Resolution germanium detector

If a semiconductor (such as hyper-pure germanium) is used instead of an Nal(Tl) scintillation detector, the resolution is improved by a factor of 30 and more. The tremendous increase in resolution compared to scintillation detectors is shown in Figure 5. Here, a spectrum is shown of lead bullet... 

To remove this interference, an associated technique such as x-ray radiography could be used to iook for copper articles. Also high-maintenance, high-resolution germanium detectors might allow... 

Solid-state detectors based on silicon- or germanium-diodes possess better resolution than gas counters, particularly when cooled with liquid nitrogen, but they allow only very low count rates. PIN diodes have also recently become available and have been developed for the instruments used in the examination of Martian soils (Sects. 3.3 and 8.3). A very recent development is the so-called silicon-drift detector (SDD), which has very high energy resolution (up to ca. 130 eV) and large sensitive detection area (up to ca. 1 cm ). The SNR is improved by an order of magnitude compared to Si-PIN detectors. Silicon drift detectors may also be used in X-ray florescence spectroscopy, even in direct combination with Mossbauer spectroscopy (see Sects. 3.3 and 8.3). 

The introduction of high-resolution, high-efficiency /-ray detectors composed of lithium-drifted germanium crystals has revolutionised /-measurement techniques. Thus, /-spectrometry allows the rapid measurement of relatively low-activity samples without complex analytical preparations. A technique described by Michel et al. [25] uses Ge(Li) /-ray detectors for the simultaneous measurements of 228radium and 226radium in natural waters. This method simplifies the analytical procedures and reduces the labour while improving the precision, accuracy, and detection limits. 

Lithium-Drifted Germanium Detectors. Two kinds of planar Ge(Li) diodes were fabricated in our Laboratory for the spectrometer (I). The chief consideration was maximum cross section with a resolution of less than 3 k.e.v. at 60Co FWHM (full width half maximum). The available single-crystal germanium material dictated the shape of the detector. The first detector was fabricated from a 15-cm. long Sylvania ingot with a trapezoidal cross section its finished dimensions were 6 cm. X 3 cm. X 1 cm. Our second detector was fabricated from circular Hoboken stock (NPC Metal and Chemical Co., Los Angeles) its finished dimensions were 2.8 cm. diameter X 1.2 cm. thick. 

Germanium detectors provide the highest resolution for y-rays possible with reasonable efficiency, so our system is based on an array of such detectors. For cascade y rays (in prompt coincidence) an improvement in the effective resolution is possible by using double- and higher-coincidence spectra rather than singles. For this reason, and to obtain good statistics, as many detectors as close to the target as is reasonably possible is desirable (see below). 

Fig. 4. Portion of the 165Ho(a,3ny)166Tm spectrum observed with the on-line bent crystal spectrometer and with a good resolution germanium detector in the inset (the corresponding region is represented with open circles). Transitions are identified by their approximate energy in keV.

The measurements of F depth profiles in chipped flints have been realised using the 4.7 keV wide 872 keV 19F(p,a12.3y)160 resonance. This reaction provides a good depth resolution (about 100 nm in Si02). The 4-7.5 MeV y-rays are detected with a BGO (bismuth germanium oxide) detector at 0°C with respect to the incident beam. The flint artefacts can be settled in the vacuum chamber as whole pieces without any sample preparation [35],... 

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