Methodology for an experimental drift velocity determination using a μTPC. Example in a 700mbar 95%He+5%CO₂ mixture

Abstract

The micro-irradiation, neutron metrology and dosimetry laboratory of the Institute for Radiological Protection and Nuclear Safety (IRSN) is a National Metrological Institute associated laboratory, is in charge of the neutron fluence distribution references and produces neutron reference fields. The laboratory is developing a primary neutron-detector based on the use of Time Projection Chamber technology. This detector, called µTPC, can use different types of gas over a range of precise pressures. The analysis of μTPC data requires the determination of both the energy and the track direction of the recoil particles. The drift velocity in the gas is a key data point for analysis. Based on several experimental measurements performed using the µTPC with monoenergetic neutron fields, a direct methodology to determine the drift velocity can be proposed. These results are compared with those found using theoretical drift velocity from the Magboltz simulation.