High-pressure Xe Research Articles

Multiphysics modeling and simulations of laser-sustained plasmas

Laser-sustained plasma (LSP), which can be utilized for a novel radiation light source, has advantages such as high irradiance, broad spectral range, and stable emission, demonstrating significant applications in wafer inspection in the field of the semiconductor industry. This paper revisits the historical development of LSP research and introduces fundamental physical processes in LSP. The mathematical description equations for LSP and methods of calculating plasma parameters are provided, thereby a time-dependent two-dimensional fluid model is established by taking into consideration a laser-thermal-hydrodynamic coupling effect. The propagation of the laser in plasma is investigated based on the established model, and the fundamental processes in LSP, including the initial evolution process, laser energy deposition, steady-state characteristics, and instability, are explored. The effectiveness of the simulation model is confirmed through comparing with the experimental results of high-pressure Xe LSP. The findings indicate that the mode, power, <i>F</i>-number of incident lasers, as well as parameters including components, pressure, and flow velocity of gas, can all affect the steady-state properties of LSPs. Under the identical power and <i>F-</i>number conditions, Gaussian mode laser and annular mode laser both produce LSPs with different shapes and positions. Notably, under the conditions of high-power annular laser incidence, large laser <i>F-</i>number, and high flow velocity, the simulation results reveal temporal and spatial instability in LSP. These simulation results contribute significantly to a more in-depth understanding of the underlying physical mechanisms of the LSP. Furthermore, they provide a theoretical basis for designing the light source system and optimizing the multiple parameters. The influence of laser parameters on LSP properties elucidated in this study not only advances the fundamental understanding of LSP but also offers crucial insights for designing and optimizing the light source systems in various applications, particularly in the field of optical detection for semiconductor wafer inspection.

Construction of three-dimensional g-C3N4/Gr-CNTs/TiO2 Z-scheme catalyst with enhanced photocatalytic activity

A three-dimensional (3D) photocatalyst was synthesized through the self-assembly of graphitic carbon nitride (g-C3N4), TiO2, graphene (Gr), and carbon nanotubes (CNTs), in which both Gr and CNTs act as electron mediators, to form an all-solid-state g-C3N4/Gr-CNTs/TiO2 Z-scheme photocatalytic system. In this Z-scheme photocatalyst, the highly interconnected CNTs not only can effectively promote the transfer of photogenerated charge carriers, but also built a 3D open frame network to harvest more incident light and provide more specific surface area for photoreactions. Benefiting from the 3D nanostructure and Z-scheme system, phenol removal over g-C3N4/Gr-CNTs/TiO2 reached up to 90% within 120 min using a high-pressure Xe short-arc lamp as light source, which was much higher than that achieved over pure g-C3N4. The 3D Z-scheme photocatalyst fabricated in this study may be an attractive material for many environmental and energy-related applications.

Status of the NEXT project

The NEXT program is developing the technology of high-pressure Xe gas Time Projection Chambers with electroluminescent amplification (HPXe-EL) for neutrinoless double beta decay searches in 136Xe. After completing the first phase of the program with prototypes containing ∼1 kg Xe, the collaboration presently operates the NEXT-White demonstrator. NEXT-White is a 1:2 model NEXT-100, planned for construction in 2020, which will serve as a 100 kg-scale demonstrator of the HPXe-EL technology towards detector masses on the ton-scale. This contribution focuses on the latest results from NEXT-White on energy resolution, topology and background rate, and briefly discusses the future plans of the collaboration.

Gaseous time projection chambers for rare event detection: results from the T-REX project. I. Double beta decay

As part of the T-REX project, a number of R&D and prototyping activities have been carried out during the last years to explore the applicability of gaseous Time Projection Chambers (TPCs) with Micromesh Gas Structures (Micromegas) in rare event searches like double beta decay, axion research and low-mass WIMP searches. In both this and its companion paper, we compile the main results of the project and give an outlook of application prospects for this detection technique. While in the companion paper we focus on axions and WIMPs, in this paper we focus on the results regarding the measurement of the double beta decay (DBD) of 136Xe in a high pressure Xe (HPXe) TPC. Micromegas of the microbulk type have been extensively studied in high pressure Xe and Xe mixtures. Particularly relevant are the results obtained in Xe + trimethylamine (TMA) mixtures, showing very promising results in terms of gain, stability of operation, and energy resolution at high pressures up to 10 bar. The addition of TMA at levels of ∼ 1% reduces electron diffusion by up to a factor of 10 with respect to pure Xe, improving the quality of the topological pattern, with a positive impact on the discrimination capability. Operation with a medium size prototype of 30 cm diameter and 38 cm of drift (holding about 1 kg of Xe at 10 bar in the fiducial volume, enough to contain high energy electron tracks in the detector volume) has allowed to test the detection concept in realistic experimental conditions. Microbulk Micromegas are able to image the DBD ionization signature with high quality while, at the same time, measuring its energy deposition with a resolution of at least a ∼ 3% FWHM @ Qββ. This value was experimentally demonstrated for high-energy extended tracks at 10 bar, and is probably improvable down to the ∼ 1% FWHM levels as extrapolated from low energy events. In addition, first results on the topological signature information (one straggling track ending in two blobs) show promising background discrimination capabilities out of reach of other experimental implementations. Moreover, microbulk Micromegas have very low levels of intrinsic radioactivity, and offer cost-effective scaling-up options. All these results demonstrate that Micromegas-read HPXe TPC remains a very competitive technique for the next generation DBD experiments.

Micro-physics simulations of columnar recombination along nuclear recoil tracks in high-pressure Xe gas for directional dark matter searches

Directional sensitivity is one of the most important aspects of WIMP dark matter searches. Yet, making the direction of nuclear recoil visible with large target masses is a challenge. To achieve this, we are exploring a new method of detecting directions of short nuclear recoil tracks in high-pressure Xe gas, down to a few micron long, by utilizing columnar recombination. Columnar recombination changes the scintillation and ionization yields depending on the angle between a track and the electric field direction. In order to realize this, efficient cooling of electrons is essential. Trimethylamine(TMA) is one of the candidate additives to gaseous Xe in order to enhance the effect, not only by efficiently cooling the electrons, but also by increasing the amount of columnar recombination by Penning transfer. We performed a detailed simulation of ionization electrons transport created by nuclear recoils in a Xe + TMA gas mixture, and evaluated the size of the columnar recombination signal. The results show that the directionality signal can be obtained for a track longer than a few μm in some ideal cases. Although more studies with realistic assumptions are still needed in order to assess feasibility of this technique, this potentially opens a new possibility for dark matter searches.

Measurements of Charge and Light in Pure High Pressure Xe towards the Study of Xe+TMA Mixtures with Dark Matter Directionality Sensitivity and Supra-intrinsic Energy Resolution for 0νββ Decay Searches

Trimethylamine (TMA) may improve the energy resolution of gaseous xenon based detectors for 0νββ decay searches through the reduction of the Fano factor by the Penning effect. This molecule may also be the key for sensing directionality of nuclear recoils induced by Weakly Interacting Massive Particles (WIMPs) in monolithic massive (ton-scale) detectors, without the need of track imaging, by making use of columnar recombination. Nuclear recoil directionality may be the path for a definite discovery of the WIMP nature of Dark Matter. An ionization chamber has been constructed and operated to explore the properties of high pressure gaseous Xe + TMA mixtures for particle detection in rare-event experiments. The ionization, scintillation and electroluminescence (EL) signals are measured as function of pressure and electric field. We present results for pure xenon at pressures up to 8bar. This work has been carried out within the context of the NEXT collaboration.

A setup for Ba-ion extraction from high pressure Xe gas for double-beta decay studies with EXO

An experimental setup is being developed to extract Ba ions from a high-pressure Xe gas environment. It aims to transport Ba ions from 10bar Xe to vacuum conditions. The setup utilizes a converging–diverging nozzle in combination with a radio-frequency (RF) funnel to move Ba ions into vacuum through the pressure drop of several orders of magnitude. This technique is intended for use in a future multi-ton detector investigating double-beta decay in 136Xe. Efficient extraction and detection of Ba ions, the decay product of 136Xe, would allow for a background-free measurement of the 136Xe double-beta decay.

Radio frequency emission from high-pressure xenon arcs: A systematic experimental analysis of the underlying near-anode plasma instability

High-pressure Xe discharge lamps at DC operation can show unwanted strong RF (radio-frequency) emission to beyond 1 GHz, correlated to a sharp periodic lamp-voltage instability in the near-anode plasma with a pulse repetition rate ε of 1–10 MHz. The physical origin of the instability is unclear. Here, its existence and pulse rate have been measured as a function of arc current I = 0.2–1.2 A and anode temperature Ta = 1700–3400 K independently, in experimental lamps with pure-tungsten electrodes and a Xe operating pressure around p = 10 MPa. Surprisingly, the instability is not affected by I or current density j but exists if Ta is lower than a threshold value around 2800–2900 K. The pulse rate ε is simply a rising linear function of the inverse anode temperature 1/Ta, with only a small I-dependent correction. The average anode heat load is slightly lower in the unstable regime and possibly depends on ε. The results allow a consistent re-interpretation of earlier and present experimental observations and should be both a valuable help in practical lamp engineering and a tight constraint for future theories of this effect.

Performance of the High Pressure Xe detector for the Radiation Monitoring System of the Nuclear Power Plants

High-pressure Xe (HPXe) ionization chamber is considered as an ideal detector for the Radiation Monitoring System (RMS) in nuclear power plants, since detector response has been shown to be uniform over large temperature ranges up to 170 �i C. By using the MCNPX simulation code, the energy spectra were calculated with respect to the thickness of the outer shell and the dependence on the incident direction of the radiation sources in the nuclear power plant. A cylindrical HPXe ionization chamber, which was configured with a shielding mesh to improve its energy resolution, was designed and fabricated. With the gas purification and injection system, Xe and 7% 4 He was purified and injected into the chamber and the performances of the chamber were evaluated. The leakage and saturation currents of the chamber were measured with an electrometer, respectively. Linearity against dose rates was also measured with 226 Ra (0.906 mCi) radiation source and the 0.994 of root-mean-square value was estimated. In a future work, energy spectra with the fabricated HPXe ionization chamber will be measured and compared with the simulated energy spectra.

Development of a Selective Light-Emitting Diode Photolytic NO2 Converter for Continuously Measuring NO2 in the Atmosphere

A photolytic converter of nitrogen dioxide (NO(2)) to nitric oxide (NO) using light-emitting diodes (LEDs) has been designed to measure NO(2) in the troposphere. The typical electrical power consumption of the photolytic converter (PLC) is only 44 W. The maximum conversion efficiency of NO(2) to NO of the photolytic converter is around 90%, which is higher than that of metal halides or high-pressure Xe arc lamps (up to ∼70%). The conversion efficiency of the PLC was almost constant for at least 2.5 months. The conversion efficiency of peroxyacetyl nitrate by the LED-PLC was measured to be 2.6 ± 0.1% (1σ). The interference of HONO using the PLC was experimentally estimated to be less than 3%, which is within the uncertainty of the instrument. An intercomparison of NO(2) measurements between the PLC-CLD and the laser-induced fluorescence (LIF) technique was conducted, and the NO(2) concentrations measured by the PLC-CLD method were in agreement with those obtained by the LIF technique, within the uncertainties of the instruments. Continuous observations were made on Fukue Island, a remote area. These results demonstrate the performance of the PLC for continuous ambient measurements.

High-pressure real-time 129Xe NMR: monitoring of surfactant conformation during the self-assembly of reverse micelles in supercritical carbon dioxide

High-pressure (129)Xe NMR has been used to monitor in real time the self-assembly of reverse water-in-supercritical carbon dioxide micelles in the absence of shear, without the need for sensitivity enhancement techniques such as hyperpolarization.

NEXT: Neutrino Experiment with high pressure Xenon gas TPC

The search of the neutrinoless double- β decay address the major Physics goals of revealing the nature of the neutrino and setting an absolute scale for its mass. The observation of a positive β β 0 ν signal, the unique signature of Majorana neutrinos, would have deep consequences in particle physics and cosmology. Therefore, any claim of observing a positive signal shall require extremely robust evidences. NEXT is a new double- β experiment which aims at building a 100 kg high pressure Xe 136 gas TPC, to be hosted in the Canfranc Underground Laboratory (LSC), in Spain. This paper address the novel design concept of NEXT TPC believed to provide a pathway for an optimized and robust double- β experiment.

Development of a High Pressure Xe Ionization Chamber for Environmental Radiation Spectroscopy

A High Pressure Xenon ionization chamber is a promising radiation detector for environmental radiation measurement due to its radiation hardness, its physical rigidity, and its capability of operation at a high temperature up to about 170 °C. A cylindrical high pressure xenon ionization chamber, which was configured with a shielding mesh to improve its energy resolution, was designed on the basis of an electron transfer simulation code (EGSnrc) to extract an optimal density of Xe gas and a thickness of the chamber wall. An electron drift simulation code, Garfield, which was coupled with a Maxwell electric filed calculator, was also employed for the electron drift simulations due to the geometry of the shielding mesh. Shielding inefficiency was also calculated. A spherical ionization chamber was also designed and fabricated to monitor environmental radiation. A noble gas system was constructed to create a noble gas with a high purity and to inject the noble gas up to 60 atm. The combination of an oxygen absorbent (Oxisorb), a molecular sieve, and a high temperature getter can minimize the electro-negative impurities, such as the O2 and N2 gas, to below about several ppb levels. Preliminary tests such as leakage currents, saturation currents, and gas leak test were performed. The performance of the two fabricated ionization chambers at a low dose rate was tested by using a conventional shadow technique with a NIST certified 33.52 MBq 226Ra source in the calibration room at KAERI.

A proposed dark matter detector based on scintillation pulse shape differences in high pressure Xe gas

We propose a dark matter detector based on high pressure gas scintillation (HPGS) using Xe as the target gas. Scintillation pulse time constants in Xe gas are an order of magnitude longer for alpha particles than for electron recoils from gammas or betas. If alpha particle pulses are typical also of recoils for heavier nuclei this offers the possibiklity of a room temperature dark matter detector which could be simpler and lower cost than detectors based on liquid xenon, liquid argon, or mK bolometric techniques. Background estimates for Xe gas detectors operating at 5–10 bar show that a single 34 kg detector module could reach a dark matter cross section sensitivity 1E−9 pb, and an array of 15–30 such detectors of total mass 500 kg–1000 kg could reach

High Photocatalytic Capability of Self-Assembled Nanoporous WO3 with Preferential Orientation of (002) Planes

Self-assembled nanoporous tungsten oxide (WO3) with preferential orientation (002) planes was successfully synthesized on the tungsten sheet by anodization in a 0.2 wt % NaF and 0.3% (V/V) HF mixture solution in a 1:1 ratio. The pores, of a highly ordered self-assembled structure, had an average size of approximately 70 nm. X-ray diffraction identified a monoclinic WO3 structure and fine preferential orientation of (002) planes. A maximum photoconversion efficiency of 17.2% was obtained for the self-assembled nanoporous WO3 under high-pressure mercury lamp illumination. The photocatalytic (PC) degradation of pentachlorophenol (PCP) in aqueous solution using the self-assembled nanoporous WO3 photocatalyst, performed under both high-pressure mercury lamp and Xe lamp illumination, showed more excellent PC capability than WO3 film and TiO2 nanotube arrays.

P‐90: Large Scale Arrays of Microcavity Plasma Devices Based on Encapsulated Al/Al2O3 Electrodes: Device Characteristics as a Plasma Display Pixel and Low Cost Wet Chemical Fabrication Processing

AbstractAddressable, large scale arrays of microcavity plasma devices have been fabricated by wet chemical processes. Dielectric encapsulated aluminum microcavity electrodes having cavities with a diameter of 100–200 μm are formed by wet electrochemical process suitable for low cost manufacturing. This presentation reports device structure and cell designs for high pressure Xe microplasmas.

Micrometer-scale discharge in high-pressure H2O and Xe environments including supercritical fluid

We generated micrometer-scale discharge in high-pressure H2O and Xe up to supercritical conditions. In our previous paper, we reported the existence of two peculiar features in the breakdown voltages under high-pressure CO2. The first one was the downward shift at the right-hand side of Paschen’s curve above about 2.5MPa, and the second one was the drastic decrease in the breakdown voltages near the critical point. We have experimentally confirmed that these features are also observed in H2O and Xe, even though there are some differences among these materials. Our theoretical fitting involving a density fluctuation term FD agrees well with the experimental results, especially for Xe. We suppose that these unique features are brought about by decreases in the electron-to-particle cross section σ, ionization potential φi, and secondary electron coefficient γ′ and changes in the discharge space.

XAS of high pressure Xe clusters in amorphous carbon and computational simulation for the fcc and hcp xenon crystalline phases

We report the investigation of Xe clusters in amorphous carbon by x-ray absorption spectroscopy (XAS) to understand the properties of solid xenon. Measurements have been performed on xenon L3 absorption edge at room temperature (300K). Using computational XANES calculation for fcc and hcp structures it was possible to study the XANES fine structure origin and a relation between the x-ray absorption near edge structure and the lattice constant. Comparing those results with our experimental data we determined that the XAS fine near edge structure has a specific behavior for solid xenon and does not have this behavior for gas Xe end Xe diluted in others chemical elements matrices.

Analyses of data acquired from high-pressure Xe+/sup 3/He gas ionization chamber

It is shown that pulse-height spectra acquired from a high-pressure Xe+/sup 3/He gas ionization chamber exposed to mixed gamma-neutron radiation fields can be unfolded into separate gamma ray and thermal neutron spectra. The procedure takes advantage of the unique shape of the recently discovered spectral response of thermal neutrons in this high pressure Xe+/sup 3/He mixture. A template spectrum formed from only the pulse-height distribution of neutron signals is subtracted from the combined gamma and neutron spectrum to provide an estimate for the count of thermal neutrons. This procedure leaves a pure gamma spectrum for standard gamma ray spectrum analyses and isotope identification.

A new generation γ-ray camera for planetary science applications: High pressure xenon time projection chamber

A new γ-ray imaging camera based on High-pressure Xe Time-Projection-Chamber (HPXe-TPC) allows us to simultaneously determine arrival direction and its energy of individual incident γ rays. HPXe-TPC is a promising γ-ray detector for planetary science which provides means of global mapping of elemental composition in planetary surface as the remote sensing spectrometer. The simulation study by Geant4 and numerical calculation show that the angular resolution is mostly affected by multiple scattering of the recoil electron, and position resolution of electrodes of TPC. It is found that the angular resolution is 9° (50%) at 2 MeV for γ rays. The feasibility of HPXe-TPC is discussed as a γ-ray imaging camera for future planetary mission.