Gas Gap Research Articles

Fine tuning of gas system and performance studies of RPC detectors in the INO's mini-ICAL detector

The India-based Neutrino Observatory's (INO) Iron CALorimeter (ICAL) experiment will be instrumented with about 28,800 large area glass Resistive Plate Chambers (RPCs) as active detector elements. The mini-ICAL, which is a 600-times scaled-down prototype version of the ICAL, is currently in operation at the Inter Institutional Centre for High Energy Physics (IICHEP), a transit campus of the INO project in Madurai, India. The 4 m×4 m detector comprises an ∼ 85 t magnet, built using 11 layers of iron plates to accommodate 10 layers of RPCs — two RPCs per layer. A closed-loop gas system (CLS) is designed to supply gas mixture of R134a (95.2%), isobutane (4.5%), and SF 6 (0.3%) to the mini-ICAL, collect the return gas from the RPCs, purify it using filters, and recirculate the mixture into the detector. Contamination of any kind into the gas mixture will severely affect the characteristics of the RPC detectors, such as the dark current and noise rates, and consequently deteriorate performance of the RPC detector. The contamination is mainly caused due to leaks within the gas system, in the gas lines and in the RPC gas gap volume. This paper deals with systematic identification and mitigation of leaks within the closed-loop gas system and performance improvement of the RPCs installed in the mini-ICAL detector.

Commissioning and first measurements with LHC collisions of BIS78 RPCs, an innovative detector for ATLAS HL-LHC upgrades

The BIS78 project, BI pilot project, consists of 16 sMDT + RPC chambers installed in the barrel–endcap transition region with the function of helping in the reduction of the fake muons produced upstream of the cryostats. The BIS78 RPCs represents a new generation of RPCs, basing their largely improved performance on a novel and highly performing front-end (FE) electronics, which is able to detect 1-2 fC of induced signals increasing rate capability by a factor of 10 with respect to the present ATLAS RPCs. BIS78 are equipped with a gas gap 1 mm thick, granting a time resolution of 350 ps and less weight and space occupancy. Additionally, the new electronics could make the BIS78 apparatus more easily compatible with the new eco-gas mixtures. The entire BIS78 apparatus has been installed successfully in the ATLAS experimental cavern and its commissioning will be illustrated along with its performance at the beginning of LHC Run-3.

Exploring the Potential of Metal-Organic Frameworks for Cryogenic Helium-Based Gas Gap Heat Switches via High-Throughput Computational Screening.

With the advantages of a long lifetime and high reliability, gas gap heat switches (GGHSs) are attractive in many thermal management applications, especially in space-borne cryogenic systems. The performance of a GGHS is significantly affected by the adsorption characteristics of the adsorbent in the sorption pump. Compared with the commonly used adsorbent in the GGHSs (activated carbon), metal-organic frameworks (MOFs) have larger surface areas, higher pore volumes, and exceptional tunability, which motivates this study to explore their potential for application in cryogenic GGHSs. To this end, two performance metrics, the required volume of adsorbent (vsor) and total input heat (qtot), were computed for about 6000 MOFs via molecular simulations and compared with those of activated carbon. It is found that over 2300 MOFs possess a smaller vsor than activated carbon, and the smallest vsor of MOFs is about 12.7% of that of activated carbon. vsor and qtot generally change in the same direction, which implies it is possible to reduce both parameters simultaneously by choosing a suitable MOF. Structure-performance analysis reveals that 1/vsor consistently increases first and then decreases with pore limiting diameter, largest cavity diameter, available pore volume, accessible surface area, helium void fraction, and bulk density. Descriptor ranges corresponding to high-performing MOFs were identified based on Precision-Recall analysis. Notably, Zr-containing MOFs are particularly likely to have smaller vsor values than activated carbon. It is anticipated that the promising MOFs identified by this study will motivate further experimental investigations, and the insights into structure-performance relationships can serve to guide the rational design of novel MOF candidates for GGHSs.

Numerical simulation and experimental validation of the heat transfer characteristics in a circuit gas gap heat switch for the dilution refrigerator

The gas gap heat switch (GGHS) used for controlling heat transfer between different stages can be an important component for the precooling process of some dilution refrigerators. In this paper, a novel circuit GGHS is a rotationally symmetric heat switch assembly with annular fin arrangements to strengthen the heat-transferring effect. A numerical model considering 4He actual gas properties is proposed to investigate the heat transfer characteristics in the circuit GGHS, in which the effects of charge pressure, cold end temperature, thickness and length of walls on the mean thermal conductance (MTC) are studied. Simulation results show that the MTC increases with the growing cold end temperature, wall thickness, and length, respectively. Given the pressure of 10 kPa, cold end temperature of 4.2 K, wall thickness of 0.97 mm, and wall height of 66 mm, the theoretical MTC is 0.828 W/K. Experimental results indicate that the proposed simulation model is reasonable. Furthermore, the increment of the MTC decreases with the growing temperature. The GGHS used in experiments had a cold end temperature of 4 K, wall thickness of 0.65 mm, and wall height of 33 mm; the measured MTC was 0.219 W/K. Only when the temperature is above 10 K does the charge pressure have a pronounced effect on the MTC. This study provides helpful theoretical guidance for the design and optimization of the circuit GGHS.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

The readout panels for the BI-RPC project for ATLAS Phase-II upgrade

To take full advantage from the LHC upgrade to high luminosity in 2029, the ATLAS community has approved an intensive detector upgrade program that includes the construction of an additional trigger layer positioned close to the BI MDT chambers of the muon spectrometer. These chambers are RPC with thin gas gap, thin High Pressure Laminate electrodes coated with graphite on one side, and only use strips orthogonal to the beam-axis to reconstruct the eta and phi coordinates of the detector point where an ionizing particle passes. A detailed description of the construction and validation of these strip panels in China and Italy assembly sites, is presented here.

Addressing the gaseous and odour emissions gap in decentralised biowaste community composting

Composting has demonstrated to be an effective and sustainable technology to valorise organic waste in the framework of circular economy, especially for biowaste. Composting can be performed in various technological options, from full-scale plants to community or even individual composters. However, there is scarce scientific information about the potential impact of community composting referred to gaseous emissions. This work examines the emissions of methane and nitrous oxide as main GHG, ammonia, VOC and odours from different active community composting sites placed in Spain, treating kitchen, leftovers and household biowaste. Expectedly, the gaseous emissions have an evident relation with the composting progress, represented mainly by its decrease as temperature or biological activity decreases. GHG and odour emission rates ranged from 5.3 to 815.2 mg CO2eq d-1 kg-1VS and from 69.8 to 1088.5 ou d-1 kg-1VS, respectively, generally being lower than those find in open-air full-scale composting. VOC characterization from the community composting gaseous emissions showed a higher VOC families’ distribution in the emissions from initial composting phases, even though terpenes such as limonene, α-pinene and β-pinene were the most abundant VOC along the composting process occurring in the different sites studied. The results presented in this study can be the basis to evaluate systematically and scientifically the numerous current projects for a worldwide community composting implementation in decentralised biowaste management schemes.

Conceptual design and supporting analysis of a double wall heat exchanger for an ARC-class fusion reactor Primary cooling system

In the fight against climate change through the progress of fusion technology, the Affordable, Robust and Compact (ARC) fusion reactor design is under development at Commonwealth Fusion Systems (CFS) and Massachusetts Institute of Technology (MIT)- Plasma Science and Fusion Center, in collaboration with the Ente Nazionale Idrocarburi (ENI) S.p.A. The reactor features demountable superconducting toroidal field coils and a replaceable vacuum vessel immersed in a Fluorine Lithium Beryllium (FLiBe) molten salt blanket. The low-pressure molten salt cools the divertors and the blanket, shields the magnets and acts as tritium breeder and tritium carrier. Tritium must be recovered efficiently from the salt to fuel the reactor, minimizing its inventory and its migration outside the FLiBe loop. The current work is aimed at presenting a preliminary design of a Double-Wall Heat eXchanger (DWHX) to be installed in an ARC-class reactor primary cooling system. The main feature is the presence of a flowing sweep gas gap which captures tritium and prevents its diffusion toward the secondary system. For the DWHX, thermal-hydraulic and tritium transport analyses were performed, considering a supercritical water Rankine power conversion system on the secondary side to carry out the calculations. To assess tritium extraction capabilities of the DWHX, the tritium extraction efficiency has been evaluated. Calculation results highlighted how the current configuration is not adequate to remove tritium, in fact the tritium extraction efficiency is very low. On the other side, it seems to act adequately as tritium permeation barrier.

A very thin MRPC developed for TOF-PET

PET (Positron Emission Tomography) is a medical molecular imaging modality employed in cancer diagnosis and monitoring. Multi-gap Resistive Plate Chambers (MRPCs) are utilized in Time of Flight (TOF)-PET due to their superior time resolution. Our research group has successfully developed a 4-chamber 32-gap MRPC prototype with 0.128 mm gap thickness. The measured time resolution for cosmic rays is 20 ps, while the time resolution for the time difference between 0.511 MeV photon pairs is 193 ps Full Width at Half Maximum (FWHM). The 23.6 mm thickness of the MRPC prototype will affect the time resolution. To investigate the influence of the number and total thickness of gas gaps on the time resolution, Geant4 software is used to simulate the interaction between particles (such as cosmic rays and photons) and MRPC detectors. Most of the gamma photons interact with the resistive plates in MRPCs. It is ejected mostly a Compton electron into one gas gap, causing the gas ionization. In this paper, two 8-gap MRPC prototypes with 0.128 mm gap thickness and 4.2 mm total thickness are fabricated and tested. The time resolution of 39 ps for cosmic rays and 166 ps FWHM for 0.511 MeV photons is obtained using the fast front-end amplifier and waveform acquisition system. So, a real time PET image can be obtained with a pair of MRPCs, and the detection efficiency for gamma can be improved by increasing the number of thin MRPCs.

A dielectric barrier discharge based low pressure narrow band far UV-C 222 nm excimer lamp and its efficiency analysis

Far UV-C light at wavelength 222 nm is gaining popularity nowadays due to its properties that it cannot penetrate even the outer dead skin of humans and the tear layer of the eyes. This wavelength has been proven to be much safer for human health. In this paper, a dielectric barrier discharge (DBD) based Far UV-C excimer lamp with a very narrow and intense spectrum peaking at a wavelength of 222 nm has been reported. Optimization of high voltage electrodes has been carried out to minimize the lamp heating without using any external cooling. The discharge produced in this configuration is diffused discharge at a low pressure of 140 mbar. Generally, at low pressure, a very wide band of spectra having full-width half maxima (FWHM) of 8–15 nm is obtained. In this case, due to the confined gas gap and bi-polar pulse power arrangements, the spectra obtained are very narrow, having an FWHM of 1.7 nm. Applied voltage, frequency and gas pressure are optimized to get high electrical-to-optical conversion efficiency of the lamp. The measured radiated intensity at the applied input electrical power of 31 W from the optimized lamp is ∼2.5 mW cm−2, which results in the electrical to optical conversion efficiency as high as 12.5%. The bacterial efficiency of the developed lamp is also examined on pathogenic gram-positive (S. aureus) and gram-negative (E. coli) bacteria. Complete inactivation of S. aureus and E. coli has been achieved at a UV dose of 3 mJ/cm2 and 12 mJ cm–2, respectively. Morphological studies of treated bacteria have also been performed to correlate the results.

Electrostatically actuated all metal MEMS Pirani gauge with tunable dynamic range

An electrostatically actuated all-metal microelectromechanical systems (MEMS) Pirani gauge with a tunable dynamic range is proposed. Contrary to the conventional fixed gap Pirani gauges, an electrostatic mechanism is employed to tune the gaseous conduction gap. Due to the electrostatic force between the heating element and heat sink, this tuning results in shifting the transition pressure to a higher pressure. As a result, the operating range of the Pirani gauge can be tuned depending on the magnitude of the actuation voltage. Theoretical estimation of the transition pressure corresponding to different gaseous conduction gaps is also presented. Depending on the available margin of gap tuning, the electromechanical and electrothermal analyses are carried out in COMSOL Multiphysics. The analytical approach is validated by experimentally characterizing the fabricated device. The experimentally tested device with the proposed actuation mechanism shows an 11.2 dB increase in dynamic range in comparison to the conventional design. In a complementary metal-oxide-semiconductor (CMOS)-compatible fabrication process flow, the proposed gauge can be used to monitor vacuum from 40 Pa to 5 × 105 Pa with the electrostatic actuation.

Energy Reconstruction with Semi-Supervised Autoencoders for Dual-Phase Time Projection Chambers

Energy Reconstruction with Semi-Supervised Autoencoders for Dual-Phase Time Projection Chambers

The Dependence of the Structure of Planet-opened Gaps in Protoplanetary Disks on Radiative Cooling

Planets can excite density waves and open annular gas gaps in protoplanetary disks. The depth of gaps is influenced by the evolving angular momentum carried by density waves. While the impact of radiative cooling on the evolution of density waves has been studied, a quantitative correlation to connect gap depth with the cooling timescale is lacking. To address this knowledge gap, we employ the grid-based code Athena++ to simulate disk-planet interactions, treating cooling as a thermal relaxation process. We establish quantitative dependencies of steady-state gap depth (Equation 36) and width (Equation 41) on planetary mass, Shakura–Sunyaev viscosity, disk scale height, and thermal relaxation timescale (β). We confirm previous results that gap opening is the weakest when the thermal relaxation timescale is comparable to the local dynamical timescale. Significant variations in gap depth, up to an order of magnitude, are found with different β. In terms of width, a gap is at its narrowest around β = 1, approximately 10%–20% narrower compared to the isothermal case. When β ∼ 100, it can be ∼20% wider, and higher viscosity enhances this effect. We derive possible masses of the gas gap-opening planets in AS 209, HD 163296, MWC 480, and HL Tau, accounting for the uncertainties in the local thermal relaxation timescale.

Measuring gas discharge in contact electrification

Contact electrification in a gas medium is usually followed by partial surface charge dissipation caused by dielectric breakdown of the gas triggered during separation of the surfaces. It is widely assumed that such discharge obeys the classical Paschen’s law, which describes the general dependence of the breakdown voltage on the product of gas pressure and gap distance. However, quantification of this relationship in contact electrification involving insulators is impeded by challenges in nondestructive in situ measurement of the gap voltage. The present work implements an electrode-free strategy for capturing discrete discharge events by monitoring the gap voltage via Coulomb force, providing experimental evidence of Paschen curves governing nitrogen breakdown in silicone-acrylic and copper-nylon contact electrification. It offers an alternative approach for characterizing either the ionization energies of gases or the secondary-electron-emission properties of surfaces without the requirement of a power supply, which can potentially benefit applications ranging from the design of insulative materials to the development of triboelectric sensors and generators.

Mechanisms for insulation recovery during repetitive breakdowns in gas gaps

The insulation recovery during repetitive breakdowns in gas gaps is a fundamental scientific issue in both traditional and emerging electrical technology fields, which has received extensive attention over the years. This paper provides a systematic review of research methods for insulation recovery in repetitive breakdowns of gas gaps, progress made in understanding the thermal–hydrodynamic processes involved in this recovery (dissipation of deposited energy and restoration of neutral gas density), as well as the memory effect resulting from repetitive discharges and breakdowns (dominant factors and their underlying mechanisms). Based on current results, it is proposed that the insulation recovery of repetitive gas gaps breakdowns results from the synergistic effect between post-breakdown thermal-hydrodynamic processes and memory effects. This review aims to clarify the boundary and interplay between hydrodynamic processes and memory effects, as well as reveal their coupling relationship and synergistic mechanism. It also seeks to overcome barriers between related research fields, ultimately facilitating a resolution to the issue.

Spatio-temporal dynamics of electrons and helium metastables in uniform dielectric barrier discharges formed in He/N2

A uniform atmospheric pressure dielectric barrier discharge is operated in helium with an admixture (0.45%) of nitrogen. The discharge is ignited in the gas gap between a driven and a grounded electrode and propagates along the dielectric surface outside the gap. Plasma conditions are characterised with current and voltage measurements and by application of absolutely calibrated optical emission spectroscopy, with a focus on nitrogen molecular emission. Plasma parameters, namely electron density and reduced electric field, are determined with spatial and temporal resolution in the frame of a collisional-radiative model using a calibrated charge coupled device camera and Abel inversion of measured images. The density of an effective helium metastable state is calculated using the measured plasma parameters and compared with values of the state density measured with tunable diode laser absorption spectroscopy.

Application of laser radiation for control of RADAN compact pulse generator

This paper presents the results of experimental and theoretical investigations of a plasma jet formed by YAG: Nd3+ laser radiation on an anode in a high-voltage gas gap. Conditions corresponding to the minimal instability of 0.3 ns and delay were experimentally found. The physical mechanisms determining the delay of the gas gap overlap by the plasma jet and the obtained instability level are discussed. A model of processes occurring on the ionization wavefront determined by the absorption/excitation of gas atoms and by the effects of a high-field domain was proposed.

The Resistive Cylindrical Chamber

A new generation of gaseous particle detectors named Resistive Cylindrical Chamber (RCC) (Cardarelli, 2021; Rocchi, 2022) [1,2] has been developed to overcome the limitations of Resistive Plate Chambers (Santonico and Cardarelli, 1981) [3] and broaden their application range. The principle behind this new technology consists in the transition from a planar to a cylindrical geometry while maintaining an almost planar electric field. The cylindrical structure of the electrodes allows to reach the following goals: increase the gas pressure to improve the intrinsic efficiency of the detector even for thin gas gaps or light gas mixtures; design the detector in order to produce an electric field gradient possibly useful to contain the development of the avalanche discharge. These features could lead to design detectors of simple mechanical realization with time resolution comparable with that of MRPCs maintaining a high efficiency of detection on a single thin gas-gap. The device pressurization could also allows to use new gases in view of the transition to eco-friendly gas.

Evolution of the electrical characteristics of an atmospheric pressure dielectric barrier discharge system over one hour operation

In this work, long-time operation of a dielectric barrier discharge (DBD) characterized by a single thin dielectric was investigated. The discharge was operated under nitrogen at atmospheric pressure in a typical filamentary regime. Electrical measurements were performed, i.e. applied voltage, current and charge were retrieved. The Lissajous figure method combined with an equivalent circuit of the DBD was used to calculate the dissipated power, estimate the gas gap voltage , evaluate the deposited charges as well as the capacitances of the discharge cell. The results over a one-hour operation indicated that the total dissipated power remained constant, but a decrease of the gas gap voltage with an increase of the charge deposited was also depicted. For the capacitances, both dielectric and cell capacitances variations were studied from the Lissajous figures. The dielectric capacitance showed a voltage dependency over half a period of applied voltage.

Experimental investigation and theoretical analysis of the breakdown time delay and jitter of multi-gap gas switch gaps.

The gas gap of a multi-gap gas switch can be classified as trigger and self-breakdown gaps based on the breakdown condition. A two-gap gas switch consisting of a trigger gap and a self-breakdown gap is developed to independently study the breakdown characteristics of these two types of switch gaps. Trigger experiments for the switch are conducted under various trigger voltage rise rates and different working coefficients. The experimental results indicate that the trigger gap has significantly more jitter than the self-breakdown gap, and the overall performance of the gas switch is determined primarily by the trigger gap. A novel pre-ionization structure with disks is implemented into the two-gap gas switch, considerably decreasing the breakdown delay of the trigger gap and reducing the jitter to a quarter or even less compared to that without pre-ionization. A calculation model of the breakdown time delay for the trigger gap is provided based on the foundational development of the avalanche. The probability distribution of the time required for the initial electron generation is derived in the absence of pre-ionization. The calculated breakdown time delay agrees well with the experimental results in cases with and without pre-ionization under most trigger settings. The method and principle of calculating the breakdown time delay can analyze the collapse of a gas gap with different electrode configurations (quasi-uniform or uniform electrical fields) and various gas media under a nanosecond pulse voltage.