- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Compact and effective detector of the fast neutrons on a base of Ce doped Gd3Al2Ga3O12 scintillation crystal
摘要： Gadolinium garnet Gd3Al2Ga3O12:Ce crystal is demonstrated to be an excellent scintillation material for detection of fast neutrons for the first time. This is achieved because the material, firstly, has high content of Gd, which absorbs neutrons with following prompt emission of γ-quanta, and, secondly, detects this radiation efficiently thanks to high stopping power and high scintillation light yield. GEANT4 modeling was used to distinguish several characteristic regions in γ-quanta pulse height spectra acquired with GAGG:Ce crystal under neutron irradiation, with energies nearly 90 and 190, and 511 keV, which have different relative intensities depending on incident neutrons kinetic energy. This was approved by measurements on Am-Be neutron source. Sensitivity of the material to neutrons from Am-Be source was compared to 6Li-based glass, and found to be superior, depending on signal selectivity.
关键词： Gamma-rays,Neutrons,Gadolinium,Solid scintillation detectors
更新于2025-09-04 15:30:14
-
Optical Passive Sensor Calibration for Satellite Remote Sensing and the Legacy of NOAA and NIST Cooperation
摘要： Post-irradiation stability of high-dose dosimeters has traditionally been an important measurement influence quantity. Though the exceptional stability of the alanine dosimeter response with time has rendered this factor a non-issue for routine work, the archival quality of the alanine dosimeter has not been characterized. Here the alanine pellet dosimeter response is measured up to seven years post-irradiation for a range of absorbed doses. This long-term study is accompanied by an examination of the environmental influence quantities (e.g., ambient light) on the relatively short-term (3-4 month) stability of both pellet and film commercial dosimeters. Both dosimeter types demonstrated exceptional stability in the short term and proved to be relatively insensitive to common influence quantities. The long-term data revealed a complex dose-dependent response trend.
关键词： dosimetry,electron paramagnetic resonance,gamma radiation,stability,alanine,time
更新于2025-09-04 15:30:14
-
Spatially inhomogeneous acceleration of electrons in solar flares
摘要： The imaging spectroscopy capabilities of the Reuven Ramaty high energy solar spectroscopic imager (RHESSI) enable the examination of the accelerated electron distribution throughout a solar flare region. In particular, it has been revealed that the energisation of these particles takes place over a region of finite size, sometimes resolved by RHESSI observations. In this paper, we present, for the first time, a spatially distributed acceleration model and investigate the role of inhomogeneous acceleration on the observed X-ray emission properties. We have modelled transport explicitly examining scatter-free and diffusive transport within the acceleration region and compare with the analytic leaky-box solution. The results show the importance of including this spatial variation when modelling electron acceleration in solar flares. The presence of an inhomogeneous, extended acceleration region produces a spectral index that is, in most cases, different from the simple leaky-box prediction. In particular, it results in a generally softer spectral index than predicted by the leaky-box solution, for both scatter-free and diffusive transport, and thus should be taken into account when modelling stochastic acceleration in solar flares.
关键词： Sun: corona,Sun: X-rays, gamma rays,Sun: flares
更新于2025-09-04 15:30:14
-
Feasibility Study of Patient Specific Quality Assurance Using Transit Dosimetry Based on Measurement with an Electronic Portal Imaging Device
摘要： This study was designed to measure transit dose with an electronic portal imaging device (EPID) in eight patients treated with intensity modulated radiotherapy (IMRT), and to verify the accuracy of dose delivery to patients. The calculated dose map of the treatment planning system (TPS) was compared with the EPID based dose measured on the same plane with a gamma index method. The plan for each patient was verified prior to treatment with a diode array (MapCHECK) and portal dose image prediction (PDIP). To simulate possible patient positioning errors during treatment, outcomes were evaluated after an anthropomorphic phantom was displaced 5 and 10 mm in various directions. Based on 3%/3 mm criteria, the mean±SD passing rates of MapCHECK, PDIP (pre-treatment QA) for 47 IMRT were 99.8±0.1%, 99.0±0.7%, and, respectively. Besides, passing rates using transit dosimetry was 90.0±1.5% for the same condition. Setup errors of 5 and 10 mm reduced the mean passing rates by 1.3% and 3.0% (inferior to superior), 2.2% and 4.3% (superior to inferior), 5.9% and 10.9% (left to right), and 8.9% and 16.3% (right to left), respectively. These findings suggest that the transit dose-based IMRT verification method using EPID, in which the transit dose from patients is compared with the dose map calculated from the TPS, may be useful in verifying various errors including setup and/or patient positioning error, inhomogeneity and target motions.
关键词： Linear accelerator,Transit dose,Gamma index,EPID
更新于2025-09-04 15:30:14
-
New Analytical Formulae to Calibrate Well-type Scintillation Detectors Efficiency
摘要： Direct Mathematical calculations for the absolute efficiency of well-type gamma ray scintillation crystals are described. Calculated detection efficiencies are drawn for two commonly used well crystals. Comparisons are made between present works and published Monte Carlo values. The present approach proved quite success in predicting the efficiency of well type detectors providing only the geometry and materials of the system formed of source, detector and shielding as well as the energy of the emitted photons.
关键词： Absolute efficiency,Well-type detector,Gamma-spectroscopy,New mathematical method
更新于2025-09-04 15:30:14