Germanium detector performance

Radionuclidic analyses are performed with either a lithium-drifted germanium or intrinsic germanium detector. The assay for Sr-82 is based upon its 777 keV photon of 13.6% abundance. Strontium-85, which is often present in amounts comparable to that of Sr-82, is assayed by its 514 keV photopeak, which must be resolved from prominent 511 keV annihilation radiation by a curve stripping procedure (12). 

The Swedish National Defence Research Institute (FOA), which from 1978 until 1983 was connected to the SSI, runs a system of high-volume aerosol samplers that normally detects very small amounts of radionuclides by high-resolution gamma spectrometry. The FOA also has access to army airplanes and helicopters to take air samples at different heights, to record measurements from the air, and to transport equipment and personnel to remote areas quickly to perform in situ measurements with portable germanium detectors. At the SSI, routine measurements of milk were run before the Chernobyl accident. Routine programs concerning environmental surveillance of nuclear power plants currently exist. 

Recently, the determination of Tc in mixed fission products by neutron activation was reported. " TcOj was separated from the bulk of fission products and other elements in dissolved nuclear fuel by an iron(IIl)-oxidc-hydrate precipitation. 1 he filtrate containing TcOj was loaded on an anion exchange resin and I c bonded on the resin was exposed to a neutron flux in a nuclear reactor for only one minute. The counting of the 539 keV y-rays of ° Tc was performed with a germanium detector and a multichannel analyzer. The minimum detectability was 0.3 pg Tc limited by resin impurities and capsule materials [27]. 

Germanium detectors are almost always cooled to 77 K with LN2. The first versions of these detectors were operated as low-bias diodes, and their noise performance was significantly worse than that of InGaAs detectors. The newer Ge detectors are fabricated from high-purity germanium elements and are biased near 100 V. These detectors cut on at about 6000 cm (3400-cm Stokes shift) and have excellent sensitivity, with an NEP that can be less than 10 W Like the InGaAs detector, the frequency response of Ge detectors... 

Bode and Graham (1963) A Comparison of the Performance of Copper-Doped Germanium and Mercury-Doped Germanium Detectors by D. Bode and H. A. Graham, Infrared Phys. 3, 129-137. 

Scattering on the Triple-Axis-Diffractometer [1,2] at the HASYLAB high-energy beamline BW5 is performed in the horizontal plane using an Eulerian cradle as sample stage and a germanium solid-state detector. The beam is monochromatized by a singlecrystal monochromator (e.g. Si 111, FWHM 5.8 ), focused by various slit systems (Huber, Riso) and iron collimators and monitorized by a scintillation counter. The instrument is controlled by a p-VAX computer via CAMAC. 

X-ray diffraction (XRD) patterns for the materials were recorded on a X-ray diffractometer using nickel-filtered CuKa (0.154 nm) radiation and a liquid nitrogen-cooled germanium solid-state detector. Thermal stability of the materials was performed using a thermogravimetric analyser. The acidity of calcined samples were determined... 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

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