Electron diffusion and scintillation in xenon doped with hydrogen for high-pressure xenon time projection chamber

High-pressure xenon time projection chamber (HPXe-TPC) is a sophisticated detector, which can determine not only an energy of gamma ray but also its arrival direction by using Compton scattering. Diffusion of electrons and scintillation yield in Xe and Xe+H₂ mixture have been investigated to realize a HPXe-TPC. The transverse characteristic energy of electrons in Xe-H₂ mixture (H₂ 0.44%) was reduced to about 40% against that of pure Xe at 1.0 MPa. Scintillation yields by alpha-particles (²⁴¹Am) in Xe+H₂ mixture (H₂ ∼ 0.23-5.7%) at 2.6 MPa were obtained as a function of E/N. The scintillation yields in Xe+H₂ mixture at 2.6 MPa and at E/N = 0.3×10^-17 Vcm² were luminous enough to generate a trigger signal of a HPXe-TPC. It is found that doping hydrogen into xenon is effective to prevent the degradation of angular resolution of a HPXe-TPC.