Optical Visualization of Beam-Driven Plasma Wakefield Accelerators

Present particle accelerator technology is at a crossroads -- new discovery science and application opportunities lie ahead, yet the particle accelerators needed to realize them have become too large and expensive. This project explores the physics underlying a new approach to particle acceleration by using plasmas to accelerate particles thousands of times faster than can be done using conventional accelerators. The goal is to make plasma-based accelerators thousands of times smaller and less expensive than their conventional counterparts. This project addresses two current challenges in plasma-based particle acceleration research: (1) generating energetic particle bunches frequently, hundreds of times per second; and (2) accelerating anti-matter particles such as positrons. The project will train early career scientists including two Ph.D. students and an undergraduate student, and will help pave the way for creating new accelerator technology for industry and medicine. This award supports execution of the experiment E-324 “Optical visualization of beam-driven plasma wakefield accelerators” at the 2nd generation SLAC Facility for Advanced Accelerator Science and Experimental Tests (FACET-II). Specific scientific goals of the experiment are: (1) to observe and understand the recovery time of a plasma following plasma wakefield excitation, which limits collider repetition rate and luminosity; (2) to observe a sharp on-axis ion-density peak predicted by computer simulations to form as a result of a strongly nonlinear electron wake after it breaks; and (3) to observe the original beam-driven electron wake at delays less than 1 picosecond for the first time. These studies will pave the way for plasma-based positron accelerators, an essential component of future electron-positron colliders. They will also enable development of reliable tabletop plasma-based accelerators which provide compact coherent x-ray sources for biological, chemical, and materials research, injectors for conventional accelerators, and medical accelerators. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.