Measurement of ionization yield of low energy ions in low pressure $\mathrm{CF}_{4}$ gas for dark matter searches

TL;DR

This paper measures the ionization yield of low-energy fluorine ions in low-pressure CF4 gas, providing essential data for improving directional dark matter detection with gaseous detectors.

Contribution

It presents the first direct measurement of ionization yields for fluorine ions in low-pressure CF4 gas at energies relevant for dark matter searches.

Findings

Ionization yield of 0.45 at 30 keV for fluorine ions.

Established a low-energy ion injection scheme into gaseous detectors.

Moderate dependence of ionization yield on ion energy.

Abstract

Direction-sensitive direct dark matter search experiments have been conducted using gaseous detectors. In spite of the long history of the study on the energy deposition of charged particles in materials, a full agreement between the measured results and theoretical predictions, especially in a low energy scale, are yet to be achieved. It is thus important to measure the ionization yields of recoil nuclei for the experiments with gaseous detectors using an ionization charge readout scheme. This study measured the ionization yield using a low-energy ion beam facility at Kanagawa University. The ionization yields for fluorine ions with an energy range of 5 $\sim$ 50 keV were measured using a dedicated proportional wire chamber filled with $\mathrm{CF}_{4}$ gas at 0.06 atm. The low-energy ion injection scheme into a gaseous detector was established and the ionization yield for fluorine ions was obtained to be 0.45 at 30 keV with a moderate dependence on the ion energy.