Yu. V. Tuboltsev

Neutron time-of-flight spectrometer gneis at the gatchina 1 GeV proton synchrocyclotron

A description of GNEIS- the Gatchina neutron time-of-flight spectrometer at the 1 GeV proton synchrocyclotron-is given together with its basic parameters, as well as a comparison with other modern pulsed neutron source facilities. The integral neutron yield from a lead target is 3 × 1014ns. The spectrometer has five flight paths and a data acquisition system equipped with a few autonomous measuring stations. Some results of the (n, γf) experiments and neutron capture cross section measurements are presented to illustrate the facilitys performance.

Neutron‐Induced Fission Cross Sections of 240Pu, 243Am, and natW in the Energy Range 1–200 MeV

A long‐range research program devoted to measurements of neutron‐induced fission cross‐sections of actinides and stable isotopes is under way at the GNEIS facility. By now the new series of experiments for measurements of fission cross‐section ratios relative to 235U has been completed for 240Pu, 243Am, and natW in a wide energy range of incident neutrons from 1 MeV to 200 MeV in the frame of the ISTC Project ♯1971. The measurements were performed using the multiplate ionization chamber and time‐of‐flight techniques. The results obtained in this measurement are presented in comparison with the other data.

A Membrane Inlet for a Portable Mass Spectrometer

A system of membrane injection of a sample into a portable mass spectrometer which is used for determining the concentration of organic components in complex mixtures is described. Spectra of samples containing alkanes from methane to hexane have been measured. The data obtained using the membrane and diaphragm inlets to are compared. The potentialities of membrane inlets for portable mass spectrometers intended for environmental and process monitoring are shown.

Spectra distortion by the interstrip gap in spectroscopic silicon strip detectors

The NUSTAR experiments to be carried out as the part of the FAIR program (Facility for Antiproton and Ion Research) now under development in GSI, Germany, require unique spectrometers for heavy ions, for an energy range between a hundred keV up to hundreds of MeV. These spectrometers are constructed on the basis of silicon double sided detectors capable of providing simultaneously the energy spectrum of the particles and the position of hit points. The double sided Si strip detectors for high resolution ion spectroscopy and tracking were developed by the PTI-RIMST consortium. Reduced sized detectors were studied with alpha-particles from a 238Pu source to define the spectral response of their p+ side. The energy resolution was measured and found to be the highest, 9.6 keV, in the p+ strips area. The energy spectrum for the particles hit at the interstrip gap was shown to be much broader and have a maximum at the low energy edges. In this study the alpha-particle spectra were measured on the p+ side of strip detector and their shape was found to depend on the p+ strip structure and potential distribution under the strip and in the interstrip gap, where the surface is passivated by SiO2 layer. Therefore, the 2D potential distribution in the interstrip gap was simulated and interpreted through the effective entrance window for alpha-particles. The calculated spectrum of a detector from alpha-particle source has a shape specific to the experimental detector spectral response, i.e., the peak at low energies. These findings are to be taken into account in the analysis of short range particle spectra and may well contribute to further development of spectroscopic single sided and double sided Si strip detectors to be used in investigations in nuclear physics.

Potential distribution in voltage terminating structures with floating p–n junction rings of silicon radiation detectors

A model of the potential distribution in voltage terminating structures (VTSs) with floating p+-n junction rings in silicon radiation detectors is proposed. The model is based on experimental current-voltage characteristic of interring gaps, measured for detectors based on high-resistivity silicon with resistivities from 1 to 25 kΩ cm. The physical basis of the model is the injection principle of current flow through VTS interring gaps, which becomes possible at a certain electric field distribution in space charge regions of p+-n junctions of the sensitive contact and rings. It is shown that the injection current flow is a universal operation principle of the VTS with floating rings, which leads to rigid stabilization of potentials of individual rings. As a result, it becomes possible to divide the potential irrespective of the semiconductor material resistivity.

Intersegment resistance in silicon p—n-Junction position-sensitive detectors

Intersegment insulation in p—n-junction arrays based on high-resistivity silicon, which controls the interaction of neighboring elements of position-sensitive detectors, was studied. It was shown that current-voltage characteristics of the intersegment gap of the p—n junction deeply depleted due to an applied reverse voltage contain a portion of a step change in the current, which controls the intersegment insulation resistance. This feature is caused by the effect of switching of a small fraction of the bulk current between neighboring segments. In this case, the effect of the ohmic conductance between segments on the intersegment insulation resistance is ten times weaker than the effect of bulk current switching.

Cherenkov gamma-ray telescopes: Past, present, future. The ALEGRO project

A brief overview of the history of atmospheric Cherenkov gamma-ray telescopes is given. Topical problems of modern astrophysics and fundamental physics to be solved with these instruments are listed. The ALEGRO project of a low-threshold gamma-ray observatory is characterized in detail. The aim of this project is to examine cosmic gamma-ray sources (especially the rapidly variable gamma-ray sources, gamma-ray transients) with high statistics of detected photons in the energy range of 5–50 GeV.

ALEGRO: A new-generation Cherenkov gamma observatory

The concept of a new-generation terrestrial Cherenkov gamma observatory is proposed on the basis of the results of numerical modeling and research and development work. The key parameters of this observatory are estimated. Its primary objective should be the observation of cosmic gamma-ray sources in the 5–50 GeV energy range. Neither ground-based Cherenkov gamma observatories nor orbital gamma telescopes are presently able to perform such observations efficiently.

A CAMAC-USB crate controller

Abstract79-83A controller providing communication between a computer and a CAMAC crate via the USB bus is described. For this purpose, the controller includes a DLP-USB245M module, which allows a programmer to work with the controller through a virtual COM port and, at the same time, provides all the advantages of the USB standard. We consider versions of interactions of the DLP-USB module with controller registers on a programmable logic array and on the microcontroller.

A Fast Analog-to-Digital Converter

A CAMAC module is described, which contains four independent 8-bit fast analog-to-digital converters. This module is intended for recording digital input signals with a minimal sampling period of 10 ns and a maximal number of samples of 512. Each analog-to-digital converter operates in the external and internal synchronization modes. In the first mode, input processes are digitized after a START signal; in the second mode, a signal exceeding a preset threshold is uninterruptedly sought for and recorded. In this case, its prehistory can be recorded.