Characteristics of High Electron Beam Generation and Dose Distribution in Laser Wakefield Accelerator for Cancer Treatment

A laser wakefield accelerator (LWFA) can accelerate electrons using the interaction between high-intensity laser pulses and plasma. We developed and studied a small cancer treatment device using a 16-TW ultra-short high power laser based LWFA system and conducted further research to build a high-efficiency LWFA using a specific plasma density structure. The optimal acceleration condition was confirmed using a two-dimensional (2D) particle-in-cell (PIC) simulation, using the EPOCH 2D code. From the plasma density up-ramp structure, an electron beam energy of 210 MeV was obtained, which is 1.5 times higher than that obtained from the uniform plasma distribution. In addition, an electron beam energy of 70 MeV was obtained by ionization injection from a gas mixture of helium containing 10% nitrogen. A Gafchromic film was used to measure the three-dimensional dose distribution of the beam. The measured dose distributions are similar to those of high-energy electron beams with a narrow pencil-beam distribution. The dose distribution along the depth is similar to that obtained using the GEANT4 code, which considers the energy distribution of the electron beam. As the electron beam energy increases, the penetration depth is expected to increase, which suggests the possibility of developing an effective cancer treatment device.