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Interview of Sean Brennan by Jon Phillips on May 10, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/48058
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In this interview, AIP Oral Historian Jon Phillips interviews Dr. Sean Brennan, emeritus physicist at the Stanford Synchrotron Radiation Laboratory. Brennan describes his early life in an academic family, undergraduate education at Catholic University, and graduate education under Arthur Bienenstock at Stanford University, where he began work with synchrotron radiation. He discusses his early work at SLAC with Jo Stohr on X-Ray absorption experiments, and his post-doc at Exxon. Brennan goes on to discuss the development of the facilities and research at SLAC over the course of his tenure there, as well as his work on the NASA Stardust project analyzing asteroid and comet samples. The interview concludes with a discussion of Brennan’s activities after retirement, including programming apps and serving as a ski patrol rescue worker.
This is Jon Phillips, the assistant oral historian at the American Institute of Physics. Today is May 10, 2021, and I am interviewing Dr. Sean Brennan of the Stanford Synchrotron Radiation Laboratory. Sean, thank you so much for talking to me today.
Thank you.
So just to get us started, can you tell me, are you currently emeritus staff or faculty at SLAC?
That’s correct. Emeritus staff, yeah.
Okay. So what is your official title?
I was officially a physicist.
Okay.
I mean, I think there was senior physicist at one point, but when I started, I think they had me as a research associate and then senior research associate, and then they switched it over to physicist, and I didn’t do anything different.
Fair enough. So like I said, we’ll start off talking about your early life. You mentioned that you grew up in the D.C. area. Where exactly were you born and grew up?
Silver Spring, Maryland, although I was actually born in GW Hospital, so I kid people that because I wasn’t born in one of the 50 United States, I can’t become president. [laughs] So, my dad was a physics professor at Catholic University.
Okay.
So, it’s sort of in the family, and we can get into more detail on that. I have four sibs, and the joke in the family is that other families have spirals of poverty, and we have spirals of academia. [laughs] Three of my four sibs ended up in the teaching profession, and the smart one went into finance.
[laughs] Okay.
So because Dad was at Catholic University, I could get free tuition there, so it was really easy to just say, “Yeah, sure, I’ll go to CU.” And because he was chair of the Physics department, I really didn’t want to be in his department.
Sure.
So, I ended up in mechanical engineering. And then starting in junior year, I realized that materials science was more interesting to me than just straight mechanical engineering. So, I started taking more physics classes and things like that and was lucky enough to get into Stanford for materials science. So, that’s where I ended up doing my graduate work.
And when you were growing up, with your dad being a physicist, was physics something that you tried to avoid, or did you have an early interest in it, or science in general?
Yes and no. I mean, I was never particularly strong as a mathematician, and my dad was a theoretical physicist, so he was very strong. So, I had decided at some point that probably I wasn’t going to do physics, because I just didn’t have the math strength. And I was always pretty good mechanically. One of my very early jobs was as a washing machine repair person.
Oh, okay.
And I’d always worked on cars and things like that. So, mechanical engineering sort of made sense from that standpoint. But clearly, I had some of the influence of physics in there, and when I realized that being an experimentalist didn’t require quite the same level of math competency as being a theoretician, I felt more comfortable moving in that direction.
Gotcha. So, I assume given your family’s history that it was expected from the get-go that you were going to college to get, at the very least, an undergraduate degree.
Oh, yeah, yeah, yeah. Yeah. And then the joke was, “You’re not allowed to get married until after you’ve gotten your Ph.D.,” which most of us did. Well, Tom — my older brother was married during grad school, but the rest of us managed to hold off.
What fields did your other siblings end up in?
My older brother Tom just retired as a history professor at the Naval Academy.
Okay.
And then my sister Kate just retired as a nursing professor at Radford and at — there’s a Virginia Tech sort of enclave there. I don’t exactly know where the nursing school is, whether it’s Radford or Blacksburg. It’s sort of complicated. But she taught nursing and was a NICU nurse — a neonatal ICU nurse.
And then James is the smart one. He’s a banker on Wall Street. And Tad is actually the smartest of the bunch, and he is a professor of classics and philosophy at Cornell.
Okay. Did you get the sense that maybe that’s maybe rebellion against the physicist in the family, going with the classics?
No. No, no, no.
Okay.
My dad was very interested in history all throughout, and very interested in philosophy. He’d gone to Scranton as an undergraduate, and that’s a Jesuit school. And of course, they take those things very seriously. So, no. I think he was squeamish, though — nursing was not his bag, but certainly philosophy and history were definitely within his range of good choices. So, that was not an issue.
And your father going to a Jesuit school and then teaching at Catholic University — your family is Catholic, I take it?
Yes. Yeah. And I’m very much a child of the ’60s, so Vatican II was very important to us. And let’s say things have drifted since then.
[laughs] Okay.
Oh, and I should say: my mom was a kindergarten primary school teacher before she married Dad and became a full-time homemaker. Dad did his graduate work at Wisconsin, and they met in Madison. So he went Scranton to Wisconsin and then back to CU.
Okay. When you were at CU as an undergraduate, you started out in mechanical engineering. Did you have any thought in mind as to where you wanted to go with that, in industry or —
There was an oil crisis, if you remember, in ’73, when I started as an undergraduate. And so, I was thinking of solar energy related stuff. And in fact, one of the reasons I chose Stanford is that they had quite a bit of research in solar cells. And as it turned out, the particular professor who was doing solar cell research, he and I didn’t really link up effectively, and so I didn’t end up doing solar-cell research. But certainly, the response to the ’73 oil crisis was a strong influence. So if you wanted to describe my area within mechanical engineering, it was really more thermal engineering than anything else. And the summer of my junior year, I worked out at the National Bureau of Standards in Gaithersburg for someone who was working on thermal engineering issues with heat pumps and things like that.
Okay. So, once you got to Stanford, how did you make the shift from — you didn’t get along with the solar energy advisor.
Yeah. Within a couple of weeks of getting to Stanford, I met three guys who just impressed the heck out of me as being really smart people. And two of them were working for Arthur Bienenstock, who ended up being my advisor. So really, it was like: I want to work with those guys. And Paul Fuoss and Steve Laderman were the two guys who were ahead of me in the queue with Artie as the professor. And Fuoss and I have collaborated essentially ever since. Steve went off to work at Hewlett-Packard and is now, I think — he’s head of research — at Agilent Labs. I don’t remember. Anyway, Steve did okay. He did fine. And then the year behind me was Brian Stephenson. And so, basically Paul and Brian and I have done quite a bit of research together over the years.
And then I should say, the other thing was that I knew that solar cell research was being done a number of different places, but this thing, this synchrotron radiation — SSRP was a project at that point — was unique. Obviously, there was something at Cornell, which was similarly small and scrappy, but it became an opportunity to really do something that wasn’t available at most other graduate programs. And that was, as much as anything, why I ended up out there.
Had you had any background, even as an undergraduate, in X-ray spectroscopy or high energy physics or anything?
None of those.
[laughs] So, you jumped into the deep end?
Pretty much, yup. And just had a lot of really smart people guiding me along the way. And again, because of my, if you will, mechanical background, I found that I ended up helping a lot more with building experiments and not so much with me saying, “we really need to understand 3D core shifts”, or whatever. It was really like: okay, that’s a good problem. How do we actually deal with that? How do we get there? And that was really my — if you will, the thrust of my career was: how do we make that a successful experiment?
Gotcha. So when you started working with Artie Bienenstock, was there a specific individual project that you were on a grant for, for funding, or what was the setup there?
I was really lucky. My first year, I was on a — it was an energy traineeship. I can’t remember whether it was an NSF energy traineeship or just what it was. But anyway, I was on a scholarship for my first year, and so I didn’t have to TA and then Artie paid for my RA. So, I never taught — I didn’t have to do TA stuff in grad school. I was able to focus just on research. SLAC was funded through — at that point, it probably was ERDA, because that was ’77, and I think that was the Carter administration, so I think it was in the transition between the AEC and then later on the DOE. But of course, the SSRP was an NSF-funded facility initially, so they were this sort of wart on the side of this AEC project, and it wasn’t until ’83, I think, that we were brought into the DOE fold.
For your own dissertation research, how did you come up with that project? Was it something that you were just handed?
Yeah. So basically, Artie was the director of the lab and was not a particularly strong experimentalist. And one of the research associates at the lab at that time was Jo Stohr. And so I ended up working with Jo. And I think really it was Jo looking for some help, and me being willing to try anything. So that’s why I ended up doing more of the vacuum-related stuff and not — so, most of Artie’s students were doing structure of amorphous materials. So, Fuoss’ thesis was on anomalous scattering from amorphous GeSe, which was then a really hard problem, and only when the — many years later did it become a pretty standard process. So initially, I worked with Jo on very low energy — sort of the oxygen edge and carbon edge, in that area. So, 70 eV up to 600 or 700 eV was where the 1-4 monochromator could give you decent flux.
But while I was there, we built the first — what Paul Cowan labeled as a tender X-ray monochromator, and that’s sort of for the 1 to 4 kilovolt range. There’s this sort of fundamental problem that the X-rays are produced in vacuum, and you either have to put a beryllium window in order to let them go into a helium or air environment, or you have to have vacuum all the way to your experiment. And 4 KeV is roughly the breakpoint where below that, the beryllium absorbs too much, so you can’t get enough X-rays through to be useful. And so, up to about a kilovolt, grating monochromators work fine, but then there is this area where, again, from 1 to 4 KeV where you need a crystal monochromator, but you need to be in vacuum. And so, the Jumbo monochromator [laughs] was designed and built at SSRL, and I ended up doing my thesis work on Jumbo.
And that was, as much as anything, because it was sort of a new energy region, and so we came up with something we could do with that, and then so — sulfur on nickel. And sulfur on nickel is clearly a hugely important problem, again, for the energy crisis, because nickel is a catalyst. And so, high sulfur oil ends up poisoning a nickel catalyst, and understanding the absorption of sulfur onto nickel was an important energy problem. We had done a number of other EXAFS experiments. One of the first EXAFS oxygen K-edge experiments, and so it was sort of a natural outgrowth of that that we would do EXAFS of sulfur on nickel. EXAFS: are you familiar with that as a technique?
Basically. I actually interviewed Jo Stohr about two weeks ago, so I learned in the preparation for that interview.
Good. So, as much as anything, it seemed like a good target of opportunity for us to use Jumbo to study sulfur on nickel. And I don’t remember whether it was Jo or I who actually came up with that plan, but it was probably Jo.
Once you had the dissertation in hand, I know you went on to do a postdoc at Exxon at the same time that Jo went to Exxon. Were you also looking for academic positions, or were you really interested in going into the more industry route?
Not yet, not really. My nirvana would have been Bell Labs, as you can imagine.
Great.
But Peter Eisenberger had just moved from Bell Labs to Exxon, and so I ended up postdoc-ing with Peter. And prior to me postdoc-ing for Peter, Paul Fuoss postdoc-ed for Peter while they were at Bell and had done this, again, pretty new set of experiments doing grazing incidence X-ray scattering. And they had a vacuum chamber which bolted onto a standard four-circle diffractometer that they were doing their experiments on. And so, my task when I joined Peter was to build a UHV vacuum chamber that could do both the preparation and analysis of samples in the same chamber.
And as it turned out, I was a year too early in my design, and these Teflon O-rings became available about a year later that allowed Paul, when he became a staff member at Bell Labs — Paul and Ian Robinson built the second UHV scattering chamber, and they were able to have a much simpler design, because they could have a rotary motion into UHV, which I was not able to do. They just weren’t available when I did my design. So, my design was pretty darn challenging and never was that user-friendly, unfortunately. But we got some good experiments out of it. The lead (Pb) experiments were done on that chamber. But after I left Exxon, I don’t think anyone tried to use the chamber after that.
When I interviewed Jo, one of the things that he mentioned about Exxon was that over the early ’80s, while he was there, there was kind of a cultural shift away from emphasis on basic science to more practically applied research. Did you get that sense while you were there? Were there any specific uses that your work there was being considered as part of?
No. I think when Peter went there, it was very much: we’re going to replicate Bell Labs, and people can do whatever they want. Exxon was just awash in money at that point. And so, we really felt like we could do almost anything. And we were all very aware that Exxon was perfectly capable of spending a billion dollars towards Project X, and then two years later saying: oh, never mind. [laughs] So, the joke is that when the salmon are spawning, you’d better catch salmon. So, we went ahead and did what we could with the money we got. And Jo stayed there much longer than I did, and I’m sure he saw much more of the redirection towards more practical problems. I was sort of buffered from that.
Okay. So, after your postdoc, were you interested in potentially staying on at Exxon, or were you done and wanted to move on?
Yeah, if they had wanted me, I would have stayed. But Peter made it clear that I was not going to get a permanent staff position there. These decisions are made by others.
Right. Of course. I know your next position was then with the National Bureau of Standards again.
Yeah.
And was that based on your earlier connection from your time as a student?
No. Dick Deslattes had done some very early experiments at SSRL, and I met him then. And he’s one of the lions of X-ray physics, in a good way. I mean, just a really smart, careful guy. And so, I think it was as much as anything — I should mention that while I postdoc-ed at Exxon, I spent essentially all my time at SSRL.
Okay.
I would visit New Jersey once a quarter, maybe. But really, I was still pretty much full-time at SSRL. And I think it was one of Dick’s trips to SSRL, we got chatting and he said: I’m building a beam-line at Brookhaven. Do you want to come help? And I was like, “Yeah, sure. Great.” And my folks were still living in Silver Spring, so it was nice to be able to spend some time with my folks at that point. And again, because I was spending at least half of my time at Brookhaven, it was actually pretty convenient. I was living home in Silver Spring, and then driving out to NBS from my folks’ home in Silver Spring, and driving out to the Bureau of Standards. And (Interstate) 270, I’m sure it’s still a disaster, but 270 was such a disaster. It got so that if I left the house at 6:40, I could be out at the Bureau by 10 after 7:00, and if I left at 6:50, I could get out there at 8:30. I mean, it was just a disaster.
[laughs] Yup.
So, that part was not so enjoyable. My lifelong aversion to stop-and-go driving is, I think — that was part of it.
Yeah, I can definitely sympathize.
Yeah. So basically, at the Bureau, again, Dick was in charge and very much a mentor, but I was working very closely with Paul Cowan. And he was an amazing person, just brilliant and very practical, and I really enjoyed working with him. He was fabulous. So I got there, and one of the things that it was clear that was missing was an actual data collection and control program for this new instrument. And so, I sort of jumped into that as, gee, I think I know how to do this.
And oh, boy. So, these were DEC 16-bit minicomputers, and basically — so, okay. You have 32K of memory. The top 4K is input/output. The operating system is another 7K. So basically, you have 21K of memory to do whatever you want to do. And I managed to write a program that would control 20-some motors and collect data and write it to disk and plot data on a screen in 21K. So, that was — at the time, I didn’t know any better, but looking back on it now, I actually write iPhone apps now, and multi-megabyte programs are sort of easy to do there. Yeah. So that was probably the — obviously, I physically bolted together a lot of parts for the beam line, but if you will, the thing that was most important for my contribution to the beam line was really the data collection program.
And when did you first start working on coding? Was that as an undergrad?
Yeah, sure, I had done onesie-twosies, but it was really when I got to the Bureau that this idea of doing interrupt-driven data collection programming became mandatory. And so, I really learned at that point. And to give you the sense of just how not-ready I was, it was while I was doing that programming that I finally learned to touch-type. [laughs]
[laughs] I can imagine it would be difficult hunting-and-pecking your way through.
Well, I know people even now who still hunt-and-peck, but it was just — it seemed at some point I decided: Let’s figure this out. And I’m glad I did. I haven’t looked back. But yeah. And again, there were some other people (at NBS) — a guy named Basil Duval, who was actually a student from Oxbridge somewhere. And he had some very useful insights into doing real-time programming. And there were was a crew at Oak Ridge who had done this very nice set of code for interpreting — so, commands, you need to say: alright, what’s the verb? What do you want to do? And so, it would take a string and parse it into a verb and a subject and things like that. So, I borrowed that code from the guys that Oak Ridge. So yeah, it was very much a learning experience, and a lot of — every character was mine, but there was a certain amount of studying other people’s code along the way.
So you were at the Bureau from ’83 to ’86.
Yeah.
Did you get the beam line fully up and running during that time?
Yeah. We did our first experiments. Paul was a bit of a perfectionist, so you will not see many papers. We did a whole bunch of work on the argon absorption edge, but I’m not a co-author on, I think, any of those. I mean, there are a bunch of beam-line papers that we wrote, but Paul was too much of a perfectionist to let an actual argon science paper out the door. And so, I left before those things happened. But in the meantime, Paul and I also did some grazing incidence X-ray work that we did mostly actually at Hamburg, at Hasylab. And Paul was very much the lead on that, and it was there that I really started to understand dynamical scattering from good single crystals. Before that, I understood Bragg’s law and Warren and things like that. But actually understanding a Darwin curve and things like that was something that I learned through Paul.
So then after three years at the Bureau of Standards, you came back to SSRL. Was that originally your plan to head back there?
Okay. So, one of the people who joined the Bienenstock group later on is my current wife, Alice. [laughs] So when I left for the Bureau in ’83, we had started dating, and so we had this long-distance relationship until ’86, and fall of ’85, she finished her Ph.D. and joined HP Labs in Palo Alto. And so, once I knew where she had settled, I knew where I wanted to be.
Right.
And until she was settled, there was no point in me rushing off anywhere. We got lucky that in the spring of ’86, SSRL was looking for a research associate and ended up hiring two of us, John Arthur and I. I guess we both seemed to — we were complementary, shall we say. John had been postdoc-ing at Oak Ridge and I, of course, had been at the Bureau. So yeah, April Fool’s Day of ’86 is when we both started back at SSRL.
Quickly, what field was your wife in?
She spent her career doing materials engineering — 17 years at HP doing MBE gallium arsenide high-speed circuitry, basically the input FET for a spectrum analyzer was her beast. You know, so, 100 gigahertz, front end gallium arsenide FETs. She spent most of the rest of her career at a company called Nanosys doing nano materials. If you go to your local Costco and see an LCD display talking about QLED, that’s the Nanosys quantum product that she was involved in. So yeah, she did materials engineering and much more actually growing things rather than analyzing things. Although, there was a period there when we worked together — there was a period when HP was interested in wafer surface cleanliness, and so she was involved in that research with me and Piero Pianetta at SSRL. So, there are a number of Brennan and Fischer-Colbrie papers out there.
Gotcha. Very cool. So when you came back to SSRL, were there specific ongoing projects that you jumped in on, or did they bring you in to start doing —
Well, in some ways, I came back to being Artie’s postdoc, because again, he’s still director of the lab. So, some of what I was doing was — well, at that point, the workhorse diffractometer was the 7-2 diffractometer on a multi-pole wiggler. All of his students were doing some kind of research on that machine, although some of them were doing research on 4-3 as well. But I was brought back into his research group and was one of the people involved in making sure that his students got the resources they needed and the problem-solving they needed. But we never — I mean, there were a few times later on when we did research truly together. Both Hope Ishii and Ling Fu were the sort of scattering experiments that Artie had an intellectual interest in, but the work I did with Anneli Munkholm was completely unrelated to Artie’s work. And Todd Hufnagel, the fourth student who I think of as one I grew, he was officially Bruce Clemens’, who was in materials science at Stanford. So Todd, Bruce, and I shared, and then Hope and Ling and Artie and I shared. But part of my challenge was I was trying to define myself independently of Artie, so you sort of have to balance those needs, such as they are.
[I realize now that I completely skipped over the many GIXS papers I worked on with folks other than Artie when I came back to SSRL. Both non-vacuum papers (e.g. Doerner and Brennan, Toney and Brennan) and the Fuoss, Kisker and Stephenson papers studying growth of GaAs under OMVPE conditions. It is obvious from my CV that I did these other things but the discussion above might lead you to believe that all I did was shepherd Artie’s students, which is clearly not the case. Not sure how (or if it is possible) to insert a sense of those experiments, but the OMVPE experiments were absolutely groundbreaking and should be mentioned somewhere. This is especially the case because Paul was at Bell Labs and Dave and Brian were at IBM, so once again two shops that would not normally be collaborating were able to come together because it was openly published in peer-reviewed journals.]
At this point at SSRL, this was — within a few years of when you got back there, that was when you started the renovations on SPEAR, right?
It took a while. Actually, I don’t know if I can give you exact dates, but we certainly were proposing SPEAR-3 very soon after I got back, but wheels in Washington move very slowly. So, I think it was more like the mid — oh, actually, no. The first thing we did was the injector. So for many years — well, from the get-go, it had been the main linac that had been the injector source for SSRL. Because again, when we started in ’77, it was still a colliding beam machine. So, that was part of the challenge, was that we’d start out with 3 milliamps of electrons and 3 milliamps of positrons, and they would decay to 1.5 mA, and then they would re-inject. And that was because they were working at such a low energy they couldn’t have more current than that. This is why some of those experiments back in the late ’70s were just brutal. The count rates were — [laughs] I think it was Jene Golovchenko who tells the story: the guy who says, “Well, I do the calculation, and it looks like we’ve got one count per day.” And his buddy says, “This is great! If it comes in the morning, we can go fishing in the afternoon.” [laughs]
So, it’s that level of experimentation. Then SPEAR became uninteresting for the high-energy physicists, so then it became a full-time dedicated synchrotron storage ring. But we were — meanwhile, SLAC is doing the single-pass linear collider, the SLC, and they really didn’t want to have to stop doing what they were doing in order to feed us electrons. There were a lot of times where we would get our morning injection — okay, don’t bother us for 12 hours — and then there would be a dump, and electrons would fall out of the machine for some reason or another. And sometimes, they really would say: yeah, yeah, we’ll get back to you at 8 p.m., and sometimes they would change and go ahead and refill us. But there was a lot of tension during that period of their trying to get their experiments done, and we’re trying to get our experiments done. So, having our own dedicated injector became pretty important. And I actually helped out a little bit on that, and somewhere in there, you’ll see a couple of papers where I’m dealing with the injector. But then after that, I’m guessing it’s sort of in the 95, 96 range is when we really got serious about SPEAR-3. So, it was almost 10 years before SPEAR-3 became something where we could actually see the difference.
Right. I’m just curious. You mentioned that the conflict over use of the accelerator —
Sure.
How did that play out? Was it internal to SLAC?
From the get-go, Dick Taylor was acting like: we’re doing important science, and you guys aren’t, so don’t bother us. And, you know, fine. They’re doing cool stuff, but we thought we were doing cool stuff. So there was always this tension between the high-energy physicists and the solid-state physicists. Almost invariably, I was never involved in that conversation. That happened way above my pay grade. So I just know that there was a certain “looking down their noses at us” attitude. We were sort of the scrappy underdogs, especially when we were still with the NSF. When we became part of the DOE, at least we had a common boss who could sort of say: well actually, we’re paying these people to do X, and we’d like you to help them do X. And so, that helped. And Burt Richter was — what’s the right word? “Self confident.” [laughs] And so, when he was director, it was — it was still a challenge.
I think my few interactions with Pief (Panofsky) were that he just liked good science. He was really a fan of good science and was — I only have good things to say about Pief. He was great. And frankly, Jonathan Dorfan, I thought, was a person who promoted science generally. But it ebbed and flowed, and money was tight. Was it ’92, when the SSC got shut down? I’m trying to remember the exact date. But it was something like that. And so, there was a period there when money was tight. Oh, and then of course, the other thing is, we had — there were real challenges with power production. We had this sweetheart deal with the Western Area Power Authority, WAPA.
Okay.
And at my home, I was spending — I’ll make it up — 10 cents a kilowatt hour, and WAPA was selling power to SLAC at 3 cents a kilowatt hour. So it was a great deal. But when demand got high, SLAC would get turned off, and there was a time when NASA was using a huge wind tunnel at Moffett Field that was also a major power consumer. So there would be this power-sharing agreement, where Monday, Wednesday, Friday, we’d get the power, and Tuesday, Thursday, Saturday, Moffett would get the power. I’m making the schedule up. But it was that sharing kind of a thing. And so, one of the challenges was to try and wean ourself off of WAPA and pay real money. But again, if money is short, it’s really nice to be able to have cheap power. So that was, again, one of the challenges of doing experiments. And of course, at nighttime, we were a 24-hour-a-day operation. So after 8:00, when the households stopped using so much electricity for their air conditioning, we’d run all night. But we became night owls.
Gotcha. Now, one thing I was kind of curious about is something else that Jo mentioned — was just that once SSRL had basically the dedicated synchrotron source, it became — basically, the protein crystallographers were very, very excited about it and worked extensively. But this time, you’re still working on surfaces and films.
Yeah.
Was there difficulty in negotiating use?
No, no. They had completely separate beam lines.
Okay.
Yeah, there was no — I mean, there was competition globally that as new beam lines came up, the question was: who got to build equipment? But very, very early on, it was clear that the protein crystallography people needed their own equipment. And I’m sure you’ve heard this before. The distinction between an experiment and a measurement — basically, the PX folks were doing measurements. There was nothing complicated about what they were doing. The data sets were horrendously complicated. Actually getting an answer once you have the, at that point, multi megabytes of data was very, very hard. But the measurements are dumb grunt simple. So, they wanted to have — and of course, as it turned out very quickly, it became clear that they needed to have the experiments done at liquid nitrogen temperature. And so, there was a whole set of equipment involved in making sure that the samples were cold throughout the entire process. So, that just required a lot of ancillary equipment that we didn’t need on our machines. So, there really was, on a day-to-day basis, no competition between the PX folks and our folks. There were staff scientists who were dedicated to those PX beam lines, and other staff scientists and supporting staff were dedicated to our beam lines. And again, some of that was — Keith Hodgson was getting this separate source of money, both from NSF and DOE. And so, there was funding there that needed to be channeled towards those specific projects.
Right. There’s another thing I wanted to ask about. This is also the mid-’90s. You started taking on students for the first time. Is that right?
Yeah.
Was that something that you —
Yeah, it was more official, is what happened.
Okay.
I mean, I’d always been supporting them, but it became something where it became — there was an acknowledgement that — initially, it was with Todd Hufnagel. It was an acknowledgement that we really were doing these experiments as a team, and that neither Bruce nor Artie were really giving primary intellectual leadership in that case. And then Hope had actually — so Hope was engineering physics at Cornell as an undergraduate and had come out to help at HP Labs on these surface cleanliness experiments as a summer intern.
Okay.
So, we convinced her she should come do research as a grad student. And she was really the first one where I was sort of the official advisor for her. Yeah.
Did it make a difference, just internally, sort of bureaucratically, whether you were a faculty appointment or a staff researcher, as far as taking on a student?
That’s a huge, huge bone of contention, shall we say. That basically, SLAC was still very much a university-oriented operation. It still is, I think. And as a result, faculty were faculty, and everyone else was not. If you look at how many theses I am a signature on, it’s more than four. And again, I think the university would not officially acknowledge me as the major professor for any of these students. But it’s my belief that my contributions were sufficient that I think of them as my students. But I think Stanford would say: oh, no, no. Artie or Bruce was the major professor for them. Yeah. So, there is definitely a chasm between we mere staff scientists and those exalted professors.
And not necessarily asking for any scandalous gossip or anything, but did that — but culturally, were there any points of contention there? Was it difficult, or was it just something that everyone —
Some of the staff just didn’t care. They were just happy to do their job. I certainly felt that distinction and was unhappy about it and made it well known, and they were like: yeah, sorry about that. So, yeah. Because we were not — I think the official term is “members of the academic senate” — we couldn’t go out and get our own money.
Oh. Okay.
Okay? So any research budget we had was through a professor. Now, that’s changed dramatically more recently, but I was part of the cohort where they started saying: well, maybe if you’re senior staff, you’re allowed to go out and get money. But as in most things, follow the money. And as long as the professors are the only ones allowed to go out and get research funds, they clearly have the power.
Was that just — I mean, was your sense that that was to reduce competition for grants? Having an institution discourage, or even forbid, certain classes of researchers from bringing in grant money seems just counterintuitive.
The argument is pretty simple. Okay, if we have chosen you as a professor, we have some confidence in your ability to do reasonable research. And of course, once you’re a tenured faculty member, all bets are off, but at least while you’re getting tenure, you’re supposed to be doing reasonable research.
Right.
And so, that was the justification, that we had not been properly vetted. And if we were good enough to do reasonable research, why weren’t we professors? It’s that level of — it’s a Catch-22 situation there.
Right. Yeah.
And I think there were a number of people who decided that, yeah, the right thing to do is to go somewhere else. So of course, Jo went somewhere else, and George Brown went to UC Santa Cruz and was a professor there for many years. So that was one of the choices.
Gotcha.
And there was this sort of weird hybrid called a “research professor” that was basically — I knew I was never going to become a full academic professor, but the hope was I’d become a research professor. And so, for instance, Piero Pianetta, I believe, was a research professor with the EE department. Oh yeah, and it was only — so initially, part of the challenge was that if I were to become a research professor, it would have to be with a campus academic department.
Okay. Gotcha.
SSRL didn’t have their own research professors. It was only much later on in my career that SSRL started having —
Did the Department of Photon Sciences — is that —
Oh, I think I was already retired at that point.
Okay. That was much later?
Yeah, much later.
Okay.
Anyway, so yeah, that was one of the tensions that I felt.
Gotcha. Yeah. When you got up to the silicon surface, the cleanliness research you were talking about that you worked with your wife on, that was an HP project that was working at SSRL. Were you attached to — institutionally, how did that work?
Okay. So, HP came to us and said: there is a need for this kind of measurement. And it was not just HP. In the end, we ended up working with teams from TI, and Intel, and DEC, and AMD —
(micro?) chips.
Yeah. So, pretty much everyone who was worried about — this was during the transition from 8- to 12-inch wafers, and they were all worried that they just couldn’t get things clean enough. So, it was not merely an HP collaboration. They were the initiators, but definitely, it was broader than that. There was a whole — this is inside baseball, but there was this whole thing about: how do we get these companies to collaborate without it looking like collusion? Because in fact, they are competitors. Right?
Right.
And so, there were — SEMI is an organization that allows collaborations, as long as they’re done out in the open (the results are published). But it required essentially building a cleanroom into a hutch, because there’s no point in testing cleanliness if it’s out in front of [laughs] — if you’ve got a Class 1000 cleanroom, your samples are just not going to stay clean. And this is where Piero and I worked together, on building the cleanroom and building a sample transfer robot and all this stuff required — there’s interlocks involved, and you have to be able to pump down the chamber. And it was a pretty complicated beastie. But I think it was really pretty successful, as far as a bunch of people bringing samples or sending samples for us to measure.
I don’t know if this is jumping too far ahead or not, but I’m curious. The cleanroom setup that you had for that, did you also use that, or something similar, for the Stardust samples?
Certainly, we used some of that technology. We had learned quite a bit about how to keep things clean. So with Stardust, we could essentially do it more like a glove box and less like a clean room…
Okay.
…if you understand the distinction. Right? So basically, we could make sure the samples stayed clean, but we didn’t have to be in that space. I mean, humans are dirty. Humans are horribly dirty.
Right.
And so, if you’re especially — initially, before our robot was operational, we were actually using vacuum wands to put wafers onto platters and put them into chambers. And so, we’re dressed up in bunny suits and the whole nine yards. Right? And even then, it was not that clean. But then once we were able to let the robots take over, then it really was a relatively clean operation. And so with Stardust, it was much less of a problem, we didn’t have to be in it, as it were. We could do sample changes and things like that in a clean environment.
Gotcha. Before we go further with Stardust, just jumping back to the cleanroom again: where did the robots come from? Did you put them together internally, or did you contract out?
We built it.
Okay.
Yeah. I mean, you have to understand that Piero knows a whole bunch of people, and one day, this platter showed up from Applied Materials, and it was a platter that basically — you start out, and you use a vacuum chuck to hold the wafer onto this platter, but then once you pump the chamber down sufficiently, the vacuum no longer becomes useful, and the wafers tend to fall off. So then, you have to turn it over to be an electrostatic chuck instead. Okay? But if you start with an electrostatic chuck, [laughs] every dust particle in the universe ends up on your wafer.
So, there’s this transition between a vacuum chuck and an electrostatic chuck, which has to work with the interlocking of the robot and stuff. So, this wafer chuck appeared. I used to tease Bruce Clemens that, in some ways I was — oh, I’m going to forget the name of the people. I’ll get back to it. It’s a stupid story. Anyway, so this thing would show up, and we would say, “Wow, this is great. This is just what we needed,” and we’d install it in the chamber. And one of the challenges of that experiment was that we were looking at very, very low levels of copper. Copper is a huge killer for silicon wafers. And most lithium drifted silicon detectors have copper in them. And so, you would end up with this background copper fluorescence signal, which would kill your sensitivity. And so, we spent quite a bit of our efforts cajoling the detector companies into improving the quality of their detectors. And that was part of the process, is — and oh, by the way, the way you roll beryllium windows is with iron rollers, so you end up with iron on the surface of the beryllium. And so, you have to find a source of ultraclean beryllium, or you end up with this huge iron signal. Cargo Cult. Do you remember Cargo Cult people?
Yes. Yes.
It’s in the —
It’s the South Pacific. Yeah.
Basically, suddenly something would show up, and they’d say, “Oh, we can use this.” And then, a while later, it would disappear. “Oh, we’re no longer able to use this.” And so, things would show up at the lab, and I’d say, “Oh, I guess I can use this.” [laughs] So anyway, that was where that was going. So this wafer chuck just showed up one day. And I’m sure Piero knew exactly who to talk to at Applied Materials, and so it worked out fine. But that was Piero.
Gotcha. Going back to Stardust, where did your first involvement in that come in? Is it just once they knew where they wanted to send the samples for — there were multiple synchrotron labs involved.
Yeah. So this is sort of a fun story. John Bradley was a researcher at Livermore, but before that, he’d been — geez, I think in Georgia somewhere. I don’t remember exactly. But John and Artie had been helping Stan Oshinsky. Does that name ring a bell?
I recognize it, but I’m not placing it.
That’s okay. Oshinsky was an inventor — did some of the first fluorine-based amorphous silicon solar cells and did a bunch of work with actually some of the first — basically, there are amorphous materials that you can hit with a laser, and they will change from amorphous to crystalline, but it’s a reversible process.
Okay.
And so, some of the first re-writeable CD materials were based on materials that Oshinsky had developed.
Okay.
And Artie and John were involved in some of the patent litigation for Stan Oshinsky. So, that’s how Artie and John knew each other. I met John because I was trying to do some work on some of these early amorphous materials for re-writable CDs. And John was very much involved in both Stardust and before that on Genesis. And Genesis was this sample return mission that arrived a little too abruptly.
[laughs] Right.
So, it was through John Bradley that I became involved in Stardust.
Okay.
After we finished our surface contamination experiment, in that space, we installed an X-ray fluorescence — a microprobe. And so, it was really the microprobe which was the gateway for Stardust. But then later on, we had an X-ray microscope, so we could do tomography on these Stardust samples as well. So we did both fluorescent scanning of samples, but then also tomography on individual particles.
Okay. I was just curious. Were there any special sort of logistics involved in receiving and handling and working with the Stardust samples?
Sure. Anytime you’re dealing with NASA, you’re dealing with massive bureaucracy.
Right.
But it was — mostly these things just sort of — I don’t remember how they got it to us. It certainly wasn’t armored car or anything like that.
Right.
It was just sort of — stuff would show up — did we mail them? Yeah, probably. I mean, they’re not very big. [laughs]
And so, they weren’t terribly fragile then, or anything.
No. No. I mean, again, it was more a cleanliness issue than anything else. They were packed. Once they’d been extracted from the aerogel, they were put on “pickle forks,” [laughs] is what the technical term is. There would be this sort of wedge of aerogel, and there was — one of the team members figured out how to lithographically create silicon pickle forks, so we would use those to hold these wedges. And once they were on the pickle fork, they were — I mean, the thing is that they have no mass. So, they have no momentum, so you can accelerate them quite a bit, and nothing happens.
Right. Okay. I was just curious, given how little material there was and how irreplaceable, I guess, it is.
Yeah.
After that point, the Wild 2 comet samples are sort of the tail end of the papers that I read from your CV. Where did your work go with SSRL from that point up and through — I think it was 2008 when you retired.
Yeah. We were very active in Stardust through 2008, and also Ling Fu experiment on water was in that sort of ’06, ’08 period. In some ways, I left abruptly. There was still a lot of work that could have been done on both Stardust and water. But at some point I decided I’d had enough. And as it turned out, in the Fall of ’08, I could officially retire from SLAC. And the critical thing there is that I was able to continue to use Stanford healthcare.
That’s important.
That’s really, really important. Yeah. I’m now under Medicare, but I’m still using Stanford healthcare for my Part B and whatever. I don’t remember. But it was really — sticking around to get “full retirement.”
Right.
So back in ’98, Alice moved from HP Labs in Palo Alto to HP Labs in Santa Rosa.
Okay.
I don’t know if you know —
Yup.
Santa Rosa California
Yeah, I know Santa Rosa.
Oh, good.
Yeah.
Lovely town.
Beautiful.
It feels about 10 years behind the peninsula. Anyway, I really enjoyed living there. So, I spent 2008 on sort of a semi-sabbatical, because I was actually looking for a job in the Sonoma area and never found one. But along the way, I decided I needed to branch out, and so I started ski patrolling at Sugar Bowl.
Okay.
Sugar Bowl is up north of Lake Tahoe, Donner Summit area. And so on top of everything else I was doing, I was volunteer patrolling from ’98 through 2008. I became pretty happy with that part of the world, and we’d actually — so, Alice and I had been skiing together since the mid-’80s and had been coming out here to Jackson Hole since the mid-’80s. And so in ’08, I said, “I’m tired of this crazy commute in the Bay area, and I’m moving to Jackson Hole.” So I did that, and — again, inside baseball, as a volunteer patroller, I don’t get worker’s comp, so I’m not allowed to throw bombs.
[laughs] That makes sense.
Which is, — oh, darn. I don’t have to throw bombs. But the ski patrol here at Jackson Hole is only a paid staff, and they want you to be able to throw bombs, and they want you to have gotten your experience somewhere else. So basically, I couldn’t be a paid patroller here, so I ended up teaching skiing.
Okay.
So from 2008 until 2019, I was a ski instructor at Teton Village, and that was sort of my winter job. And the joke is, it was like being at a gym where they pay you $50 a day. It was just — this is not how you’re going to make your second million, by being a ski instructor. But it was great. It got me out of the house every day, and it was really a lot of fun.
Yeah, I can imagine. I’m curious. Do you have any memorable stories from your time as a ski patrol?
Well, it’s people doing stupid things. The terrain park is very exciting. I mean, fundamentally, 18 to 25 year old males are not very smart. They’ve got too many other things going on in their life. And so, we would regularly haul people out on backboards, and some of them were pretty unhappy. I was on one — we found somebody basically just lying there on the slope, and it was pretty clear he’d had a heart attack. And by the time we got there, he was yellow-gray, and we did the best we could, and he didn’t make it.
Oh.
So, these things happen. Right?
Yeah.
I don’t feel any guilt there. He was an older male who had a heart attack skiing. Well, these things happen.
Right.
It’s an amazing experience being up on top of a mountain in a blizzard. When everyone else has been told, “Go home. It’s too dangerous,” and you’re out there trying to make sure that everyone has gone home, it’s exciting. But we worked as a team, and we all made it back safely. So, I enjoyed it very much. It was a lot of fun. The National Ski Patrol has an outdoor emergency care program, where you learn how to basically deal with trauma med. The challenge, of course, is that they can’t drive the ambulance up to where the victim is, so you have to manage to get the victim — the patient — sufficiently stabilized that they can get to where the ambulance is. Right? So, that’s our task. Get to advanced care. But then in ’03, I did the wilderness EMT course with NOLS, the National Outdoor Leadership School, here in Lander. So, I have a certain amount of medical training, and it’s not like I’ve delivered babies or anything like that, but it’s certainly something where I’m happy to continue to hold onto those skills.
Yeah. You also mentioned a little while ago that you also programmed apps. You code.
Oh, yeah.
So I’m curious. Just how did you get into that, and what sort of apps are you creating?
I think it was 2014 — Apple came out with Swift as a programming language. So when I started programming seriously, which was in — was when I went to the Bureau in ’83. DEC was — the single-user operating system was RT-11, and what they had was a FORTRAN compiler.
Right.
So, I learned FORTRAN. First, FORTRAN-IV, and then FORTRAN F77 was next, I think, and then it kept going. So, I joke that I can write FORTRAN in any language. [laughs] So while I’m conversant in C, it’s not my first choice. It was sort of never my first choice. In the ’90s, MATLAB became useful, and so I did all of my data analysis work in Matlab. And then of course more recently, I’ve been doing some work in Python. But it was really — I said: I really want to learn an object-oriented programming language, and Swift is this brand-new language. And so, I thought I’d do that. So, the first app that I wrote was a diffractometer emulator.
Okay.
So, the idea is: if you want to know — let’s say I have a crystal of wafnium, and I want to know whether I can get to a particular reflection in that crystal. You can use this app to say: okay, I’m going to need to be at least this energy in order to be able to get to this reflection, and that depending on whether it’s a 4-circle diffractometer or a Z-axis diffractometer — sort of the different kinds of diffractometers, you have access to different reflections in different ways. And so, this was just an emulator app that allowed me to take advantage of a lot of the code that I had written for — oh yeah. So, I should explain that when I came back to SSRL, they were still using a program that they had borrowed — so, the program had again started at Oak Ridge, went to Bell Labs, and then moved to SSRL. But it was a teletype printer-based program. Okay? And it was called “SUPER,” which was short for “supervisor.” And so, I basically then rewrote SUPER so that it would work on a CRT, because I had done that for the program at the Bureau of Standards. And then when we finally got MicroVAXes, I rewrote it for the MicroVAX. So, I had all this background in writing diffractometer code and the angle equations for that. So, it was easy for me to do that in Swift. I think I finished writing that — I mean, I haven’t updated — I haven’t improved it since, I think, 2016.
Okay.
More recently, during the pandemic, I’ve written both a night clock app and a weather app, and in each of those cases, what I was finding was that the commercially available apps really wanted to know all about you and where you were, and “oh, give me your contact list,” and all this stuff. [laughs] So, I wanted to write things where I basically say, “Once you buy the app, I know nothing about you. I don’t phone home. I don’t do anything.” So, it’s a way of fighting against the user as a revenue source model of apps.
For as many times as I’ve heard people say that they wish they could just pay for something and not have to deal with the intrusiveness of every platform and app and program out there, there aren’t that many available. Maybe it’s just more profitable than —
Oh, no, no. It’s hugely more profitable. It’s clear. For those of us who care about our data being out there, [laughs] — again, the joke is, I’ve faxed my MySpace people, and they haven’t gotten back to me yet. I don’t do social media, and I don’t want them — I mean, I know they know all about me despite my best efforts. But I don’t have a Facebook account. So, this is sort of my way of fighting back at that, it’s just — even when you go to Weather.gov, if you type in a city, state, it’s actually a third-party program that turns that into a latitude and longitude.
Huh. I did not realize that.
Yeah.
And I guess it’s not that surprising, but a little bit, yeah.
Yeah. So I basically said, you know what? there are 1,700 or so weather stations associated with airports.
Right.
And if you say: okay, so KBWI is a weather station, so I can ask — there’s a specific URL you can go to that will give you the current weather at KBWI. And you can then say: okay, actually, I want to offset that to this other lat/lon, and I can go to any mapping app and figure out what the lat/lon is for Silver Spring, and then plug that in, so I can get a forecast for Silver Spring, but the current data are from DCA or BWI or where-ever.
Yeah. I worked for an airline for a couple of years a while back, and in the crew rooms, you could just go in and punch in an airport code, and it would just spit out the FAA forecast for that region. But I guess the public doesn’t get that access.
Right. Right.
So I guess the last thing I just wanted to ask you is — we’ve covered your time at SLAC and your life in general. Is there anything that we didn’t discuss that we should have talked more about, or that we didn’t talk about and should have, that you wanted to bring up? What do you think?
No. I think we pretty much covered it all.
Okay.
I will say that when I was initially at SSRL, it was a very small, very dedicated crew that was just interested in everyone’s experiment being a success, and people worked hugely long hours to make that happen. And when I’ve come back more recently to SLAC, the inevitable bureaucracy has just made it that much harder to get stuff done, and I realize that the lab is so much safer than it was. [laughs] But —
[laughs] That’s a good thing.
I remember discovering the hard way that someone had put a 3-kilovolt power supply attached to a sample in order to float the sample, and I got between it and ground, and — it can be painful.
Yeah.
These things happen. But I don’t know. I don’t know how people get things done now, given the bureaucracy that is required of them, but I guess they do.
Well, thank you so much for taking the time to speak with me today.
My pleasure. Thanks for asking all these questions.
Oh, of course.