Increase In Counting Efficiency Research Articles

Research of the Single Crystal and Multilayer Composite Detectors Response Under Irradiation by Fast Neutrons

The object of this work was to study the response of the detectors based on the oxide scintillators under irradiation by a flux of fast neutrons from 239Pu-Be source by counting photomultiplier tube pulses. In the process of the research the counting efficiency of the detectors was measured in units of (pulse×s-1×cm-2)/(neutron×s-1×cm-2) for single-crystal and multilayer composite detectors ZWO (ZnWO4), CWO (CdWO4), BGO (Bi4Ge3O12, composite). The measured response for ZWO detector was ~ 64 pulse/neutron, for CWO ~ 36 pulse/neutron, for BGO ~ 0.44 pulse/neutron. The detectors response was registered by a fast preamplifier with the operation speed of up to 500 MHz, based on high-speed operational amplifiers with voltage feedback. The statistical error of measurement for the neutron registration efficiency by the broadband channel made 7% for the detectors with the effective thickness of ~ 40-50 mm, which is due to the spherical geometry of the experiment. The formation of the detector response is affected by the following parameters of neutron reactions: cross section of inelastic and resonant scattering of scintillator nuclei, density of composite nuclei levels, resonance region width, lifetimes of long-lived states and their number. The measured values of the counting efficiency of fast neutrons registration are accounted for the fact that the inelastic scattering reaction for some nuclei is the starting point that triggers the cascade process of the nuclear states discharge. The registration of the cascade of the discharge gamma-quanta, ranging from nanoseconds to a few microseconds, causes an increase in the detector counting efficiency and, as a consequence, an increase in the detector sensitivity to neutron detection. The observed increase in the counting efficiency of secondary gamma quanta is realized when the neutrons are slowed down in the detectors having sufficiently noticeable thickness and appropriate isotopic composition.

Geometrical parameters and scattered radiation effects on the extrinsic sensitivity and counting efficiency of a rectangular gamma camera

A point source is used to investigate the effect of water phantom thickness and source-to-detector distance (SDD) on the sensitivity and counting efficiency of a rectangular detector gamma camera. The increase in water thickness resulted in an increase in scatter fraction, a decrease in sensitivity, and counting efficiency. The increase in SDD resulted in a decrease in sensitivity and an increase in counting efficiency. An SDD of 0.79±0.02m is found to provide a good compromise for acceptable sensitivity and reasonable counting efficiency.

Enhanced counting efficiency of Cerenkov radiation from bismuth-210

This paper describes the measurement of210Bi by Cerenkov counting in a commercial liquid scintillation counter. The counting efficiency in water is 0.17 counts per second per Becquerel (17%). When the enhancers Triton X-100 (15% v/v) and sodium salicylate (1% m/v) are added to the solution the counting efficiency for210Bi increases from 17% to 75%. The210Po daughter of210Bi causes interference of 0.85 counts per second per Becquerel in the presence of the enhancers but not in water. When210Bi and210Po are present in secular equilibrium the total counting efficiency is 160%. When210Bi and210Po are not in secular equilibrium the210Po can be removed immediately before counting by plating onto silver foil. The use of the enhancers gives a substantial increase in counting efficiency compared to counting in water. Compared with solutions used in liquid scintillation counting the enhancer solution is inexpensive and can be disposed of without environmental hazard.

Improved counting efficiencies for measuring 239Pu in the lung in the sitting position.

For a study sponsored by the International Atomic Energy Agency (IAEA), Pacific Northwest Laboratory (PNL) made lung counting measurements of lung deposition in 10 women who had inhaled 92mNb in England. These women were measured in both the supine and sitting (torso 45 degrees from horizontal) positions with a counting system of Ge planar detectors and another counting system of Phoswich detectors. The average increase in counting efficiency from the supine to the sitting position was 108% for the Ge detectors and 310% for the Phoswich detectors. Individual counting efficiency increases ranged from 15-260% for the Ge detectors and from 40-480% for the Phoswich detectors. The increase in counting efficiency was roughly proportional to the total chest wall thickness of the measured individuals. By using the equivalent muscle tissue thickness of the individual's chest wall, the increase in counting efficiency could be attributed to the decrease in the tissue absorption in the sitting position. The decreased distance between the lungs and the detector achieved in the sitting positions may also account for some of the improvement in counting efficiency. In addition, some undetermined internal change in activity distribution (source-to-detector geometry) and tissue absorption may possibly contribute to the improved counting efficiency of the sitting vs. the supine position.

Photoelectron spectroscopy of supersonic molecular beams

A high-resolution photoelectron spectrometer which uses molecular beam sampling is described. Photons from a rare-gas resonance lamp or UV laser are crossed with the beam from a differentially pumped supersonic nozzle source. The resulting photoelectrons are collected by an electrostatic analyzer of a unique design consisting of a 90° spherical sector preanalyzer, a system of lenses, and a 180° hemispherical deflector. A multichannel detection system based on dual microchannel plates with a resistive anode position encoder provides an increase in counting efficiency by a factor of 12 over the equivalent single channel detector. The apparatus has demonstrated an instrumental resolution of better than 10 meV FWHM, limited largely by the photon source linewidth. A quadrupole mass spectrometer is used to characterize the composition of the molecular beam. Extensive differential pumping is provided to protect the critical surfaces of the analyzer and mass spectrometer from contamination. Because of the near elimination of Doppler and rotational broadenings, the practical resolution is the highest yet obtained in molecular PES.

Routine Counting of 32P in Colored Solutions from Dry Ashed Plant Samples Utilizing Čerenkov Radiation

AbstractA technique for routine liquid scintillation counting of 32P in dry ashed plant tissue by utilizing Čerenkov radiation was shown to be effective when corrections for color quenching in the samples were made by the use of an external standard source of radioactivity. A comparison of this method with that of counting plant tissue briquettes with a G‐M tube indicated a great increase in counting efficiency. This technique requires no contamination of the 32P samples with liquid scintillator substances.

計数管のAnode Wire Effectとその応用

The increase in counting efficiency for gamma rays due to the effect of the anode wire of counter tubes is measured by utilization of a collimated gamma -ray sheet. The distribution of the number of gamma photons emitted from a slit is measured by means of the effect of anode wire. A divergency of gamma rays from a slit is discussed by measuring the distribution of the number of gamma photons (energy 0.662 Mev) at each position from the slit.

Gas-Flow Proportional Counter for Soft X-Ray Detection

One of the major problems of analysis in the soft x-ray region is the limitation due to low transmission of the window materials of sealed-off x-ray detectors. This paper describes the properties and use of a gas-flow proportional counter system for the x-ray analysis of elements in the third period of the periodic table, with special reference to aluminum and silicon. The use of gases flowing continuously through the counter at atmospheric pressure in conjunction with helium also at atmospheric pressure in the optical path permits the use of ultra-thin nonvacuum-tight windows with high transmission in this region. Comparative data, obtained on a Norelco fluorescence spectrometer, show a tenfold increase in counting efficiency for AlKα over detectors previously available for this application.

The gamma-ray counting efficiency for a lead-cathode G-M counter.

The dependence of gamma-ray counting efficiency on energy has been determined in the range 0.17 Mev to 2.76 Mev for a G-M counter with a lead cathode. The efficiency for six energy values was found by coincidence measurements utilizing the disintegration of In111, Au198, Co60, and Na24. The result indicates a smooth increase in counting efficiency for increasing energy over the range of energies investigated.