Ray Detection Efficiency Research Articles

Sparse Angle CBCT Reconstruction Based on Guided Image Filtering.

Cone-beam Computerized Tomography (CBCT) has the advantages of high ray utilization and detection efficiency, short scan time, high spatial and isotropic resolution. However, the X-rays emitted by CBCT examination are harmful to the human body, so reducing the radiation dose without damaging the reconstruction quality is the key to the reconstruction of CBCT. In this paper, we propose a sparse angle CBCT reconstruction algorithm based on Guided Image FilteringGIF, which combines the classic Simultaneous Algebra Reconstruction Technique(SART) and the Total p-Variation (TpV) minimization. Due to the good edge-preserving ability of SART and noise suppression ability of TpV minimization, the proposed method can suppress noise and artifacts while preserving edge and texture information in reconstructed images. Experimental results based on simulated and real-measured CBCT datasets show the advantages of the proposed method.

Эзэлхүүнт дээжийг судлах гамма-спектрометрийн үнэмлэхүй арга

The Absolute Method for determination of gamma-emitting radionuclides in environmental samples using gamma spectrometry was described. Density correction coefficients of Gamma:Ray Detection efficiency taking into account absorption of gamma-quants in environmental samples were calculated by the this method (standard Marinelli beaker geometry).

A computational modelling of low-energy gamma ray detection efficiency of a cylindrical NaI(Tl) detector

Measurements show the detection efficiency of the NaI(Tl) detector depends on the source-detector configuration. In this work, the geometrical and intrinsic detection efficiencies of the 2in both in height and diameter and 3in both in height and diameter cylindrical NaI(Tl) detectors have been calculated for low-energy gamma ray. In these calculations, the effects of cover layers of NaI(Tl) (aluminum housing and reflector) have been taken into consideration. To evaluate the calculation model, the detection efficiency of the detector is measured and modelled using MCNP simulation tool. Isotropic 241Am was used as a point source. Results show the calculation model is in good agreement with the experiment and Monte Carlo simulation.

Tomographic imaging with Compton PET modules: ideal case and first implementation

In our previous studies, we demonstrated that the Compton PET module, a layer structure PET detector with side readout, can provide high performance in terms of spatial/energy/timing resolution, as well as high gamma ray detection efficiency. In this study, we investigate how to translate the high performance of the detector module into good quality reconstructed tomographic images. This study is performed using GATE simulation, as well as with physical experiments. Similar detector geometry is used in the simulation and experiment: two identical 4-layer detector modules are placed with face to face distance of 56 mm. In the simulation study, each layer consists of a 1-mm-pitch pixelated crystal array. In the experimental study, each layer is a monolithic crystal, which is virtually binned into 1 mm^2 cells to group single events according to the gamma ray interaction locations. A customized Derenzo phantom was placed between the two detector modules. By rotating the phantom using a motorized rotary stage, data along lines of response (LORs) at different angles were collected for reconstructing the tomographic image. The same reconstruction algorithm was used for both simulation and experimental studies. The results demonstrate that the simulation study could resolve 0.8 mm rods while the experimental study was able to resolve 1.0 mm rods.

Segmented YSO scintillation detectors as a new β-implant detection tool for decay spectroscopy in fragmentation facilities

A newly developed segmented YSO scintillator detector was implemented for the first time at the RI-beam Factory at RIKEN Nishina Center as an implantation-decay counter. The results from the experiment demonstrate that the detector is a viable alternative to conventional silicon-strip detectors with its good timing resolution and high detection efficiency for ${\rm \beta}$ particles. A Position-Sensitive Photo-Multiplier Tube (PSPMT) is coupled with a $48\times48$ segmented YSO crystal. To demonstrate its capabilities, a known short-lived isomer in $^{76}$Ni and the ${\rm \beta}$ decay of $^{74}$Co were measured by implanting those ions into the YSO detector. The half-lives and ${\rm \gamma}$-rays observed in this work are consistent with the known values. The ${\rm \beta}$-ray detection efficiency is more than 80~\% for the decay of $^{74}$Co.

A method to calculate the gamma ray detection efficiency of a cylindrical NaI (Tl) crystal

Given a wide range application of NaI(Tl) detector in industrial and medical sectors, computation of the related detection efficiency in different distances of a radioactive source, especially for calibration purposes, is the subject of radiation detection studies. In this work, a 2in both in radius and height cylindrical NaI (Tl) scintillator was used, and by changing the radial, axial, and diagonal positions of an isotropic 137Cs point source relative to the detector, the solid angles and the interaction probabilities of gamma photons with the detector's sensitive area have been calculated. The calculations present the geometric and intrinsic efficiency as the functions of detector's dimensions and the position of the source. The calculation model is in good agreement with experiment, and MCNPX simulation.

A high-efficiency gas target setup for underground experiments, and redetermination of the branching ratio of the 189.5 keV 22Ne(p, $\gamma$ γ )23Na resonance

The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory (INFN-LNGS), Italy, and high intensity, 250-500 $\mu$A, proton and $\alpha$ ion beams. In order to fully exploit these features, a high-purity, recirculating gas target system for isotopically enriched gases is coupled to a high-efficiency, six-fold optically segmented bismuth germanate (BGO) $\gamma$-ray detector. The beam intensity is measured with a beam calorimeter with constant temperature gradient. Pressure and temperature measurements have been carried out at several positions along the beam path, and the resultant gas density profile has been determined. Calibrated $\gamma$-intensity standards and the well-known $E_p$ = 278 keV $\mathrm{^{14}N(p,\gamma)^{15}O}$ resonance were used to determine the $\gamma$-ray detection efficiency and to validate the simulation of the target and detector setup. As an example, the recently measured resonance at $E_p$ = 189.5 keV in the $^{22}$Ne(p,$\gamma$)$^{23}$Na reaction has been investigated with high statistics, and the $\gamma$-decay branching ratios of the resonance have been determined.

Calculation of the low-energy gamma ray detection efficiency for a GM tube

Experiment and Monte-Carlo calculations indicate that the efficiency of the Geiger-Müller (GM) tube for gamma ray detection depends on the radial and axial positions of the point source. Given the extensive use that is made of this type of detector in industry and dosimetry, an accurate geometric model of the detector efficiency as a function of the source position would be welcome. In this paper, by calculating the solid angle of photons incident on the cathode wall and considering the probability of interaction of photons with the detector components, we obtain a calculation model for the detection efficiency of GM tubes (for soft gamma rays). This model is in good agreement with measurements and MCNPX simulations. We used isotropic 241Am as source.

Luminescence properties of the Mg co–doped Ce:SrHfO3 ceramics prepared by the Spark Plasma Sintering Method

1300 or 1400 °C pre–sintered Al/Ce/Mg:SrHfO3 and Al/Ce:SrHfO3 ceramics were prepared by the Spark Plasma Sintering (SPS) in order to search for a new scintillation material with a high–effective atomic number(Zeff) and good light output. The SrHfO3 has a high Zeff of 60, and high gamma–ray detection efficiency is expected. Meanwhile it has a high melting point of over 2500 °C, and single crystal is hard to be grown. On the other hand, high melting materials can be prepared as ceramics, and the SPS method is a simple process to fabricate the ceramics within a few hours. Thus, we prepared the samples using the SPS method, and their optical and scintillation properties were investigated. We found that Al/Ce/Mg:SrHfO3 and Al/Ce:SrHfO3 ceramics had an emission wavelength at around 400 nm originating from 5d–4f transition of Ce3+. Moreover, Al/Ce/Mg:SrHfO3 pre-sintered at a temperature of 1400 °C had a light output of approximately 5,000 ph/MeV. In this paper, the light output of Mg-co-doped samples was improved compared with the Mg-free ones. The light output also depends on the pre-sintering temperature.

Internal efficiency calibration for bulk samples using a peak-by-peak cascade technique

A procedure for gamma ray detection efficiency calibration for bulk samples using an internal reference is proposed. The technique involves peak-by-peak cascade correlation to overcome the problem, arising when using standard reference material, due to diversity of attenuation to gamma ray among samples. The procedure is used for calibration for 214Bi, 228Ac, and all associated radionuclide using 40K as reference. The experimental validation was done with environmental samples as well as neutron activated indium chloride sample. The peak-by-peak analysis results emphasise the effect of gamma ray attenuation inside the sample on the overall efficiency calibration and give the accurate calibration without need to more sophisticated procedures. The uncertainty analyses of the measurements of efficiency are discussed in order to minimise the systematic uncertainty.

A γ probe for radionuclide diagnostics of cancer

A miniature γ probe for nuclear medicine based on a LaBr3:Ce scintillation crystal and a silicon photomultiplier is described. The γ ray detection efficiency is 29% for 137Cs (662 keV) and 70% for 57Co (122 keV). The spatial resolution and selectivity measured with a tungsten collimator for 57Co are 8 mm and 26°, respectively.

Effect of Ba substitution in CsSrI3:Eu2+

CsSrI3:Eu2+ was previously reported by our group as a highly efficient scintillator, and we now report the advantages of partial replacement of Sr by Ba. Scintillation and physical properties of CsSr1−xBaxI3:Eu2+ crystals are presented for 0≤x≤0.24. We found that the hygroscopicity decreased with increasing Ba concentration while density and effective atomic number increased, thus enhancing the X-ray and gamma ray detection efficiency. The scintillation light yield ranged from 22,000 to 28,000 photons per MeV for Ba concentrations between 3% and 24%. The principle scintillation decay time ranged from 1.8 to 2.1μs.

Study of gamma ray response of R404A superheated droplet detector using a two-state model

The superheated droplet detector (SDD) is known to be gamma ray insensitive below a threshold temperature which made them excellent candidates for neutron detection in the presence of gamma rays. Above the threshold temperature, the gamma ray detection efficiency increases with increase in temperature. In this work the gamma ray threshold temperature has been studied for SDD using R404A as the active liquid and is compared to the theoretical prediction. The temperature variation of gamma ray detection efficiency and interstate transition kinetics has also been studied using a two-state model. The experiments are performed at the ambient pressure of 1atm and in the temperature range of 17–32°C using a 662keV 137Cs gamma ray source.

A New Scintillator Geometry for Positronium Time of Flight Measurement

The positronium time of flight (Ps-TOF) spectroscopy is a novel technique for studying the microstructure in porous materials, in which the high-efficient detection of γ rays generated from ortho-positronium annihilation is the key point for the apparatus setup. In this paper, a new geometry of the scintillator was proposed to improve the γ ray detection efficiency which was indicated by the 22.1% promotion using the simulation results.

A novel 2-dimensional cosmic ray position detector based on a CsI(Na) pixel array and an ICCD camera

A novel 2-D cosmic ray position detector has been built and studied. It is integrated from a CsI(Na) crystal pixel array, an optical fiber array, an image intensifier and an ICCD camera. The 2-D positions of one cosmic ray track is determined by the location of a fired CsI(Na) pixel. The scintillation light of these 1.0×1.0 mm CsI(Na) pixels is delivered to the image intensifier through fibers. The light information is recorded in the ICCD camera in the form of images, from which the 2-D positions can be reconstructed. The background noise and cosmic ray images have been studied. The study shows that the cosmic ray detection efficiency can reach up to 11.4%, while the false accept rate is less than 1%.

Test and simulation of a MICROMEGAS detector

We report on the recent test results of a MICROMEGAS detector in terms of position resolution, time resolution and efficiency. With a Ar+CO2 (10%) gas mixture and a strip pitch of 200 μm an accuracy of 80 μm in sigma on the position has been measured. The time resolution is better than 20 ns and a cosmic ray detection efficiency of 94% was obtained. A Monte Carlo simulation indicates that transverse diffusion, gain fluctuation and electronic noise limit the position resolution.

Neutron detection gamma ray sensitivity criteria

The shortage of 3He has triggered the search for effective alternative neutron detection technologies for national security and safeguards applications. Any new detection technology must satisfy two basic criteria: (1) it must meet a neutron detection efficiency requirement, and (2) it must be insensitive to gamma-ray interference at a prescribed level, while still meeting the neutron detection requirement. It is the purpose of this paper to define measureable gamma ray sensitivity criteria for neutron detectors. Quantitative requirements are specified for: intrinsic gamma ray detection efficiency and gamma ray absolute rejection. The ratio GARRn is defined, and it is proposed that the requirement for neutron detection be 0.9 < GARRn < 1.1 at a 10 mR/h exposure rate. An example of results from a 3He based neutron detector are provided showing that this technology can meet the stated requirements. Results from tests of some alternative technologies are also reported.

Large sample neutron activation analysis of a ceramic vase

Large Sample Neutron Activation Analysis (LSNAA) was applied to perform non-destructive elemental analysis of a ceramic vase. Appropriate neutron self-shielding and gamma ray detection efficiency calibration factors were derived using Monte Carlo code MCNP5. The results of LSNAA were compared against Instrumental Neutron Activation Analysis (INAA) results and a satisfactory agreement between the two methods was observed. The ratio of derived concentrations between the two methods was within 0.7 and 1.3. Estimation of the activity level decay with time showed that the vase could be released from regulatory control at about 3 months post-irradiation. This study provided an analytical procedure for bulk sample analysis of precious and archaeological objects that need to be preserved intact and cannot be damaged for sampling purposes.

Determination of the isomeric fraction in a postaccelerated radioactive ion beam using the coupled decay-chain equations

A method based on the coupled decay-chain equations for extracting the isotopic and the isomeric composition of a postaccelerated radioactive ion beam is presented and demonstrated on a data set from a Coulomb excitation experiment. This is the first attempt of analyzing the content of a postaccelerated radioactive ion beam using this technique. The beam composition is required for an absolute normalization of the measurement. The strength of the method, as compared to present online-based methods, lies in the determination of the isomeric fraction of a partially isomeric beam using all data accumulated during the experiment. We discuss the limitations and sensitivity of the method with respect to the γ -ray detection efficiency and the accumulated flux.

Improved accuracy of γ-ray intensities from basic principles for the calibration reactionN14(n,γ)N15

The {sup 14}N(n,{gamma}){sup 15}N reaction is a primary source of high-energy {gamma} rays for use in the calibration of detectors for other neutron-capture reactions. The {gamma}-ray intensities of {sup 15}N produced by thermal neutron capture and the {gamma}-ray detection efficiency function have been simultaneously determined from {gamma}-peak areas alone using the basic principle of intensity balance. A least-squares fit was made to a new type of intensity balance calculation, combined with traditional efficiency fitting of radioactive sources. This latter ensures the compatibility with low-energy efficiencies, while providing an unbiased efficiency function for higher (up to 10 MeV) {gamma}-ray energies. The calculation is based on the assumption that the {sup 15}N decay scheme is complete. From the internal consistency of the resulting intensities, it is believed that they are more accurate than previously published values. The same is true for the derived efficiency function.