Calibration of the NEXT-White detector using $^{83m}\mathrm{Kr}$ decays

TL;DR

This paper details the calibration of the NEXT-White detector using $^{83m}$Kr decays, achieving high energy resolution crucial for double beta decay experiments, and introduces calibration methods to correct for detector effects.

Contribution

It presents a comprehensive calibration procedure for the NEXT-White detector using krypton decays, improving energy resolution and correction techniques for large xenon gas TPCs.

Findings

Achieved 4.55% FWHM energy resolution at 41.5 keV in the full chamber.

Achieved 3.80% FWHM energy resolution at 41.5 keV in a fiducial volume.

Projected energy resolution at $Q_{etaeta}$ energy within target range.

Abstract

The NEXT-White (NEW) detector is currently the largest radio-pure high-pressure xenon gas time projection chamber with electroluminescent readout in the world. NEXT-White has been operating at Laboratorio Subterr\'aneo de Canfranc (LSC) since October 2016. This paper describes the calibrations performed with $^{83m}\mathrm{Kr}$ decays during a long run taken from March to November 2017 (Run II). Krypton calibrations are used to correct for the finite drift-electron lifetime as well as for the dependence of the measured energy on the event position which is mainly caused by variations in solid angle coverage. After producing calibration maps to correct for both effects we measure an excellent energy resolution for 41.5 keV point-like deposits of (4.553 $\pm$ 0.010 (stat.) $\pm$ 0.324 (sys.)) % FWHM in the full chamber and (3.804 $\pm$ 0.013 (stat.) $\pm$ 0.112 (sys.)) % FWHM in a restricted fiducial volume. Using naive 1/$\sqrt{E}$ scaling, these values translate into resolutions of (0.516 $\pm$ 0.0014 (stat.) $\pm$ 0.0421 (sys.)) % FWHM and (0.4943 $\pm$ 0.0017 (stat.) $\pm$ 0.0146 (sys.)) % FWHM at the $Q_{\beta\beta}$ energy of xenon double beta decay (2458 keV), well within range of our target value of 1%.