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We investigate the performance of Opticks , a NVIDIA OptiX API 7.5 GPU-accelerated photon propagation tool compared with a single-threaded Geant4 simulation. We compare the simulations using an improved model of the NEXT-CRAB-0 gaseous time projection chamber. Performance results suggest that Opticks improves simulation speeds by between 58.47 ± 0.02 and 181.39 ± 0.28 times relative to a CPU-only Geant4 simulation and these results vary between different types of GPU and CPU. A detailed comparison shows that the number of detected photons, along with their times and wavelengths, are in good agreement between Opticks and Geant4 .

A critical element in the realization of large liquid and gas time projection chambers (TPCs) is the delivery and distribution of high voltages into and around the detector. Such experiments require of order tens of kilovolts to enable electron drift over meter-scale distances. This paper describes the design and operation of the cathode feedthrough and high voltage distribution through the field cage of the NEXT-100 experiment, an underground TPC that will search for neutrinoless double beta decay \\(0\\). The feedthrough has been demonstrated to hold pressures up to 20~bar and sustain voltages as high as -65~kV, and the TPC is operating stably at its design high voltages. The system has been realized within the constraints of a stringent radiopurity budget and is now being used to execute a suite of sensitive double beta decay analyses.

We report on a new measurement of the energy resolution that can be attained in liquid xenon when recording only the scintillation light. Our setup is optimized to maximize light collection, and uses state-of-the-art, high-PDE, VUV-sensitive silicon photomultipliers. We find a value of 3.7 \\(\\) 0.4% at 511 keV, once saturation effects are corrected for, a result close to the Poissonian resolution that we expect in our setup (2.8 \\(\\) 0.4% \\(\\) at 511 keV). Our results in the intrinsic resolution (2.3 \\(\\) 0.8 %) are compatible, within errors, at 511 keV, with those found by theoretical estimations which have been standing for the last twenty years, 1.8%. Our work opens new possibilities for apparatus based on liquid xenon and using scintillation only. In particular it suggests that modular scintillation detectors using liquid xenon can be very competitive as building blocks in segmented calorimeters, with applications to Positron Emission Tomography technology.

New detector approaches in Positron Emission Tomography imaging will play an important role in reducing costs, lowering administered radiation doses, and improving overall performance. PETALO employs liquid xenon as the active scintillating medium and UV-sensitive silicon photomultipliers for scintillation readout. The scintillation time in liquid xenon is fast enough to register time-of-flight information for each detected coincidence, and sufficient scintillation is produced with low enough fluctuations to obtain good energy resolution. The present simulation study examines a full-body-sized PETALO detector and evaluates its potential performance in PET image reconstruction.

We report on a new measurement of the energy resolution that can be attained in liquid xenon when recording only the scintillation light. Our setup is optimized to maximize light collection, and uses state-of-the-art, high-PDE, VUV-sensitive silicon photomultipliers. We find a value of 3.7 \\(\\) 0.4% \\(\\) at 511 keV, once saturation effects are corrected for, a result close to the Poissonian resolution that we expect in our setup (2.8 \\(\\) 0.4% \\(\\) at 511 keV). Our results in the intrinsic resolution (2.3 \\(\\) 0.8 % \\(\\)) are compatible, within errors, at 511 keV, with those found by theoretical estimations which have been standing for the last twenty years, 1.8% \\(\\). Our work opens new possibilities for apparatus based on liquid xenon and using scintillation only. In particular it suggests that modular scintillation detectors using liquid xenon can be very competitive as building blocks in segmented calorimeters, with applications to Positron Emission Tomography technology.

This work explores the combination of liquid xenon as a scintillating medium and silicon photomultipliers as a readout in Positron Emission Tomography (PET) for enhanced Time-Of-Flight resolution. We present the results of our first prototype optimized to maximize light collection using high-PDE, VUV-sensitive sensors and to minimize time fluctuations. We report a coincidence time resolution of 281 \\(\\) 2 ps FWHM, obtained using a \\(^22\\)Na calibration source. This result is competitive with the current state-of-the-art PET scanners and represents a significant step forward in the development of liquid xenon as a viable alternative to conventional scintillators in PET technology.

This work explores the combination of liquid xenon as a scintillating medium and silicon photomultipliers as a readout in Positron Emission Tomography (PET) for enhanced Time-Of-Flight resolution. We present the results of our first prototype optimized to maximize light collection using high-PDE, VUV-sensitive sensors and to minimize time fluctuations. We report a coincidence time resolution of 281 \\(\\) 2 ps FWHM, obtained using a \\(^22\\)Na calibration source. This result is competitive with the current state-of-the-art PET scanners and represents a significant step forward in the development of liquid xenon as a viable alternative to conventional scintillators in PET technology.

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 0.01~(sta.)~^+0.07_-0.09~(sys.)~\\%\\) for xenon and \\(1.07 0.01~(sta.)~^+0.06_-0.08~(sys.)~\\%\\) for argon. With PMT readout, we measure a LCE of \\(0.45 0.01~(sta.) 0.05~(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 \\(457~(sta.)~^+4_-5~(sys.)~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.

The NEXT-100 detector at the LSC aims at the first competitive search for the decay using a high-pressure 136 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 activity is found to be (0.95\\(\\)0.04(stat)\\(\\)0.09(sys)) Bq/m\\(^3\\), while no traces of 220 have been observed. Most of the 222 progeny plate-out on the surface of the cathode of the detector, leading to a rate of Rn-induced 214 of (0.97\\(\\)0.05(stat)\\(\\)0.10(sys)) Hz for visible energies above 400 keV. The corresponding background index in the 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.

The NEXT-DEMO++ detector, a high-pressure xenon gas time projection chamber serving as a prototype for the NEXT-100 experiment, was used to measure the electroluminescence (EL) yield as a function of reduced electric field (\\(E/p\\)) across pressures from 2.0 to 9.4 bar, utilizing the 41.5 keV de-excitation peak of \\(^83m\\)Kr. These measurements were made to examine the pressure dependence of the slope of the reduced EL yield \\(Y/p\\), which has shown inconsistencies in the literature. The reduced yield was fitted with a linear model, revealing a modest (\\(\\)5%) change in slope, beginning around 5 bar and increasing with pressure up to 9.4 bar.