Ratio of Transverse Diffusion Coefficient to Mobility of Electrons in High-Pressure Xenon and Xenon Doped with Hydrogen

We have obtained the ratio of the transverse diffusion coefficient to the mobility of electrons multiplied by the elementary charge, in Xe and Xe+H2 under electric fields at a higher pressure of 1 MPa in comparison with those in preceding experiments. The results show that the density effect (nonlinear effect) of the ratio in both pure Xe and Xe+H2 is ≤15% below 1 MPa over the reduced electric field range from 0.08 to 0.6×10-17 Vcm2. We also found that the diffusion of an electron swarm is suppressed by adding trace amount of hydrogen to high-pressure xenon gas. We discuss the application of Xe+H2 gas to a new gamma-ray camera.