High-pressure Xenon Gas Research Articles

A new coplanar-grid high-pressure xenon gamma-ray spectrometer

High-pressure xenon (HPXe) gas is a desirable radiation detection medium for many reasons, including its large atomic number, high density, low mean energy to produce an electron-ion pair, and the ability to produce devices with large detection volumes. While past work in HPXe has produced relatively successful detectors with energy resolution at 662 keV as good as approximately 2% FWHM, an expected limitation of these chambers in field operation is resolution degradation due to the vibration of their Frisch grids. Progress on a detector without a Frisch grid is reported in this submission; it is expected that the proposed anode design will provide competitive energy resolution with minimal degradation from mechanical vibration. Simulations accounting for charge carrier statistics, changes in the charge induced on the anode as a function of interaction location, and electronic noise predict a best-case energy resolution of 2.3% FWHM at 662 keV. Experimental data is compared with these simulations.

Ratio of Transverse Diffusion Coefficient to Mobility of Electrons in High-Pressure Xenon

We constructed a parallel plate drift chamber for measuring the ratio of the transverse diffusion coefficient Dt to the mobility µ of electrons multiplied by the elementary charge e, eDt/µ, which is called the transverse characteristic energy, in high-pressure xenon gas. The characteristic energies of electrons in Xe were obtained at a high pressure of 1.0 MPa and the reduced electric field, E/N, from 0.77 to 7.7 ×10-18 V·cm2, where E denotes an electric field and N the number density of Xe atoms. At the same E/N, our results agreed well with the data at pressures from 107 to 193 kPa previously obtained by Koizumi et al. [J. Phys. B 19 (1986) 2331]. The characteristic energies of electrons in Xe were found to be constant as a function of E/N from a low pressure to 1.0 MPa.

Scintillation luminescence for high-pressure xenon gas

Scintillation and ionization yields in xenon gas for 5.49MeV alpha-particles were measured in the range of pressure from 0.35 to 3.7MPa and the electric field strength (E) over the number density of xenon atoms (N), E/N from 0 to 5×10−18Vcm2. When our data are normalized at the data point measured by Saito et al., the number of scintillation photons is 2.3×105 while the number of ionization electrons is 2.0×105 at 2.6MPa and at 3.7×10−18Vcm2. The scintillation and ionization yields of xenon doped with 0.2% hydrogen, High-Pressure Xenon gas[H2-0.2%], at 2.6MPa was also measured. Scintillation yield of the Xe–H2 mixture gas is 80% as high as that of pure xenon. It is found that the scintillation yield is luminous enough to generate a trigger pulse of the high-pressure xenon time projection chamber, which is expected as a promising MeV Compton gamma-ray camera.

High-efficiency, high-power, stable 172 nm xenon excimer light source

Stable, continuous-wave light sources at 172 nm, based on the Xe2* excimer molecule, with conversion efficiency of electrical energy to vacuum ultraviolet (VUV) light greater than 50%, are reported. In high-pressure xenon gas, “Saint Elmo’s Fire” corona discharges serve as localized point electron sources with a metal grid at a few kilovolts providing an accelerating electric field. An extended VUV light-emitting region with high-energy conversion efficiency indicates that electron energy loss is predominantly by excitation of Xe atoms rather than by ionization. A room-temperature prototype lamp with variable VUV power to 35 mW/cm2 has been demonstrated.

Mercury-free HPS Lamp with High CRI Operated on Inductive Ballast and its One Application for Plant Growth.

Mercury-free HPS 150W lamp with high CRI operated on inductive ballast was developed. It has a slender arc tube with high-pressure xenon gas compared with that of mercury-contained arc tube. It has nearly the same haracteristics as those of mercury-contained HPS lamp with high CRI and shows nearly the same hue as that of incandescent lamp. This lamp is suitable for general lighting, such as indoor lighting, flood lighting, street lighting and so on. We present another one application, that is, seedling growth by supplemental lighting. We examined with lettuce and broccoli and got good results by 2 hours supplemental lighting before sunrise, compared with those of only daylight.

Observations of xenon gas-treated barley cells in solution by atomic force microscopy.

Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution.

Wire chambers revisited

Detectors used for radioisotope imaging have, historically, been based on scintillating crystal/photomultiplier combinations in various forms. From the rectilinear scanner through to modern gamma cameras and positron cameras, the basic technology has remained much the same. Efforts to overcome the limitations of this form of technology have foundered on the inability to reproduce the required sensitivity, spatial resolution and sensitive area at acceptable cost. Multiwire proportional chambers (MWPCs) have long been used as position-sensitive charged particle detectors in nuclear and high-energy physics. MWPCs are large-area gas-filled ionisation chambers in which large arrays of fine wires are used to measure the position of ionisation produced in the gas by the passage of charged particles. The important properties of MWPCs are high-spatial-resolution, large-area, high-count-rate performance at low cost. For research applications, detectors several metres square have been built and small-area detectors have a charged particle resolution of 0.4 mm at a count rate of several million per second. Modification is required to MWPCs for nuclear medicine imaging. As gamma rays or X-rays cannot be detected directly, they must be converted into photo- or Compton scatter electrons. Photon-electron conversion requires the use of high atomic number materials in the body of the chamber. Pressurised xenon is the most useful form of "gas only" photon-electron convertor and has been used successfully in a gamma camera for the detection of gamma rays at energies below 100 keV. This camera has been developed specifically for high-count-rate first-pass cardiac imaging. This high-pressure xenon gas MWPC is the key to a highly competitive system which can outperform scintillator-based systems. The count rate performance is close to a million counts per second and the intrinsic spatial resolution is better than the best scintillator-based camera. The MWPC camera produces quantitative ejection fraction information of the highest quality. The detection of higher energy gamma rays has proved more problematical, needing a solid photon-electron convertor to be incorporated into the chamber. Several groups have been working on this problem with modest success so far. The only clinical detectors have been developed for positron emission tomography, where thin lead or lead-glass can provide an acceptable convertor for 511 keV photons. Two MWPC positron cameras have been evaluated clinically and one is now in routine use in clinical oncology. The problems of detection efficiency have not been solved by these detectors although reliability and large-area PET imaging have been proven.(ABSTRACT TRUNCATED AT 400 WORDS)

Application of cadmium telluride detectors to high energy computed tomography

15 years ago, cadmium telluride detectors have been investigated in our laboratory as possible detectors for medical scanners [1]. Today most of these machines are using high pressure xenon gas as multicells detectors, and BGO or CdWO4 scintillators for industrial computerized tomography. Xenon gas detectors are well suited for the detection of 100 keV X-rays and enables one to built 1000 cells of homogeneous detector with a dynamic range of 3 decades. BGO and CdWO4 scintillators, associated with photomultipliers or photodiodes, are used for higher energy (400 keV). They present a low afterglow and a dynamic range of 4–5 decades. Nondestructive testing of very absorbing objects (e.g. 2 m diameter solid rocket motor) by X-ray tomography requires much higher energy X-rays (16 MeV) and doses up to 12 000 rad/min at 1 m. For this application cadmium telluride detectors operating as photoconductors are well suited. A prototype tomograph machine, able to scan ∅ 0.5 m high density objects has been realized with 25 CdTe detectors (25×15×0.8 mm3). It produces good quality 1024×1024 tomographic images.

Development of the wave-shifter fiber readout for SIGHT

The Scintillation Imaging Gas-filled Hard X-ray Telescope (SIGHT) is a balloon-borne telescope with a planned first flight in fall 1993; the telescope will image X-rays in the 35-300 keV range. The heart of the telescope is a high-pressure xenon gas scintillation drift chamber (GSDC) which combines gas scintillation with the time projection concept. The wave-shifter fiber readout for the GSDC is described. The authors present results of light attenuation studies and technical details of handling the fibers in a high-pressure environment. Techniques for coupling optical fibers to photomultiplier tubes in a manner that increases both the phototube quantum efficiency and the response uniformity are detailed. >

High pressure xenon proportional counter up to 10 atm

The characteristics of a conventional cylindrical geometry proportional counter filled with high pressure xenon gas up to 10 atm were investigated for

SIGHT: a balloon hard X-ray telescope

The authors report on progress toward developing a large-area, high-pressure xenon gas scintillator for use in hard X-ray astrophysics. Proof test results for a low-mass pressure vessel are presented. The design of a high-voltage multiplier board operating inside the scintillation chamber is discussed. The development of tetrakis-dimethylamine-thylene (TMAE)-based proportional tubes for detecting primary scintillation in the xenon is described. Finally, Monte Carlo tests of a scheme to use conventional photomultiplier tubes are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High pressure gas scintillation drift chambers with wave shifter fiber readout

The authors present results from a prototype xenon-gas scintillation drift chamber. It was operated at pressures up to 20 atm, and the scintillation light yield was measured at various pressures and reduced fields. Scintillation-reduced fields ranged from 1.3 to 3 kV/cm/atm in a 5.4-mm scintillation gap. Drift fields ranged from 45 to 100 V/cm/atm in an 8-cm drift region. The chamber was exposed to an /sup 241/Am source in a port either 2.7 or 5.4 cm from the secondary scintillation region. The authors also describe the high-voltage problems encountered during operation at high pressures. Further tests with the wave shifter fiber readout showed that the problem of gas contamination by the fibers is manageable but that the interaction between the optical fibers and the high pressure xenon gas can lead to fiber damage. A solution to this problem is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design and construction of a high pressure xenon time projection chamber

The design and construction of a 300 1 high pressure xenon gas time projection chamber (TPC) is discussed. This detector has been built to perform a sensitive search for double beta decay of 136Xe.

Stimulated Brillouin scattering and phase conjugation of hydrogen fluoride laser radiation

Stimulated Brillouin scattering (SBS) of hydrogen fluoride laser radiation has been demonstrated for the first reported time. A flash-lamp-pumped pulsed chemical laser, operating single-line at 2.91 microm, was used to generate backward-stimulated Brillouin scattering in high-pressure xenon gas with power reflectivities of ~50%. Intentional aberration and subsequent restoration of a high-spatial-quality beam provided evidence of phase conjugation by the SBS process.

Monte Carlo simulation of electron trajectories in high pressure xenon gas

A Monte Carlo calculation was developed to simulate electron trajectories in high pressure gas. In this report we discuss the calculation and some of the results relevant for the design of a high pressure xenon gas time projection chamber suitable for double beta decay experiment. Our calculation is quite general and can be extended towards a larger range of gas pressures and electron energies.

Demonstration of temporal coherence, spatial coherence, and threshold effects in the molecular xenon laser

Stimulated emission has been observed at 1722 ± 1 Å in high-pressure xenon gas originating from the bound-free continuum of the Xe ∗ 2 molecule. This emission exhibits strong line narrowing, spatial coherence corresponding to a few times the diffraction limit, a sharp oscillation threshold, and an output time dependence radically different from the spontaneous emission observed without an optical cavity or below threshold. The confluence of all these observations is an explicit and unequivocal demonstration of a coherent stimulated emission process. Specific data detailing the pressure dependence of the stimulated output and results with rare-gas mixtures are given.