A benign, low Z electron capture agent for negative ion TPCs

TL;DR

This paper introduces nitromethane as a safer and effective electron capture agent for negative ion TPCs, with potential applications in X-ray polarimetry, supported by drift and diffusion measurements.

Contribution

It demonstrates that nitromethane is a benign alternative to CS₂ for negative ion TPCs, enabling new applications in X-ray polarimetry.

Findings

Nitromethane effectively captures electrons in NITPCs.

Nitromethane is safer and less toxic than CS₂.

Low atomic number of nitromethane enables X-ray polarimetry.

Abstract

We have identified nitromethane (CH$_3$NO$_2$) as an effective electron capture agent for negative ion TPCs (NITPCs). We present drift velocity and longitudinal diffusion measurements for negative ion gas mixtures using nitromethane as the capture agent. Not only is nitromethane substantially more benign than the only other identified capture agent, CS$_2$, but its low atomic number will enable the use of the NITPC as a photoelectric X{}-ray polarimeter in the 1{}-10 keV band.