Semiconductor gamma-detectors

Cooling the material will reduce the number of electrons in the conduction band, thereby reducing the background current (in detector terms, the leakage current) and make it much easier to detect the extra excitation due to the gamma-ray interactions. This is the basis of the semiconductor gamma-ray detector. 

K. Debertin and R. G. Helmer, Gamma- and X-raj Spectrometry With Semiconductor Detectors North-HoUand, Amsterdam, the Netherlands, 1988. 

A gamma-ray spectmm is produced nondispersively by pulse-height (multichannel) analysis using scintillation or semiconductor detectors. Resolving power, typically - 100 at 100 keV and - 700 at 2 MeV, is quite modest compared with that achievable in other spectral regions, but is sufficient to identify nucHdes unambiguously. 

Electronic and Optoelectronic Applications of TeUurides. Most metal teUurides are semiconductors with a large range of energy gaps and can be used in a variety of electrical and optoelectronic devices. AUoys of the form HgCdTe and PbSnTe have been used as infrared detectors and CdTe has been employed as a gamma ray detector and is also a promising candidate material for a thin-fUm solar ceU. 

Gamma- and x-ray spectrometry with semiconductor detectors. North Holland, Amsterdam... 

The measurement of natural gamma rays from rocks and minerals requires basically the same equipment as 7-ray spectrometry in neutron activation, the only difference being that large crystal or semiconductor detectors in a more sophisticated arrangement are necessary to record the low natural activity (Adams and Gasparini, 1970). 

Now that these organic/inorganic heterostructure semiconductors can be made, we can use them to increase the range of potentially harmful materials that can be detected in time to prevent a dangerous incident. I ll briefly discuss the applications of these semiconductor materials to national security needs, including devices such as infrared (IR) detectors and sources, gamma-ray detectors, and chemical/biological sensors. 

Semiconductor detectors, made from single crystals of very pure germanium or silicon, are the highest performance detector type. The superior resolution of these detectors has revolutionized data-gathering for X-ray and gamma-ray measurements. The comparison of the pulse resolving ability of the three types of X-ray detectors scintillator, gas proportional and Si(Li) is shown in Fig. 5.18. 

Like scintillation detectors, semiconductor detectors are usually used in gamma spectrometer set-ups to identify radionuclides and determine their activities in a sample. A semiconductor detector is much more expensive and somewhat more troublesome to operate than a scintillation detector, but it can distinguish much better between different radiation energies and is better for nuclide identification. 

Gamma spectroscopy is a radiochemical measurement method that allows identification and quantitative determination of activity of radionuclides, which emit gamma radiation or x-rays. The equipment used in gamma spectroscopy includes an energy-sensitive radiation detector, such as semiconductors, scintillators or proportional counters, and a multichannel analyzer. The energies and the photon yields are characteristic for specific nuclides. 

Activation analysis has been proposed to obtain more reliable analytical information.73 The sample is irradiated with neutrons, photons (gamma radiation), or charged particles the radioactivity generated is measured by sensing the entire gamma spectrum with a semiconductor detector. The most reliable variant is neutron activation analysis (NAA).73... 

Determination of radioactivity is by counting emitted beta or gamma radiation with beta or gamma counters. Most INAA determinations are by gamma spectrometry using Ge(Li) semiconductor detectors, multichannel analyzers and associated dedicated computers. 

Assume that the energy resolution of a scintillation counter is 9 percent and that of a semiconductor detector is 1 percent at energies around 900 keV. If a source emits gammas at 0.870 MeV and 0.980 MeV, can these peaks be resolved with a scintillator or a semiconductor detector ... 

Radiation from radioactive sources can be detected and measured in essentially Ihe same way as X-radialioii (Sections l2B-4and 12B-S). Gas-filled chambers, scintillation counters, and semiconductor detectors are all sensitive to alpha and beta particles and to gamma rays because absorption of these particles produces ionization or photoelectrons, which can in turn produce thousands of ion pairs. A detectable electrical pulse is thus produced for each particle reaching the transducer. 

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