Abstract The NEXT-White detector, a high-pressure gaseous xenon time projection chamber, demonstrated the excellence of this technology for future neutrinoless double beta decay searches using photomultiplier tubes (PMTs) to measure energy and silicon photomultipliers (SiPMs) to extract topology information. This analysis uses 83mKr data from the NEXT-White detector to measure and understand the energy resolution that can be obtained with the SiPMs, rather than with PMTs. The energy resolution obtained of (10.9 ± 0.6)%, full-width half-maximum, is slightly larger than predicted based on the photon statistics resulting from very low light detection coverage of the SiPM plane in the NEXT-White detector. The difference in the predicted and measured resolution is attributed to poor corrections, which are expected to be improved with larger statistics. Furthermore, the noise of the SiPMs is shown to not be a dominant factor in the energy resolution and may be negligible when noise subtraction is applied appropriately, for high-energy events or larger SiPM coverage detectors. These results, which are extrapolated to estimate the response of large coverage SiPM planes, are promising for the development of future, SiPM-only, readout planes that can offer imaging and achieve similar energy resolution to that previously demonstrated with PMTs.

Abstract Noble element time projection chambers are a leading technology for rare event detection in physics, such as for dark matter and neutrinoless double beta decay searches. Time projection chambers typically assign event position in the drift direction using the relative timing of prompt scintillation and delayed charge collection signals, allowing for reconstruction of an absolute position in the drift direction. In this paper, alternate methods for assigning event drift distance via quantification of electron diffusion in a pure high pressure xenon gas time projection chamber are explored. Data from the NEXT-White detector demonstrate the ability to achieve good position assignment accuracy for both high- and low-energy events. Using point-like energy deposits from $$^{83\textrm{m}}$$ 83 m Kr calibration electron captures ( $$E\sim 45$$ E ∼ 45 keV), the position of origin of low-energy events is determined to 2 cm precision with bias $$< 1~$$ < 1 mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks ( $$E\ge ~1.5$$ E ≥ 1.5 MeV), from radiogenic electrons, yielding a precision of 3 cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1% FWHM at Q $$_{\beta \beta }$$ β β in pure xenon, as well as the potential for event fiducialization in large future detectors using an alternate method that does not rely on primary scintillation.

NEXT-100 is currently being constructed at the Laboratorio Subterráneo de Canfranc in the Spanish Pyrenees and will search for neutrinoless double beta decay using a high-pressure gaseous time projection chamber (TPC) with 100 kg of xenon. Charge amplification is carried out via electroluminescence (EL) which is the process of accelerating electrons in a high electric field region causing secondary scintillation of the medium proportional to the initial charge. The NEXT-100 EL and cathode regions are made from tensioned hexagonal meshes of 1 m diameter. This paper describes the design, characterization, and installation of these parts for NEXT-100. Simulations of the electric field are performed to model the drift and amplification of ionization electrons produced in the detector under various EL region alignments and rotations. Measurements of the electrostatic breakdown voltage in air characterize performance under high voltage conditions and identify breakdown points. The electrostatic deflection of the mesh is quantified and fit to a first-principles mechanical model. Measurements were performed with both a standalone test EL region and with the NEXT-100 EL region before its installation in the detector. Finally, we describe the parts as installed in NEXT-100, following their deployment in Summer 2023.

The primary scintillation signal in gaseous detectors can be used to obtain the initial interaction time of a detected event, but existing results in the literature for its yield in gaseous xenon are scarce and there is not a good agreement between them. In this work, a standard Gas Proportional Scintillation Counter (GPSC) was used to measure the absolute primary scintillation yield of gaseous xenon at 800 Torr for 5.9 keV X-rays, in order to try to clarify its value. The experimental determination was carried out using the ratio between the primary and secondary scintillation signals. The detection efficiencies of both signals were determined by Monte Carlo simulation results were used to correct the measured ratios. A primary scintillation yield of 73.4 +/- 8.8 photons by 5.9 keV X-ray was obtained, from which a wp-value, i.e, the average energy necessary to produce a primary scintillation photon in xenon, of 80 +/- 12 eV was obtained.Also, in the same conditions, the primary scintillation was studied in Xenon-Trimethylamine (TMA - (CH3)3N), mixtures with TMA fraction between 0.1% and 1.0%. The primary scintillation signal was only observable at the lowest TMA fraction in the mixture (0.1%). For higher fractions, the primary scintillation signal was not observable, indicating that these may not be suitable mixtures for experiments that use the primary scintillation signal.

The search for neutrinoless double beta decay (0 νββ ) remains one of the most compelling experimental avenues for the discovery in the neutrino sector. Electroluminescent gas-phase time projection chambers are well suited to 0 νββ searches due to their intrinsically precise energy resolution and topological event identification capabilities. Scalability to ton- and multi-ton masses requires readout of large-area electroluminescent regions with fine spatial resolution, low radiogenic backgrounds, and a scalable data acquisition system. This paper presents a detector prototype that records event topology in an electroluminescent xenon gas TPC via VUV image-intensified cameras. This enables an extendable readout of large tracking planes with commercial devices that reside almost entirely outside of the active medium. Following further development in intermediate scale demonstrators, this technique may represent a novel and enlargeable method for topological event imaging in 0 νββ .

A new experimental system was recently developed to measure the mobility of both positive and negative ions: the Dual-Polarity Ion Drift Chamber (DP-IDC). This system is intended to better understand the transport properties of ions in gases relevant for the performance of large volume gaseous detectors like the Negative Ion Time Projection Chambers (NITPCs). In this work, we present a description of the experimental setup and technique used, and the initial studies carried out in Xe-S F 6 mixtures, whose interest has attracted attention as a possible alternative in searches for the neutrinoless double-beta decay.

A bstract The NEXT experiment aims at the sensitive search of the neutrinoless double beta decay in 136 Xe, using high-pressure gas electroluminescent time projection chambers. The NEXT-White detector is the first radiopure demonstrator of this technology, operated in the Laboratorio Subterráneo de Canfranc. Achieving an energy resolution of 1% FWHM at 2.6 MeV and further background rejection by means of the topology of the reconstructed tracks, NEXT-White has been exploited beyond its original goals in order to perform a neu- trinoless double beta decay search. The analysis considers the combination of 271.6 days of 136 Xe-enriched data and 208.9 days of 136 Xe-depleted data. A detailed background modeling and measurement has been developed, ensuring the time stability of the radiogenic and cosmogenic contributions across both data samples. Limits to the neutrinoless mode are obtained in two alternative analyses: a background-model-dependent approach and a novel direct background-subtraction technique, offering results with small dependence on the background model assumptions. With a fiducial mass of only 3.50 ± 0.01 kg of 136 Xe-enriched xenon, 90% C.L. lower limits to the neutrinoless double beta decay are found in the $$ {T}_{1/2}^{0\nu } $$ T 1 / 2 0 ν > 5 . 5 × 10 23 − 1 . 3 × 10 24 yr range, depending on the method. The presented techniques stand as a proof-of-concept for the searches to be implemented with larger NEXT detectors.

Polytetrafluoroethylene (PTFE) is an excellent diffuse reflector widely used in light collection systems for particle physics experiments. In noble element systems, it is often coated with tetraphenyl butadiene (TPB) to allow detection of vacuum ultraviolet scintillation light. In this work this dependence is investigated for PTFE coated with TPB in air for light of wavelengths of 200 nm, 260 nm, and 450 nm. The results show that TPB-coated PTFE has a reflectance of approximately 92% for thicknesses ranging from 5 mm to 10 mm at 450 nm, with negligible variation as a function of thickness within this range. A cross-check of these results using an argon chamber supports the conclusion that the change in thickness from 5 mm to 10 mm does not affect significantly the light response at 128 nm. Our results indicate that pieces of TPB-coated PTFE thinner than the typical 10 mm can be used in particle physics detectors without compromising the light signal.

In this work, a new device developed to measure the transverse diffusion of electrons in gases is described. In this device, electrons are generated in a semitransparent cesium iodide (CsI) photocathode, exposed to xenon VUV light from a pulsed Xe lamp. Electrons are allowed to drift a fixed distance, which can be varied between 3.5 and 60 mm, and the charge is collected in a multistrip anode electrode. In the present work, we report the results obtained in xenon and in methane under reduced electric fields of 0.92 and 1.53 Td, for drift distances between 3.5 and 11.5 mm. The electron characteristic energy associated with the transverse diffusion, as measured with this new device, is 5.75 ± 0.45 eV and 7.15 ± 0.63 eV at 0.92 and 1.53 Td, respectively, for xenon and 0.065 ± 0.005 eV and 0.097 ± 0.008 eV at 0.92 and 1.53 Td, respectively, for methane, which are in good agreement with results from the literature.

The knowledge of the electron transverse diffusion in detection media is mandatory to assess the accuracy in systems that require precise event tracking. A new experimental system was developed to measure the transverse diffusion of electrons in gases. Electrons are generated in a transmissive CsI photocathode by Xe VUV light from a pulsed Xe lamp, and drift a fixed distance that can be varied from 4 to 60 mm. The charge is then multiplied in a GEM and collected in a multistrip target. The results were obtained for Xe and CH4 at two different E/N values, at 800 Torr, for drift distances between 4 and 12 mm. The characteristic energy associated with the transverse diffusion obtained were (5.75±0.45) eV and (7.15±0.63) eV for Xe, and (0.065±0.005) eV and (0.097±0.008) eV for CH4, respectively for 0.92 and 1.53 Td. All values are in good agreement with results from the literature.

We present a tunable metal ion beam that delivers controllable ion currents in the picoamp range for testing of dry-phase ion sensors. Ion beams are formed by sequential atomic evaporation and single or multiple electron impact ionization, followed by acceleration into a sensing region. Controllability of the ionic charge state is achieved through tuning of electrode potentials that influence the retention time in the ionization region. Barium, lead, and cadmium samples have been used to test the system, with ion currents identified and quantified using a quadrupole mass analyzer. Realization of a clean Ba 2+ ion beam within a bench-top system represents an important technical advance toward the development and characterization of barium tagging systems for neutrinoless double beta decay searches in xenon gas. This system also provides a testbed for investigation of novel ion sensing methodologies for environmental assay applications, with dication beams of Pb 2+ and Cd 2+ also demonstrated for this purpose.

A new experimental system was recently developed to measure the mobility of both positive and negative ions: the Dual-Polarity Ion Drift Chamber (DP-IDC). In this work, we present a detailed description of the experimental setup and technique used, as well as the initial studies carried out. The reduced ion mobilities of SF5− and SF6− were measured in pure SF6, SF6-CF4 and SF6-N2, for pressures between 10 and 30 Torr and reduced electric fields ranging from 10 to 40 Td. The results were compared with experimental and theoretical data available, and a good performance was found. The study of the mobility of positive ions in Ne-CF4 gas mixtures was also performed, with the results obtained showing a good agreement with those determined in a similar setup previously developed by our group. The importance of this type of studies is also discussed, along with the future prospects for this experimental system.

Electrode sectorization is an important design principle for large area GEM based detectors. It reduces the energy of discharges and permits to disconnect defective or shorted sectors, but induces a local signal distortion and a potential efficiency loss. We implemented and evaluated a new design approach for the insulating gaps between electrode sectors, to minimize or mitigate distortions and dead regions. By preserving the hole pattern of GEMs even in the insulating region between electrode sectors, the response of the detector in these regions was partly recovered resulting in reduced distortions. Single-side sectored GEMs were optically read out to study the influence of different sectorization patterns. Recorded images show a clear improvement with full holes both aligned with the rows and with a random alignment as compared to the traditional blank insulating strip between sectors. A sectored GEM manufactured on a substrate coated with a resistive DLC layer was evaluated and shown to minimize distortions. The investigated sectorization patterns provide a way of recovering signals in the insulating or resistive regions between sectors in GEM-based detectors.