Spectrometer Gamma-ray

In a different example, traceability in the amount-of-substance analysis of natural potassium, thorium, and uranium by the method of passive gamma-ray spectrometry was demonstrated by Nir-El (1997). For an absolute quantitative determination, accurate values of two parameters were required (i) the emission probability of a gamma-ray in the decay of the respective indicator radionuclides, and (2) the detection efficiency of that gamma-ray. This work employed a number of CRMs in the critical calibration of the detection efficiency of the gamma-ray spectrometer and the establishment of precise emission probabilities. The latter results compared well with literature values and provided smaller uncertainties for several gamma-rays that were critical for the traceabUity claim. The amount-of-substance analytical results of the long lived naturally occurring radionucHdes K, Th, and... 

The only in situ chemical data for asteroids are from the NEAR Shoemaker spacecraft, which orbited 433 Eros in 2000-1, and from the Japanese Hayabusa spacecraft, which visited 25143 Itokawa in 2003. NEAR obtained numerous measurements of the surface composition using X-ray fluorescence and gamma-ray spectrometers, and Hayabusa carried an XRF. The magnesium/silicon and aluminum/siUcon ratios for both asteroids are consistent with the compositions of chondrites. However, sulfur is depleted in Eros relative to chondritic compositions, possibly due to devolatilization by impacts or small degrees of melting. 

NEAR-Shoemaker also carried a gamma-ray spectrometer (Evans et al., 2001). Gamma-ray photons are emitted from the radioactive decay of long-lived radioisotopes and from other elements that are excited by cosmic-ray bombardment. The gamma rays are... 

Gamma-ray spectrometers use scintillator detectors. These spectrometers sense y-rays from all directions, and hence have large "footprints" (commonly hundreds of kilometers diameter) with sizes determined by orbital elevation above the surface. The y-rays come from depths of less than a meter in the target material. 

Figure 13.6, which plots 120 versus Mg/(Mg+Fe) from Lunar Prospector gamma-ray spectrometer data in 5° bins, shows that the global data overlap major rock types in the Apollo collection. Such comparisons give confidence that major geologic units have not been overlooked by biased sampling. 

Comparison of titanium contents of lunar mare basalts, as measured from neutrons by the Lunar Prospector gamma-ray spectrometer and from reflectance spectra by the Clementine spacecraft. After Prettyman et al. (2006). 

Lawrence, D. J., Feldman, W. C., Barraclough, B. L. et al. (1998) Global elemental maps of the Moon the Lunar Prospector gamma-ray spectrometer. Science, 281, 1484-1489. 

A Ge(Li) Gamma-Ray Spectrometer of High Sensitivity and Resolution for Biological and Environmental Counting... 

Figure 2. The anticoincidence-shielded, high resolution, Ge(Li) gamma-ray spectrometer. The annulus is in position for inserting a large environmental sample...

Figure 3. Schematic of the gamma-ray spectrometer shown in Figure 2. Details of the Ge(Li) chamber and cooled FET preamplifier are given in the...

Anticoincidence Gamma-Ray Spectrometer for Environmental and Biological Problems, Nucl. Instrum. Methods (1969) 74, 197-212. 

It is recommended that gamma ray spectrometer measurements should be taken at each sampling site. See Damley et al. (1995) for instructions, and section 4.2 of this document. 

Gamma ray spectrometer measurements should be taken at every sample site ... 

Gamma ray spectrometer measurements at residual soil sample sites are taken at only one subsite (first soil sample pit) instead at each subsite as recommended by Damley et al. (1995). 

The isotope 203Pb is produced by bombardment of thallium with protons in a cyclotron. The radioactive half-life is 52 h and decay is by electron capture. The associated 279-keV gamma ray enables the activity in the lung and other organs of volunteer subjects to be detected by external gamma ray spectrometers (Chamberlain etal., 1975). 

In Part 2B, the student will calibrate a germanium (Ge) gamma-ray spectrometer with certified standard solutions for counting efficiency as function of energy and sample volume, and perform quality assurance (QA) counting tests. 

To analyze by gamma-ray spectrometer a sample that contains a mixture of fission products from neutron-irradiated fissile material. (If a reactor is unavailable, the instructor may synthesize a mixture of radionuclides that emit gamma rays.)... 

Neutron activation has been used to determine the concentrations of trace elements in polyethylene. A procedure has been optimized which involves three irradiations with a SICWFOKE nuclear reactor and four counts with a gamma-ray spectrometer. Phosphorus is determined with beta-ray spectrometry. The detection limits, most of which are below one ppm, have been determined for 42 elements. The merits of the method are discussed in terms of sensitivity, accuracy, ease of use, interferences, and freedom from contamination. 

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