Use Of Semiconductor Detectors Research Articles

Characteristics of semiconductor pion stop tagging system

A determination of the coordinates of charged particle stops is one of the tasks that have to be solved in a wide class of experiments. A method based on the use of semiconductor detectors (SCD) to determine the stops of particles (muons and pions) was proposed and experimentally tested. The dependence that allows calculating the stopping point of the pions in the tagging system was obtained experimentally. This dependence can be used to optimize the thickness values of monitor detectors.

Estimation of dose distribution irregularity in the mode of total therapeutic irradiation at dosimetry in vivo with the use of semiconductor detectors

Estimation of dose distribution irregularity in the mode of total therapeutic irradiation at dosimetry in vivo with the use of semiconductor detectors

On the possibility of eliminating the energy threshold for electron detection in semiconductor detectors

A method of eliminating the energy threshold for electron detection in semiconductor devices is described. The class of devices used for the detection and measurement of electron emission is sufficiently large, including electrostatic analyzers, gas-filled devices, microchannel plates, etc. An alternative to these types of devices for electron detection is offered by semiconductor radiation detectors based on the p-n junctions, which are widely used in the spectrometry of nuclear particles including medium-and high-energy electrons (102 keV and above). These detectors are obviously advantageous in comparison to the devices of other types, but there are several factors hindering the use of semiconductor detectors for the detection and analysis of low-energy electrons (in the kiloelectronvolt range). We propose an approach that allows the energy threshold for electron detection in semiconductor detectors to be eliminated by means of preliminary acceleration of the detected particles in an electrostatic field created between the emitter and the detector. This approach removes the basic factor limiting the use of semiconductor detectors in a number of diagnostic methods based on the analysis of electron emission, such as the extended X-ray absorption fine structure (EXAFS), surface EXAFS, and X-ray absorption near-edge structure (XANES) techniques.

Quality assurance in radiotherapy by in vivo dosimetry. 1. Entrance dose measurements, a reliable procedure

Entrance dose measurements were performed with semiconductor detectors on patients treated for head and neck and brain tumors with a 6 MV X-ray beam. A total number of 554 treatment set-ups were measured. The results showed a gaussian distribution with a mean value of 97.8% and a standard deviation of 2.8%. A systematic error of 2.2% on the mean value was shown to be due to a systematic deficiency in the algorithm used in the planning system and to a systematic error in the application of the dosimetry protocol. Two treatment techniques were identified leading to an erroneous dose delivery. Finally, large deviations (more than 2 S.D.) of the measured dose from the expected dose were detected in 3% of the measured treatment set-ups, the sources of the errors could in all cases be identified and eliminated in the further treatment sessions. This study demonstrated the reliability of the use of semiconductor detectors for in vivo dosimetry and its usefulness as part of a departmental quality assurance program.

Use of semiconductor detectors with synchrotron radiation

Silicon and germanium semiconductor detectors are widely used as photon and charged-particle spectrometers. Semiconductor detectors combine wide energy bandwidth with good energy resolution to make useful spectrometers for use with the high-intensity X-ray sources available at synchrotron facilities. High-quality silicon and germanium single-crystal starting material is now available for the fabrication of large-volume detector. Techniques have also been developed to reliably make detectors with passivated surfaces, thin windows and complex geometries. New low-noise preamplifiers and pulse-shaping networks allow higher counting rates and improved pulse throughput. For applications where accurate flux measurements of intense photon beams are required, a semiconductor detector with a current-measuring voltage-to-frequency converter provides a simple system which has excellent linearity and stability. Examples are given where semiconductor detectors have been used in experiments at synchrotron facilities.

Correlation of annihilation γ-ray polarization

The angular correlation of Compton-scattered photons coming from positron annihilation in copper has been measured. As is well known, such an experiment may test the validity of certain hiddenvariable theories. Our experiment differs from previous ones of the same type by the use of semiconductor detectors. These allow an accurate determination of the sum of the energies deposited by the annihilation photons in the scatterer and in the absorber of the Compton polarimeter. Our result is in complete agreement with the prediction of quantum mechanics.

Aspects of Semiconductor Current Mode Detectors for X-Ray Computed Tomography

For all types of X-ray CT-scanners the basic problem is quantitative measurement of X-ray attenuation with high accuracy. Quantum noise should be the limiting factor for spatial and contrast resolution to avoid unnecessary radiation hazards to the patient. Together with short exposure times and the required dynamic range this results in a number of serious demands to CT-detectors. After illustrating the fundamental aspects of semiconductor current mode detector operation, candidates for CT application are discussed in detail. Principally there are chances for the use of semiconductor detectors in CT, but the detector materials and the preparation technique have to be considerably improved.

Delayed coincidence measurements using semiconductor detectors

The use of semiconductor detectors in delayed coincidence measurements of shor nuclear half-lives is considered. Their use is illustated by an accurate measurement of the half-life of the 86.5 keV excited state in 233Pa. A result of (37.7±0.2) ns was obtained. The result of a measurement of the half-life of the 59.6 keV level in 237Np is also reported. The value obtained was (68.5±0.4) ns. Both these results are in good agreement with previous recent determinations.

Dosimetry of π--mesons using silicon detectors and plastic scintillators

The dosimetry of both π+ and π- beams by use of semiconductor detectors and plastic scintillators, is described. Depth-dose distributions, isodose distributions and integral and differential range curves are presented. By use of a time-of-flight system, the dosimetric information for a pure pion beam is obtained. The muon and electron contamination reduce the peak-to-plateau ratio. Pion beams of low energy give better depth-dose distributions. Nearly 50% of the dose at the peak of the depth-dose distribution of a π--beam is found to be due to nuclear events. Depth-dose distributions measured by semiconductor detector and tissue-equivalent ionization chamber, are in close agreement with each other.

Use of semiconductor detectors with a p-n junction for the dosimetry of x-rays and ?-radiation in the low-energy range

Use of semiconductor detectors with a p-n junction for the dosimetry of x-rays and ?-radiation in the low-energy range

Instrumental activation analysis for determining the composition of micro-ingots of multi-constituent alloys

A procedure for the instrumental neutron activation analysis of micro-ingots of alloys containing In, Sb, Au, Ga, Ni, Sn and Bi is proposed. The non-destructive analysis of the irradiated samples is performed by γ-spectrometry techniques including one-crystal scintillation detectors, dual-crystal sum-coincidence scintillation detectors and Ge(Li) semiconductor detectors. As a result, the cumbersome operations of radiochemical separation can be eliminated. The sensitivity of quantitative determinations using scintillation detectors in alloys of the above composition is 10−10 g for indium, gold, antimony and gallium and 10−6 g for nickel and tin. The use of semiconductor detectors yields sensitivities of 10−10 g for indium and gold and 10−9 g for gallium and antimony.

Use of semiconductor detectors in isotopic X-ray fluorescence method

Use of semiconductor detectors in isotopic X-ray fluorescence method

SHALLOW LEVEL TRAPPING AND DETRAPPING IN Si(Li) DETECTORS AT LOW TEMPERATURES

Trapping-detrapping pulse shapes have been observed in two Si(Li) detectors in the temperature range 8.5–70°K. A semiquantitative treatment leads to the conclusion that shallow trapping levels are responsible for the observed phenomena. It appears likely that these levels correspond to the donor (Li) and acceptor (B) dopants; if this hypothesis is confirmed by further experimental work it establishes a low-temperature limit on the use of semiconductor detectors for γ-ray and high-energy particle spectroscopy.

The decay of 97Ru

The decay of 97Ru to the levels in 97Tc has been studied with the use of semiconductor detectors, a NaI(Tl) crystal and coincidence equipment. Gamma-ray energies and relative gamma-ray intensities were determined as well as conversion coefficients for some transitions. Excited states were found at 215, 324, 784 and 976 keV. The level structure has been compared to current theoretical calculations.

Use of semiconductor detectors for determination of neutron yield in D-D and D-T reactions

Use of semiconductor detectors for determination of neutron yield in D-D and D-T reactions