves too early on which scientific area is most important. We’re going to open it up. The best ideas get beam time and the winners will emerge.” This was our management philosophy.
Japan also built a free electron laser called SACLA which has become a great success. Initially, I felt that they played their cards closer to their chest but the facility is now open to scientists from other countries. I always thought that the openness of science in the US was one of its great strengths. Avoid protectionism, open things up for competition – even to foreigners – science is international. In retrospect, I would argue that the success of LCLS was partly based on allowing scientists of all countries to apply for beamtime. Due to previous experience with a lower energy XFEL, called FLASH, in Hamburg, European scientist played an important role and the early LCLS experiments were typically conducted by collaborative teams from the US and Europe.
I had all along envisioned going back full time to science and I did so in 2013, repeating what I did earlier at IBM. The LCLS science program had ramped up well and reached a certain maturity - it had gone through the typical S growth curve to a plateau. [Laughing] Once we got to the plateau, it lost its excitement for me, although the next expansion, LCLS-II, was on the horizon. But I wanted to return to my roots as a scientist with the goal of writing a new book and leave the rat race behind me. [Laughs]
In that 2009 to 2013 window, was there a clear sort of winner sort of analogous to the crystallographers at SSRL?
Yes.
What was that?
You mean LCLS.
At LCLS, was there something comparable to what you had had at SSRL with the crystallographers in the ’70s?
It was the crystallographers again.
Oh, okay! [Laughs]
I believe the killer application of XFELs is the unravelling of the structure and function of the worker molecules of life in our bodies. Bio-chemists have to spend an enormous amount of time coaxing the individual proteins to arrange into a crystal. In crystals the macromolecular units are stacked together in a periodic array. When you put an x-ray beam through such a crystal, the signals from all the units add up in unison to a strong diffraction pattern that allows you to figure out the internal structure of the units.
Now, there are a whole bunch of worker molecules, called membrane proteins who are very happy in their natural fluid state and don’t want to be packed together into a crystal. In some cases people succeeded, and these heroic efforts led to Nobel Prizes. Interestingly, LCLS was partly sold on the idea that we did not have to make crystals anymore, that with the high-intensity ultrafast x-ray pulse you could get a diffraction pattern from a single macromolecule and see what it looks like. So we developed a way to inject the molecules into the x-ray beam through a tiny nozzle. When the x-ray pulse hits the molecule the detector lights up giving you a pattern. At first there were a lot of blank shots because synchronization wasn’t perfect. That’s all overcome by now and we are homing in on the individual molecule case, through smaller and smaller crystals. We haven’t reached the ultimate goal yet and still need crystals but they can be very small.
There is another great advantage of using XFELs which is counterintuitive. The x-ray pulse is so intense that when the x-ray beam hits the molecule, it is blown to pieces. But the trick is that atoms move slow enough so by the time the bonds break and the molecule explodes the picture is already in the camera.
That is fantastic!
You beat the speed of sound, by which the atoms move, with the speed of light! We all know this phenomenon – we see lightning before we hear the thunder. [Laughs] So this turned out to be a winner, and I’m sure, Nobel Prizes will be won in the future where scientists unravel the structure of membrane proteins. So again, one of the big winners in the development of modern x-ray sources has been protein crystallography.
Another area is catching a glimpse of atoms and molecules in action – which has been termed femto-chemistry. The idea is to make a movie of how chemical bonds are broken or formed. Remember, the smaller the faster and one therefore needs both, ultrashort x-ray pulses to catch the molecule in action and sufficient x-ray intensity to get a good picture in the form of a diffraction pattern or an energy spectrum into the “camera”.
Yeah. Yeah, that would be fascinating, too.
It’s the trick used when taking a picture with a flash. When you take a picture of a hummingbird in flight, the wings are blurry because the mechanical shutter speed of the camera is too slow. So you use a flash which is faster. The flash-photographs are then assembled into a molecular movie, right?
Yeah! It’s been a long time since I took chemistry or organic chemistry, but that would be fascinating.
Now when it comes to what is called materials or condensed matter science, we’re still struggling a bit, in my opinion, to find the killer app of XFELs. Like the chemistry case it will most likely involve the study of the temporal evolution of phenomena - dynamics. But when you study materials or solids, the intense beam melts them or blows them up (evaporates them). For molecules and macromolecules you can just inject new ones into x-ray beam, but the sample refreshment process is more difficult for solid samples. In principle, the sample has to be replaced after every shot. So novel schemes and techniques have to be developed. There will certainly be applications, but I still see the use of synchrotron radiation as the main tool for the study of solids.
There is another area where x-ray lasers will undoubtedly have an impact. A question, Lawrence Livermore or Los Alamos National Labs are interested in is what matter looks like in extreme conditions. Such conditions may exist in stars but can be created on earth only for an instance of time, like by explosion of a bomb. [Laughing] Again, we want to catch a glimpse of the newly formed state of matter that only exists for a fleeting moment. You can actually produce such states of matter by zapping a material with an extremely powerful laser or with an XFEL pulse, but to see what you have created you need an XFEL to see the atomic structure. This field of study goes by the name “matter under extreme conditions”.
Are there any comparable facilities to LCLS being planned?
Oh yeah, we haven’t talked about that yet. I should say that it wasn’t LCLS alone that opened people’s eyes about the capabilities of XFELs. XFELs have been built in Germany, Japan, Italy, Korea and Switzerland and plans exist in other countries. In a sense, LCLS got lucky. It benefitted from the prior existence of the FLASH facility in Hamburg, Germany, which gave us a glimpse of what fast and intense pulses of deep ultraviolet radiation can do. Also the European XFEL facility which was conceived around the same time as LCLS was delayed due to its more ambitious scope and because it was politically more difficult to get the buy in from the different countries.
[Chuckles] Right.
So that’s actually how LCLS won out. We beat them because we could move faster. We didn’t have to consider the national interests of various European countries that had to be negotiated and put on paper. In fact, the Russians actually played an important part in getting the European facility built through a significant financial contribution. Some European countries are developing plans to build their own XFELs and so is China. So they are being built around the globe.
XFELs are partly the impetus for a new book “The Nature of X-Rays and their Interactions with Matter” that I have been working on for 7 years. My retirement in 2017 actually increased my freedom to work on it and dig into the literature. Lately I have greatly enjoyed interacting with Pietro Gambardella from ETH Zurich who has been sharing his beautiful work in electronic form for me to include in the book. Writing a book is not a brain dump because you need to understand things more deeply than ever before. I underestimated how complex the nature of x-rays or “light” truly is, although this had been articulated by great scientist like Einstein and Feynman. Today, the complete nature of light is described by what is called quantum electro-dynamics, QED. It is the jewel of physics, which however is extremely complex itself. Since our minds can only comprehend natural phenomena by describing them by approximations or simple pictures, we have thought of light as rays or waves. In QED, this turn out to be only the first step in an infinite series of smaller and smaller steps, representing increasingly better approximations and understaning. My new book is intended to elucidate the limits of this description, which become apparent when you use XFEL radiation. These sources will give us the opportunity to not only sharpen our understanding of x-rays but in the process understand the properties of matter beyond our present models.
Great. If you don’t mind, I had a couple of just sort of more personal questions about you that go sort of way back further to the beginning of our conversation, if you don’t mind a few more minutes.
No, no. It’s fine.
Great. Thank you. One of the things I was curious about. We talked a little bit about your education at Bonn, but you were a university student then in 1968 in West Germany. I’m curious if you were aware of, paying much attention to, or involved with the student movements at the time, with any of that activity.
Yes, of course I knew about it. I mean, it was all around me. The names Rudi Dutschke, ‘der rote Rudi’ and Daniel Cohn-Bendit, ‘Dany le Rouge’, come to mind. ‘Red’ because of their political views. Cohn-Bendit was French-German and also had red hair like me [laughs]. But I have to say that I just didn’t have the time. I knew what was going on. I was following it. Some of it appeared kind of weird to me. Some of it I supported – that they wanted to change the rigid and antiquated structure of society and inherited ways of thinking, riddled with prejudices. I remember the phrase “Der Muff von tausend Jahren steckt unter den Talaren” (the musty smell of thousand years lingers below the long robes). The black gowns or robes, you know…
Sure.
…so there were definitely good parts to it because it led to rethinking old ideas and moving us forward. A lot of it I supported, but I wasn’t politically active. As I said, many of the other students had the time to go to these things, and I felt I needed to hunker down and study.
And that’s something else I was just kind of curious about. Was it your sense that natural science students, and maybe specifically physics students, were maybe less involved because of the work that it required?
Yes.
I mean, the stories that I’m familiar with are from humanities students.
I would argue that it was almost impossible to study a science curriculum and be heavily involved in the political movement. There just weren’t enough hours in the day.
And then I’m curious. Going from that environment, West Germany in 1968, directly to Pullman, Washington—that seems like it would just--
Well, I got to experience the hippie movement and the music in the US! [Laughter] Which I loved very much. Flower power and peace rang true to me, after growing up after the war in Germany. But Pullman, of course, was quite different from Berkeley. Berkeley was out there and influenced by the hippie movement in San Francisco. I saw that for the first time, actually, in the summer of ’70 when my brother came over from Germany and we went down the coast and toured the west all the way to Colorado. It was just starting up in Pullman, right? Even people’s hair was still short up there, and in Berkeley everybody had long hair. I have to say, personally, I was very fascinated with the hippie movement and the freedom of breaking away from societal conventions and prejudices – and it was accompanied by great music.
It’s interesting that you mention the hippie movement in Pullman. My experience in Pullman—it’s a much more conservative town.
Oh, you know Pullman?
Yes. Oh, yes. I had many friends who went to Wazzu. At least these days… I shouldn’t say these days. 15, 20 years ago it was a much more conservative town than… I wouldn’t be… I didn’t encounter much of a sort of countercultural element there.
So I was there for two years, ’69 to ’71, and met my wife who grew up in Pullman. I enjoyed the changes on campus and as a graduate student I was there in the summer of ’70 when school was out. I grew my hair long and went to rock festivals with friends. People were smoking weed and stuff and enjoying the music – I thought it was great! [Laughter] Oh, I didn’t tell you an interesting side story.
Oh yeah, please.
Actually, when I came to WSU as a graduate student, the University had arranged for me to live in a fraternity, Sigma Alpha Epsilon. There were about 70 students living in a big frat house - I cleaned the toilets and set the tables for the meals with the freshmen who had to do the chores but since I was 21 could go to the pub with the seniors to drink beer. Fraternities were rather conservative, but I learned the American way of life and it was an amazing period. Of course I rapidly learned the language with all the slang. I had learned English in school but didn’t know slang. “This guy really turned me off.” What does that mean? You didn’t like him or he didn’t like you? “Oh, what a turkey!” So I picked up that lingo right away. I guess, my fraternity brothers thought I was interesting because some had never really got to know anybody from a foreign country and they were amazed at my stories. I was invited a lot by my fraternity brothers, like when they went home over Thanksgiving or even on ski trips to Sun Valley over Christmas. I became completely immersed and Americanized. [Laughs] As my mother always said, “I have a German son and an American son.” [Laughing]
So when you were in Munich, then, were you always sort of planning to move back to the US?
I was sitting on the fence at the time. No, I would not say that. I also thought possibly about going into industry, but I had loved my time in America and my wife was American, so there were definitely good reasons to go back. I thought of maybe staying in academia in Germany, but the German career system appeared antiquated to me – after your PhD you first had to do a habilitation and only then could you become a professor I saw that some younger guys went to America, worked at Bell Labs or so for a few years and came back and jumped right into a professorship. When I decided to go to Berkeley, that was still kind of on my mind. I thought it might also be a good opportunity to go back and jump in at a higher level. For a while there I thought, “Well, if I got offered a full professorship in Germany, I might go back,” but I think once I was back for two or three years I said, “No, I’m not going back there. I’m staying.”
So I guess the final question that I’d like to close up with is, is there anything that we missed, that you think is important that we didn’t discuss and would like to talk about?
Well, I’m sure that after we hang up I will have some thoughts.
Oh, of course.
By the way, if you have some follow-up questions, please feel free to contact me. I’m very happy to talk to you. I always thought it was interesting to talk about more than science. When I had students at Stanford, the formal science education was only part of the process. I thought it was interesting to find out what they envisioned to do later in life and talking to them about my experiences. I wish I had gotten a little more guidance as a student. Many people just slide into jobs without sufficient information. So I talked to my students about careers and other things I had learned too late - like taking advantage of institutions matching contributions to retirement plans. During my time at Stanford my weekly highlights were the lunches and Friday group meetings with my students and postdocs.
Absolutely. I didn’t do it for as long, but yeah, teaching is a fantastic experience.
Yeah. The irony is that I never really formally had to teach…
Oh!
…because I had a lot of other responsibilities at SLAC, but I tried to make up for it through my books! [Laughs]
That is important, too!
So I’ve written two books and working on my third. That’s actually how I still try to get the younger people excited about science.
Yeah. I’ll see about coming up with more questions because this has been a fantastic interview, and I would be happy to talk to you some more.
All right. Any time.
Wonderful. Well, thank you so much again. [End of recording]