High-purity Ge detectors

An advertisement for a high-purity Ge detector quoted its relative efficiency as being 200%. Is that possible Please explain. 

D-ACAR spectroscopy, eq. (14) Lineshape spectroscopy has two advantages (1) it is rapid a profile is obtained in less than one hour (2) it is technically simple, making use either of one (Hautojarvi and Vehanen 1979) or two (Ashoka-Kumar et al. 1996) high-purity Ge detectors. The rather low resolution of lineshape spectroscopy (0.4-0.6 a.u.)... 

Ishikawa, Y., Murakami, H., Sekine, T., Saito, T., and Yoshihara, K. (1994) Non-destructive determination of low level Pb and Ra with an ordinary high-purity Ge-detector. 

Germanium is very similar to Si, but its band gap is too small for many practical applications. Large crystals of ultra-high-purity Ge have been grown for use as gamma-ray detectors. In such crystals, the net concentration of... 

The basic characteristics of EDS detectors, their limitations and methods for improvement of performance have been documented by a number of workers r9.101. Lithium-drifted Si and high-purity Ge are the two types of solid-state devices currently used in EDS detectors on AEMs. A compilation of EDS detection principles and characteristics, including less commonly used devices, such as Hgl detectors, is given by Heinrich et al. riOl. 

Fig. 1. (Top) y-Ray energy spectrum of the reaction 19F(p,ay)160 measured by a 3-inch Nal detector. Proton energy is 2.7 MeV, sample material is fluorapatite. (Middle) y-Ray energy spectrum for the same reaction acquired by a high purity germanium detector. The sample is meteoritic material. Low energy lines from several other nuclear reactions can be identified. (Bottom) Low-energy y-ray spectrum from 19F(p,p y)19F inelastic scattering recorded with a thin Ge(Li) detector. Reproduced with permission from Grambole and Noll [59],...

By 1975 the Ge(Li) detector had been supplanted by a newer, more rugged device the high-purity germanium detector. This germanium detector construction is produced without the lithium-drift compensation. Consequently, it is as impervious to warm-up as the Si(Li) detector. 

Exploiting the first effect described above is called the fluorescence collection mode (Jaklevich, 1977). In this case, an energy-selective detector (namely solid state detectors such Si Li, high purity Ge,. . . ) is used to separate the fluorescence from the background (consisting of coherent and incoherent scattering), fluorescence of other materials and so on. 

Photon emissions from physical or biological samples are usually detected by Nal(Tl) scintillators or semiconductor detectors such as high purity Ge (see Section 4). Special counting methods are needed for very low energy X rays, such as those emitted by several radioisotopes of transuranic elements. 

I. The yields and purity were determined by gamma spectroscopy. Iron-52 from the nickel target contains a trace of 44.6-d Fe-59 impurity (average 0.33% at end of bombardment). The 2.7-y Fe-55 impurity, which emits 5.9-keV (24.3%) and 6.5-keV (3.3%) x-rays and no gamma rays, is determined by means of a high-resolution Si(Li) x-ray detector or thin window Ge detector. It amounts to... 

The analysis scheme for the 10 evaluation samples used two aliquots ( 25 cm2 of filter paper/aliquot). One aliquot was encapsulated in polyethylene and irradiated in a polyethylene rabbit for 5 min in a thermal neutron flux of approximately 1014 n/cm2/sec. This sample was counted at decay times of 5 min, 30 min, and 24 hrs. The other aliquot was encapsulated in high purity synthetic quartz and irradiated in an aluminum rabbit 12-24 hrs. These samples were counted twice, after decay periods of 10 days and 3 wks. Sample counting equipment included one 4096-channel y-ray spectrometer and a Ge(Li) detector. 

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