Measurement of electron drift velocities in the mixture of Xe and He for a new high-pressure Xe gamma-ray detector

Drift velocities of electrons in a mixture of Xe (20 atm)-He (3 atm) were measured using a cylindrical high-pressure xenon chamber. The drift velocities were found to be greater than 3 x 10(5) cm/s above the reduced electric field of 2.0 x 10(-18) V.cm(2) at room temperature, which are close to those in Xe-H-2 (0.3%). The mixture of He gas into high-pressure xenon improved the resolving time of detectors because it increased the electron drift velocities. This implies that a high-pressure xenon chamber mixed with He-3 instead of He gas operates as a gamma-ray detector sensitive to thermal neutrons.