Effects of Ionization Processes on Laser Plasma Proton Acceleration

SzJie Lee^1*, Han-Wei Chen¹, Yao-Li Liu¹, Shih-Hung Chen¹

¹Physics, National Central University, Zhongli, Taoyuan City, Taiwan

* Presenter:SzJie Lee, email:jerry944877@cc.ncu.edu.tw

Energetic proton accelerators have become important tools for cancer therapy. Former studies have revealed the Bragg peak, which shows that a properly selected proton beam can efficiently destroy cancer cells in a precise way with much less damage to healthy organs as compared to X-ray therapy. To make a proton accelerator more compact with lower cost is an important issue right now.
Radiation Pressure Acceleration (RPA) based on laser-plasma interaction is potentially an effective method to accelerate protons. When a circularly polarized laser pulse hits a solid or gas target, the ponderomotive force pushes electrons forward and separates them from protons to form acceleration field to protons. Previous studies have demonstrated that stable RPA can be achieved by the balance of light pressure and electrostatic pressure, and the monoenergetic proton energy can be scaled to GeV level [1]. But these studies are mostly based on the assumption of an initially pre-ionized plasma target.
In the study, different ionization models are used in one-dimensional particle-in-cell simulation of radiation pressure acceleration of protons. The simulation results can reveal the effect of ionization processes on the quality of accelerated proton beams and provide another degree of freedom for the design of the target.

Keywords: laser plasma proton acceleration, radiation pressure acceleration, field ionization, particle-in-cell simulation