Simulation of beam-induced plasma in gas-filled rf cavities

Abstract

Processes occurring in a radio-frequency (rf) cavity, filled with high pressure gas and interacting with proton beams, have been studied via advanced numerical simulations. Simulations support the experimental program on the hydrogen gas-filled rf cavity in the Mucool Test Area (MTA) at Fermilab, and broader research on the design of muon cooling devices. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code with atomic physics support, was used in simulation studies. Plasma dynamics in the rf cavity, including the process of neutral gas ionization by proton beams, plasma loading of the rf cavity, and atomic processes in plasma such as electron-ion and ion-ion recombination and electron attachment to dopant molecules, have been studied. Through comparison with experiments in the MTA, simulations quantified several uncertain values of plasma properties such as effective recombination rates and the attachment time of electrons to dopant molecules. Simulations have achieved very good agreement with experiments on plasma loading and related processes. The experimentally validated code SPACE is capable of predictive simulations of muon cooling devices.

Simulation of plasma loading of high-pressure RF cavities

“…They include ionization by muon impact, electron attachment to dopant molecules, formation of cascades of heavier hydrogen ions, electron-ion and ion-ion recombination processes, as well as experimental data-based models of electron and ion mobilities in the dense gas. The atomic physics module has been validated in our previous work [11] by comparing simulations with experiments in the Fermilab MTA facility which operated HPRF cavities filled with pure hydrogen gas and hydrogen gas containing dry air dopant interacting with intense proton beams. Simulations showed a very strong reduction of the RF field magnitude in equilibrium for pure hydrogen plasma, much smaller reduction in the presence of dry air dopant, and achieved very good agreement with experiments.…”

“…is the average energy loss by plasma particle pairs per computational node j during one RF cycle [11]. Here E 0 (x, y, z), and ω denote the local amplitude and the angular frequency of the RF field, respectively, p e is a fraction of electron in an effective electron-ion pair, and µ e , µ + , and µ − denote mobilities of electrons, and positive and negative ions.…”

“…The atomic physics module of SPACE was validated in our previous work [11]. The validation data were provided by a series of experiments performed in the Mucool Test Area (MTA) at Fermilab [6,7,8] using the HPRF cavity interacting with intense proton beams.…”

Simulation studies of modulator for coherent electron cooling

“…The electrostatic solvers implement the traditional PIC method as well as a new method of Adaptive Particle-in-Cloud [11]. The code has been recently used for the study of plasma dynamics in a dense gas filled rf cavities [12], designed for ionization cooling experiments, simulation of laser-induced wakefields in plasma, and processes in a particle beam-induced plasma relevant to the mitigation of beam-beam effects [13].…”

SPACE: 3D Parallel Solvers for Vlasov-Maxwell and Vlasov-Poisson Equations for Relativistic Plasmas with Atomic Transformations

“…Since its development, SPACE has been successfully used in several projects in the area of plasma science and particle accelerator science and engineering. These include experiments on high-pressure radio frequency cavity at Fermi National Accelerator Laboratory [9,10], coherent electron cooling program at Brookhaven National Laboratory [11], and the laser wakefield acceleration experiments driven by CO 2 laser at the Accelerator Test Facility (ATF) of Brookhaven National Laboratory [12,13]. The AP-Cloud module of SPACE has been extensively used for the simulation of coherent electron cooling of relativistic ion beams [11,14].…”