Longitudinal and transverse diffusion of electrons in high-pressure xenon

High-pressure xenon is an attractive medium for radiation detection in that the time projection chambers can be constructed by combined measurements of charge and light signals. The electron transport properties are essential information for developing and operating high-pressure xenon detectors. In this paper, our recent experimental results of electron diffusion coefficients in high-pressure xenon are presented. We measured the longitudinal diffusion coefficient of electrons under external applied electric fields in high-pressure xenon, ranging from 0.17 to 5.0 MPa in pressure at room temperature. A significant pressure dependence was found in the density-normalized longitudinal diffusion coefficient for low electric field region. We compared the longitudinal diffusion coefficient with the transverse one at a pressure of 1.0 MPa, and obtained the difference between both the diffusion coefficients. The longitudinal diffusion was found to become smaller than the transverse one when increasing the external electric field.