Characterization of Energetic Protons Generated in the ShenGuang-II UP Petawatt Laser Interactions with Foil Targets

Huiya Liu,Yao Zhao,Honghai An,Shenlei Zhou,Zhiyong Xie,Jianqiang Zhu,Anle Lei,Baoqiang Zhu,Ning Kang,Mingying Sun,Wei Wang

doi:10.1155/2021/7205383

Abstract

The characterization of energetic protons generated in the ShenGuang-II UP petawatt laser interactions with foil targets has been systematically studied. The proton energy spectra and angular distributions are measured with a radiochromic film stack. It shows that the proton energy spectra have a Boltzmann distribution with temperature of about 2.8 MeV and cutoff energy of about 20 MeV. The divergence angles of protons vary from 10° to 60°, dependent on the proton energy. The proton source size and location are investigated via the proton point-projection mesh imaging. The proton virtual sources are found to locate tens to hundreds of microns in front of the foil target, depending on the proton energies. A Monte Carlo simulation estimates the diameter of the virtual proton source to be about 12 μm for the protons with energy of 16.8 MeV, which is much smaller than the laser focus size of about 50 μm. The spatial resolution of the 16.8 MeV proton imaging is quantified with the point spread function to be about 15 μm, which is consistent with the proton virtual source size. These results will be important for the users conducting experiments with the protons as a backlighting source on the ShenGuang-II UP petawatt laser.

Highlights

Huiya Liu,1 Anle Lei,1,2,3 Ning Kang,1 Honghai An,2 Zhiyong Xie,2 Yao Zhao,1 Shenlei Zhou,1 Mingying Sun,1 Baoqiang Zhu,1 Wei Wang,2 and Jianqiang Zhu1
It shows that the proton energy spectra have a Boltzmann distribution with temperature of about 2.8 MeV and cutoff energy of about 20 MeV. e divergence angles of protons vary from 10° to 60°, dependent on the proton energy. e proton source size and location are investigated via the proton point-projection mesh imaging. e proton virtual sources are found to locate tens to hundreds of microns in front of the foil target, depending on the proton energies
A Monte Carlo simulation estimates the diameter of the virtual proton source to be about 12 μm for the protons with energy of 16.8 MeV, which is much smaller than the laser focus size of about 50 μm. e spatial resolution of the 16.8 MeV proton imaging is quantified with the point spread function to be about 15 μm, which is consistent with the proton virtual source size. ese results will be important for the users conducting experiments with the protons as a backlighting source on the ShenGuang-II UP petawatt laser

Summary

Research Article

Huiya Liu ,1 Anle Lei ,1,2,3 Ning Kang, Honghai An, Zhiyong Xie, Yao Zhao, Shenlei Zhou, Mingying Sun, Baoqiang Zhu, Wei Wang, and Jianqiang Zhu. E characterization of energetic protons generated in the ShenGuang-II UP petawatt laser interactions with foil targets has been systematically studied. E proton source size and location are investigated via the proton point-projection mesh imaging. E proton virtual sources are found to locate tens to hundreds of microns in front of the foil target, depending on the proton energies. E spatial resolution of the 16.8 MeV proton imaging is quantified with the point spread function to be about 15 μm, which is consistent with the proton virtual source size. E proton point-projection imaging with Cu meshes in combination with a radiochromic film (RCF) stack was used to characterize the protons. It shows that about 50% of the laser energy is contained within a 60 μm diameter, resulting in laser intensity over 1.5 × 1018 W/cm2. e experimental results measured in each shot are shown in Figure 2(c), and the shot number 1 is chosen as a typical shot. e incident laser energies are stable at 130 J ± 15%, and the proton cutoff energies measured with the RCF stacks are all higher than 15 MeV

Experimental Results and Analysis

Shot number

Conclusions