Intrinsic Germanium Detector Research Articles

Properties of intrinsic germanium detectors at low engergies by escape peak spectroscopy

AbstractThe study of the energy resolution and linearity of germanium, x‐ray detectors at very low energies is difficult due to the degradation of the spectral line shapes resulting from incomplete charge collection in the detectors's surface dead layer. The use of low‐energy, K escapes peaks obviates this difficulty as they are absorbed at depths characteristic of their full‐energy parent photons. Measurements have been performed using particle‐induced x‐ray emission analysis of targets having characteristic K and L x‐ray energies just above the Ge K‐edge. The escape peaks retain pure Gaussian shapes down to the noise level of the detector and open up the possibility of a selective field of high‐resolution escape‐peak spectroscopy.

Measurement of the dead-layer thickness of a planar intrinsic high-purity germanium detector

The thickness of the dead layer of a high-purity De detector was measured by comparing the efficiency ratio of the As K α and K β x-rays for the Ge detector with that for a Si(Li) detector for the same x-rays: the energies of these x-rays bracket that of the Ge K edge.

Identification of 241Am in the Axillary Lymph Nodes With an Intrinsic Germanium Detector

Identification of 241Am in the Axillary Lymph Nodes With an Intrinsic Germanium Detector

Identification of 241Am in the Axillary Lymph Nodes With an Intrinsic Germanium Detector

Identification of 241Am in the Axillary Lymph Nodes With an Intrinsic Germanium Detector

Precision mass difference measurements in light rubidium and krypton isotopes utilizing beta-endpoints

A technique for precise determination of β- endpoints with an intrinsic germanium detector has been developed and checked with 27Si and 58Cu sources; Q EC values of 5272 ± 26, 8063 ± 42 keV have been obtained for mass-separated samples of 77Rb, 75Rb and 77Kt, respectively. Mass surface systematics in this region have been examined and found to be consistent.

A resolution measurement of an inclined-plane sector magnet made with an intrinsic germanium detector

The focusing properties of an inclined-plane electron spectrometer have been measured with a narrow-slit and intrinsic-germanium detector. The aberrational width of 3.2 ± 1.0 keV obtained from this measurement is in agreement with ray-trace calculations.

Fusion cross-section measurements for the 13C+ 13C reaction

Absolute γ-ray yields from characteristic low-lying levels in nuclei produced in the 13C+ 13C reaction have been measured from E c.m. = 4.0 to 15.8 MeV using an intrinsic germanium detector. Statistical-model calculations of the decay modes of the compound nucleus have been used to deduce absolute cross sections for the production of the observed residual nuclei and to determine the fusion cross section. Consistency checks on the adopted procedure lead to an estimated absolute uncertainty of ± 15 % on the deduced cross sections. Over the energy range covered, no striking evidence has been found for either broad single-particle resonances or for narrow non-statistical resonances in the cross sections for individual channels. Comparisons are made with optical-model calculations of the reaction cross section and with different expressions for the fusion cross section.

The measurement of trabecular bone mineral density using coherent and Compton scattered photons in vitro.

A photon scattering method for measuring the trabecular bone mineral density (TBMD) in vitro is described. This method involves the measurement of the ratio of coherent to Compton 90 degrees scattered photons from Am-241 by using a narrow beam geometry with an intrinsic germanium detector. The feasibility of using smaller scattering angles for better counting efficiency and the associated problems in their application for in-vivo measurements were investigated. Calibration of the system with fresh trabecular bone samples showed a linear relationship between the coherent to Compton ratio R of the detected counts and the TBMD (r = 0.94). The effect of the overlying soft tissue on the R ratio was significant while the effect of self-attenuation by the trabecular bone itself and the cortical layer was negligible. It was found that the marrow fat content could alter the value of the R ratio. Our results show that for a 10% increase in the fat content in the interstices of the trabecular bone there is a 2.5% decrease in the R ratio. This technique together with soft tissue corrections will enable us to measure the TBMD of the calcaneum in vivo, assuming a small variation in the trabecular fat content. The estimated absorbed dose to the bone marrow is about 139 mrad.

Suitability of detectors for imaging applications

Interest in computer assisted tomography has seen in recent years an increase in applications on a wider basis extending beyond medical investigations. Technological developments have made available a larger selection of detectors which may be employed in imaging studies. Limited resources in a university research group and the fact that some of the types of detectors are still at the research stage of production, e.g. cadmium telluride, demanded the investigation of parameters by which detectors may be selected for specific applications. Experiments using a scanning rig were carried out to measure efficiency, energy resolution, scatter, spatial resolution and detection limit for sodium iodide, bismuth germanate, caesium fluoride, cadmium telluride and intrinsic germanium detectors.

Intrinsic germanium detectors used in a high counting rate system

This paper describes the fabrication of various geometries of fully depleted intrinsic germanium detectors suitable for operating at counting rates up to two million counts per second. At these high counting rates it has been observed that charge generation in undepleted regions of a detector give rise to slow current injection into the depleted region of the diode. This results in spectral degradation at high counting rates. To avoid this effect, detector geometries have been used in which the detector volume is totally depleted. The signal processing system is also described.

Calculated response of intrinsic germanium detectors to narrow beams of photons with energies up to ∼300 keV

The response of small intrinsic Ge detectors has been calculated for photons incident with energies up to ∼300 keV. The results include the effects of scattering and escape from the detector of the photons and of Ge characteristic X-rays produced in photoelectric absorption. Included also are the effects of the backscattering of photons from material behind the detector. The results, based on Monte Carlo calculations for various photon energies and detector sizes, have been generalized on the basis of a single-scatter model and are given as a set of formulae that can be evaluated for any photon energy and detector size in the range of interest. The predictions obtained with the formulae are shown to agree well with available data from measurements and from Monte Carlo calculations made by other authors. The formulae are used to tabulate photopeak efficiencies for a large number of commercially available detectors, and to generate response functions for unfolding measured pulse-height distributions obtained for continuous incident spectra.

Pr�ziseQ ? -Wert-Messungen mit einem Intrinsic-Germanium-Detektor an schweren, neutronenreichen Spaltprodukten

An intrinsic germanium detector was used to measure the beta endpoint energies of heavy fission products supplied by the on line mass separator OSTIS installed at the high flux reactor of the Institut Max von Laue-Paul Langevin, Grenoble.

A gamma-spectrometric method for the determination of plutonium isotope ratios

A gamma-spectrometric method using an intrinsic high resolution germanium detector has been developed for the determination of isotope ratios of plutonium from samples in solution form. The method is based on the assay of low energy gamma-rays of238Pu,239Pu,240Pu and241Pu and does not require the use of branching intensities or the knowledge of detection efficiencies for different gamma rays. Since low energy gamma-rays are used, the effect of241Am has also been studied. It is found that results are not affected up to 0.5 wt% of241Am in plutonium samples. An accuracy of 3% is achievable in the determination of240Pu/239Pu and241Pu/239Pu atom ratios as demonstrated by carrying out measurements on isotopic standards of plutonium.

A Dual Germanium Detector System for the Routine Assay of Low Level Transuranics in Soil

As an outgrowth of previous work on soil radioassay, we have developed an automated assay system for determining the transuranic radionuclide content of soils, with particular interest in Pu. The system utilizes two commercial planar intrinsic germanium detectors in opposition. The large area of the detectors (2100 mm2) and the thinness of the detector crystals (7 mm) permit sensitive analysis of the L x-ray emission region of the transuranics (13-21 keV). With counting times of 5 hours, we obtain detection limits of <15 pCi/g for Pu and <0.1 pCi/g for 241Am.

An in-Situ Neutron Activation Analysis System for Assaying Metal Ores

The topic of this paper is a method of in-situ neutron activation using high resolution gamma ray spectroscopy and a californium 252 neutron source. The paper is divided into three parts: a description of the authors' high resolution gamma ray spectrometer probe, results to date using a Cf-252 source and applications made possible by a small accelerator. The basic tool of measurement is the PGT probe - a high resolution gamma ray spectrometer that incorporates an intrinsic germanium detector and a computerized multichannel analyzer. The system is capable of operating at data rates as high as 100,000 counts per second and can record 4000-channel gamma ray spectra in-situ. The probe is 2.5 inches diameter and 12 feet long. All data are transmitted digitally over standard 4-H-O armored cable to a computer-based logging system. Complete analysis can be performed on site.

The level structure of85Rb and87Rb from (n, n??) reaction measurements

Detection of gamma rays resulting from inelastic scattering of neutrons in the energy range 550 to 2,100 keV from a natural rubidium sample was used to determine the level structure of85Rb and87Rb. Decay gammas were observed with time-gated Ge(Li) and intrinsic germanium detectors with good energy resolution. Level and decay schemes up to 2 MeV excitation were constructed for both85Rb and87Rb. Several new levels were found, some seen previously in particle reactions were confirmed and their energies accurately established. Comparison of the excitation functions with Hauser-Feshbach theory led to the assignment of spins and parities for several levels.

The determination of molybdenum and tungsten by high resolution spectrometry of alpha-induced prompt photon emission

A simple, rapid and non-destructive method is described for determining molybdenum and tungsten in steels over the concentration range 0.07 to about 20% by mass. The method uses high resolution spectrometry of the low energy gamma-rays induced by 5 MeV alpha-particle beams. The precision for molybdenum is 2.7% and for tungsten is 0.55% using respectively the 204 and 100.1 keV gamma-rays. Results obtained by Ge(Li) and intrinsic germanium detectors are compared. The extent of interference from other elements is discussed.

PreciseQ ? -values with an intrinsic Germanium detector for light, neutron-rich fission products

PreciseQ ? -values with an intrinsic Germanium detector for light, neutron-rich fission products

A Monte-Carlo evaluation of an improved-sensitivity, 76Ge double-beta-decay experiment

Monte Carlo calculations have been made of the sensitivity of a 200 cm 3 intrinsic germanium detector, guarded by a large NaI(Tl) Compton suppression annulus, for the observation of the hypothesized neutrinoless double beta decay of 76Ge. It was assumed apriori that the background levels would be similar to those achieved by Fiorini and his co-workers in the original experiment. It was determined, for example, that an annulus 51 cm in diameter and 61 cm long, would suppress the continuum background in the vicinity of the 2.045 MeV neutrinoless double beta decay peak, so as to allow the observation of a decay with a half-life of 2.6 × 10 25 y.

The decay of141Ce

The decay of141Ce has been reinvestigated using different experimental methods. The efficiency extrapolation technique applied to 4πβ —γ coincidence measurements has been employed for the determination of the disintegration rate of the sources and of the total internal conversion coefficient. TheK X-ray andγ-ray emisssion rates have been measured with a calibrated Si(Li) and an intrinsic germanium detector. Additionally the photon intensities have been determined from the internal conversion coefficients. Electron experiments with a magneticβ-spectrometer yielded the relative intensities, the shape factors and the maximum energies of the two β−-transitions and the internal conversion ratiosK/L andK/(L + M+...). TheK-shell internal conversion probability has been determined with an electronK X-ray coincidence technique using the magneticβ-spectrometer together with a high energy resolution Si(Li) detector. New values for the following decay properties have been deduced:β −-intensities (p 1 =0.306 + 0.006,p 2= 0.694±0.006), shape factorsC = const (1+Ae) (A 1 = −(0.24±0.03),A 2=−(0.22±0.04)), maximumβ −-energies (E 01 = (582.2±2.6) keV,E 02= (436.7±4.6) keV),K- shell internal conversion coefficient (α K = 0.376±0.008), total internal conversion coefficient (α = 0.438±0.010), internal conversion ratios (K/L = 7.29±0.24, K/(L + M + ...) = 5.78±0.18),γ-ray intensity (I γ = 0.482±0.003),K X-ray intensity (IK X = 0.168±0.002) and the photon intensity ratio (I K X /I γ = 0.349±0.005). The procedure of uncertainty quotation is presented in some detail. The results are discussed with respect to existing experimental data.