We report on the effects of large-area 4H-SiC Schottky barrier diodes on the radiation response to ionizing particles. Two different diode areas were compared: 1 mm × 1 mm and 5 mm × 5 mm.
LiF and
B
...C films, which were placed on top of the diodes, were used as thermal neutron converters. We achieved a thermal neutron efficiency of 5.02% with a
LiF thermal neutron converter, which is one of the highest efficiencies reported to date. In addition, a temperature-dependent radiation response to alpha particles was presented. Neutron irradiations were performed in a JSI TRIGA dry chamber and an Am-241 wide-area alpha source was used for testing the alpha response of the 4H-SiC Schottky barrier diodes.
In this work, we present the improved efficiency of 4H-SiC Schottky barrier diodes-based detectors equipped with the thermal neutron converters. This is achieved by optimizing the thermal neutron ...converter thicknesses. Simulations of the optimal thickness of thermal neutron converters have been performed using two Monte Carlo codes (Monte Carlo N–Particle Transport Code and Stopping and Range of Ions in Matter). We have used 6LiF and 10B4C for the thermal neutron converter material. We have achieved the thermal neutron efficiency of 4.67% and 2.24% with 6LiF and 10B4C thermal neutron converters, respectively.
We report the response of newly designed 4H-SiC Schottky barrier diode (SBD) detector prototype to alpha and gamma radiation. We studied detectors of three different active area sizes (1 × 1, 2 × 2 ...and 3 × 3 mm2), while all detectors had the same 4H-SiC epi-layer thickness of approximately µm, sufficient to stop alpha particles up to 6.8 MeV, which have been used in this study. The detector response to the various alpha emitters in the 3.27 MeV to 8.79 MeV energy range clearly demonstrates the excellent linear response to alpha emissions of the detectors with the increasing active area. The detector response in gamma radiation field of Co-60 and Cs-137 sources showed a linear response to air kerma and to different air kerma rates as well, up to 4.49 Gy/h. The detector response is not in saturation for the dose rates lower than 15.3 mGy/min and that its measuring range for gamma radiation with energies of 662 keV, 1.17 MeV and 1.33 MeV is from 0.5 mGy/h–917 mGy/h. No changes to electrical properties of pristine and tested 4H-SiC SBD detectors, supported by a negligible change in carbon vacancy defect density and no creation of other deep levels, demonstrates the radiation hardness of these 4H-SiC detectors.
In the final phase of clot formation, fibrinogen constitutes frame, whereas factor XIII (FXIII) active form is responsible for the covalent cross-linking of fibrin fibres and plasmin inhibitor (PI), ...thus contributing to clot stability. It could be expected that any change of coagulation factors' structure affects the clot formation and modulates the atherothrombotic risk. The aim was to determine the frequency of four single nucleotide polymorphisms: (
) A > G in codon 312 of the fibrinogen α-chain gene (rs6050, Thr312AlaFGA), (
) C > T at position 10034 of the 3 - untranslated region in the fibrinogen γ-chain gene (rs2066865, 10034C > T FGG), (
) C > T in codon 564 of the FXIII-A subunit gene (rs5982, Pro564LeuFXIII-A), and (
) C > T in codon 6 of the plasmin inhibitor gene (rs2070863, Arg6TrpPI) in Croatian patients and their association with coronary artery disease (CAD).
We performed the unrelated case-control association study on the consecutive sample of patients 18 years old, who had undergone coronary angiography for investigation of chest pain and suspected CAD. The cases were patients with confirmed CAD (N=201), and the controls were the subjects with no CAD (N=119). Samples were genotyped using PCR-RFLP analysis.
Observed frequencies of the rare alleles of Thr312Ala FGA, 10034C > T FGG, Leu564Pro FXIII-A and Arg6Trp PI polymorphisms were 21%, 17%, 14%, 20%, respectively. Patients with 10034C > T FGG CC genotype had 3.5 times (95% CI 1.02-12.03) higher adjusted odds for CAD than patients with 10034C > T FGG TT genotype. Patients with Arg6Trp PI CC genotype had 3.86 times (95% CI 1.23-12.12) higher odds for CAD than patients with Arg6Trp PI TT genotype. It seems that those genotype-related higher odds are also male-gender related. No difference was observed regarding any other investigated polymorphism.
Our finding suggests that 10034C > T FGG and Arg6Trp PI are associated with CAD.
Individual hand monitoring for workers who manipulate unsealed radioactive
sources in nuclear medicine is a necessity and the results can serve as the
base for optimization processes. We performed an ...analysis of individual hand
doses for medical staff preparing and applying radiopharmaceuticals (99mTc,
123I, 201Tl, 131I, or 125I) in three Croatian clinical hospitals, for a
period of one year since extremity monitoring became legally mandatory in
Croatia. The majority of annual hand doses for workers were below or slightly
above 150 mSv per year with only a few workers exceeding the annual dose
limit of 500 mSv. The analysis confirmed that the radiation protection
expert's role in an individual monitoring programme and personal dosimetry is
crucial in order to achieve the optimal radiation protection of workers.
nema
In 2016, the “E-SiCure” project (standing for “Engineering Silicon Carbide for Border and Port Security”), funded by the NATO Science for Peace and Security Programme was launched. The main objective ...is to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), with the end goal to enhance border and port security barriers. Prototype neutron detectors, configured as 4H-SiC-based Schottky barrier diodes, were developed for the detection of secondary charged particles (tritons, alphas and lithium atoms) which are the result of thermal neutron reactions on
10
B and
6
LiF layers above the surface of the 4H-SiC diodes. We designed a stand-alone prototype detection system, consisting of a preamplifier, shaping amplifier and a multichannel analyser operated by a laptop computer, for testing of neutron detector prototypes at the Jožef Stefan Institute (JSI) TRIGA reactor using a broad beam of reactor neutrons. The reverse bias for the detector diode and the power to electronic system were provided by a standalone battery-powered voltage source. The detector functionality was established through measurements using an
241
Am alpha particle source. Two dedicated experimental campaigns were performed at the JSI TRIGA reactor. The registered pulse height spectra from the detectors, using both
10
B and
6
LiF neutron converting layers, clearly demonstrated the neutron detection abilities of the SiC detector prototypes. The computed neutron detection sensitivity of the single prototype detectors demonstrates that scaling SiC detectors into larger arrays, of dimensions relevant for border and port radiation detectors, could enable neutron sensitivity levels matching gas-based detector technology.
Large-area SiC Schottky barrier diodes can significantly improve the sensitivity in radiation detection due to the increased interacting SiC volume. In this work, we tested a large SiC detector with ...an area of 1 × 1 cm2. Extensive electrical characterization was performed at temperatures ranging from 150 K to 390 K, demonstrating the impact of barrier inhomogeneities on the electrical performance of the diode. Forward current-voltage (I-V) measurements of the diodes revealed two distinct regions caused by Schottky barrier inhomogeneity present throughout the entire temperature range. The barrier heights in the low- and high-current forward voltage regions were extracted from Richardson plots corrected for the Gaussian distribution of barrier heights, yielding values of 1.52 eV and 1.79 eV, respectively. Deep-level transient spectroscopy (DLTS) revealed only one deep-level defect, Z1/2, with an activation energy for electron emission of 0.67 eV, which was assigned to the known carbon vacancy. The DLTS study showed no correlation between electrically active defects and barrier inhomogeneity. An excellent energy resolution of 3.2 % was measured using a large area 241Am radiation source, consistent with values for small area SiC detectors that exhibited no barrier height inhomogeneities. The impact of temperature on the alpha particle radiation response was determined within a temperature range of 200 K to 390 K.
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•Large 1 × 1 cm2 SiC Schottky diodes enhance radiation detection sensitivity.•Current-voltage measurements show barrier inhomogeneities impact diode characteristics.•The radiation response is not affected by barrier inhomogeneities.•DLTS reveals only Z1/2 with 0.67 eV activation energy.•Alpha particle radiation response measured in a temperature range from 200 K to 390 K.
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