Nuclear material detection, scintillators

A major use for photomultiplieis has been in (he scintillation counter wherein combination with a fluorescent material, it is used to detect nuclear radiation. They also have been used ill star and planet tracking for guidance systems as well as in star photometry and quantitative measurements of soft x-rays in outer space. Additional uses include facsimile transmission, spectral analysis, process control, and wherever extremely low-liglit levels must be detected. For applications in photometers, see also Photometers. 

Electronic counters are devices in which absorption of an x-ray photon or a neutron generates a short electric pulse in the associated electronic circuitry. By counting the rate of generation of such pulses, the flux of the x-ray or neutron beam to which the device is exposed can be measured. These counters are the outgrowth of the initial efforts made by nuclear physicists for detection of radioactivities of materials. Most useful among them for x-ray and neutron scattering studies are the proportional and scintillation counters described in Section 2.4.1. Further elaboration on these counters led to the development of position-sensitive detectors, explained in Section 2.4.2. Very recently, a number of novel devices based on new technologies have become available, and these are briefly introduced in Section 2.4.4. 

Better candidates for the study of acoustic emission are composite materials. The extremely brittle polyvinyltoluene sample which showed easily detectable acousic emission (6) was indeed to some extent such a composite material since it was a sample used for scintillation counting of nuclear radiation. The crystalline particles of the inorganic scintillator embedded in the rather rigid polymer matrix differ enough in elastic properties from those of the matrix that a substantial stress enhancement occurs on the interface between the two components. One has about twice the bulk stress on the poles and one third on the equator of a perfectly rigid spherical particle. Such a stress increase in the poles leads rather early to adhesion failure of the particle-matrix boundary and to microcrack formation. This finally makes the sample fail at small strain-to-fracture, cb = 0.5%. The microcracks act as nuclei for crazing. The opening of a fissure between the particle and the matrix is sufficiently... 

The radiation detection systems employed in radioanalytical chemistry laboratories have changed considerably over the past sixty years, with significant improvement realized since the early 1980s. Advancements in the areas of material science, electronics, and computer technology have contributed to the development of more sensitive, reliable, and user-friendly laboratory instruments. The four primary radiation measurement systems considered to be necessary for the modern radionuclide measurement laboratory are gas-flow proportional counters, liquid scintillation (LS) counters. Si alpha-particle spectrometer systems, and Ge gamma-ray spectrometer systems. These four systems are the tools used to identify and measure most forms of nuclear radiation. 

Scintillation counter a device that detects nuclear radiations from flashes of fight generated in a material by the radiation. (213) Second (s) the SI base unit of time. (1.6)... 

Neutron diffraction is a very powerful technique for investigating the structure of condensed matter. Crystal structures can be studied, either by diffraction from a polycrystalline powder or from a single crystal sample. Neutron diffraction is also a very important tool for the study of the structure of noncrystalline forms of matter, such as liquids and glasses. This article considers in detail the instrumentation for studying isotropic samples, either polycrystalline powders or non-crystalline materials. Neutrons may be obtained either from a nuclear reactor or from an accelerator-based source. They may be detected using either gas detectors or scintillator detectors. Typical neutron diffractometers at both reactor and accelerator-based sources are described, and a consideration of the resolution is given in each case. 

---