Brendan Stassel, a doctoral student at the University of Michigan, has been selected as this year’s Office of Science Graduate Student Research (SCGSR) scholar. The SCGSR program prepares doctoral students for career success in areas that support the U.S. Office of Science mission. This includes “delivering scientific discoveries and tools that help advance the country’s energy, economic, and national security.” The program is sponsored by the Department of Energy (DOE) Office of Science’s Office of Workforce Development for Teachers and Scientists (WDTS) in collaboration with the DOE National Laboratories.

Stassel, who will join researchers at the BELLA Center in the Accelerator Technology & Applied Physics (ATAP) Division for an 8-month-long research project starting in August, says, “I am excited to have access to the facilities’ resources, and there are multiple experts in my field with decades of experience who are available for me to bounce ideas off.”

His project aims to improve the models used to describe the interactions of lasers with targets and will be supervised by BELLA Center Research Scientist Lieselotte Obst-Huebl. Obst-Huebl leads the high-energy-density science experiments at the Center and is the co-lead of ATAP’s contribution to LaserNetUS, a scientific ecosystem established by the U.S. Department of Energy to advance the development of intense, ultrafast lasers and their applications.

“The research will focus on investigating the onset of relativistic transparency in the interaction of ultra-high intensity laser pulses with thin targets using the iP2 beamline at the BELLA Petawatt facility,” says Obst-Huebl. “This will improve our understanding of how these pulses interact with ultrathin foil targets—less than 100 nanometers in thickness—and will involve, among other things, varying the target thickness and intensity of the pulses.”

Recently, interest in using thin targets for laser-plasma interactions has increased. While initially opaque, these interactions between the laser pulse and target evolve throughout the interaction, during which the target can become relativistically transparent to the laser light. This relativistic transparency can provide more efficient ion acceleration for applications in radiobiology and fast ignition inertial fusion with laser-driven ion beams, which are essential for advancing accelerator designs based on laser-plasma acceleration.

“Brendan’s work will involve measuring in detail the transmitted fraction and the reflected fraction of the laser pulse following interaction with the target,” explains Obst-Huebl. “This will provide important information about what’s happening inside the target as, ultimately, these processes determine the quality of the ion beam produced by the accelerator.”

Although diagnosing the dynamical processes taking place inside these laser-plasma interactions is challenging as they occur at the micron-level scale over very short time intervals—in the femtosecond to picosecond range. “I am confident that Brendan’s project will deliver interesting results and am looking forward to working with him on the BELLA iP2 beamline,” she says. “He has worked with the team before and is already familiar with the BELLA laser facilities and the research the team is conducting.”

Stassel says the research conducted at the BELLA Center “will provide the content for the last chapter of my thesis, and I expect it will also lead to a published paper or two.”

While Obst-Huebl says this is her first time mentoring an SCGSR scholar, she previously mentored Anya Jewell, an intern in the Science Undergraduate Laboratory Internship (SULI) program, who also worked on the BELLA Center iP2 beamline.

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