[en] Vano et al.'s empirical relation has been proved to be valid for HPGe detectors with large active volume range. New values of a and b are 0.6246 and -2.136 respectively. The slope of the efficiency curve is charcteristic of detectors and independent of the geometry conditions within 2% error. It can be calculated within an error less than 3% in a certain energy range. (orig.)

[en] For the in vivo monitoring of radiation workers a new measurement system has been installed at PSI, Switzerland. A single p-type high purity germanium detector of 102% relative efficiency is mounted in a shielded room located in a subterranean shelter. The room has internal dimensions of 270 cm x 190 cm x 220 cm and is constructed of iron from old railway rails. The detector is mounted on a mechanical support fixed on the ceiling, which permits movements in three directions and two axes. Measurements of radionuclides in the body are performed in a sitting position. The system is used to detect the presence of radionuclides that emit photons with energies between 50 keV and 2 MeV. A description of the system is presented. The results of calibration of the detector for total-body activity measurements are discussed. The performances of the new system and the old NaI(Tl) body monitor used at PSI are compared. (author)

[en] The current HPGe camera consists of two detectors of 3.2 x 3.2-cm² each, 1 cm-thick. Orthogonal electrodes define coordinates on the surfaces of the detectors so that 512 image elements are defined, each 2x2-nm². These electrodes are read by a 16x32 set of individual preamplifiers, and an analog switch circuit allows the 32 preamplifiers along one axis to feed their signals to a main spectroscopic amplifier without summing their individual noise contributions. A separate logic circuit rejects events where more than one image element registers a signal. This avoids contributions to the output image by events where the gamma-ray has undergone multiple scattering in the detector. In this manner the spatial resolution function is square, without exhibiting the tails seen in conventional continuous-detectors cameras. The main performance parameters of the HPGe camera are: energy resolution of 2.2% FWHM at 140 keV; spatial resolution of 2mm FW; paralyzable and non-paralyzable dead times 100 nsec and 8 μsec, respectively; a maximum count rate of 4,000 cts/sec/preamplifier, or 130,000 cts/sec in the present camera; and a sensitivity that approaches or exceeds that of a 1/2-in NaI crystal camera, depending on radionuclide. Additional advantages of the HPGe camera are distortion-free imaging; energy linearity over the full range of imaging energies; and high stability, both over time and a wide range of ambient temperatures

No abstract available

[en] The average fluence rate F as a function of source to detector-centre distance D+L/2 for several detector volumes V, detector radii R and detector lengths L for unattenuated radiation incident on the flat face of cylindrical detector has been determined by the numerical integration method. It is shown that: (1) for a small value of D+L/2 , and (i) keeping the value of R constant, F increases with L (or V), (ii) keeping the value of L constant, F decreases when R increases (or V), (iii) for equal value of V, F increases when both R decreases and L increases, (iv) when either V increases or remains constant, F increases with L, and (v) when V increases, F does not necessarily increase, as explained in (i) and (ii) above, (2) when D+L/2 increases, F decreases for a particular value of V, (3) when D+L/2 is large (* 1000 mm), F converges to a single value for any volume. Suggestion for the determination of F for attenuated radiation is given

[en] In order to calculate the efficiency of a cylindrical sample, it can be divided into disks parallel to the face of the detector and the activities of all disks can be integrated according to their distance Tom the detector face. Two factors lead to the decreasing contribution of the disk as it's distance from the detector face increases, i.e. the absorption of the gamma photons in the sample and the decrease of the angle of the detector with increase of the distance. As a first step the dependence of the efficiency for a radioactive disk was studies in order to eliminate the absorption factor and single out the geometric one. It was found experimentally that high volume Ge detectors can be taken as an average effective plate detector with an efficiency function

[en] Recent results obtained from studies of solid phase epitaxy, of ion-implantation and of regrowth of amorphous layers are summarized. Many of these new results have been applied to detector making. Recent results obtained from experiments with zone refining, ''monodes,'' hydrogen in germanium and infrared photoelectric spectroscopy with stressed crystals illustrate the ongoing development of high-purity germanium. 26 refs

[en] Semiconductor detectors are now applied to a very wide range of problems. The combination of relatively low cost, excellent energy resolution, and simultaneous broad energy-spectrum analysis is uniquely suited to many applications in both basic and applied physics. Alternative techniques, such as magnetic spectrometers for charged-particle spectroscopy, while offering better energy resolution, are bulky, expensive, and usually far more difficult to use. Furthermore, they do not directly provide the broad energy-spectrum measurements easily accomplished using semiconductor detectors. Scintillation detectors, which are approximately equivalent to semiconductor detectors in convenience and cost, exhibit 10 to 100 times worse energy resolution. However, their high efficiency and large potential size recommend their use in some measurements

[en] The distinguishing characteristic of high purity germanium (HPGe) detectors, as opposed to the lithium-drifted variety, is their ability to be cycled between ambient and liquid nitrogen temperatures without degradation of operating characteristics. Since the commercial introduction of HPGe crystals in 1972, several important applications of this unique material have been under development by the authors and by other investigators. The purpose of our research has been to develop detector fabrication techniques which are appropriate for the construction of gamma ray detector systems which have applications in nuclear medicine, portable gamma ray spectrometers, and orbiting satellite gamma ray telescopes. Over the past three-year period, approximately two dozen gamma ray detectors have been fabricated from high purity germanium in the authors' laboratories. A detailed discussion of the detector fabrication and testing process as it has evolved is given, and some theoretical considerations which have a direct bearing upon proper fabrication and successful operation of HPGe spectrometers are presented

[en] The electric field at the edge of the p⁺-type layer of a high-purity Ge detector was reduced by an additional electric singular zone, 'buffer ring', cut in the neighborhood of the edge where breakdown is unlikely to take place until a high field gradient occurs. The buffer ring successfully accomplished the edge protection, and greatly improved the volt-ampere characteristics and the stability of the detector. (orig./HP)