Si Semiconductor Detector Research Articles

(BZA)2PbBr4: A potential scintillator for photon-counting computed tomography detectors

Due to recent development in detector technology, photon-counting computed tomography (PCCT) has become a rapidly emerging medical imaging technology. Current PCCT systems rely on the direct conversion of X-ray photons into charge pulses, using CdTe, CZT, or Si semiconductor detectors. Indirect detection using ultrafast scintillators coupled to silicon photomultipliers (SiPM) offers a potentially more straightforward and cost-effective alternative. In this work a new 2D perovskite scintillator, benzylamonium lead bromide (BZA)2PbBr4, is experimentally characterised as function of temperature. The material exhibits a 4.2 ns decay time under X-ray excitation at room temperature and a light yield of 3700 photons/MeV. The simulation tool developed by Van der Sar et al. was used to model the pulse trains produced by a SiPM-based (BZA)2PbBr4 detector. The fast decay time of (BZA)2PbBr4 results in outstanding count-rate performance as well as very low statistical fluctuations in the simulated pulses. These features of (BZA)2PbBr4, combined with its cost-effective synthesis make (BZA)2PbBr4 very promising for PCCT.

Recoil and charged particle energy spectra from the natSi(n,x) reaction and the Si semiconductor detector response to the 14 MeV neutrons

The energy spectra of light and heavy charged particles generated by the 14 MeV neutrons in silicon nuclei and in the Si semiconductor detector (SSD) were analysed. The existing measurements were used to validate the corresponding energy differential cross sections from major evaluations ENDF/B-VIII.0 and JEFF-3.3. The required data were extracted by the various codes: NJOY21, SPKA and MCNP6. It was shown that both evaluations underestimate the high energy part of the 28Si(n,x)p- and α-particle spectra by ≤50%, whereas at smaller emission energies no experimental data even exist. The calculation of the atom displacement damage in SSD reveals that the secondary protons produce additionally ≈15% of damage, whereas the contribution from secondary alphas is impossible to estimate since the Si(α,x) recoil data are not available.The single experiment, carried out by K. Yageta and co-workers in 1988, reported the energy spectra in the Si semiconductor down to the rather low energy of ≈0.3 MeV, at which the production of reaction recoils dominates over the light ions. The Monte Carlo simulation of this experiment was performed by MCNP6. The generation and transport of all relevant ions were taken in account. The energy depositions from protons or alphas were summed with their associated recoils after correction for non-ionization losses. The neutron reactions in the dead layer of the SSD were shown to increase the counts in active layer by (1–20)% depending on sort of ions. The impact of the field funneling effect was studied. Consideration of all these underlying processes has eventually allowed a reasonable reproduction of this experiment.

Improved non-destructive method for 90Sr activity determination in aqueous solutions using Monte Carlo simulation

The development of new methods and improvements of existing methods for the specific activity determination of 90Sr and other distinct beta emitters has been of considerable interest. The reason for this interest is that the notably small number of methods that are able to meet all the set criteria, such as reliability of the results, measurement uncertainty and time, and minimum production of radioactive waste, as well as applicability to various samples with reference to their nature, geometry and composition. In this paper, two methods for rapid 90Sr activity determination based on Monte Carlo simulations are used, one for a Si semiconductor detector for beta spectrometric measurements and the other for the Geiger-Muller (GM) ionization probe. To improve the reliability of the measurement results, samples with high and low strontium activity solutions were prepared in the form of dry residues. The results of the proposed methodology were verified with a standard method using a liquid scintillation counter, and notably good agreements are achieved.

K to L shell vacancy transfer probabilities and Auger electron emission ratios for elements in the atomic range 30 ≤ Z ≤ 58

The K to L shell vacancy transfer probabilities for some elements in the atomic range 30 ≤ Z ≤ 58 were determined using the semi-empirical values of K shell fluorescence yield and the experimental values of Kβ/Kα X-ray intensity ratio. Furthermore, the KLX/KLL and KXY/KLL Auger electrons emission ratios for the same elements were obtained using the experimental values of Kβ/Kα X-ray intensity ratio. The experiments were performed using a 241Am annular radioisotope source and a high-resolution Si(Li) semiconductor detector. The experimental values of K to L shell vacancy transfer probabilities, and KLX/KLL and KXY/KLL Auger electrons emission ratios were compared with the fitted, theoretical, semi-empirical, and other available experimental values. To the best knowledge of the author, the KLX/KLL and KXY/KLL Auger electrons emission ratios of ruthenium, palladium, and tellurium have been obtained for the first time in the present work.

Measurements of gamma-ray emission probabilities of 241, 243Am and 239Np

ABSTRACTGamma-ray emission probabilities of 241, 243Am and 239Np have been precisely measured with gamma- and alpha-ray spectroscopic methods. The activities of the samples were determined by measuring alpha particles using a Si semiconductor detector. Gamma rays emitted from the samples were measured with a planar type High-Purity Germanium (HPGe) detector. An efficiency curve of the HPGe detector was derived with uncertainties from 0.7% to 2.5% by combining measured efficiencies and Monte Carlo simulation. The gamma-ray emission probabilities for the major gamma rays of these nuclides were determined with uncertainties less than 1.2%.

Determination of inorganic nutrients in wheat flour by laser-induced breakdown spectroscopy and energy dispersive X-ray fluorescence spectrometry

Laser-induced breakdown spectroscopy (LIBS) and energy dispersive X-ray fluorescence spectrometry (EDXRF) were evaluated for the determination of P, K, Ca, Mg, S, Fe, Cu, Mn and Zn in pressed pellets of wheat flours. EDXRF and LIBS calibration models were built with analytes mass fractions determined by inductively coupled plasma optical emission spectrometry after microwave-assisted acid digestion in a set of 25 wheat flour laboratory samples. Test samples consisted of pressed pellets prepared from wheat flour mixed with 30% mm−1 cellulose binder. Experiments were carried out with a LIBS setup consisted of a Q-switched Nd:YAG laser and a spectrometer with Echelle optics and ICCD, and a benchtop EDXRF system fitted with a Rh target X-ray tube and a Si(Li) semiconductor detector. The correlation coefficients from the linear calibration models of P, K, Ca, Mg, S, Fe, Mn and Zn determined by LIBS and/or EDXRF varied from 0.9705 for Zn to 0.9990 for Mg by LIBS, and from 0.9306 for S to 0.9974 for K by EDXRF. The coefficients of variation of measurements varied from 1.2 to 20% for LIBS, and from 0.3 to 24% for EDXRF. The predictive capabilities based on RMSEP (root mean square error of prediction) values were appropriate for the determination of P, Ca, Mg, Fe, Mn and Zn by LIBS, and for P, K, S, Ca, Fe, and Zn by EDXRF. In general, results from the analysis of NIST SRM 1567a Wheat flour by LIBS and EDXRF were in agreement with their certified mass fractions.

Development of a Si-PM based alpha camera for plutonium detection in nuclear fuel facilities

Alpha particles are monitored for detecting nuclear fuel material (i.e., plutonium and uranium) at nuclear fuel facilities. Currently, for monitoring the airborne contamination of nuclear fuel, only energy information measured by Si-semiconductor detectors is used to distinguish nuclear fuel material from radon daughters. In some cases, however, such distinguishing is difficult when the radon concentration is high. In addition, a Si-semiconductor detector is generally sensitive to noise. In this study, we developed a new alpha-particle imaging system by combining a Si-PM array, which is insensitive to noise, with a Ce-doped Gd3Al2Ga3O12(GAGG) scintillator, and evaluated our developed system׳s fundamental performance. The scintillator was 0.1-mm thick, and the light guide was 3.0mm thick. An 241Am source was used for all the measurements. We evaluated the spatial resolution by taking an image of a resolution chart. A 1.6lp/mm slit was clearly resolved, and the spatial resolution was estimated to be less than 0.6-mm FWHM. The energy resolution was 13% FWHM. A slight distortion was observed in the image, and the uniformity near its center was within ±24%. We conclude that our developed alpha-particle imaging system is promising for plutonium detection at nuclear fuel facilities.

English

The K shell x-ray intensity ratios Kβ/Kα for 9 elements in the atomic range 40 ≤ Z ≤ 50 have been determined for an excitation energy of 59.537 keV. The K-L total vacancy transfer probabilities (ηKL) for these elements have been determined, also. K x-rays emitted by samples were detected using a high resolution Si(Li) semiconductor detector. The measured values were compared with the theoretical values calculated using Scofield's tables based on the Hartree-Slater and Hartree-Fock theories, and available experimental values. The agreement of measured values of intensity ratios and vacancy transfer probabilities were quite satisfactory with theoretical calculations. Key words: K shell intensity ratio, vacancy transfer probability, X-ray.

Dosimetry study using an anthropomorphic head phantom for stereotactic radiosurgery

A dosimetry study using an anthropomorphic head phantom (Radiosurgery Verification Phantom (RSVP)) and a micro-ionization chamber for stereotactic radiosurgery was performed. To study the characteristics of the micro-ionization chamber, tissue maximum ratios (TMRs), off-axis ratios (OARs) and output factors were measured and compared, using a Si semiconductor detector and the film method. The directional difference in sensitivity and the effect of the polarity of the micro-ionization chamber were measured. According to the results obtained, the measured values and the values obtained through calculation were in agreement within 6.3%. The difference was due to the larger size of the micro-ionization chamber as compared to the other method. Therefore we applied a correction for this size effect and obtained better agreement within 2%. On the basis of the results of the present study we were able to confirm the overall accuracy and establish a means of quality assurance (QA) for stereotactic radiosurgery.

Alpha-particle energy distributions from thin sources measured with small solid angles

The energy distribution of the alpha particles emitted from a source is in general complex. Only under particular circumstances, as in the case of very thin sources measured at large distances from the detector, can the energy distribution be approximated theoretically. In this work, we used the well-known code SRIM to simulate the interaction of alpha particles within a thin radioactive source and within the entrance window of a typical Si semiconductor detector. We considered several thin alpha particle sources measured at a large source-to-detector distance (small solid angle), in order to compare the distributions obtained by simulation with those determined by the theoretical model applied to this case. The study was performed for a variety of realistic alpha particle sources: UF4, UO2, U3O8, Gd2O3, and BaSO4, considering as alpha emitters 235U, 233U, 148Gd and 226Ra. For all these cases, we obtained the distributions due to the source and due to the entrance window of the detector, and also the final distribution given by the convolution of these two distributions. All the energy distributions obtained by simulation showed, in general, good agreement with the predictions given by the theoretical model, which includes corrections for Bohr straggling.

Comparisons of an external magnetic field effect and chemical effect on X-ray Kβ/Kα intensity ratio and line-shape of some Chromium compounds

The effect of chemical composition and external magnetic field on the Kβ/Kα intensity ratio and line-shape of some chromium compounds have been investigated using the energy dispersive X-ray fluorescence analysis. The measurements were done using the 22.69 keV photon energy and energy dispersive Si(Li) semiconductor detector. The samples are located in the external magnetic field of intensities 0.6 T and 1.2 T. The experimental results obtained for B = 0 are compared with other experimental and theoretical values. The results have shown that the X-ray Kβ/Kα intensity ratios, chemical shifts, asymmetry indices and full widths at half maximum (FWHM) values can change when irradiation is conducted in a magnetic field.

Design of Active-Type Personal Dosemeter for High-Energy Neutrons

*In order to design an active-type personal dosemeter having sufficient sensitivity to high-energy neutrons up to 100 MeV, the characteristic response of several types of silicon (Si) semiconductor detectors has been investigated experimentally and theoretically. At first, the response of each detector has been checked to protons accelerated by a Van de Graff accelerator installed at Kobe University. A fully-depleted Si detector was selected as a promising detector element owing to a simple structure and comprehensive characteristics. In the next step, neutron irradiation experiments were carried out in a monoenergetic reference field in JAEA. On the other hand, theoretical distributions of the deposited energy were estimated in a simplified geometry consisting of Si and PE layers. An agreement in the relative shape was confirmed between the theoretical and experimental results. Applying this calculation procedure to other neutron energies and various thickness of sensitive layer, it was found that the energy dependence could be improved by the two-window technique by setting different discrimination levels on the pulse height. Another important characteristic of the angular dependence was also discussed for practical application of a personal dosemeter for high energy neutrons.

ELEMENTAL ACCUMULATION PATTERNS OF THE LICHEN SPECIES PHYSCIA TRIBACOIDES NYL., HETERODERMIA DISSECTA AND BACIDIA BECKHAUSII KÖRBER FROM THE WALAYAR RF REGION, TAMIL NADU, INDIA

Lichens have been used extensively as biomonitors of air quality (Richardson 1992; Seaward 1995, 2005). Lichen thalli lack a protective layer and hence accumulate airborne pollutants and particulate matter from the environment by wet and dry deposition (Nash 1996). The elements accumulated on lichen thalli can be quantitatively analysed using techniques such as Proton Induced X-ray Emission (PIXE) and Electron probe microanalysis. These techniques yield two-dimensional, quantitative element information with micron-level spatial resolution. This study used Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) and PIXE to quantify elements accumulated on lichen thalli of selected species collected from polluted and unpolluted areas of the Madukkarai – Walayar forests. Thalli of selected lichen species from the study site (polluted and unpolluted) were irradiated using 1.7 MV tandem accelerator with Proton beam energy of 2 MeV. The ion induced X-rays were detected by Si ( Li ) semiconductor detector. The morphological analysis and localization of elements accumulated on these lichen samples were also carried out with the use of a SEM-EDX microanalysis using environmental scanning electron microscopy (ESEM) as supporting evidence. PIXE spectral elemental output revealed the presence of elements such as As , Ba , Br , Ca , Cu , Fe , K , Mn , Zn , Cl , Ti , Cr and Pd with the incidence of increased Calcium levels. IAEA 336 lichen reference material was used for standardization.

Elemental content in deionized water by total-reflection X-ray fluorescence spectrometry

This study aimed to evaluate minor and trace elements in the water during different water purification steps of a deionized water production plant, located at CENA, by total-reflection X-ray fluorescence (TXRF) technique, using Ga as internal standard for elemental quantification. This approach was capable of determining Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Se, Br, Rb at concentrations higher than 40–100 μg L−1, and for K, Ca, Sc, Ti, V and Sr at concentrations higher than sub mg L−1 in the water samples. TXRF spectrometer encompasses an X-ray tube with a Mo target with a Zr filter. The elemental characteristic X-rays were recorded by a Si(Li) semiconductor detector and the X-ray spectra deconvoluted by AXIL software.

Polarimetric performance of Si/CdTe semiconductor Compton camera

A Compton camera has been developed based on Si and CdTe semiconductor detectors with high spatial and spectral resolution for hard X- and γ ‐ray astrophysics applications. A semiconductor Compton camera is also an excellent polarimeter due to its capability to precisely measure the Compton scattering azimuth angle, which is modulated by linear polarization. We assembled a prototype Compton camera and conducted a beam test using nearly 100% linearly polarized γ ‐ rays at SPring-8.

LVR-15 reactor epithermal neutron beam parameters—Results of measurements

The epithermal neutron beam of the LVR-15 reactor provides the appropriate conditions for varied BNCT activity. The principal parameters have been frequently determined. The following detectors have been used for the measurement: set of activation monitors of different nuclides irradiated in free beam and in the water phantom, Si semiconductor detector with 6LiF converter, twin ionization chambers, thermoluminescence dosimeters, gel dosimeters used for imaging of separate part of dose, neutron spectrometer of Bonner type. Obtained results of measured parameters are presented in the paper.

Response of materials to single ion events

Response of materials to single radiation events is fundamental to research and many technological applications that involve energetic particles. Ion–solid interactions lead to energy loss of ions, production of electron–hole pairs, and light emission from excitation-induced luminescence. Employing a unique time-of-flight system, material response to single ion irradiation has been utilized to measure electronic energy loss, and to evaluate materials performance for radiation detection. Measurements of electronic energy loss of single ions in a thin ZrO2 foil over a continuous energy range exhibit good agreement with SRIM predictions for He and Be ions. For O and F ions, slight over- and under-estimation of SRIM prediction is evident at energies around 250 (near the stopping maximum) and above 800keV/nucleon, respectively. For a Si semiconductor detector, its response to single ion irradiation shows that pulse height defect is clear for elements heavier than Si, and nonlinear energy response is significant for all elements at energies below ∼100keV/nucleon. For a single crystal CsI:Tl scintillator, the response to H ion events is used to determine relative light yield and absolute energy resolution over a wide energy region, where energy resolution of ∼5.3% is achieved at 2MeV.

Development of a Prototype Compton Camera for In Vivo Imaging Using Si and CdTe Semiconductor Detectors

Development of a Prototype Compton Camera for In Vivo Imaging Using Si and CdTe Semiconductor Detectors

The comparison of doses measured by radiochromic films and semiconductor detector in a 175 MeV proton beam

We wanted to verify the response of radiochromic films in a 175 MeV clinical proton beam used at the Joint Institute for Nuclear Research in Dubna against doses measured using semiconductor detectors and compare the results with published data from other centres. Radiochromic films (RCFs) MD-55 and a Vidar VXR-16 scanner were used. The films were irradiated in an unmodulated proton beam and with a beam modulated with a bolus and a ridge filter. Obtained dose distributions were compared with dose distributions measured with a Si-semiconductor detector. For the unmodulated beam the difference between the RCF and the semiconductor detector was 12% in the Bragg peak top. For the modulated beam the difference inside the spread-out Bragg peak region was 4%. Observed deviations between doses measured with RCF and Si-detector outside the Bragg peak were caused by the inhomogeneity of radiochromic emulsion. In the Bragg peak region the RCF doses were lower than those measured by semiconductors. The results were in agreement with published data from other proton therapy centres.

Effect of an External Magnetic Field on the Kα and Kβ x-Ray Emission Lines of the 3d Transition Metals

The effect of an external magnetic field on the K shell energy shift (ΔE), FWHM (Wi), asymmetry index, and Kβ/Kα intensity ratio for diamagnetic (Cu and Zn), paramagnetic (V and Mn), ferromagnetic (Fe, Co and Ni), and antiferromagnetic (Cr) elements have been investigated using Cd-109 point source in the external magnetic field intensities 0.6 T and 1.2 T. The K x-rays from different targets were detected using a high resolution Si(Li) semiconductor detector. An accurate analytic representation of each line was obtained by a fit to a Gaussian. For B = 0, the measured Kβ/Kα intensity ratios were compared with the experimental and theoretical data in the literature. The results show that the atomic parameters can change when the irradiation is conducted in a magnetic field.