Intrinsic Detector Research Articles

The majorana neutrinoless double-beta decay experiment

The proposed Majorana double-beta decay experiment is based on an array of segmented intrinsic Ge detectors with a total mass of 500 kg of Ge isotopically enriched to 86% in 76Ge. A discussion is given of background reduction by material selection, detector segmentation, pulse shape analysis, and electroformation of copper parts and granularity. Predictions of the experimental sensitivity are given. For an experimental running time of 10 years over the construction and operation oft he Majorana setup, a sensitivity of T 0ν1/2 ∼4×1027 yr is predicted. This corresponds to 〈mν〉∼0.003−0.004 eV according to recent QRPA and RQRPA matrix element calculations.

Status and perspectives of detectors for experiments in HEP and related fields

Developments in the field of particle detectors are reviewed. Due to increasing physics demands, intrinsic detector limitations are becoming more and more of an issue, necessitating fundamental R&D. The example of high-resolution jet spectroscopy is chosen to illustrate this.

An advanced Compton telescope based on thick, position-sensitive solid-state detectors

The development of high-resolution, position-sensitive solid-state detectors enables γ-ray instruments with improved sensitivity and imaging capabilities. For γ-ray astronomy, an improvement in sensitivity of 20–50 over previous missions is anticipated with the Advanced Compton Telescope (ACT) mission. The γ-ray astrophysics group at NRL has been developing germanium strip detectors for several years. We have shown that 3D locations for γ-ray interactions can be determined with mm accuracy, and have also demonstrated imaging capability within a single germanium strip detector and in detector arrays. Based on the realization that three Compton interactions would enable the energy and direction cone of the incident γ-ray to be determined, even when the total incident γ-ray energy is not deposited in the detector, we have also initiated work on thick silicon strip detectors. We are investigating the use of both thick Si(Li) and thick intrinsic silicon detectors. Progress on this work, including initial tests of the multiple-Compton imaging technique, is presented.

STJ X-ray detectors with titanium sublayer

Superconducting tunnel junctions (STJs) with the structure Ti/Nb/Al, AlOx/Al/Nb/NbN and corresponding layer thickness 30/100/8/13/150/30nm were investigated as X-ray detectors at T=1.35K. STJs with one active electrode in which the response of the other one is suppressed due to trapping layer on the surface opposite to the tunnel barrier have a number of potential advantages. The best line width (FWHM) is 78eV for 6400μm2 junction. Contribution of the electronic noise is about 50eV. The intrinsic detector line width is less than 60eV. The collected charge from inactive electrode is more than 8 times less than that from the active one. Titanium proved to be an appropriate material for a sublayer and a trap.

Josephson device for simultaneous time and energy detection

The development of a detection device for simultaneous measurement of energy and impact time, to be used in time-of-flight mass spectrometry, is reported. In this device, two superconducting tunnel junctions are coupled through a passive network. The first junction operates in the quasiparticle regime in order to measure the energy of a molecule impact and to act as a proportional detector. The second one operates in the Josephson regime in order to act as a fast discriminator for the impact time of a molecule impinging on the detector junction. In this way, a very accurate time determination can be achieved limited only by the intrinsic detector response, thus improving the spectrometer mass resolution. To demonstrate the feasibility of this detection scheme in mass spectrometry, calibration measurements have been carried out using a Fe55 x-ray source to simulate the molecule impact. The experimental results successfully demonstrated simultaneous detection of energy and arrival time in coincidence with photon impacts, with a time resolution limited, in practice, only by the electronics used.

Natural radioactivity levels in river, stream and drinking water of the northwestern areas of Pakistan

Natural radioactivity in the aquatic media has been determined by collecting samples of river, stream and drinking water from the northwestern areas of Pakistan. The concentrations of 40K, 226Ra and 232Th have been measured using a low background gamma-spectrometer and a 10 cm3 planar intrinsic high purity germanium detector. The annual ingestion of these radionuclides, using local consumption rates (average over the whole population) of 0.9 l.d-1, were estimated to be 49.2, 6.2 and 1.1 Bq.y-1 for 40K, 226Ra and 232Th, respectively. A comparison of the annual intakes of these radionuclides, using annual consumption rates of NCRP, ICRP and FBSP shows that the contribution from natural radionuclides to annual intake is slightly greater for NCRP than for ICRP and FBSP consumption rates. However, the estimated values and weighted means of these radionuclides compare well with the world average. The annual effective dose equivalent from drinking water was found to be 3.6.10-6 mSv.y-1 (226Ra), 3.2.10-12 mSv.y-1 (232Th) and 2.1.10-6 mSv.y-1 (40K). These values are lower than those given by NCRP.

An ultrafast NbN hot-electron single-photon detector for electronic applications

We present the latest generation of our superconducting single-photon detector (SPD), which can work from ultraviolet to mid-infrared optical radiation wavelengths. The detector combines a high speed of operation and low jitter with high quantum efficiency (QE) and very low dark count level. The technology enhancement allows us to produce ultrathin (3.5 nm thick) structures that demonstrate QE hundreds of times better, at 1.55 μm, than previous 10 nm thick SPDs. The best, 10 × 10 μm2, SPDs demonstrate QE up to 5% at 1.55 μm and up to 11% at 0.86 μm. The intrinsic detector QE, normalized to the film absorption coefficient, reaches 100% at bias currents above 0.9 Ic for photons with wavelengths shorter than 1.3 μm.

A quantum dot infrared photodetector with lateral carrier transport

In this contribution we present a normal-incidence quantum dot (QD) infrared detector structure. It is based on intra-conduction band transitions between the p-states of the QD and the wetting layer subband and lateral transport of photoexcited carriers in a channel next to the quantum dot layers. The photoresponse is peaked at 6.5 μm (186 meV ) and reaches several A/W up to 60 K . The intrinsic detector response time is determined to be about 0.8 ms . Temperature and frequency dependence of the detector structure are discussed.

Random and channeled energy loss of 33.2-TeV Pb nuclei in silicon single crystals

Measurements of the energy loss and the energy-loss distributions of 160 GeV/amu fully stripped lead ions traversing a silicon single crystal are presented. The energy loss is measured using the silicon crystal as an intrinsic detector. Hence the measured energy loss is a restricted energy loss excluding very large energy transfers. For random incidence, the observed energy-loss distributions are very narrow and Gaussian-like. For well-channeled particles, the energy loss is strongly reduced as compared to so-called random particles. The observed energy loss is compared to calculations as well as simulations. Due to the small straggling, the energy-loss distributions are reflecting directly the distribution in transverse energy.

Response uniformity of a large size RPC

The response uniformity of a 90×290 cm 2 RPC prototype working in avalanche mode has been tested using cosmic rays. The high statistics needed for the test has also been used for accurate efficiency studies. The intrinsic detector inefficiency free, from spacers effects has been measured.

Techniques to improve the spatial sampling of MicroPET-a high resolution animal PET tomograph

A method is described to improve the spatial sampling of microPET, a high resolution PET scanner designed for imaging small laboratory animals. The high intrinsic resolution of the microPET detector (1.58 mm FWHM), in combination with the stationary ring geometry of the tomograph, generate an imaging system which is inherently spatially undersampled. As a result the imaging resolution measured with a three-dimensional (3-D) filtered backprojection (FBP) algorithm for a point source at the center of the field of view (CFOV) is only 1.8 mm FWHM and has large fluctuations at positions near the CFOV. A small wobble motion was introduced via a circular motion of the scanner bed in the transverse plane, with a wobble radius of 300 /spl mu/m. The data was acquired with a step-and-shoot method by dividing the wobble circle into a number of equidistantly sampled intervals. The separate sinograms were interpolated to a finely resampled sinogram, which was reconstructed with the 3-D filtered backprojection algorithm. The resulting images demonstrated full recovery of the intrinsic detector resolution and elimination of the local nonuniformities of the point spread function (PSF) at the CFOV, with three wobble samples. The resulting average resolution improvement fur the central 5 cm of the FOV was approximately 13% in the radial and 19% in the tangential direction, with an associated 50% penalty in the reconstructed image noise.

Level sructure in 206At

The high-spin states of 206At have been studied in the reaction 197Au (12C,3n) 206At at 12C energies from 60 to 80 MeV. In-beam measurements of γ-ray excitation functions, γ-γ-t coincidences, and γ-ray angular distributions were carried out with seven BGO(AC)HPGe detectors and one intrinsic Ge planar detector. A level scheme for 206At with 25 γ rays was established for the first time, including a 10− isomer with a measured half-life of 410 ± 80 ns. The level scheme of 206At consists of two disconnected cascades, probably corresponding to the proton excitations and the neutron-hole excitations, respectively.

Uranium and plutonium solution assays by transmission-corrected x-ray fluorescence spectrometry

An x-ray fluorescence analysis technique was developed for uranium and plutonium solutions, which compensates for variations in the absorption of the exciting gamma rays and fluorescent x-rays. 57Co is used to excite efficiently the K lines of the elements, and a mixed 57Co plus 153Gd transmission source is used to correct for variations in absorption. The absorption correction is a unique feature of the technique which permits accurate calibration with a single solution standard and the measurement of a wide range of concentrations (up to 300 g l−1). Without this correction procedure, up to six solution standards are required to correct for non-linearity over this concentration range. In addition, other elements present in the specimens and not present in the standards would otherwise reduce the accuracy or even invalidate the analyses. Specially designed equipment incorporates a planar intrinsic germanium detector, excitation and transmission radioisotopes and specimen holder. The apparatus can be inserted into a rubber glove of a glove-box, keeping the apparatus outside and the solutions inside the glove-box, thereby protecting the user and the equipment from possible contamination. This technique will be tested at the Bochvar Institute of Inorganic Materials in Moscow for possible use in the Russian complex of nuclear facilities. This is part of a cooperative program between laboratories in the USA and Russia to strengthen systems of nuclear materials protection, control and accountability (MPC&A) in both countries. A part of this program is to measure accurately and track inventories of materials, hence the need for good non-destructive analytical techniques. Copyright © 1999 John Wiley & Sons, Ltd.

Uranium and plutonium solution assays by transmission‐corrected x‐ray fluorescence spectrometry

An x-ray fluorescence analysis technique was developed for uranium and plutonium solutions, which compensates for variations in the absorption of the exciting gamma rays and fluorescent x-rays. 57Co is used to excite efficiently the K lines of the elements, and a mixed 57Co plus 153Gd transmission source is used to correct for variations in absorption. The absorption correction is a unique feature of the technique which permits accurate calibration with a single solution standard and the measurement of a wide range of concentrations (up to 300 g l−1). Without this correction procedure, up to six solution standards are required to correct for non-linearity over this concentration range. In addition, other elements present in the specimens and not present in the standards would otherwise reduce the accuracy or even invalidate the analyses. Specially designed equipment incorporates a planar intrinsic germanium detector, excitation and transmission radioisotopes and specimen holder. The apparatus can be inserted into a rubber glove of a glove-box, keeping the apparatus outside and the solutions inside the glove-box, thereby protecting the user and the equipment from possible contamination. This technique will be tested at the Bochvar Institute of Inorganic Materials in Moscow for possible use in the Russian complex of nuclear facilities. This is part of a cooperative program between laboratories in the USA and Russia to strengthen systems of nuclear materials protection, control and accountability (MPC&A) in both countries. A part of this program is to measure accurately and track inventories of materials, hence the need for good non-destructive analytical techniques. Copyright © 1999 John Wiley & Sons, Ltd.

Self-assembled InAs-GaAs quantum-dot intersubband detectors

The use of self-assembled InAs-GaAs quantum dots in photoconductive intersubband detectors in the far-infrared is presented. Far-infrared absorption is observed in self-assembled quantum dots in the 6-18-/spl mu/m range for subband-subband and subband-continuum transitions. Photoconductive quantum-dot intersubband detectors were fabricated and demonstrate tunable operating wavelengths between 6-18 /spl mu/m using subband-subband or subband-continuum transitions. The use of AlAs barriers allows further tuning to shorter wavelengths of 3-7 /spl mu/m. Subband-continuum quantum dot intersubband detectors show encouraging normal incidence performance characteristics at T=40 K, with responsivities of 10-100 mA/W, detectivities of 1-10 /spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W and large photoconductive gain up to g=12 for a ten-layer quantum-dot heterostructure. With improvements in device structure, self-assembled quantum dots can be expected to provide intrinsic normal incidence broad-band detectors with advantages over quantum wells.

Instrumentation of the ESRF medical imaging facility

At the European Synchrotron Radiation Facility (ESRF) a beamport has been instrumented for medical research programs. Two facilities have been constructed for alternative operation. The first one is devoted to medical imaging and is focused on intravenous coronary angiography and computed tomography (CT). The second facility is dedicated to pre-clinical microbeam radiotherapy (MRT). This paper describes the instrumentation for the imaging facility. Two monochromators have been designed, both are based on bent silicon crystals in the Laue geometry. A versatile scanning device has been built for pre-alignment and scanning of the patient through the X-ray beam in radiography or CT modes. An intrinsic germanium detector is used together with large dynamic range electronics (16 bits) to acquire the data. The beamline is now at the end of its commissioning phase; intravenous coronary angiography is intended to start in 1999 with patients and the CT pre-clinical program is underway on small animals. The first in vivo images obtained on animals in angiography and CT modes are presented to illustrate the performances of these devices.

Methodology for the U.S. Food and Drug Administration's radionuclides in foods program

The U.S. Food and Drug Administration (FDA) is responsible for the wholesomeness of the nation's food supply. The FDA modified its food monitoring program in January, 1973, to include radioactive isotopes. The methodology used to perform, analyses on these food products are taken from the standerd setting societies such as the AOAC International, American Society for Testing Materials and American Public Health Association Standard Methods. In addition, methods not tested by these societies are taken from the literature or from Department of Energy manuals such as the Health and Safety Laboratory and also from Environmental Protection Agency, Public Health Service, and Food and Agricultural Organization manuals. These include the methods for long-lived radionuclides such as tritium, strontium-90, cesium-137 and plutonium. Also, the short-lived radionuclides such as iodine-131, radiocesium, radiocerium and radioruthenium. In addition, they include the natural occurring radionuclides such as radium and uranium isotopes. The activity concentrations of gamma-emitters such as radiocesium, iodine-131 and radioruthenium are determined by gamma-ray spectrometry. This is done using intrinsic germanium detectors with the appropriate hardware and software. The alpha and “pure” beta-emitters are determined by various radiochemical methods and techniques. The radiochemical methodology and equipment used in analyzing these radionuclides are described and discussed. Also, the methodology and equipment for the gamma-emitters are described in more detail in this paper. In addition, the limits of detection for the methods used will be discussed.

Validation of induced radioactivity calculations for candidate fusion materials through measurements in a graphite-centered assembly

Abstract Induced radioactivity measurements were carried out jointly by the USA and Japan in a graphite-centered assembly, in the framework of ITER Task T-218 entitled ‘Shielding Blanket Neutronics Experiments’. An intense, accelerator-based D-T rotating target neutron source at JAERI, with a nominal intensity of 5 × 1012 s–1, was used. Two locations, providing different neutron energy spectra, were chosen for irradiating samples of a range of materials of interest to ITER. Three independent experimental campaigns were conducted so as to accommodate a large number of samples, on one hand, and as many short and long half-life products as possible, on the other. The total neutron fluence ranged from 4.7 × 1011 to 1.5 × 1014 ncm–2. Altogether, samples of Mg, Al, SiO2, Ti, V, Cr, Mn, Fe, Co, Ni, FH82 steel, SS316LN steel (ITER grade), Cu, Zn, KCl, Zr, Nb, Mo, Ag, In, Sn, Dy, Ta, Hf, Re, Au, Ir, and Pb were irradiated. The irradiated samples were cooled for variable periods ranging from 30 s to 250 days before their decay gamma-ray spectra were counted on high purity intrinsic germanium detectors. The half lives of the observed radioisotopes have ranged from 18.7 s (46mSc from Ti) to 5.3 years (60Co from Ni). The neutron energy spectra for the two locations were calculated using Monte Carlo code MCNP with FENDL-1 and ENDF/B-VI data libraries. The analysis of isotopic activities, expressed in Bq cc–1, of the irradiated materials has been carried out using REAC-3 radioactivity code, with FENDL-2A and FENDL-1A activation cross-section and decay data libraries. Typically, C/E lies in a band of 0.5–1.5 for the results being reported.

Real-time airborne radiation analysis and collection (RTARAC) searching for airborne species characteristic to nuclear proliferation

An effective means of detecting airborne radioactive aerosol plumes has been developed and tested on aircraft platforms. The Real-Time Airborne Radiation Analysis and Collection (RTARAC) system was mounted in the wing pod of a Navy P-3 where it sampled 20 cubic meters of air per minute on each of eleven sequentially advanced filters. A 140% intrinsic gemanium detector counted radioactive particles collected on the 15 cm circular filters in real-time. Gamma-energy spectrum and near real-time analysis of the sample were displayed on a laptop computer.

EDS from then Till Now—A Chronology of Innovation

Abstract Since its introduction in 1968 on both the EPMA and SEM, the energy-dispersive spectrometer has become widely used from research laboratories to production testing. It has become the mainstay for microanalysis in many scientific disciplines. A discussion of energy-dispersive spectrometry (EDS) logically divides into two lines of development: X-ray detector/hardware and X-ray analyzer/software. Of the several types of EDS detectors, only Si(Li) and intrinsic germanium detectors (IG) will be covered in this review, as they are the most common on electron microscopes. The 1960s— The use of a solid state EDS detector on an EPMA was first described by Fitzgerald, et al. in 1968.1 They realized at the time that the high collection efficiency of about 80% permitted analysis at lower beam current for the same counting statistics and electron dose on the specimen. The first installation of a Si(Li) detector on an SEM came later the same year.