V. V. Dmitrenko

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 Vcm2, 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.

New modification of xenon gamma-ray detector with high energy resolution

Abstract. Performance of a new modification of xenon gamma-ray detector (XGD) is presented. This detector differs from the previous ones by virtue of improved energy resolution (1.7±0.1)% at 662 keV and the ability to function in the presence of external acoustic noise (up to 100 dB) with virtually no degradation of spectrometric characteristics. These results have been achieved by developing a digital method of processing every electric signal coming from the XGD. For this method, digital electronics based on field-programmable gate array has also been developed.

A scintillation response and an ionization yield in pure xenon and mixtures of it with methane

The scintillation response to an α source (241Am) and the ionization yield in pure gaseous xenon and its mixtures with 0.2–2% of methane were measured at a pressure of 26 atm and different values of reduced electric field E/N. Both light and ionization yields in xenon were shown to decrease with increasing percentage of methane.

Detection sensitivity for special nuclear materials with an advanced high-pressure xenon detector and robust fitting analysis

The sensitivity for detection of two special nuclear materials, /sup 235/U and /sup 239/Pu, using an advanced high-pressure xenon detector (HPXe) and robust fitting analysis (RFA) with RobWin is experimentally determined for a set of collections with varying attenuation thicknesses of lead. These measurements provide essential information that enables comparisons with other detector systems for nuclear portal monitoring applications. Advantages of the combined use of HPXe and RFA for nuclear portal monitors are discussed, and recent progress with them is described briefly. An experiment designed to provide data from which models for nuclear portal monitor design can be grounded is described. Spectra were collected at CEA/Saclay with an HPXe unit from MEPhI for both /sup 235/U and /sup 239/Pu With attenuating thicknesses of lead ranging from zero to four millimeters. A single analysis procedure that yielded consistent results for all spectra was developed to simulate the automated application of analysis without user intervention and without advance knowledge of shielding thickness. These two spectrum series were then analyzed with RFA methodology for detection sensitivity and is reported in a form that can be used for comparison with other detector systems and for optimization of design parameters for HPXe/RFA portal monitor systems.

High-pressure xenon cylindrical ionization chamber with a shielding mesh

Construction of cylindrical ionization chamber with shielding mesh is considered. The chamber has sensitive volume 2 liters filled by xenon with pressure about 50 atm. Main characteristics of this detector such as energy resolution and efficiency of gamma-rays with energy 0.1 - 2.0 MeV are presented. It is shown that the detector energy resolution for Eequals0,662 MeV line at optimal electric field strength in the chamber is about 4%. Comparison of experimentally measured characteristics of this detector and standard scintillator NaI(T1) is fulfilled. Applications of the high pressure xenon cylindrical ionization chamber with a shielding mesh in geology, geophysics and diagnostic of oil and gas wells are considered.

High-pressure-xenon-filled cylindrical gamma-ray detector

The construction of a cylindrical ionization chamber, filled with high pressure xenon (55 bar) is described. The main characteristics of this detector are given. It is shown that the energy resolution of this detector, at 662 keV, is 4% FWHM for the optimal parameters of the gas mixture, applied electric field and shaping time. The detector was tested within a temperature interval between 20°C and 170°C. The dependence of the energy resolution of the cylindrical gamma-ray detector is quite stable. This detector can be used in geology, geophysics, oil and gas well logging.

Xenon detector with high energy resolution for gamma-ray line emission registration

A description of the xenon detector (XD) for gamma-ray line emission registration is presented. The detector provides high energy resolution and is able to operate under extreme environmental conditions (wide temperature range and unfavorable acoustic action). Resistance to acoustic noise as well as improvement in energy resolution has been achieved by means of real-time digital pulse processing. Another important XD feature is the ionization chamber’s thin wall with composite housing, which significantly decreases the mass of the device and expands its energy range, especially at low energies.

Scintillation Light, Ionization Yield and Scintillation Decay Times in High Pressure Xenon and Xenon Methane

Scintillation light, ionization yield and scintillation decay times have been measured in xenon and in its mixture with a 0.05% concentration of methane as a function of the reduced electric field (E/N) - the ratio of the electric field strength to the gas density - at a pressure of 21 atm. The measurements of scintillation decay times in the xenon-methane mixture have been made for the first time as a function of the reduced electric field (E/N). An ionization chamber has been constructed to simultaneously measure electrons and photons from a 239Pu source, which is placed in the center of a cathode in the chamber. The main peculiarity of the chamber is a moveable cathode to measure scintillation light and ionization yield at various distances from the anode and monitor the purity of the investigated gas. It has been observed that both scintillation light and ionization yield decrease when methane is added into the xenon gas. Scintillation decay times in the xenon-methane mixture are observed to be longer than in the pure xenon when the electric field strength increases.

Measurements and calculations of gamma rays from proton-irradiated thick targets

Abstract To help understand planetary gamma-ray spectra, the energies and intensities of gamma rays produced by energetic particles interacting in thick targets were simulated experimentally and numerically. Using the accelerator at RIKEN, thick targets of iron, granite, and gabbro were exposed to 180 or 210 MeV proton beam, and characteristic gamma rays emitted from the targets were measured by Ge detectors. The experimental results were compared with the values calculated by Geant4. The relative intensities of gamma-ray lines from the iron target in the experiment were consistent with those in the calculation within the error of ∼5%. As for stone targets, strong inconsistencies were observed. Further improvement in the calculation code and cross section files, as well as experimental resemblance to space missions are indispensable for gamma-ray spectroscopy.

High-pressure xenon gamma-ray large-volume spectrometer

Design of the cylindrical ionization chamber with shielding mesh is considered. The chamber has sensitive volume 5 liters and is filled with xenon at the pressure about 35 atm. Main characteristics of this detector are submitted: the energy resolution, efficiency of detection and position of the peak of full absorption for various energies of gamma-rays. It is shown that the energy resolution at 662 keV is 2.9% at the optimum electrical field in the chamber. Prospects of use of cylindrical compressed xenon ionization chamber with a shielding mesh in various fields of science and engineering are considered.