Berkeley Lab

SCGSR Program Brings Three Graduate Scholars to ATAP

Clockwise from top left: Lauren Cooper, Kyle Jensen, and Roland Hesse.

Clockwise from top left: Lauren Cooper, Kyle Jensen, and Roland Hesse.

The DOE’s prestigious Office of Science Graduate Student Research (SCGSR) Program is enabling three graduate students to spend time in ATAP’s BELLA Center this spring: experimentalists Lauren Cooper of the University of Michigan and Kyle Jensen of the University of Nebraska, as well as computational modeler Roland Hesse, also of Nebraska.

The SCGSR program helps prepare graduate students for science, technology, engineering, or mathematics (STEM) careers crucial to the DOE Office of Science mission, by providing supplemental funds and an opportunity to conduct part of their thesis research at a DOE laboratory in collaboration with scientists there.

ATAP Division Director Cameron Geddes described the SCGSR program as “an important way for top doctoral students to connect with the team-science environment and leadership facilities at the national laboratories, while combining the strengths of research from their home institutions with those at the Lab to create new projects and capabilities.”

Lauren Cooper: Stacking pulses for the lasers of tomorrow

Lauren Cooper

Lauren Cooper (courtesy University of Michigan)

A doctoral student in electrical engineering and computer science at the University of Michigan, Cooper is building broadband laser pulse stackers at Berkeley Lab; these pulse stackers will test coherent combining techniques at the limits of ultrashort pulses.

If successful, “this will be the first demonstration of its kind, showing temporal stacking of very short pulses,” said Tong Zhou, Berkeley Lab advisor for Cooper’s SCGSR project, and will be a stepping stone for future experiments involving higher power. The overall project is developing coherent laser combining, a leading prospect for next-generation lasers that can deliver high average power with high peak powers, including the Laboratory’s kBELLA initiative.

Cooper’s undergraduate degree was in mechanical engineering, but an undergraduate research opportunity in a laser laboratory, and an internship with a beamline group at the Stanford Linear Accelerator Center, inspired her to do graduate work in laser science.

“I really like the national lab environment, because there are so many different cool projects going on at same time,” said Cooper, quoted in an article by the University of Michigan’s Hayley Hanway. “It’s really motivating and inspiring to me.”

Kyle Jensen: From an inspiring AMO seminar to LPAs

Kyle Jensen

Kyle Jensen, a doctoral student from the University of Nebraska-Lincoln, will be working with BELLA Center Deputy Director for Experiments Jeroen van Tilborg and Research Scientist Sam Barber. His SCGSR project—twelve months in duration—will examine whether metallic or dielectric wakefield accelerator structures can be used to measure longitudinal emittance of electron beams. In a nutshell, the leading electrons in a narrow evacuated tube could drive a wakefield strong enough to affect (and thus diagnose) the trailing electrons.

This plays into Jensen’s long-term interest in laser-plasma accelerators (LPAs). A key goal of his work is to demonstrate control over the electron and photon beams’ spectral distribution and brightness. This level of control is useful for any LPA applications—particularly “staging,” the use of the output of one LPA as the input to another in order to achieve higher electron energies. (Staging is key to many LPA applications and especially the eventual goal of a high-energy-physics collider. It was first demonstrated at BELLA Center in 2016, and staging experiments will be an important use of the Second Beamline project on the BELLA Petawatt laser.) “Whether it is a new laser that drives the 2nd stage wakefields, or an electron beam from the first stage that is applied as a driver, these are options worth exploring,” said van Tilborg.

Jensen’s undergraduate degree was from a small liberal-arts college. There he’d gotten some experience with computation and with small-scale lasers, which sparked an interest in atomic, molecular, and optical (AMO) physics. When he entered graduate school, a department seminar series included a talk by Professor Matthias Fuchs, leader of the Ultrafast and High-Field X-ray Science Group. “There was something about my advisor’s research that really resonated with me,” recalled Jensen, and in a group that did “everything under the sun” related to that field, he became interested in LPAs.

Jensen, a doctoral student from the University of Nebraska-Lincoln, will be working with BELLA Center Deputy Director for Experiments Jeroen van Tilborg and Research Scientist Sam Barber. His SCGSR project—twelve months in duration—will examine whether a dielectric wakefield accelerator structure can be used to measure longitudinal emittance of electron beams.

This plays into Jensen’s long-term interest in laser-plasma accelerators. A key goal of his work is to demonstrate control over the electron and photon beams’ spectral distribution and brightness. This level of control is useful for any LPA applications — particularly “staging,” the use of the output of one LPA as the input to another in order to achieve higher energies. (Staging is key to many LPA applications and especially the eventual goal of a high-energy-physics collider. It was first demonstrated at BELLA Center in 2016, and staging experiments will be an important use of the Second Beamline project on the BELLA Petawatt laser.) He is also intrigued by the potential of the dielectric wakefield accelerator as one stage in an LPA system.

Jensen’s undergraduate degree was from a small liberal-arts college. There he’d gotten some experience with computation and with small-scale lasers, which sparked an interest in atomic, molecular, and optical (AMO) physics. When he entered graduate school, a department seminar series included a talk by Professor Matthias Fuchs, leader of the Ultrafast and High-Field X-ray Science Group. “There was something about my advisor’s research that really resonated with me,” recalled Jensen, and in a group that did “everything under the sun” related to that field, he became interested in LPAs.

Roland Hesse: Putting laser-plasma physics and software in touch

Roland Hesse

Roland Hesse

Roland Hesse, a doctoral student at the University of Nebraska-Lincoln, is applying numerical tools to study particle distribution in intense standing-wave fields set up in plasmas by high-powered lasers.

Hesse works on computational models for understanding laser plasmas, focusing in particular on how to improve certain modeling techniques. His work has focused on developing a paradigm for redistributing computational resources according to kinetic activity, using a type of simulation called a Vlasov-Maxwell code after its mathematical basis. These codes are very well suited to the physics he is modeling, but seldom used in that field because they are so computationally intensive.

In his SCGSR work, Hesse, who has already written a one-dimensional Vlasov code, will apply his expertise to a better understanding of nonlinear wave-breaking. “The goal is to put what I’ve been learning about model design to use once we better understand the physics, and have structured feedback between the physical problem and the mathematical problem,” Hesse said.

“Electromagnetic theory is one of the more interesting things to me,” he added, “and a kinetic plasma is a place where you can toy around with that and come to a real understanding of what’s going on. ‘How does this work?’ That’s the thing that fascinates me.”

Connections among people make for scientific progress

Connections between Berkeley Lab and the academic laser science and technology community are key to matching top students with research opportunities. “This is a big SCGSR cohort, said Schroeder. “The faculty advisors are interested in collaborating with us, and SCGSR is a good mechanism to further that collaboration and do some good work.”

“In each case, the combination of the resources and expertise of the Lab with important new ideas move both the students and the research forward,” said Geddes.

Cooper is a student of Professor Almantas Galvanauskas, whose research group at the University of Michigan also produced Zhou, and who has been a collaborator in that work from the beginning. She performed doing simulation work during her first few weeks in Berkeley and since has begun experimental work.

Jensen was steered toward both the SCGSR program and Berkeley Lab by his advisor Matthias Fuchs, who had a budding collaboration with BELLA Center.

Hesse was put in touch with his Berkeley Lab mentor—BELLA Center Deputy Director for Theory Carl Schroeder—by his graduate advisor Bradley Shadwick, formerly a Berkeley Lab scientist and now Professor of Physics at the University of Nebraska-Lincoln.

Persevering through the pandemic

Cooper and Jensen, both experimentalists, are at Berkeley Lab, working under the Lab’s pandemic precautions. Hesse was originally headed our way more than a year ago, but the pandemic intervened, with Berkeley Lab going into its shelter-in-place phase as he was planning his SCGSR summer. More recently, he revised his plans… just as the omicron variant came along. The delays brought him close to the end of his doctoral studies, with graduation expected in December. As his work is more theoretical, Hesse is collaborating virtually.

SCGSR Application Cycle Begins

The Office of Science has opened applications for the next SCGSR cycle (deadline May 4). The prestigious and competitive program invites applications from current Ph.D. students who are in qualified graduate programs at accredited U.S. academic institutions; who are conducting their graduate thesis research in targeted subject areas; and who are US citizens or lawful permanent residents. ATAP encourages interested students to reach out to scientists in the Division to discuss potential projects.