arXiv subjects

D. González-Díaz

Publications and source records attributed to D. González-Díaz.

At least 19 recordsLinked to original sources

arXiv2026

Production of GEM-like structures for cryogenic applications, using laser-cutting techniques

A novel concept for electroluminescence (EL) structures was recently proposed. In it, a wavelength-shifting material is deposited inside the holes of GEM-like structures which, after suitable optical treatment of its electrodes, improves the light collection and detection efficiency in noble gas TPCs. This new development directly addresses problems related with the scalability of future dual-phase TPCs for rare-event searches, matching (and potentially exceeding) the performance of conventional EL techniques. We report the newest developments on the production of such structures using laser-based techniques, namely the manufacture of a first batch of the so-called FAT-GEMs. This process allows low-cost and reproducible manufacturing of a high volume of such structures. In addition to the detailed description of the production, we present a performance assessment in pure argon, at a gas density close to the one expected in LAr conditions. An energy resolution of 23.5$\pm$1~\% (FWHM) at 5.9~keV was obtained, indicating a consistent improvement over previous batch. The optical treatment of the electrode surfaces has been greatly simplified and modestly improved, while charging-up effects arising from the use of laminates eliminated.

physics.ins-det↗

arXiv2025

Gas contamination and mitigation in a 100 m$^3$ / 10 bar argon TPC with optical readout: a viability study

Gaseous Optical Time Projection Chambers (OTPCs) aimed at Neutrino Physics and Rare Event Searches will likely exceed the tonne scale during the next decade. This will make their performance sensitive to gas contamination levels as low as 100 ppb, that is challenging at room temperature due to outgassing from structural materials. In this work we discuss gas distribution and impurity mitigation in a 5 m-length/5 m-diameter 10 bar TPC filled with Ar/CF$_4$ admixed at 99/1 per volume (1.75 tonne), loaded with technical plastics in order to enhance light collection and readout. Different distributor topologies, outgassing and flow rates are discussed. Specifically, our work is aimed at illustrating the conceptual viability of the optical readout of ND-GAr's TPC (within the DUNE Near-Detector complex), in terms of material compatibility. For our proposal, with perforated distributors aligned with the electric field, and under realistic assumptions, the concentration of contaminants can be controlled within a week after chamber filling. In the case of N$_2$, injection of fresh gas at %-level seems to represent the safest strategy to keep the concentration within operability limits.

physics.ins-det↗

arXiv2024

On the determination of the interaction time of GeV neutrinos in large argon gas TPCs

Next-generation megawatt-scale neutrino beams open the way to studying neutrino-nucleus scattering using gaseous targets for the first time. This represents an opportunity to improve the knowledge of neutrino cross sections in the energy region between hundreds of MeV and a few GeV, of interest for the upcoming generation of long-baseline neutrino oscillation experiments. The challenge is to accurately track and (especially) time the particles produced in neutrino interactions in large and seamless volumes down to few-MeV energies. We propose to accomplish this through an optically-read time projection chamber (TPC) filled with high-pressure argon and equipped with both tracking and timing functions. In this work, we present a detailed study of the time-tagging capabilities of such a device, based on end-to-end optical simulations that include the effect of photon propagation, photosensor response, dark count rate and pulse reconstruction. We show that the neutrino interaction time can be reconstructed from the primary scintillation signal with a precision in the range of 1-2.5 ns ($σ$) for point-like deposits with energies down to 5 MeV. A similar response is observed for minimum-ionizing particle tracks extending over lengths of a few meters. A discussion on previous limitations towards such a detection technology, and how they can be realistically overcome in the near future thanks to recent developments in the field, is presented. The performance demonstrated in our analysis seems to be well within reach of next-generation neutrino-oscillation experiments, through the instrumentation of the proposed TPC with conventional reflective materials and a silicon photomultiplier array behind a transparent cathode.

physics.ins-det↗

arXiv2024

Primary scintillation yields induced by $α$ particles in gas mixtures of Argon/CF$_4$ at 9.5 bar

We report time and band-resolved scintillation from $α$-particles in Ar/CF$_4$ mixtures at a pressure of 9.5 bar. Our results show that %-level addition of CF$_4$ enables strong wavelength-shifted scintillation in the visible range, with yields at the level of 1000 ph/MeV, scintillation decay times of 9-25 ns and formation times well below 10 ns. Such a performance is a priori sufficient for accurate time-tagging of MeV-particles, without the need to resort to a pure noble gas, thus opening an appealing technological path for next-generation time projection chambers.

physics.ins-det↗

arXiv2024

Abundances in eight bulge stars from the optical and near-infrared

Context: The abundances of the $α$-elements are key for understanding the early chemical enrichment of the Galactic bulge. The elements of interest present lines in different wavelength regions, and some of them show lines only in part of the spectra. In the present work, the CNO trio, the alpha-elements Mg, Si, Ca, and Ti, and odd-Z Na and Al are examined as measured from optical and H-band lines. Aims: The aim of this work is to carry out a detailed comparison of stellar parameters and abundances derived in the optical and near-infrared (H-band). We also inspect the best available lines for a list of bulge stars previously analyzed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) team in the H-band and by our group in the optical. This work is mainly of interest to spectroscopists. Methods: In the present work, we compared the stellar parameters and abundance results derived from APOGEE H-band spectra with optical analyses based on Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope (VLT/UVES) data for eight bulge stars. Results:We point out the most suitable wavelength region for each of the studied elements, and highlight difficulties in the derivation of stellar parameters both in the optical and H-band. The near-infrared will allow observations of a large number of stars in the near future given new instruments soon to be available. The identification of spectral lines in this spectral region and the investigation of their reliability are ongoing efforts worldwide. New instruments will also allow simultaneous observation of H-band and optical.

astro-ph.SR↗

arXiv2024

Scintillation of Ar/CF$_4$ mixtures: glass-THGEM characterization with 1% CF$_4$ at 1-1.5 bar

Argon gas doped with 1% wavelength-shifter (CF$_4$) has been employed in an optical time projection chamber (OTPC) to image cosmic radiation. We present results obtained during the system commissioning, performed with two stacked glass-THGEMs and an EMCCD camera at 1 bar. Preliminary estimates indicate that the combined optical gain was of the order of 10$^6$ (ph/e), producing sharp and high-contrast raw images without resorting to any filtering or post-processing. A first assessment of the impact of pressurization showed no change in the attainable gains when operating at 1.5 bar

physics.ins-det↗

arXiv2024

FAT-GEMs: (Field Assisted) Transparent Gaseous-Electroluminescence Multipliers

The idea of implementing electroluminescence-based amplification through transparent multi-hole structures (FAT-GEMs) has been entertained for some time. Arguably, for such a technology to be attractive it should perform at least at a level comparable to conventional alternatives based on wires or meshes. We present now a detailed calorimetric study carried out for 5.9~keV X-rays in xenon, for pressures ranging from 2 to 10~bar, resorting to different geometries, production and post-processing techniques. At a reference voltage 5~times above the electroluminescence threshold ($E_{EL,th}\sim0.7$~kV/cm/bar), the number of photoelectrons measured for the best structure was found to be just 18\%~below that obtained for a double-mesh with the same thickness and at the same distance. The energy resolution stayed within 10\% (relative) of the double-mesh value. An innovative characteristic of the structure is that vacuum ultraviolet (VUV) transparency of the polymethyl methacrylate (PMMA) substrate was achieved, effectively, through tetraphenylbutadiene (TPB) coating of the electroluminescence channels combined with indium tin oxide (ITO) coating of the electrodes. This resulted in a $\times 2.25$-increased optical yield (compared to the bare structure), that was found to be in good agreement with simulations if assuming a TPB wavelength-shifting-efficiency at the level of WLSE=0.74-1.28, compatible with expected values. This result, combined with the stability demonstrated for the TPB coating under electric field (over 20~h of continuous operation), shows great potential to revolutionize electroluminescence-based instrumentation.

physics.ins-det↗

arXiv2023

Development of Fe$_2$O$_3$/YSZ ceramic plates for cryogenic operation of resistive-protected gaseous detectors

We present a ceramic material based on hematite (Fe$_2$O$_3$) and zirconia stabilized with yttria at 8% molar (YSZ), that exhibits stable electrical properties with transported charge and that can be tuned to the resistivities necessary to induce spark-quenching in gaseous detectors ($ρ= 10^9-10^{12}$ $Ω\cdot$cm), from room temperature down to the liquid-vapor coexistence point of nitrogen (77 K). It, thus, allows covering the operating temperatures of most immediate interest to gaseous instrumentation. The ceramics have been produced in a region of mass concentrations far from what has been usually explored in literature: optimal characteristics are achieved for Fe$_2$O$_3$ concentrations of 75%wt (LAr boiling temperature), 35%wt (LXe boiling temperature), and 100%wt (room temperature). The nine order of magnitude enhancement observed for the electrical conductivity of the mixed phases relative to that of pure Fe$_2$O$_3$ is startling, however it can be qualitatively understood based on existing literature. Plates of 4 cm x 4 cm have been manufactured and, prior to this work, operated in-detector at the LXe boiling point (165 K), demonstrating spark-free operation. Preliminary results obtained for the first time on a spark-protected amplification structure (RP-WELL) at around the LAr boiling point (90 K) are now presented, too.

physics.ins-det↗

arXiv2023

Observation of strong wavelength-shifting in the argon-tetrafluoromethane system

We report the scintillation spectra of Ar-CF$_4$ mixtures in the range 210-800~nm, obtained under X-ray irradiation for various pressures (1-5~bar) and concentrations (0-100%). Special care was taken to eliminate effects related to space charge and recombination, so that results can be extrapolated following conventional wisdom to those expected for minimum ionizing particles under the typical electric fields employed in gaseous instrumentation. Our study sheds light into the microscopic pathways leading to scintillation in this family of mixtures.

physics.ins-det↗

arXiv2023

NEXT-CRAB-0: A High Pressure Gaseous Xenon Time Projection Chamber with a Direct VUV Camera Based Readout

The search for neutrinoless double beta decay ($0νββ$) 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 $0νββ$ 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 $0νββ$.

physics.ins-det↗

arXiv2022

Measurement of the ${}^{136}$Xe two-neutrino double beta decay half-life via direct background subtraction in NEXT

We report a measurement of the half-life of the ${}^{136}$Xe two-neutrino double beta decay performed with a novel direct background subtraction technique. The analysis relies on the data collected with the NEXT-White detector operated with ${}^{136}$Xe-enriched and ${}^{136}$Xe-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of $2.34^{+0.80}_{-0.46}\textrm{(stat)}^{+0.30}_{-0.17}\textrm{(sys)}\times10^{21}~\textrm{yr}$ is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double beta decay searches.

nucl-ex↗

arXiv2022

Development of very-thick transparent GEMs with wavelength-shifting capability for noble element TPCs

A new concept for the simultaneous detection of primary and secondary scintillation in time projection chambers is proposed. Its core element is a type of very-thick GEM structure supplied with transparent electrodes and machined from a polyethylene naphthalate plate, a natural wavelength-shifter. Such a device has good prospects for scalability and, by virtue of its genuine optical properties, it can improve on the light collection efficiency, energy threshold and resolution of conventional micropattern gas detectors. This, together with the intrinsic radiopurity of its constituting elements, offers advantages for noble gas and liquid based time projection chambers, used for dark matter searches and neutrino experiments. Production, optical and electrical characterization, and first measurements performed with the new device are reported.

physics.ins-det↗

arXiv2022

Time and band-resolved scintillation in time projection chambers based on gaseous xenon

We present a systematic study of the time and band-resolved scintillation in xenon-based time projection chambers (TPCs), performed simultaneously for the primary (S1) and secondary (S2) components in a small, purity-controlled, setup. We explore a range of conditions of general academic interest, focusing on those of relevance to contemporary TPCs: pressure range ([1- 10] bar), pressure-reduced electric fields ([0-100] V/cm/bar in the drift region (S1) and up to the proportional scintillation regime in the multiplication region (S2)), wavelength-band ([145-250], [250-400], [400-600] nm), and primary excitation ($α$, $β$-particles). Attention is paid to the possibility of non-conventional scintillation mechanisms such as the 3rd continuum emission, recombination light from $β$-electrons at high pressure (for S1), emission from high-lying excited states and neutral bremsstrahlung (for S2). Time constants and, specially, scintillation yields have been obtained as a function of electric field and pressure, the latter aided by Geant4 simulations.

physics.ins-det↗

arXiv2022

Ba$^{2+}$ ion trapping by organic submonolayer: towards an ultra-low background neutrinoless double beta decay detector

If neutrinos are their own antiparticles, the otherwise-forbidden nuclear reaction known as neutrinoless double beta decay ($ββ0ν$) can occur, with a characteristic lifetime which is expected to be very long, making the suppression of backgrounds a daunting task. It has been shown that detecting (``tagging'') the Ba$^{+2}$ dication produced in the double beta decay ${}^{136}\mathrm{Xe} \rightarrow {}^{136}$Ba$^{+2}+ 2 e + (2 ν)$ in a high pressure gas experiment, could lead to a virtually background free experiment. To identify these \Bapp, chemical sensors are being explored as a key tool by the NEXT collaboration . Although used in many fields, the application of such chemosensors to the field of particle physics is totally novel and requires experimental demonstration of their suitability in the ultra-dry environment of a xenon gas chamber. Here we use a combination of complementary surface science techniques to unambiguously show that Ba$^{+2}$ ions can be trapped (chelated) in vacuum by an organic molecule, the so-called fluorescent bicolour indicator (FBI) (one of the chemosensors developed by NEXT), immobilized on a surface. We unravel the ion capture mechanism once the molecules are immobilised on Au(111) surface and explain the origin of the emission fluorescence shift associated to the trapping of different ions. Moreover, we prove that chelation also takes place on a technologically relevant substrate, as such, demonstrating the feasibility of using FBI indicators as building blocks of a Ba$^{+2}$ detector.

hep-ex↗

arXiv2021

Neutral Bremsstrahlung in TPCs

Traditionally, it has been assumed that electroluminescence (EL) in time projection chambers was purely an excimer-based emission. This idea changed when neutral bremsstrahlung (NBrS) was observed first in argon and subsequently in xenon a few years ago. In this work we explore further the framework used to explain these observations, presenting results for noble gas -based mixtures, as well as mixtures including small fractions of a molecular additive (`quencher'). Spectral content and yields are discussed in some cases of contemporary interest, together with their pressure-scalings.

physics.ins-det↗

arXiv2021

The Dynamics of Ions on Phased Radio-frequency Carpets in High Pressure Gases and Application for Barium Tagging in Xenon Gas Time Projection Chambers

Radio-frequency (RF) carpets with ultra-fine pitches are examined for ion transport in gases at atmospheric pressures and above. We develop new analytic and computational methods for modeling RF ion transport at densities where dynamics are strongly influenced by buffer gas collisions. An analytic description of levitating and sweeping forces from phased arrays is obtained, then thermodynamic and kinetic principles are used to calculate ion loss rates in the presence of collisions. This methodology is validated against detailed microscopic SIMION simulations. We then explore a parameter space of special interest for neutrinoless double beta decay experiments: transport of barium ions in xenon at pressures from 1 to 10 bar. Our computations account for molecular ion formation and pressure dependent mobility as well as finite temperature effects. We discuss the challenges associated with achieving suitable operating conditions, which lie beyond the capabilities of existing devices, using presently available or near-future manufacturing techniques.

physics.ins-det↗

arXiv2021

Boosting background suppression in the NEXT experiment through Richardson-Lucy deconvolution

Next-generation neutrinoless double beta decay experiments aim for half-life sensitivities of ~$10^{27}$ yr, requiring suppressing backgrounds to <1 count/tonne/yr. For this, any extra background rejection handle, beyond excellent energy resolution and the use of extremely radiopure materials, is of utmost importance. The NEXT experiment exploits differences in the spatial ionization patterns of double beta decay and single-electron events to discriminate signal from background. While the former display two Bragg peak dense ionization regions at the opposite ends of the track, the latter typically have only one such feature. Thus, comparing the energies at the track extremes provides an additional rejection tool. The unique combination of the topology-based background discrimination and excellent energy resolution (1% FWHM at the Q-value of the decay) is the distinguishing feature of NEXT. Previous studies demonstrated a topological background rejection factor of ~5 when reconstructing electron-positron pairs in the $^{208}$Tl 1.6 MeV double escape peak (with Compton events as background), recorded in the NEXT-White demonstrator at the Laboratorio Subterráneo de Canfranc, with 72% signal efficiency. This was recently improved through the use of a deep convolutional neural network to yield a background rejection factor of ~10 with 65% signal efficiency. Here, we present a new reconstruction method, based on the Richardson-Lucy deconvolution algorithm, which allows reversing the blurring induced by electron diffusion and electroluminescence light production in the NEXT TPC. The new method yields highly refined 3D images of reconstructed events, and, as a result, significantly improves the topological background discrimination. When applied to real-data 1.6 MeV $e^-e^+$ pairs, it leads to a background rejection factor of 27 at 57% signal efficiency.

physics.ins-det↗

arXiv2021

Sensitivity of the NEXT experiment to Xe-124 double electron capture

Double electron capture by proton-rich nuclei is a second-order nuclear process analogous to double beta decay. Despite their similarities, the decay signature is quite different, potentially providing a new channel to measure the hypothesized neutrinoless mode of these decays. The Standard-Model-allowed two-neutrino double electron capture ($2νECEC$) has been predicted for a number of isotopes, but only observed in $^{78}$Kr, $^{130}$Ba and, recently, $^{124}$Xe. The sensitivity to this decay establishes a benchmark for the ultimate experimental goal, namely the potential to discover also the lepton-number-violating neutrinoless version of this process, $0νECEC$. Here we report on the current sensitivity of the NEXT-White detector to $^{124}$Xe $2νECEC$ and on the extrapolation to NEXT-100. Using simulated data for the $2νECEC$ signal and real data from NEXT-White operated with $^{124}$Xe-depleted gas as background, we define an optimal event selection that maximizes the NEXT-White sensitivity. We estimate that, for NEXT-100 operated with xenon gas isotopically enriched with 1 kg of $^{124}$Xe and for a 5-year run, a sensitivity to the $2νECEC$ half-life of $6 \times 10^{22}$ y (at 90% confidence level) or better can be reached.

hep-ex↗