Yu.S. Anisimov

Proportional chamber device for thin-layer radiochromatogram analysis

Abstract A device consisting of proportional chambers has been constructed for the analysis of thin-layer radiochromatograms. The device enables one ot localize radioactive zones, to identify radionuclides and to measure their activities.

MRS silicon avalanche detectors with negative feedback for time-of-flight systems

Investigation of time characteristics of silicon avalanche detectors with negative feedback based on Metal-Resistive layer-Semiconductor structure, proposed for Time-of-Flight systems, is described in this paper. Time resolutions of 550 ps on β-electrons and 250 ps on LED light pulses were obtained. Design and principles of operation are described briefly.

Tensor analyzing power T20 for cumulative pion production from deuterons in the GeV energy region

Abstract The tensor analyzing power T 20 for the reaction d ↑ + 12 C → π ± (0°) + X has been measured with a polarized deuteron beam from 6.2 to 9.0 GeV/ c at a pion momentum3.0 GeV/ c . This experiment is focused on “cumulatively produced pions”, which are produced beyond the kinematically allowed limit for free nucleon-nucleon collisions. The measured values of T 20 turn out to be close to zero. They are in disagreement with the results of our impulse approximation calculation which is based on a single NN → πNN interaction and takes into account the internal motion of nucleons in the deuteron. Possible explanations of the result are discussed.

Automatic coordinate detectors based on MWPC for applied studies

Abstract Automatic coordinate detectors constructed at the High Energy Laboratory, JINR, on the basis of multiwire proportional chambers are used for (1) X-ray diffraction of single protein crystals, (2) quantitative analysis of thin layer chromatograms, (3) radio-isotope medicine diagnostics, and (4) neutron radiography. The detectors operate on-line with a computer, have a large sensitive area, high detection efficiency, spatial resolution and count rate. Image displays are presented on a TV-monitor. These devices allow the time of carrying out the studies and the dose to be reduced and the accuracy to be increased. The work has been performed at the High Energy Laboratory, JINR.

A two-coordinate proportional chamber with high resolution for X-ray diffraction studies of protein crystals

Abstract A two-coordinate proportional chamber used for X-ray diffraction studies of protein crystals is described. The chamber was filled with a Xe + 20% CH4 + 3% C2H5OH mixture. The coordinate information was read out with electromagnetic delay lines. The studies showed a high (70%) detection efficiency and a high spatial resolution for Cu Kα radiation (8 keV). The maximum resolution of the detector was 350 × 250 elements. The work has been performed at the High Energy Laboratory, JINR, Dubna, U.S.S.R.

Multiwire proportional chambers in the devices for molecular biology constructed at JINR

Abstract The automation of measuring processes in molecular biology is a current problem. In order to solve this problem, conventionally used methods should be changed for an up-to-date technique which allows the processes of data measurement and analysis to be automated. Toward this end two-coordinate proportional chambers (MWPCs) are coming widely into use. The use of MWPCs in devices for radiochromatography and X-ray diffractrometry is discussed in this paper. A new device consisting of proportional chambers has been constructed for an automated analysis of thin layer radiochromatograms. The device enables one to localize radioactive zones (labelled with 3H, 14C, 32P), to identify radionuclides and to measure their activities. The device has a high sensitivity (5 pCi for tritium), a small dead time, good space resolution (in the case of 3H zones space 1–2 mm apart are separated) and high reproducibility. For X-ray diffractrometry of single crystals, a high counting rate device has been constructed on the basis of a MWPC with a total number of channels amounting to 350 × 200 = 70 000. The dead time of the device is about 0.6 μs which allows to detect 3 × 105 events/s at counting losses of no more than 20%. The quantum efficiency (Cu Kα) is about 73%. The X and Y space resolution (fwhm) is equal to 1 mm and 1.7 mm, respectively. The work has been performed at the High Energy Laboratory, JINR.

SEARCH FOR RESONANT STRUCTURE IN THE PION PRODUCTION REACTION ON THE NUCLOTRON INTERNAL BEAM

We have searched for an enhancement in the excitation function of the yield of pions in the pion production reaction by protons and deutrons at bombarding energies near 350 MeV/nucleon. The measurements was carried out on the JINR Nuclotron internal beam and target in March and June 2004 Nuclotron Runs for Ag, Cu, Al and C targets.

TARGET DEPENDENCE OF RELATIVISTIC DEUTERON FRAGMENTATION INTO CUMULATIVE PIONS

The power value of the A-dependence of the cross-section for 4.5 GeV/nucleon deuteron fragmentation into cumulative pions has been measured on carbon, aluminium, copper and lead nuclei for cumulative numbers within 0.8-1.2. The mean value is equal to 0.27 ± 0.09 in this interval. The target atomic weight dependence significantly differs from the volume type dependence on the atomic weight of fragmenting nucleus.

Relativistic hypernuclei at Dubna

At the Laboratory of High Energies (JINR, Dubna) a unique approach was elaborated with hypernuclei produced by the excitation of the beam nuclei and their decays observed at a distance of tens of cm behind the production target. While the very first experiments were carried out in the Synchrophasotron beams, more extensive hypernuclei research programme is planned for the Nuclotron accelerator and the new spectrometer created by the authors. At the time of the conference the first test run in the Nuclotron beam was in progress. Investigation of hydrogen hypernuclei isotopes is in the first line of the experimental research plans. Namely, lifetimes and production cross sections of Λ 4 H and Λ 3 H will be measured. Search for Λ 6 H is also among the tasks.

Development and investigation of a neutron radiography imaging system with a low-pressure multistep chamber

An imaging system of thermal neutrons for an investigation of digital neutron radiography has been developed and tested. Some characteristics obtained on a neutron radiography beam of an experimental reactor are reported. The coordinates of each event are determined in this system. After processing in a LSI 1123 computer, a radiograph, accumulated in a histogramming memory of 64 K 16-bit words, is presented on a colour display. A 230 × 180 mm2 low-pressure multistep chamber is used as a detector. Neutron conversion takes place in a 6 μm boron layer enriched to 86% in 10B. The detection efficiency of thermal neutrons is no less than 3%. The count rate of the system reaches up to 2 × 105 events per second. A radiograph can be obtained within 10 minutes. The sensitivity of this system to gamma-background is low. One event/s is detected for a background of 1 R/h. The spatial resolution is found to be 0.7 mm (FWHM) using a cadmium knife edge. The integral nonlinearity is less than 0.4%. The possibility of using a hydrogeneous converter in this system for neutron radiography is discussed.