A
bstract
NEXT-100 is an electroluminescent high-pressure xenon gas time projection chamber that will search for the neutrinoless double beta (0
νββ
) decay of
136
Xe. The detector possesses two ...features of great value for 0
νββ
searches: energy resolution better than 1% FWHM at the
Q
value of
136
Xe and track reconstruction for the discrimination of signal and background events. This combination results in excellent sensitivity, as discussed in this paper. Material-screening measurements and a detailed Monte Carlo detector simulation predict a background rate for NEXT-100 of at most 4 × 10
−4
counts keV
−1
kg
−1
yr
−1
. Accordingly, the detector will reach a sensitivity to the 0
νββ
-decay half-life of 2.8 × 10
25
years (90% CL) for an exposure of 100 kg·year, or 6.0 × 10
25
years after a run of 3 effective years.
The NEXT White (NEW) detector Monrabal, F.; Gómez-Cadenas, J.J.; Toledo, J.F. ...
Journal of instrumentation,
12/2018, Letnik:
13, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Conceived to host 5 kg of xenon at a pressure of 15 bar in the fiducial volume, the NEXT-White apparatus is currently the largest high pressure xenon gas TPC using electroluminescent amplification in ...the world. It is also a 1:2 scale model of the NEXT-100 detector for 136Xe ββ0ν decay searches, scheduled to start operations in 2019. Both detectors measure the energy of the event using a plane of photomultipliers located behind a transparent cathode. They can also reconstruct the trajectories of charged tracks in the dense gas of the TPC with the help of a plane of silicon photomultipliers located behind the anode. A sophisticated gas system, common to both detectors, allows the high gas purity needed to guarantee a long electron lifetime. NEXT-White has been operating since October 2016 at the Laboratorio Subterráneo de Canfranc (LSC), in Spain. This paper describes the detector and associated infrastructures, as well as the main aspects of its initial operation.
Abstract
In this paper, we report the development and performance of
a detector module envisaging a tritium-in-water real-time activity
monitor. The monitor is based on modular detection units whose
...number can be chosen according to the required sensitivity. The full
system is being designed to achieve a
Minimum Detectable
Activity
(
MDA
) of 100 Bq/L of tritium-in-water activity
which is the limit established by the E.U. Council Directive
2013/51/Euratom for water intended for human consumption. The same
system can be used as a real-time pre-alert system for nuclear power
plant regarding tritium-in water environmental surveillance. The
first detector module was characterized, commissioned and installed
immediately after the discharge channel of the Arrocampo dam
(Almaraz nuclear power plant, Spain) on the Tagus river. Due to the
high sensitivity of the single detection modules, the system
requires radioactive background mitigation techniques through the
use of active and passive shielding. We have extrapolated a
MDA
of 3.6 kBq/L for a single module being this value
limited by the cosmic background. The obtained value for a single
module is already compatible with a real-time environmental
surveillance and pre-alert system. Further optimization of the
single-module sensitivity will imply the reduction of the number of
modules and the cost of the detector system.
The calculated position resolutions for X-ray photons (1–60 keV) in pure noble gases at atmospheric pressure are presented. In this work we show the influence of the atomic shells and the detector ...dimensions on the intrinsic position resolution of the used noble gas. The calculated results were obtained by using a new software tool, Degrad, and compared to the available experimental data.
Abstract
A new design of a Gas Proportional Scintillation Counter (GPSC) for X-ray spectrometry is presented and a proof of concept is demonstrated. The proposed design is much simpler, having only ...one electrode, the anode. In addition, this electrode has an annular shape with its axis aligned with the photosensor axis. Since the scintillation region is limited to a small region near the anode, the solid angle subtended by the photocathode is similar relative to any position in the scintillation region and the amount of scintillation reaching the photosensor is independent from the position where the radiation interaction occurs. Standard GPSCs with uniform electric field design have the scintillation region parallel to the photosensor active area resulting in a dependence of the amount of light collected by the photosensor on the axial distance of the radiation interaction due to solid angle effects. These effects impose limitations on the size of the detector radiation window relative to the photosensor active area. Therefore, the annular anode allows to obtain a GPSC design with a larger radiation window relative to the photosensor area. A first GPSC prototype with a 10-cm diameter annular anode placed at a distance of 4.4 cm from the photosensor has an energy resolution of 14% for anode voltages of 8 kV and, according to simulations, it can reach 11% for anode voltages of 12 kV. This is worse than the values of 8–9% obtained with a standard GPSC which, on the other hand, have a window-to-photosensor diameter ratio lower than 0.8. Simulations have shown that the main factor degrading the energy resolution in this new design is the low number of photons impinging the photosensor due to the low solid angle subtended by the photosensor relative to the electroluminescence region of the detector. A compromise has to be made between the anode-to-photosensor diameter ratio as well as between the anode-to-photosensor distance and the energy resolution that can be achieved with the annular anode design.
The time-dependent gain variation of detectors incorporating Thick Gas Electron Multipliers (THGEM) electrodes was studied in the context of charging-up processes of the electrode's insulating ...surfaces. An experimental study was performed to examine model-simulation results of the aforementioned phenomena, under various experimental conditions. The results indicate that in a stable detector's environment, the gain stabilization process is mainly affected by the charging-up of the detector's insulating surfaces caused by the avalanche charges. The charging-up is a transient effect, occurring during the detector's initial operation period; it does not affect its long-term operation. The experimental results are consistent with the outcome of model-simulations.
Charging-up processes affecting gain stability in Thick Gas Electron Multipliers (THGEM) were studied with a dedicated simulation toolkit. Integrated with Garfield++, it provides an effective ...platform for systematic phenomenological studies of charging-up processes in MPGD detectors. We describe the simulation tool and the fine-tuning of the step-size required for the algorithm convergence, in relation to physical parameters. Simulation results of gain stability over time in THGEM detectors are presented, exploring the role of electrode-thickness and applied voltage on its evolution. The results show that the total amount of irradiated charge through electrode's hole needed for reaching gain stabilization is in the range of tens to hundreds of pC, depending on the detector geometry and operational voltage. These results are in agreement with experimental observations presented previously.
Experiments at the future Electron Ion Collider require excellent hadron identification in a broad momentum range, in harsh conditions. A RICH capable to fulfill the PID requirements of the EIC could ...use MPGD-based photon detectors with solid photocathodes for covering large surfaces at affordable cost, providing good effciency, high resolution and compatibility with magnetic field. Photon detectors realized by coupling THGEMs and Micromegas have been successfully operated at the RICH-1 detector of the COMPASS Experiment at CERN since 2016. A similar technology could be envisaged for an EIC RICH, provided a large improvement in the photon position resolution is achieved. An R&D effort in this direction is ongoing at INFN Trieste. Few prototypes with smaller pixel size (down to 3 mm x 3 mm) have been built and tested in the laboratory with X-Ray and UV LED light sources. A modular mini-pad detector prototype has also been tested at the CERN SPS H4 beamline. New data acquisition and analysis software called Raven DAQ and Raven Decoder have been developed and used with the APV-25 based Scalable Readout System (SRS), for the modular mini-pad prototype tests. The main characteristics of the new mini-pad hybrid MPGD-based detector of single photons are described and preliminary results of laboratory and beam tests are presented.
The response of a sealed MicroPatterned Gaseous Detector (MPGD), with an enclosed gas purification system based on getters, was monitored for several weeks. An average of 2 discharges per day was ...registered during the monitoring period and the charge gain varied a maximum of 15% during the more stable period. The temperature of the getters was varied from 180ˆC to 250ˆC and no significant influence was registered in the detector response. A reactivation of the getters also did not affect the charge gain, which means that their gettering rate was at full efficiency before the reactivation. However, careful attention is paid to charge gain reduction for long times of operation which can denote a loss of getters efficiency along time and the need of getter reactivation. On the other hand, turning off the getters lead to a rapid decrease in the charge gain. This allows concluding that a purification system based on getters is really effective in removing gas impurities, being a crucial component of the detection system for a sealed gaseous detector.
Gaseous time projection chambers (TPC) are a very attractive detector technology for particle tracking. Characterization of both drift velocity and diffusion is of great importance to correctly ...assess their tracking capabilities. NEXT-White is a High Pressure Xenon gas TPC with electroluminescent amplification, a 1:2 scale model of the future NEXT-100 detector, which will be dedicated to neutrinoless double beta decay searches. NEXT-White has been operating at Canfranc Underground Laboratory (LSC) since December 2016. The drift parameters have been measured using 83mKr for a range of reduced drift fields at two different pressure regimes, namely 7.2 bar and 9.1 bar. The results have been compared with Magboltz simulations. Agreement at the 5% level or better has been found for drift velocity, longitudinal diffusion and transverse diffusion.
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