Background Reduction Techniques Research Articles

Detection of bremsstrahlung radiation of 90Sr-90Y for emergency lung counting

This study explores the possibility of developing a field-deployable (90)Sr detector for rapid lung counting in emergency situations. The detection of beta-emitters (90)Sr and its daughter (90)Y inside the human lung via bremsstrahlung radiation was performed using a 3″ × 3″ NaI(Tl) crystal detector and a polyethylene-encapsulated source to emulate human lung tissue. The simulation results show that this method is a viable technique for detecting (90)Sr with a minimum detectable activity (MDA) of 1.07 × 10(4) Bq, using a realistic dual-shielded detector system in a 0.25-µGy h(-1) background field for a 100-s scan. The MDA is sufficiently sensitive to meet the requirement for emergency lung counting of Type S (90)Sr intake. The experimental data were verified using Monte Carlo calculations, including an estimate for internal bremsstrahlung, and an optimisation of the detector geometry was performed. Optimisations in background reduction techniques and in the electronic acquisition systems are suggested.

The Target Motion Detection Algorithm Based on Gauss Mixture Model

Background reduction technique not only has the characteristics of pixels identify changes and small time complexity, but also can provide better detection results. The paper puts forward the running average method constructing background image by Gaussian mixture mode detecting background region and foreground region, and then adopting background reduction realizes the detection of moving target. Experimental results show that the algorithm effectively may realize background extraction and updating, and then completely and accurately detects moving targets. The algorithm has been achieved good results in the video vehicle detection.

Pulse shape analysis to reduce the background of BEGe detectors

A simple technique for pulse shape discrimination in HPGe-detectors of the so-called BEGe type, based on just one parameter obtained from one signal read out, is presented here. This technique allows discriminating between pulses generated when the deposited energy is located within a small region of about 1 mm3 from the pulses generated when the energy is deposited at different locations several mm or cm apart. Two possible applications using this technique are: (i) experiments that look for neutrinoless double β decay in 76Ge, such as GERDA; (ii) γ spectrometry measurements where the Compton continuum can be reduced and the efficiency for cascading γ-rays can remain high. With this active background reduction technique a Compton suppression factor of about 3 was obtained. The detector response may be influenced by the detector size. The detector used for this study had a diameter of 6 cm, a thickness of 2.6 cm and a relative efficiency of 19%. The results obtained with this detector were consistent with the results obtained by Budjas et al. [J Instrum 4:10, 2009] with a 50% relative efficiency BEGe detector.

Systematic effects in pulse shape analysis of HPGe detector signals for [formula omitted

Pulse shape analysis is an important background reduction and signal identification technique for next generation of 76Ge 0 ν β β experiments. We present a study of the systematic uncertainties in one such parametric pulse-shape analysis technique for separating multi-site background from single-site signal events. We examined systematic uncertainties for events in full-energy gamma peaks (predominantly multi-site), double-escape peaks (predominantly single-site) and the Compton continuum near Q β β (which will be the dominant background for most 0 ν β β searches). In short, we find total (statistical plus systematic) fractional uncertainties in the pulse shape cut survival probabilities of: 6.6%, 1.5% and 3.8% for double-escape, continuum and γ ‐ ray events, respectively.

Ultra-low background measurements of decayed aerosol filters.

Aerosol samples collected on filter media were analyzed using HPGe detectors employing varying background-reduction techniques in order to experimentally evaluate the opportunity to apply ultra-low background measurement methods to samples collected, for instance, by the Comprehensive Test Ban Treaty International Monitoring System (IMS). In this way, realistic estimates of the impact of low-background methodology on the sensitivity obtained in systems such as the IMS were assessed. The current detectability requirement of stations in the IMS is 30 μBq/m3 of air for 140Ba, which would imply ~106 fissions per daily sample. Importantly, this is for a fresh aerosol filter. One week of decay reduces the intrinsic background from radon daughters in the sample allowing much higher sensitivity measurement of relevant isotopes, including 131I. An experiment was conducted in which decayed filter samples were measured at a variety of underground locations using Ultra-Low Background (ULB) gamma spectroscopy technology. The impacts of the decay and ULB are discussed.

The G erda muon veto Cherenkov detector

The GERmanium Detector Array, G erda, is a new experiment designed to examine the neutrinoless double beta decay 0 ν β β of 76Ge which has a lifetime of at least 10 26 years and a single energy deposition of 2039 keV. To reach the goal of 10 - 3 background events/( keV kg y ), several background reduction techniques like anti-coincidence and pulse shape analysis will be used. Cosmic muons can produce background in form of particles and radioactivity. To reject them, two independent detector systems will be integrated in G erda. One of these is a Cherenkov muon veto detector, that uses the water tank around the cryostat in which the crystals will be operated. It is equipped with 66 photomultipliers (PMTs) with 8 in. diameter. The PMT distribution was found via extensive Monte Carlo studies to reach the highest efficiencies for dangerous muons (these are muons that cause an energy deposition of around 2 MeV in the germanium detectors), even though the PMTs cover less than 0.1% of the water tank surface. High efficiencies depend strongly on the amount of detected photons. For this, as many surfaces as possible will be covered with ‘VM2000’, a highly reflective foil from 3 M. This foil has a high reflectivity in a wide range of wavelength and it also shifts photons from the UV into the optical range. It, more or less, doubles the amount of detectable photons, because the photomultipliers used, have an detection maximum between 370 and 400 nm. Thus, a detection efficiency of 98% should be easily achieved.

CosmogenicC11production and sensitivity of organic scintillator detectors topepand CNO neutrinos

Several possible background sources determine the detectability of pep and CNO solar neutrinos in organic liquid scintillator detectors. Among such sources, the cosmogenic 11C nuclide plays a central role. 11C is produced underground in reactions induced by the residual cosmic muon flux. Experimental data available for the effective cross section for 11C by muons indicate that 11C will be the dominant source of background for the observation of pep and CNO neutrinos. 11C decays are expected to total a rate 2.5 (20) times higher than the combined rate of pep and CNO neutrinos in Borexino (KamLAND) in the energy window preferred for the pep measurement, between 0.8 and 1.3 MeV. This study examines the production mechanism of 11C by muon-induced showers in organic liquid scintillators with a novel approach: for the first time, we perform a detailed ab initio calculation of the production of a cosmogenic nuclide, 11C, taking into consideration all relevant production channels. Results of the calculation are compared with the effective cross sections measured by target experiments in muon beams. This paper also discusses a technique for reduction of background from 11C in organic liquid scintillator detectors, which allows to identify on a one-by-one basis and remove from the data set a large fraction of 11C decays. The background reduction technique hinges on an idea proposed by Martin Deutsch, who suggested that a neutron must be ejected in every interaction producing a 11C nuclide from 12C. 11C events are tagged by a three-fold coincidence with the parent muon track and the subsequent neutron capture on protons.

Next-generation germanium spectrometer background reduction techniques at 2 Me

The Majorana project, a next-generation 76Ge neutrinoless double-beta decay experiment being undertaken by a large international collaboration, has the goal of measuring the neutrinoless double-beta decay rate by observing monochromatic events at 2039 keV in 500 kg of isotopically enriched 76Ge gamma-ray spectrometers. In order to achieve the desired sensitivity limit, the background in the 2037-2041 keV region must be reduced to <1 event per year in the entire germanium array. The effects of various background reduction techniques, and the combination thereof, to produce a huge 76Ge spectrometer array with virtually zero background are discussed.

Challenges encountered in extending the sensitivity of US Environmental Protection Agency Method 314.0 for perchlorate in drinking water

Concerns about the potential adverse health effects of perchlorate at concentrations below the minimum reporting level (MRL) of US Environmental Protection Agency (EPA) Method 314.0 (generally recognized as 4.0 μg/l) have led to an interest in increasing the sensitivity of the method. This work describes the use of 2 mm columns with a large-loop direct injection method, a column concentration technique and this concentration technique with a background reduction step, to increase the sensitivity for the analysis of trace levels of perchlorate in high ionic strength matrices. The concentrator columns studied were the Dionex TAC LP-1 and a new Dionex high capacity Cryptand concentrator column. The use of a surrogate to monitor trapping efficiency for the concentration technique and the use of confirmational columns to minimize the potential for false positives are also discussed. The large-loop direct injection method and the column concentration methods provided acceptable data when the samples were pre-treated with solid phase pretreatment cartridges. The background reduction technique did not provide acceptable data with either of the concentrator columns evaluated.

Monte Carlo simulation of induced radioactive background in gamma-ray detector materials

Induced activation in detector materials constitutes a major source of background for spaceborne /spl gamma/-ray instruments. Future detector systems will utilise a variety of background reduction techniques and novel detector materials to maximise signal-to-noise and resolution of the measurements taken, and assessment of the merits of different designs will require detailed attention to a wide range of physical processes. The Integrated Radiation Transport Suite (IRTS) has been applied to simulate the effects of spacecraft shielding against Van Allen and galactic cosmic-ray protons, the production of secondary hadrons, and induced radioactivity in and the response of /spl gamma/-ray detector materials. This paper discusses the physics requirements for these simulations, and the degree of success of the models through comparisons with experimental data obtained from Space Shuttle flights and proton-beam irradiation of detector materials.

Influence of target properties on prompt in-beam electron spectra

Some important physical factors influencing in-beam e-γ measurements are briefly discussed. The close implication between target and beam properties including the reaction products on high resolution in-beam electron spectroscopy is worked out. The influence of the target properties on their Doppler broadening of an electron line analyzed by axial symmetric spectrometers is discussed in detail. A few examples of the target influence on prompt in-beam electron spectra are also presented in the perpendicular geometry, while the important role of electron background reduction techniques is stressed in the forward collinear geometry.

The Broad Band X-Ray Telescope (BBXRT) on Astro-1

AbstractBBXRT is one of four pointed instruments comprising NASA’s Astro-1 mission, currently scheduled for a 9–10 day flight in May 1990 on board the Space Shuttle Columbia. X-ray Spectra of over 150 sources will be obtained in the energy range 0.3 to 12 keV, with energy resolution of ~100 eV FWHM and timing resolution of 64 μS. BBXRT’S large throughput, broad band mirrors, coupled to segmented cooled Si(Li) detectors, give us the first opportunity to study in detail X-ray spectral features, from oxygen to the iron K band. In developing this instrument, we have made extensive use of detector background reduction techniques in order to be able to observe the many faint extra-galactic sources discovered with the Einstein observatory. Sources in our observing plan have been selected to give us in a 2–4 ks observation &lt; 103 net counts with negligible background. Specific scientific objectives range from refinements of spectra previously obtained at lower resolution, such as a search for relativistic line shifts in compact objects, to observations of faint extragalactic sources for which spectral information is, at best, sketchy, viz. elliptical galaxies and distant quasars. High on our priorities are a search for emission from SN1987A and the first simultaneous observations in the UV and X-ray band of selected sources such as cataclysmic variables and late-type stars.