K. F. Vlasik

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.

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.

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.

Xenon gamma-ray spectrometer in the experiment Signal on board the spacecraft Interhelioprobe

In the experiment SIGNAL, which is planned to take place on board spacecraft INTERHELIOPROBE, a xenon gammaray spectrometer is to be used. The gamma-ray spectrometer in question has been chosen because of its characteristics permitting detailed study of solar gamma-radiation under rough experimental conditions. The equipment is able to provide: high energy resolution (5-6-fold better than that of scintillation detectors), performance at high temperatures, steady operation under significant vibroacoustic load, and high radiation resistance of the working medium. The aforesaid properties of the xenon gamma-ray spectrometer meet goals and objectives of the experiment SIGNAL. The description of ballistics scenario and operation orbit of the INTERHELIOPROBE spacecraft (SC) are presented.

Electromagnetic shields based on multilayer film structures

Electrodeposited multilayer-film electromagnetic shields are very promising for protecting various devices due to high shielding efficiency and the possibility of depositing on complex-shaped objects. In this communication, we present the results of measurements of the shielding efficiency of such shields. The shields represent alternating layers of materials with high magnetic permeability (Ni-Fe) and high conductivity (Cu). The maximum number of double layers is 45. It is shown that the shielding efficiency in the weak magnetic fields (0.1–0.2 mT) is 8–10; at higher magnetic field strengths (1.5–2.5 mT), it reaches 80–100. It is shown that the shielding factor increases with the number of layers in the shield at the same thickness of a soft magnetic material. A permalloy shield at the same amount of a soft magnetic material has an efficiency lower by a factor of 3–15 depending on the magnetic field strength.

Measurement of Electron Drift Velocities in the Mixture of Xe and He for a New High-Pressure Xe Gamma-Ray Detector

Drift velocities of electrons in a mixture of Xe (20 atm)–He (3 atm) were measured using a cylindrical high-pressure xenon chamber. The drift velocities were found to be greater than 3 ×105 cm/s above the reduced electric field of 2.0 ×10-18 Vcm2 at room temperature, which are close to those in Xe–H2 (0.3%). The mixture of He gas into high-pressure xenon improved the resolving time of detectors because it increased the electron drift velocities. This implies that a high-pressure xenon chamber mixed with 3He instead of He gas operates as a gamma-ray detector sensitive to thermal neutrons.