Intrinsic Germanium Detector Research Articles

A study of the beta-ray response function and performance of an intrinsic-germanium detector mounted in a superconducting solenoid

A semi-empirical detector response function for a beta spectrometer consisting of an intrinsic germanium detector mounted in the bore of a superconducting solenoid is given and discussed. The performance of this type of beta spectrometer is examined by means of the results obtained from it when spectra from ten well studied nuclei are analyzed. It is found that endpoint-energy determination with an accuracy of ∼ 10 keV is achievable in such a system. The system exhibits sufficient sensitivity to provide information on the shape factors of beta-decay transitions. Information on the beta-decay scheme of nuclei can be obtained from such a system, and thus can provide a useful check on the gross features of decay schemes obtained from γ-ray intensity balances. The large solid angle for β-rays achievable with this type of spectrometer, together with the ease of precise calibration and lack of γ-ray contributions to the beta spectra, make the system an attractive instrument for beta-ray spectroscopy.

A241Am spectrometer for Compton scattering studies

A gamma ray Compton spectrometer, which uses a 1.85*1011 Bq (5 Ci) 241Am annular source and an intrinsic germanium detector, has been designed and built. Compared with previous instruments using weaker 241Am sources an order of magnitude improvement in intensity and reproducibility has been realised. The potential of the technique, particularly for the study of electron momentum distributions in light materials is discussed. The effect of multiple Compton air scattering upon the symmetry of the final profile is stressed.

High-resolution electronic emission spectrum of molecular nitrogen at 15300 Å

The 5 m Jarrell-Ash Czerny-Turner spectrograph at the Institute for Molecular Physics has been adapted to spectrometric operation in the 1–2 μm wavelength region. A lead screw assembly with a stepping motor drive has been installed to translate an exit slit that is focused onto a cooled intrinsic germanium detector. The exceptional sensitivity of this detection system has produced good signal-to-noise ratios in the third order of a 300 line/mm echelle grating which yields a reciprocal dispersion of 1.44 A/mm at the exit slit. The resolution achieved was energy limited at 0.046 cm−1 and the precision of frequency measurement was 0.007 cm−1. The 0-0 band of the B′ Σ3u-→B Π3g system of molecular nitrogen was the subject of the investigation. Although this system is known as the infrared afterglow system, the band emits strongly in a dc glow discharge and it has been possible to resolve nearly 1000 lines in the band. The preponderance of the lines in the region are from the 0-0 B′ → B transition, with only a small 1 PG emission toward the red end of the band.

Radioisotope Probe System for On-Stream Process Analysis and Control

A radioisotope x-ray fluorescence probe system has been developed for the automatic analysis of medium and heavy elements in mineral slurries and solutions. In this system the probes are located at separate positions in the process. A minicomputer controls and commands the probes via a communication loop. There are two probe types, one equipped with a high resolution sealed proportional counter and the other with an intrinsic germanium detector. Each probe can simultaneously analyze up to five elements and slurry density. An automatic sampling and sample cell system has been developed for the probes. The stabilizing control of a flotation process based on assays has proved profitable in many installations. The small digital distributed controllers and on-stream analyzers make more productive operation of small plants possible. The digital controller can handle from 8 to 32 control loops and the most common control algorithms, and it can be expanded by simply adding similar controllers and/or more complex second stage control devices.

Design and performance of an 8 cm thick intrinsic germanium detector telescope

A detector telescope consisting of eight 1 cm thick intrinsic Ge diodes is described. The diodes have thin dead layer Li junctions (∼15 ωm) and are mounted in interchangeable holders. Designs of the holders and the mounting assembly are presented. The major problem in using stopping detectors at medium energies is the tail of low pulse height events produced by nuclear reactions and scattering out. A technique for rejecting these events is described and the results obtained with deuterons from p-d elastic scattering of 800 MeV protons are presented. Analysis of the nuclear reaction tail for 120, 220, and 250 MeV deutrons yields an average total reaction cross section for deuterons on Ge of σ R = (1490±130) mb.

βdecay and mass of the new neutron-rich isotopeTi53

The new isotope $^{53}\mathrm{Ti}$ has been produced with the $^{48}\mathrm{Ca}(^{7}\mathrm{Li}, pn)^{53}\mathrm{Ti}$ reaction at ${E}_{^{7}\mathrm{Li}}=14\ensuremath{-}20$ MeV. The $\ensuremath{\beta}$-decay scheme of $^{53}\mathrm{Ti}$ was determined from $\ensuremath{\gamma}$-ray singles and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence experiments using high-resolution Ge(Li) and intrinsic germanium detectors. The four strongest decay $\ensuremath{\gamma}$ rays have energies of 100.8, 127.6, 228.4 (all \ifmmode\pm\else\textpm\fi{} 0.1), and 1675.5 \ifmmode\pm\else\textpm\fi{} 0.3 keV, with relative intensities of 50.9 \ifmmode\pm\else\textpm\fi{} 2.7, 115.4 \ifmmode\pm\else\textpm\fi{} 12.0, 100, and 62.5 \ifmmode\pm\else\textpm\fi{} 6.7, respectively. The $^{53}\mathrm{Ti}$ half-life was determined to be 32.7 \ifmmode\pm\else\textpm\fi{} 0.9 sec. Three new levels with excitation energies of 1958, 2550, and 2931 keV were observed in the daughter $^{53}\mathrm{V}$. The total $^{53}\mathrm{Ti}$ decay energy of 5.02 \ifmmode\pm\else\textpm\fi{} 0.10 MeV was measured by performing a $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ coincidence experiment using a plastic scintillation detector for the $\ensuremath{\beta}$ rays. This yields a $^{53}\mathrm{Ti}$ mass excess of -46.84 \ifmmode\pm\else\textpm\fi{} 0.10 MeV. The decay scheme provides ${J}^{\ensuremath{\pi}}$ restrictions for the observed states of $^{53}\mathrm{V}$, and these are compared with previous measurements and shell model calculations. The measured mass of $^{53}\mathrm{Ti}$ is compared with various predictions.RADIOACTIVITY $^{53}\mathrm{Ti}$ [from $^{48}\mathrm{Ca}(^{7}\mathrm{Li}, pn)$]; measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ${E}_{\ensuremath{\beta}}$, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coin, $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ coin; deduced decay scheme, $log\mathrm{ft}$, mass excess. $^{53}\mathrm{V}$ deduced levels, $J$ restrictions, $\ensuremath{\pi}$. Enriched targets, multiple rabbit facility; Ge(Li), intrinsic Ge, and plastic detectors.

Detection of Mössbauer γ-rays from 73Ge and 181Ta

Lithium-drifted silicon and intrinsic germanium detectors are compared as detectors for the recoilless γ-rays from 73Ge at 13.3 keV and from 181Ta at 6.2 keV. In both cases it is found that the ratio of recoilless gamma counts to noise counts is substantially better with the intrinsic germanium detector. As a result of this improved background rejection, large Mössbauer absorption effects are seen with both isotopes. It is believed that the possibilities discussed here for reducing detector background will be of value in many experiments involving low energy X- or γ-ray fluorescence.

Characteristics of Large Intrinsic Germanium Detectors Operated at Elevated Temperatures

The operational characteristics of two large (25 and 75 cm3, coaxial) intrinsic germanium detectors have been investigated as a function of temperature in order to establish definitive base lines and design criteria for satellite-borne spectrometer systems. The selection of a cooling system and the optimization of the design are critically dependent upon the acceptable temperature limits for the operation of a germanium detector. To establish the usable range for operation we have studied the temperature dependence of critical parameters such as the energy resolution, pulse height and reverse current. The data, although based on only two detectors, indicate the possibility of operating large intrinsic detectors at temperatures significantly higher than that observed for Ge(Li) detectors of comparable size.

Development of a plutonium-americium monitor for in situ soil surface and pond bottom assay

An intrinsic germanium detector has been found to provide in situ monitoring of the depth and concentration of 239Pu and 241AAm in soil surfaces and pond bottoms. The detector can simultaneously measure the three uranium X-ray peaks from plutonium decay and the 26 and 60 keV gamma ray peaks from 241Am. Average 241Am depths are determined from the change in the 26 to 60 keV peak ratio relative to the ratio observed for a thin source of 241Am on the surface of the soil. The 241Am activity is then determined from the depth-corrected intensity of the 60 keV photopeak, and the 241Am contribution to the uranium X-ray measurements of 239Pu is calculated. The average depth and activity of the 239Pu deposit is calculated from the corrected X-ray peaks in the same manner as for 241Am. Detection limits for the method are 6.1 dpm/cm 2 241Am and 72 dpm/cm 2 239Pu for soil depths up to several millimeters. Americium-241 can be measured at soil depths of several centimeters at 10 dpm/cm 2. The effect of soil composition was also examined. The intrinsic Ge detector was determined to be most suitable for this type of monitoring after comparison with the response of NaI(Tl) scintillators, gold surface barrier alpha detectors, and gas proportional ionization chambers.

Intrinsic germanium detector used in borehole sonde for uranium exploration

A borehole sonde (∼1.7 m long; 7.3 cm diameter) using a 200 mm 2 planar intrinsic germanium detector, mounted in a cryostat cooled by removable canistersof frozen propane, has been constructed and tested. The sonde is especially useful in measuring X- and low-energy gamma-ray spectra (40–400 keV). Laboratory tests in an artificial borehole facility indicate its potential for in-situ uranium analyses in boreholes irrespective of the state of equilibrium in the uranium series. Both natural gamma-ray and neutron-activation gamma-ray spectra have been measured with the sonde. Although the neutron-activation technique yields greater sensitivity, improvements being made in the resolution and efficiency of intrinsic germanium detectors suggest that it will soon be possible to use a similar sonde in the passive mode for measurement of uranium in a borehole down to about 0.1% with acceptable accuracy. Using a similar detector and neutron activation, the sonde can be used to measure uranium down to 0.01%.

States excited inNd146by thermal and average-resonance neutron-capture gamma rays

Thermal neutron capture in enriched and natural neodymium targets and average-resonance neutron capture in natural-neodymium targets yield high- and medium-energy $\ensuremath{\gamma}$-ray spectra. These spectra are compared with each other to determine the energies and relative intensities of $\ensuremath{\gamma}$ rays from $^{146}\mathrm{Nd}$ which are then used to construct a partial level scheme for $^{146}\mathrm{Nd}$. A cooled intrinsic-germanium detector is used in both coincidence and anticoincidence modes of operation to measure the spectra. Of 146 $\ensuremath{\gamma}$ rays observed in the 400 to 2800 keV range, 56 are located as transitions among 33 states. Thirty-one primary transitions following average neutron capture are used to describe all but one of the excited states. Most of the states are newly reported here with definite parity assignments and restricted spin choices. A search for the ${2}^{+}$ member of a previously suggested two-phonon triplet indicates that the existence of this member is not likely. The capture state energy is determined to be 7564.7 \ifmmode\pm\else\textpm\fi{} 0.4 keV.NUCLEAR REACTIONS $^{145}\mathrm{Nd}(n,\ensuremath{\gamma})$, ${E}_{n}=\mathrm{thermal}$, measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, 0.45-2.85 MeV, 4.5-7.1 MeV, intrinsic germanium detector (IGD), thermal neutrons; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, 4.5-7.1 MeV, average resonance reutrons IGD; level scheme for $^{146}\mathrm{Nd}$, ${J}^{\ensuremath{\pi}}$, $\ensuremath{\gamma}$-ray branching.

The determination of 125I and 129I using an intrinsic-germanium detector for x-ray spectroscopy.

Abstract An analytical method for the determination of 125I and 129I in environmental samples is described. Samples are treated to convert all iodine to a common oxidation state prior to chemical separation and purification. The iodine is reduced to I2; then the elemental iodine is extracted into CCl4, back extracted into water and precipitated as PdI2. The chemical recovery is determined gravimetrically. The PdI2 precipitate is counted on an intrinsic-germanium detector, and the intensities of the Kalpha X-rays from 125I and 129I are measured. A matrix solution is used to correct for the interference of one spectral region to the other. If 131I is present, as indicated by an independent measurement, a correction for 131I interference is also made.

Efficiency calibration of semiconductor detectors in the X-ray region

A method is outlined for the accurate determination of detection efficiencies of thin planar semiconductor detectors. The method involves experimental measurement of the detection efficiency, combining values obtained from standard sources with values obtained from two experimental techniques developed to provide a larger number of reliable experimental values. A theoretical model, independent of the measured efficiency is then used to interpolate between experimental values. The reliability of the model is verified by an absolute comparison of the calculated efficiency with the experimental efficiency. The theoretical values for a typical intrinsic germanium detector are shown to agree within 3% with all experimental values between 6 keV and 60 keV.