Engineering topics

Arnquist, I. J. [PNL, Richland] (ORCID:0000000256438330)

Publications and source records attributed to Arnquist, I. J. [PNL, Richland] (ORCID:0000000256438330).

3 records

DOE OSTI2026

Radon-induced backgrounds in the NEXT-100 experiment

The NEXT-100 detector at the LSC aims at the first competitive search for the 0νββ decay using a high-pressure $^{136}$Xe electroluminescent time projection chamber. The first low-background run of NEXT-100 at 3.95 bar has been devoted to the measurement of the radon-induced backgrounds impacting this search. The contributions from both the internal and external airborne radon have been evaluated. The internal $^{222}$Rn activity is found to be (0.95±0.04(stat)±0.09(sys)) Bq/m$^{3}$, while no traces of $^{220}$Rn have been observed. Most of the $^{222}$Rn progeny plate-out on the surface of the cathode of the detector, leading to a rate of Rn-induced $^{214}$Bi of (0.97±0.05(stat)±0.10(sys)) Hz for visible energies above 400 keV. The corresponding background index in the 0νββ region of interest is evaluated as (7.3±1.5(stat)±0.8(sys))×10$^{−4}$ counts/(keV·kg·yr) after selection of the fully contained events. This background index is reduced to ∼4×10$^{−5}$ counts/(keV·kg·yr) by applying a topological selection requiring only one double-electron-like track in the events. This value is one order of magnitude below the total radiogenic background expectation in NEXT-100. By analyzing the correlation of the airborne radon activity and the measured rate of events in NEXT-100, it is concluded that the detector operates in a virtually radon-free environment thanks to the radon abatement system of the LSC.[graphic not available: see fulltext]

Cortes-Parra, C. [Valencia U., IFIC] (ORCID:000000↗

DOE OSTI2026

Detection of scintillation light in noble gases with wavelength-shifting optical fibers

Wavelength-shifting (WLS) techniques enable particle detectors based on noble gases, whose scintillation light is predominantly emitted in the vacuum-ultraviolet. We investigate WLS fibers coated with tetraphenyl butadiene (TPB) for scintillation light detection in gaseous xenon and argon at pressures up to 8.5 bar, motivated by future high-pressure xenon time-projection chambers of the NEXT program. Two detector configurations are studied: an elongated high-pressure vessel with four PTFE panels equipped with WLS fibers read by temperature-stabilized SiPMs, and a compact box-shaped detector operated at 1 bar Xe with WLS fibers read out by PMTs. Both operate with continuous gas purification. The detector response is characterized using cosmic muons and alpha particles from a $^{241}$Am source. With the SiPM setup, we measure a light collection efficiency (LCE) of ${1.18 \pm 0.01~\mathrm{(sta.)}~^{+0.07}_{-0.09}~\mathrm{(sys.)}~\%}$ for xenon and ${1.07 \pm 0.01~\mathrm{(sta.)}~^{+0.06}_{-0.08}~\mathrm{(sys.)}~\%}$ for argon. With PMT readout, we measure a LCE of ${0.45 \pm 0.01~\mathrm{(sta.)} \pm 0.05~\mathrm{(sys.)}~\%}$ in xenon, in agreement with the SiPM result once photon detection efficiency is accounted for. Average scintillation waveforms in xenon and argon are studied to assess the time structure of the emitted light. Cosmic-muon measurements yield a mean energy required to produce a scintillation photon $45\pm7~\mathrm{(sta.)}~^{+4}_{-5}~\mathrm{(sys.)}~\mathrm{eV}$ at 1.5 bar, in agreement with the literature. The results demonstrate that TPB-coated WLS fiber systems can reliably detect scintillation light in high-pressure gaseous noble detectors, with a LCE representing an upper limit for realistic large-scale TPCs, where additional photon losses from materials and fiber attenuation are expected.

Soleti, S. R. [Donostia Intl. Phys. Ctr., San Seba↗

DOE OSTI2026

First results of the NEXT-100 detector using $^{83m}$Kr decays

The NEXT collaboration is investigating the double beta decay of $ ^{136}\mathrm Xe$ using high-pressure gas electroluminescent time projection chambers, which provide excellent energy resolution together with a robust topological signature. Operating at the Laboratorio Subterráneo de Canfranc (LSC) and building on the success of the NEXT-White detector, the NEXT-100 apparatus began commissioning in May 2024 and started operation with xenon at a pressure of 4 bar in October 2024. We report here the first results obtained with NEXT-100 using low-energy calibration data from $^{83\text {m}}\textrm{Kr}$ decays, which allow mapping of the detector response in the active volume and monitoring of its stability over time. After homogenizing the light response, we achieve an energy resolution of 4.37% FWHM at 41.5 keV for $^{83\text {m}}\textrm{Kr}$ point-like energy deposits contained in a radius of 425 mm. In a fiducial region representing the operating conditions of NEXT-100 at 10 bar we obtain an improved energy resolution of 4.16% FWHM. These results are in good agreement with that obtained in NEXT-White, and an $E^{-1/2}$ extrapolation to $Q_{\beta \beta }$ yields an energy resolution close to 0.5% FWHM, well below the 1% FWHM design target.

Martínez-Lema, G. [Donostia Intl. Phys. Ctr., San ↗