Electrical breakdown and optical emission properties of high pressure pulsed RF gas discharges

摘要

A fundamentally new technique for the measurement of the number of subexcitation electrons produced by the passage of ionizing radiation through a gas has ben developed by us during the past few years. The new detector is based on the digital characterization of the electrons in the particle track produced by the ionizing radiation where the charged particle track is registered by measuring the number of electrons found in given subvolumes of the gas in the ionization chamber. The track is thus characterized by a set of integers in each volume clement, from which parameters such as the track length and energy can be measured. We have specifically developed this technique for use in the field of microdosimetry, where the study of the fluctuations in the energy deposition in the charged particle track on the order of the molecular to cellular dimensions is important in understanding the chemical and biological effects of ionizing radiation. If the charged particle is a recoil nucleus produced by a neutron interaction, the energy deposited and the linear energy transfer can be inferred from this information, allowing the detector to act as neutron spectrometer. In this paper the experimental apparatus used to make these measurements and the optical and pulsed RF electric field optimization we have performed are described. Images of particle tracks produced by (alpha) and (beta) particles, and recoil protons from the interaction of high energy neutrons with hydrogenous materials, are also presented to illustrate the sensitivity and track imaging resolution. The quality of the information gained from the detector is a very sensitive function of the gas mixture constituents, purities and pressures used in the chamber, along with the magnitude, duration, and frequency of the pulsed RF electric field.