Mary Ann Mort and Sergey Mistyuk, both Ph.D. students in Prof. Charles E. Hunt’s Group in ECE, won Best Presentation Awards at the LLNL Student Intern Research Symposium. Approximately 1,000 students came to Lawrence Livermore National Laboratory (LLNL) this summer from all over the world for the opportunity to engage in work-study employment in science, technology, engineering, mathematics (STEM) and administrative fields as part of the LLNL Summer Internship Program. The Laboratory sponsors an annual poster symposium, giving student interns an opportunity to present summer research projects to the Lab community and sponsors.  The posters on display showcased world-class scientific and technical research and collaborations between students and their LLNL mentors. This summer’s symposium, held August 13-14, was the largest to date

Graduate students from over 30 top-tier research universities participated in the two-day symposium. LLNL representatives described the wide variety of presentation topics, ranging from Computing and Cybersecurity to Nuclear Fusion and Weapons-Complex Integration. Besides Mary Ann and Sergey’s projects, other projects included a ground-penetrating radar, tantalum x-ray detectors and weapons tests.

Only eight students in LLNL’s engineering directorate receiving awards.  Mary Ann and Sergey were the only winners from the University of California, and both are Prof. Hunt’s advisees.

Mary Ann Mort was awarded for her presentation, “Simulating Space Charge Effects of Photocathode in SLOS

Sergei “Sergey” Mistyuk was awarded for his presentation, “Simulation and Measurement of High Speed Germanium Photodiodes

Mary Ann Mort and Sergey Mistyuk, both doctoral students of Prof. Charles E. Hunt, both worked on high-speed x-ray diagnostic systems for the National Ignition Facility (NIF), an experimental inertial-confinement fusion reactor located on site.  Several complex and poorly-understood physical phenomena currently impede progress in reaching commercialization of a self-sustained fusion reaction, useful in providing virtually limitless clean electrical energy. Both Mary Ann’s and Sergey’s projects investigated different elements of these challenges.  The two different diagnostic systems that image implosion progress which they worked on, hSLOS and Daedalus, respectively, will one day give physicists a deeper understanding of the implosion process, help plot the course to green energy from nuclear fusion.

Mary Ann, working under Dr. Charles Brown, spent her summer simulating space-charge effects in hSLOS with CST Microwave and Particle Studio, as well as Python, two tools commonly used in research and industrial applications.  The device operates by converting the incoming x-ray photons to an electron beam drifting through vacuum and dilates it temporally through interaction with a time varying electric field, which imparts different amounts of kinetic energy on the electrons and allowing them to drift through a magnetostatic focusing field.  However, experimental data from SLOS did not match temporal and spatial expectations, and this was attributed to the space charge effects of interacting electrons as they travel through the vacuum tube. The 3D electromagnetics simulations quantified the problem, and were used to create a model to help set up input signals, dimensions and materials, and to simulate the nuclear fusion event temporally and spatially.

Sergey, working under Arthur Carpenter (a graduate of the UC Davis ECE graduate program) spent his summer modeling and measuring physical properties of germanium p-i-n photodiodes that will ultimately be used to develop a high-speed backside imager of hard x-rays.  A radiographic image of the nuclear event is currently captured with a (“Daedalus”) silicon photodiode array coupled with a CMOS Read-Out IC. Silicon however has insufficient electron velocities as well as poor stopping power for imaging higher-energy (hard) x-rays.  Therefore, germanium, which has a higher atomic number, as well as substantially greater carrier velocities than silicon, is being investigated as a more suitable semiconductor for this task. This is the first step in a longer doctoral project in which a high-speed germanium imager will be developed.

We also asked Sergey and Mary Ann about their experience at LLNL and what they hope for the future of their project.

Sergey replied “Working at LLNL as a summer intern for both the Engineering Directorate, and NIF and Photon Science was a whirlwind of events to get used to. I’ve never worked in a large national lab before.  So it was exciting, and often intimidating, to work with people that are nothing less than brilliant. You learn a lot whether you want to or not. My hope for this project is to be able to keep working on it, refining designs of the final camera step by step as results come in through simulations and laboratory results and ultimately accumulate enough information to publish a dissertation on high speed germanium imaging systems.”

Mary Ann replied, detailing her schedule and work within her respective lab. “Each week the interns in my building were expected to stay on schedule with their tasks, go to intern seminars and social events, and present our progress and updates on our projects. This prepared us for the Student Poster Symposium … My personal experience working with my project, mentors, and at LLNL, has definitely been positive. However, I was surprised the first day on-site at the New Employee Orientation: I got the impression I could be recruited as a spy since there is top secret information about weapons, nuclear fusion, and the stockpile at the lab.” With regard to potential future work for this and similar projects: “The better these resolutions are, the more useful the data is to the physicists designing all aspects of NIF. The plan for my dissertation will heavily rely on the knowledge I gained this summer about x-ray imagers.”

After accomplishing such a feat, we asked Mary Ann and Sergey to yield some wisdom to aspiring undergraduates and fellow graduate students regarding participating in such influential events.

Sergey stresses the importance of organization and prior planning, since working in a laboratory environment means small windows for systems testing. He recollects the difficulty of adapting, stating that Coming from a background where I can go into the laboratory whenever I please, day or night, this was a very frustrating adjustment to have to make, but with this forced adjustment came superior planning and communication skills needed for efficient project completion.”

Mary Ann encourages students to step out of their comfort zone despite feeling underprepared for such an experience. Her story is inspiring for any students who are hoping to participate in similar opportunities. She states “There’s never any harm in asking for help.  After a 2 year hiatus from my undergraduate experience, jumping into a project at LLNL that was meant to be for a postdoc, it was hard for me. Everyday I had so many questions and didn’t know how the system I was supposed to be modeling worked. So I took it day by day and started with the basics.  Every time I didn’t know a word, I wrote it down and looked it up. By the end of the summer I had pages worth of definitions. Each time I got stuck, I would go through a debugging process, and if that took too long or became moot, I would ask for help.”

Outside of being awarded a $150 cash prize and certificate, Mary Ann and Sergey were given the opportunity to meet and present before all LLNL Department heads. Their most valuable achievement comes from a private lunch event with Anantha Krishna, Associate Director of Engineering at LLNL. This prodigious outcome bequeaths the winning students budding relationships with industry top-level people in addition to recognition as top percentile of all interns. Due to the turnout from prestigious universities such as Caltech, UC Berkeley, Harvard, and MIT the value of a strong network and future job opportunities cannot be understated.


Mary Ann and Sergey have made UC Davis ECE proud with their accomplishments at a national laboratory, and we are looking forward to your bright futures.