Type Of Scintillation Detector Research Articles

Metrological approach of γ-emitting radionuclides identification at low statistics: application of sparse spectral unmixing to scintillation detectors

This paper presents a metrological approach of spectral unmixing for automatic identification and quantitative analysis of γ-emitting radionuclides in natural background radiation at low statistics. Based on full-spectrum analysis, the proposed method relies on the maximum likelihood estimation based on Poisson statistics that accounts for the spectral signatures of the γ-emitters to be identified and natural background. In order to obtain robust decision-making at low statistics, a sparsity constraint is implemented along with counting estimation given by spectral unmixing. In contrast with the standard approach, this technique relies on a single decision threshold applied for a likelihood ratio test. Standard deviations on estimated counting are determined using the Fisher information matrix. The robustness of decision-making and counting estimation was investigated by means of Monte Carlo calculations based on experimental spectral signatures of two types of scintillation detectors [NaI(Tl), plastic]. This study demonstrates that sparse spectral unmixing is a reliable method for γ-spectra analysis based on low-level measurements. The sparsity constraint acts as an efficient technique for decision-making in the case of complex mixtures of γ-emitters with significant contribution of natural background. This method also yields unbiased counting estimation related to the identified radionuclides. Reliable assessment of standard deviations are obtained and the Gaussian approximation of the coverage intervals is validated. The proposed method can be applied either by non-expert users for automatic analysis of γ-spectra or to help experts in decision-making in the case of complex mixtures of γ-emitters at low statistics.

Detection of Prompt Gamma Radiation Near the LVR-15 Research Reactor.

The paper describes a method of pulse height spectrum measurement in a wide energy range. The LVR‑15 research reactor building was chosen to demonstrate this method. Pulse height spectra were measured on the third floor of the reactor building. Two types of scintillation detectors, NaI (Tl) and a plastic scintillator, were used. The detectors were placed for about 25 m from the reactor core, thus, separated from the primary circuit water in the reactor pool, biological shielding, building wall and other constructional materials. Spectra were measured in a wide energy range from 30 keV to 1000 MeV, in which signals were recorded from natural and man-made radionuclides, prompt gamma radiation and cosmic radiation. Experimental data were collected both while the reactor was in operation and while it was out of operation. This study confirms that differences in these spectra can be detected remotely over relatively large distances from the reactor core by adequately simple detection means.

Beam energy measurement on LINAC-200 accelerator and energy calibration of scintillation detectors by electrons in range from 1 MeV to 25 MeV

Abstract Accurate determination of the energy of LINAC-200 fast electrons was performed using several photonuclear reactions carried out on natural Indium after conversion of electron energy in bremsstrahlung in thick Tungsten target. Natural Indium was used as an activation detector and the ratios of saturation activities R( 113m In)/R( 115m In), R( 114m In)/R( 115m In) and R(111In)/R ( 115m In) were used as a measure of the endpoint energy of the bremsstrahlung beam (and energy of electrons striking the bremsstrahlung target as well). Energy dependence of the three ratios of saturation activities were determined by using the bremsstrahlung produced by electrons accelerated by Microtron to the energies known with accuracy not worse than 0.1 MeV. Three types of scintillation detectors (LaBr3:Ce, BGO and plastic) were calibrated using electrons having energies from 1.17 MeV to 25 MeV. In low energy region photoelectrons produced by 60 Co gamma radiation in the detector itself were used, as well as high energy electrons (from 11 MeV to 25 MeV) accelerated by LINAC-200.

Geant4 code for simulation attenuation of gamma rays through scintillation detectors

Geant4-based Monte Carlo simulations have been carried out for studying mass attenuation for different types of scintillation detectors at different photon energies. The simulations showed that the calculated mass attenuation values are close to experimental values better than the other obtained theoretical data base for the same detector. The results indicate that Geant4 can be applied to estimate mass attenuation for various materials and energies.

Development and Studies of Novel Microfabricated Radiation Hard Scintillation Detectors With High Spatial Resolution

A new type of scintillation detector is being developed with standard microfabrication techniques. It consists of a dense array of scintillating waveguides obtained by coupling microfluidic channels filled with a liquid scintillator to photodetectors. Easy manipulation of liquid scintillators inside microfluidic devices allow their flushing, renewal, and exchange making the active medium intrinsically radiation hard. Prototype detectors have been fabricated by photostructuration of a radiation hard epoxy resin (SU-8) deposited on silicon wafers and coupled to a multi-anode photomultiplier tube (MAPMT) to read-out the scintillation light. They have been characterized by exciting the liquid scintillator in the 200 micrometers thick microchannels with electrons from a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{90}{\rm Sr}$</tex> </formula> yielding approximately 1 photoelectron per impinging Minimum Ionizing Particle (MIP). These promising results demonstrate the concept of microfluidic scintillating detection and are very encouraging for future developments.

Comparative measurements of thermal neutron fluxes at ground level at the baksan neutrino observatory and LGNS laboratory

Thermal neutron fluxes were measured using two types of scintillation detectors based on the inorganic scintillator ZnS(Ag): 6LiF+ZnS(Ag) and 10B2O3 + KCl+ZnS(Ag). The preliminary results from these measurements are given. The thermal neutron concentration as a function of altitude above sea level was determined. The measurements were performed at three locations: in Moscow, at the Baksan Neutrino Observatory of the Russian Academy of Sciences, and at the Gran Sasso National Laboratory. Variations of neutron count rates associated with lunar cycles were observed at the remote laboratories.

Parameters of the new scintillation detectors

The parameters of two types of scintillation detectors—LGSO + solid state photomultiplier and LaBr3 + ΦЭУ-184 photomultiplier tube—are experimentally estimated. These detectors are interesting from the standpoint of γ-ray measurements.

Long Scintillation Detector Using Composite Light Guide for β-ray Survey Measurement

In this paper, we describe a new type of scintillation detector that can be inserted into long, narrow tubes used in nuclear power plants to measure radioactive contamination of their inner surfaces. The sensitive area of the detector needs to cover the entire circumference and extend along the longitudinal axis, and its performance must be equivalent to that of a conventional survey meter. To construct such a sensitive area, we bonded six long, thin plastic scintillator strips around a hexagonal center core. For the hexagonal center core, we proposed a novel light collection structure called a “composite light guide,” using a wavelength-shifting technique to maintain the counting efficiency while achieving better uniformity along the longitudinal axis. We conducted basic experiments, and also established a simple light propagation model of the composite light guide, focusing on the light intensity, and confirmed its effectiveness. Using this light propagation model, we determined the optimum design and incorporated it into the manufacture of a prototype detector. From tests of the prototype detector, we verified that its performance satisfied the design requirements and that the composite light guide functioned effectively.

Pulsed Neutron Facility for Research in Illicit Trafficking and Nuclear Safeguards

The Joint Research Centre has taken into operation a new experimental facility designed for research in the fields of illicit trafficking and nuclear safeguards. The research projects currently undertaken include detection of shielded contraband materials (drugs, explosives, nuclear materials), and mass determination of small fissile materials in shielded containers. The facility, called the Pulsed Neutron Interrogation Test Assembly (PUNITA), incorporates a pulsed 14-MeV D-T neutron generator and a large graphite mantle surrounding a sample cavity. The sealed generator emits neutrons in 10-microsecond pulses. After a slowing-down time of approximately 300 mus, an average thermal neutron lifetime of approximately one millisecond is achieved in the graphite moderator and the sample cavity. By pulsing the neutron generator with a frequency between 10 to 150 Hz, a sample may be interrogated first by fast neutrons, and a few hundred microseconds later by a pure thermal neutron flux. For the detection of materials such as explosives the facility employs gamma detectors for characteristic prompt gamma rays from inelastic scattering by fast neutrons, and from thermal neutron capture. The gamma detectors include HPGe detectors and lanthanum bromide scintillation detectors. This new type of scintillation detector is particularly suited for the detection of activation gamma rays in the MeV range. For the purpose of fissile material assay (nuclear safeguards) the PUNITA facility employs 96 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He proportional counters located on the outside of the graphite liner and embedded in cadmium covered polyethylene modules. The paper reports about the design and characterization of the new research facility as well as the different experimental configurations employed for the research activities in the fields of illicit trafficking and nuclear safeguards.

Comparison of four types of gamma- and X-ray detectors for environmental applications in the 10–450 keV energy range

The performance of four types of γ- and X-ray radiation detectors for environmental applications was evaluated in the 10–450 keV energy range. Two cadmium zinc telluride (CdZnTe) room temperature semiconductor detectors were evaluated along with a cryogenically cooled semiconductor detector and two different types of scintillation detectors. The energy resolution, absolute peak detection efficiency and peak-to-background ratio of each of the detectors were calculated and intercompared. The advantages and disadvantages of environmental applications of each detector, along with their performance results, are summarized.

The Absorbed Dose in Air of Photons Generated from Secondary Cosmic Rays at Sea Level at Nagoya, Japan

Investigations have been carried out to determine the absorbed dose in air of photons generated from secondary cosmic radiation at sea level at Nagoya, Japan. To isolate the contribution from cosmic photons, the pulse-height distributions due to µ particles and electrons were eliminated from the observed pulse-height distribution of a measurement with a 3" diam. spherical NaI(Tl) detector. The pulse height due to µ particles and electrons was inferred from the coincidence technique using two types of scintillation detectors with different sensitivities to photons. To obtain the photon fluence rate for further dose calculation, the pulse-height distribution of cosmic photons was unfolded by the iterative method. The mean and its standard deviation of the absorbed dose in air and fluence rate due to cosmic photons calculated from a one year observation are 2.86±0.05 nGy.h-1 and 0.1342±0.0015 photons.cm-2.s-1, respectively. The absorbed dose in air from cosmic photons was 0.5% lower during autumn to winter and 0.6% higher during spring to summer than the mean taken over the year.

An associated gamma ray time of flight spectrometer with high neutron efficiency

A high efficiency, associated gamma ray time of flight spectrometer for the study of (n, γ) angular correlations following (charged particle, n) reactions is described. The neutron detector employs eight XP1040 photomultiplier tubes viewing four tanks of NE213 liquid scintillator, and subtends a solid angle of 0.092 sterad at the target when the neutron flight path is two metres. Neutron events in the scintillator are identified by means of pulse shape discrimination. The use of constant fraction pulse height discriminators to provide fast timing pulses, enables the use of a wide dynamic pulse height range in both the neutron and gamma ray detectors. This method of timing enables the gamma ray detector to be changed from a Ge(Li) counter, to a NaI(Tl) or other type of scintillation detector with only a minimal rearrangement of the electronic system.

A detector for neutral and charged particles

A type of scintillation detector is described that counts low and high energy charged particles with high efficiency. Its application to the detection of low energy neutral particles has also been investigated. The use of glass scintillators in a bakable version of the device is also discussed.