Optical transmittance measurements of sheet resistors for the $\rm {CF}_4$ scintillating light in a gaseous time-projection chamber

TL;DR

This study measures the optical transmittance of sheet resistors in a CF4 gas TPC, demonstrating the potential for detecting charge and scintillation light for dark matter searches and track reconstruction.

Contribution

It provides the first measurement of sheet resistor transmittance for CF4 scintillating light and discusses detection prospects with various photodetectors for low-energy tracks.

Findings

Optical transmittance of sheet resistors is approximately 24.5%.

Detected about 20 photoelectrons for 5.3 MeV alpha particles.

Discussed detection capabilities with photomultiplier tubes and SiPMs.

Abstract

A gaseous time-projection chamber (TPC) with a reconstructable $z$ coordinate for nuclear recoil tracks has been developed for dark-matter searches and $\alpha$ particle imagings in a low radioactivity background. A TPC with a sheet-resistor field cage shows a potential to detect charge and photons produced by tracks if the sheet resistor has optical transmittance for visible light, and determine a drift length from a time difference between these signals. In this study, an optical transmittance of sheet resistors was measured to be $24.5\pm0.1_{\rm stat}\pm0.6_{\rm syst}\%$ for the $\rm {CF}_4$ gas scintillating light using an $\alpha$-particle source. The number of photoelectrons is observed to be $\rm\sim20~p.e.$ for 5.3~MeV$\alpha$ with the existence of a sheet resistor in the $\rm CF_4$ gas. Then, it is discussed how many photoelectrons to be observable by using multi-alkali-cathode phototubes and SiPMs for near-infrared light in order to detect lower energy tracks.