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.
The Neutrino Experiment with a Xenon TPC (NEXT) searches for the neutrinoless double-beta (0νββ) decay of 136Xe using high-pressure xenon gas TPCs with electroluminescent amplification. A scaled-up ...version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of 0νββ decay better than 1027 years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.
We introduce a simulation framework for the transport of high and low energy electrons in xenon-based optical time projection chambers (OTPCs). The simulation relies on elementary cross sections ...(electron–atom and electron–molecule) and incorporates, in order to compute the gas scintillation, the reaction/quenching rates (atom–atom and atom–molecule) of the first 41 excited states of xenon and the relevant associated excimers, together with their radiative cascade. The results compare positively with observations made in pure xenon and its mixtures with CO2 and CF4 in a range of pressures from 0.1 to 10 bar. This work sheds some light on the elementary processes responsible for the primary and secondary xenon-scintillation mechanisms in the presence of additives, that are of interest to the OTPC technology.
The transmission efficiency of photoelectrons emitted from CsI photocathodes operated in Ar–CH
4 and Xe–CH
4 mixtures is experimentally investigated and compared to Monte Carlo simulation results; ...the ratio between the number of photoelectrons collected in the gas media and in vacuum is determined as a function of the pressure-reduced electric field
E/
p at the photocathode surface, for irradiation with the VUV photons from an Hg(Ar) lamp. The addition of a small percentage of CH
4 to Ar and Xe results in a significant increase of the photoelectron transmission, in particular for electric fields below
E/
p∼1
V
cm
−1
Torr
−1. Below
E/
p∼0.5
V
cm
−1
Torr
−1 the transmission efficiency
f in Ar–CH
4 mixtures reaches values higher than in pure CH
4, going through a maximum in the range of 10–30% CH
4. The addition of 5% and 20% CH
4 to Xe increases
f by a factor of about 2 and 3, respectively, when compared to pure Xe.
The imaging of individual Ba\(^{2+}\) ions in high pressure xenon gas is one possible way to attain background-free sensitivity to neutrinoless double beta decay and hence establish the Majorana ...nature of the neutrino. In this paper we demonstrate selective single Ba\(^{2+}\) ion imaging inside a high-pressure xenon gas environment. Ba\(^{2+}\) ions chelated with molecular chemosensors are resolved at the gas-solid interface using a diffraction-limited imaging system with scan area of 1\(\times\)1~cm\(^2\) located inside 10~bar of xenon gas. This new form of microscopy represents an important enabling step in the development of barium tagging for neutrinoless double beta decay searches in \(^{136}\)Xe, as well as a new tool for studying the photophysics of fluorescent molecules and chemosensors at the solid-gas interface.
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 \(^{83m}\text{Kr}\) 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 \(\pm\) 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.
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 \(^{83\mathrm{m}}\)Kr calibration electron captures (\(E\sim45\)keV), the position of origin of low-energy events is determined to \(2~\)cm precision with bias \(< 1\)mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks (E\(\geq\)1.5MeV), yielding a precision of 3cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1% FWHM at Q\(_{\beta\beta}\) 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.
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