In-situ high voltage generation with Cockcroft-Walton multiplier for xenon gas time projection chamber

TL;DR

This paper presents a novel in-situ high voltage generation method using a Cockcroft-Walton multiplier integrated into a xenon gas TPC, enabling stable operation and high energy resolution for neutrinoless double beta decay searches.

Contribution

The development and successful demonstration of an integrated Cockcroft-Walton multiplier inside a high-pressure xenon TPC for stable high voltage generation.

Findings

Successfully operated the TPC for 40 days at 6.8 bar pressure.

Achieved an energy resolution of 0.67% (FWHM) at 2615 keV.

Demonstrated stable high voltage generation with the CW multiplier.

Abstract

We have newly developed a Cockcroft-Walton (CW) multiplier that can be used in a gas time projection chamber (TPC). A TPC requires a high voltage to form an electric field that drifts ionization electrons. Supplying the high voltage from outside the pressure vessel requires a dedicated high-voltage feedthrough. An alternative approach is to generate the high voltage inside the pressure vessel with a relatively low voltage introduced from outside. A CW multiplier can convert a low AC voltage input to a high DC voltage output, making it suitable for this purpose. We have integrated a CW multiplier into the AXEL (A Xenon ElectroLuminescence detector), a high pressure xenon gas TPC to search for neutrinoless double beta decay of $^{136}$Xe. It uses silicon photomultipliers to detect the ionization electrons through elecrtoluminescence, making it strong against electronic noise. Operation of the CW multiplier was successfully demonstrated; the TPC was operated for 40 days at 6.8 bar, and an energy resolution as high as (0.67 $\pm$ 0.08) % (FWHM) at 2615 keV was obtained.