Persis Drell was named the fourth director of the Stanford Linear Accelerator Center in December. In January, she had to announce the largest layoff in the history of the lab—125 jobs—plus the closure of two key projects, the B-factory (BaBar) which enables the study of anti-matter and the International Linear Collider. She spoke with Stanford about her vision for the future of the physics research laboratory.
Despite the challenges of the first few months on the job, are you encouraged about the future of SLAC because of the renovation that’s going on—the construction of the $420 million Linac Coherent Light Source?
Absolutely. It will be the world’s first X-ray free electron laser. It’s fully funded, and it will be the backbone of the programs going forward. It’s a very exciting tool that will enable many areas of science—biology, chemistry, atomic physics, materials science. We’re really breaking a new frontier in terms of the kind of tool we have to deliver X-rays to study these disparate, varied fields of science.
You’re talking about a light source that will be ultra-fast and study ultra-small things?
X-rays are powerful tools for studying things of atomic and molecular dimensions. What makes the LCLS special is that the pulse of X-rays is very, very short in time—200 femtoseconds. The best analogy is the shutter speed of a camera. If you have a really long shutter speed and something is moving, then you just get blurry motion. That’s all we’ve been able to do with X-rays so far. With LCLS, it’s extremely intense, but in a very, very short time period, and that short time period is well matched to the dynamics of molecular motion. So we can start to do, if you will, stop-action photography.
Was this new facility one of the reasons you came to SLAC from Cornell in 2002?
Any decision that involves a two-career couple with three children and two sets of parents on either coast is really, really complicated! My husband, Jim Welch, is an accelerator physicist working on the LCLS, and that was clearly a factor.
Sometimes we might ask people how they explain their work to their spouses or partners—but your husband is an accelerator physicist. Or we might ask someone how she would describe her work to her parents—but your father, Sidney Drell, was deputy director of SLAC from 1969 to 1998.
Yes. And I have far more interesting things to talk to my mother about than physics.
Did you grow up hearing about physics from your dad?
I grew up with the Nobel Prize-winning particle physicists of the century. Physicists were coming in and out of the house—literally. Richard Feynman was in our living room. And Hans Bethe. I would sit in the corner and just hope that no one would see me and send me to bed. And I would just listen. And watch. But it had nothing to do with physics.
It was a physics professor at Wellesley College, Phyllis Fleming, who ultimately hooked you, with her Modern Physics course?
Yes, she was just an inspiring teacher. And I think you hear that over and over again, that one teacher can make such a difference. The way I did the physics major at Wellesley was that I took every course Miss Fleming taught. And in my junior and senior years I took some physics classes at MIT. In fact, in my senior year I took a graduate course at MIT, which was extremely important for my self-confidence. And I then went to grad school at Berkeley and was the only woman in my class of 48. That was a culture shock.
One hears about the incredible amount of time that scientists are spending today writing grants. And they aren’t getting the funding they used to regularly receive. They say funding cuts are driving younger scientists to look for careers elsewhere. Is that the case in physics?
In the fields of biology and chemistry and materials science, which will do experiments at LCLS, I am worried, but not as dramatically as I am worried about the particle physics community. Because in the particle physics community, we have 150 graduate students on the BaBar experiment, and many of those students were counting on the final run to do their thesis. Now, by the stroke of a process that no one can explain [federal budget cuts], their thesis experiment just got cut off at the knees. What sort of message does that send to a young person?
How would you compare this period to other periods of discovery in the past?
Despite this horrible budget and the terrible cuts, this is the most exciting time in the field of particle physics and astrophysics in my career lifetime. And the reason is that up until the late ’90s, every experiment either agreed with theoretical expectation, or the experiment was wrong. We had a very successful model and it kept correctly predicting the results of experiments.
But in the late ’90s, everything broke open. There was a huge surprise in our discovery that in particle physics we had spent 40 years studying the basic building blocks of matter, but they were the basic building blocks of only about 5 percent of what makes up the universe. And that 95 percent of the universe is dark matter and dark energy. These are new forms of matter and energy, and we have no idea what they are. So we were getting arrogant; we knew we were getting close to the answer; and then, all of a sudden, we were confronted with a huge mystery. And that’s really, really exciting.
In the case of photon science, with the turn-on now of the fourth-generation sources, what I’d say is that we have a tool whose capability we really haven’t fathomed yet. I really believe the Nobel Prizes on [the LCLS] are going to be won for experiments we haven’t thought of yet, because the tool itself is so transformational. It’s a very different driver, in a sense, than in the case of particle physics and astrophysics where we have well-defined questions, big mysteries, and the means to answer them within our grasp. On the photon side, we have new tools that will transform our ability to ask questions, and I think it will be the tools that will drive the science.
The following did not appear in the print edition of STANFORD.
You’ve actually gone out and walked the tunnel that’s being constructed for the new LCLS?
Yeah, in the last rainstorm, just for fun. We were looking for leaks. The tunnel didn’t leak.
What will be some of the first experiments in the LCLS?
What are the early victories? What are going to be the first papers that you write? I don’t know the answer to that yet, but we’re getting a much better sense of how the machine will turn on, and I think it’s time to start defining those early victories. I’m a big believer that you define them and you celebrate them as you go along, so you show progress. You don’t just have the gold ring at the end, as success.
You sound absolutely excited.
Oh, I am, yes. If I wasn’t, I’m not sure why I’d be doing this job.
Is this kind of facility something people have envisioned for years?
Well, half-a-billion-dollar facilities don’t get generated in a short period of time. So I think what one is seeing here is the result of the vision of a lot of people. There were the specific accelerator scientists and physicists in the early 1990s who first recognized that the beams we were producing in the linear accelerator, if they were put through an undulator, could potentially make an X-ray laser. So there’s the technical piece. And then I’d say there is the vision of the lab director at the time, Burton Richter, who saw that at some time in the future, the lifeblood of the laboratory was going to be to have a forefront accelerator of some sort. And when the technical people came up with these exciting ideas, he pushed them. Subsequently that was carried on by my predecessor, Jonathan Dorfan, to get the project off the ground. But the seeds of this are in the early ’90s, in my view. And so I’m really here—I feel like I won the lottery! I get to be here when we turn on. It’s incredibly exciting.
And it’s the making of the X-ray laser that’s been the Holy Grail?
That’s exactly right. That’s the Holy Grail, and at the moment we’re just making electrons, and trying to get them to behave exactly as we want them to do, so that when we send them into the undulators, which aren’t in the tunnel yet—but when they are in the tunnel, we’ll be ready to send a beam into them and make the X-rays.
You and your husband met in graduate school and both taught at Cornell?
Yes, playing in a chamber group.
There must be a story to that?
Well, I was playing chamber music with a quartet, and the first violinist and the violist weren’t getting along, so the first violinist kicked out the other violist and brought Jim in. I think we played together for two years, and then decided maybe we were interested in more than just playing music, and we got married two years later. It was a long courtship.
So it was difficult to make the decision to leave Cornell?
I think what drew us here were the professional opportunities. And what was holding us at Cornell was several things. First, my deep, deep loyalty to the institution. They had been extraordinarily supportive of me. I mean, I literally interviewed for an assistant professorship with a 6-week-old under one arm. And our children had been born there, and we had a strong community there. So that was the pull there. So the scientific opportunity was great here, and somehow the personal one looked better there. So it was a very painful decision, putting all the elements of our very complex life into opposition, and trying to make that decision.
What do you talk about when you testify on Capitol Hill?
I go to talk to staffers. That’s part of my job—to interact with staffers and make sure they understand the excitement of our programs. But I don’t ever go to advocate for our programs. I go to advocate for science broadly. I think that’s the right way to carry the message. I think if you have every lab director in there advocating for his program, staffers are going to say, “How am I supposed to know what the priorities are?” You’ve got to go and advocate for science.
In the bigger picture, I am concerned with the numbers of [students in science]. I was on graduate admissions for the physics department and director of graduate studies for the physics department at Cornell for several years. And the number of U.S. young people going into science is diminishing. It’s not seen as an attractive career, and that’s bad. There have been a series of reports [in recent years], by very high profile blue-ribbon panels making the case that the biggest threat to our national security, to our energy security, to our economic security. is the lack of investment in the physical sciences, and in the education and training of a scientifically literate population. Students may be drawn to science because in their idealism and youthful passion, very esoteric fields like particle physics are attractive. They want to find the questions of the universe. [But] they don’t all spend their lives in particle physics. They go off and do wonderful things in many more practical areas. But to draw them in is the important thing, and when things happen like they happened this year, they will get very cynical very fast. So, yes, I’m very concerned.
