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10 Questions for a Beamline Scientist: Apurva Mehta

November 4, 2011 - 1:02pm

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Apurva Mehta | Image courtesy of SLAC

Apurva Mehta | Image courtesy of SLAC

Fifteen years ago, SLAC National Accelerator Laboratory (SLAC) scientist Apurva Mehta volunteered to help a friend build beamline parts at the Stanford Synchrotron Radiation Lightsource (SSRL). Today, he's "still mucking around with beamlines."
 


In the latest 10 Questions, Dr. Mehta shares how he landed at SLAC and his adventures in a wide range of projects, from advanced semiconductors to ancient Greek pottery. 
 


Question: Why did you pursue a career in science?
 


Apurva Mehta: My father was an engineer and he loved his job and loves science.  Tucked away among assortment of books in the house, from Tolkien and Steinbeck to Tagore, Shaw and Woodehouse, were popular books on science and mathematics.  As a kid I would randomly pull down a book and read it until it lost my interest.
 


As long as I remember, I wanted to be an engineer or a scientist. I began as an engineer, and ended up a scientist. But I didn't know what it really meant to be one until grad school. Naively, I thought science is as it's described in popular textbooks -- someone thinks of a big scientific problem, like gravity or the structure of an atom, does one or two key experiments and gets an answer that matches one at the back of the textbook and then moves on to the next problem.
 


It turned out to be very different from that.  First, there are no answers at the back of the textbook.  And then often the experiments didn't work out as I imagined, the data was noisy and there was a lot of hard thinking on how to deal with the uncertainties and ambiguities.  But I also discovered that while scientists have very different approaches from each other, they often still arrive at the same conclusions.  Science had space for individuality and more creativity than I had imagined.   Luckily, the real boots-on-the-ground science that I discovered in grad school still held my interest.
 


Q: What led you to your current position at SLAC?
 


AM: A long, meandering path.  I did my first synchrotron experiment at Brookhaven National Laboratory while I was a post-doc at Princeton studying instabilities in correlated electron systems.  I started collecting more x-ray and then neutron diffraction data.  Then, I heard through one of my mentors (a neutron scientist) that a friend of his from graduate school was looking for someone to design and commission a x-ray powder diffractometer at a beamline at SSRL.  I volunteered to do so.
 


Again, naively, I thought I'll design the instruments, engineers will build them and I will move on.  But the design kept changing as I started talking to other scientists about what types of experiments they would like to do with such an instrument, and changed more again as I talked to the engineers about how to build a machine that was sufficiently flexible to do many different experiments, but was still reliable and easy to maintain.  At first, it was frustrating to discover that the perfect instrument I had designed did not work well for some experiments, but then it was exhilarating when we found a novel solution and the instrument evolved.  In the end, when the beamline was opened to users two years later, I was very proud of it. Thirteen years later I am still mucking around with beamlines.
 


Q: Do you have advice for students interested in science careers?
 


AM: Deep scientific insights, though often shocking and non-intuitive, are fundamentally simple and cool.  The rush I feel when I first encounter one is incredible.  But science often uses the current body of science to reach for a newer insights.  So newer and sometime very cool insights are buried in the nuts and bolts of the old structure and working them out takes work and time.  But let the time worry you not.
 
All the scientists I admire are very curious -- curious about big picture, but also about small details.  They are also skeptical.  They don't completely believe everything they hear (even stories that they hear in their own voice). That speck of doubt keeps them alert and on the search for new science.
 

Q: What projects are you working on right now? What do you hope they will lead to?
 


AM: Currently, I am involved in three broad classes of projects (it changes every few years):

  • Characterizing the structure and defects in semiconductors and other thin films: By shrinking device size, the density of devices on a computer chip has been doubling every 18 months for the last 40 years.  But the device dimensions are quickly approaching fundamental atomic limits and to continue this explosive growth, people are trying to also increase the speed of the electrons in these devices.  We are attempting to create the scientific underpinning for these next generation semiconductor devices.

  • Exploring picosecond (one-trillionth of a second) dynamics in materials: Many of the scientifically interesting and technologically important processes, such as the trapping of charge carriers in photosynthesis, charging/discharging reactions in the electrodes of Li-ion batteries, or liberation of hydrogen during water splitting at a catalyst's surface, happen in a hundred femtoseconds to few tens of picoseconds.  At SLAC, we have begun to study these ultrafast processes.

  • Applying state of the art material characterization to objects of importance to our cultural heritage.
 
Q: What projects/research are your watching (beside your own)?
 
AM: At the lab I am watching several interesting scientific developments in the realm of sustainable energy generation, from organic photovoltaics to next generation lithium ion batteries.  I am also watching with keen interest - and some befuddlement - how proteins and other biomolecules are structured and function. Additionally, I am fascinated by the galloping glimpses that the field of neuroscience and neuropsychology has brought to functioning of brains, from yours and mine to that of a bird.
 


Q: You've used x-rays to analyze ancient pottery. What did you find? How will this improve analysis of other surfaces?
                                                                  


AM: First, we learned that these objects were structured on many hierarchies - from scales of tens of millimeters where the decorative design was executed to tens of nanometers where the chemistry that it resulted from occurred. So they had to be studied as various length scales to fully understand how they were manufactured and how they functioned.
 


Many of the materials of interest and technological importance today, such as biomaterials and battery electrodes, have similar hierarchically complex structure.  We are finding that the approach we devised, and techniques we pushed to study these fragments of ancient ceramic are becoming useful in studying other hierarchically complex materials.
 


We, also found that the technology used to create some of these objects - in what I used to think of as primitive dark ages - is incredibly sophisticated.  The master potters, it seems, controlled their raw material and the temperature and atmosphere of their kilns with a precision surpassed only very recently by some of our high-tech manufacturing.
 


It changed my view of how progress in engineering is made as well.  Any engineering technology is built on a very wide web of know-how, using tools and tricks from various unrelated fields in an unpredictable way (not unlike how modern medical imaging technology is built on an obscure chemistry tool of nuclear magnetic resonance). It also taught us that many of these past cultures' highly sophisticated technologies existed in a very precarious balance.  They thrived as long as the dominant culture supported them but very quickly disappeared when the patronage was lost.
 


Q: After pottery, what other surfaces do have your eye on?
 


AM: Thin film diodes and transistors because that is where several new technologies (from solar cells to high-speed computers) are heading.  The surfaces and near surface regions of these materials are where all the action is.
 
The surface and near surface regions of a painting are even more complex.  Often a painter working in oils builds up a very layered surface to achieve the visual effect. Furthermore, very often degradation of a painting is driven by a reaction with the environment (humidity, salt and UV radiation) and the pollutants it contains (SO2, nitrous oxides, ozone) over tens to hundreds of years.
 


Q: What is your favorite gadget in the lab?
 


AM: I used to love knurled knobs on finely engineered instruments - such as on shafts of micrometers.  SSRL was teeming with them but slowly, about 10 years ago, they started disappearing as computer control became cheaper and ubiquitous.  So now I spend an unhealthy number of hours watching flickering electrons create subtly changing swiggly lines on LED monitors.  And SSRL is now teeming with TV  monitors that show us everything, from status of the electron orbit through the SPEAR3 ring to real-time updates of my current data scan.
 


Q: Switching gears, what are your hobbies outside of the lab?
 


AM: The usual: reading, hiking, and lately snorkeling.
 


Q: What is on your reading list right now?
 


AM: Several back issues of The New Yorker, a book on path integrals, and A.R. Burn's history of Greece.
 

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