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Influence of Neodymium on the Light Attenuation Length in a Liquid Organic Scintillator
摘要： The influence of the concentration of neodymium on the light attenuation length in aqueous and organic solutions is measured in a 1-m-long optical cell. The emission spectrum of scintillation crystal NaI(Tl) with a size of 25 × 25 mm irradiated with gamma rays from a Cs-137 source is used as a photon source. The photons are detected with a Hamamatsu R878 photomultiplier. A two-exponent approximation is used to model the light attenuation length in water (Nd 7.5, 15 g/L) and linear alkylbenzene (LAB) (Nd 4.7 g/L). For a Nd concentration in LAB of 4.7 g/L, the light attenuation length amounts to LNd = 1.95 ± 0.14 m.
关键词： light attenuation length,liquid organic scintillator,neodymium,Hamamatsu R878,Cs-137,NaI(Tl)
更新于2025-09-11 14:15:04
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Joint activity and attenuation estimation for PET with TOF data and single events
摘要： Maximum likelihood reconstruction of activity and attenuation (MLAA) for PET data with time-of-flight (TOF) information can determine the activity distribution up to a scale, and the attenuation map Radon transform up to a related constant. Prior knowledge is widely used for the determination of the constant. However, prior knowledge could be inaccurate due to patient variation and may result in quantitation errors. Our goal is to develop a method that can determine the scale and the related constant in the TOF-MLAA algorithm to obtain quantitatively accurate activity and attenuation maps. Our idea is to utilize the single events which have depth dependent attenuation factors, contrary to coincidence events. We show that in a 2D case, with the combination of TOF information and single events, a unique solution of attenuation and activity can be achieved. A three-step iterative image reconstruction algorithm is developed. In each iteration, the activity distribution is first updated using the MLEM approach with TOF PET data; the attenuation map is then updated using MLTR with non-TOF data; finally, both activity distribution and attenuation map are updated using a scale estimated from single events. Noisy and noise-free projection data are generated for 2D XCAT phantoms through analytical simulation. Both scatter information and randoms information are assumed to be known. The proposed method and the conventional TOF-MLAA algorithm are used to reconstruct the simulated data. Conventional MLEM method with known attenuation map is implemented for comparison as well. Normalized root mean square error (NRMSE) and optimal constant are defined for the quantitative analysis of reconstructed images. Our proposed image reconstruction method achieves ~1% NRMSE for the activity map and ~5% NRMSE for the attenuation map with a correct scale after 150 iterations for noise-free data. Results of noisy simulations are consistent with noise-free data. In summary, we have proposed to use the single events for constant determination in TOF-MLAA algorithm to obtain a unique solution of attenuation map and activity distribution without prior information. Future work will be dedicated to the extension of our method to the 3D situation.
关键词： constant determination,single events,attenuation correction
更新于2025-09-10 09:29:36
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[IEEE 2018 2nd International Conference on Biomedical Engineering (IBIOMED) - Bali, Indonesia (2018.7.24-2018.7.26)] 2018 2nd International Conference on Biomedical Engineering (IBIOMED) - Could Water Replace Muscle Tissue Used in Electron and Photon Beams?: A Monte Carlo Study
摘要： This study was conducted to evaluate the use of different phantom materials (muscle_ICRP, muscle_ICRU, and water) using Geant4-GAMOS Monte Carlo method. GAMOS which based on the Geant4 toolkit developed by European Organization for Nuclear Research (CERN) is a Monte Carlo simulation software. The material composition and density of muscle skeletal (ICRP), muscle striated (ICRU), and water (ICRU) used in this simulation were provided by Geant4 cross section data. Simulation objects consist of world, detector, source, and phantom. The phantom material used was distinguished. The source was placed inside a tube while detector was placed inside phantom. The detector was separated 2 cm from source in +x direction. The photon and electron beam with varied energies 0.5, 1.0, 1.5, and 2.0 MeV was used as source. The simulation time for each simulation was different depend on the incident particle type, particle energy, and phantom material composition. Electron beam takes longer time simulation than photon beam for varied phantom materials. The Rayleigh scattering, Compton scattering, and the photo-electric effect were occurred in each simulation but gamma conversion into electron and positron pairs only discovered in 1.5 and 2.0 MeV photon beam. The positron was produced because of pair production interaction. The energy histogram collected in this simulation shows that the muscle (ICRP and ICRU) material can be replaced by water if the muscle depth from the skin surface is not more than 2 cm. This results also were confirmed by comparing the mass coefficient attenuation and stopping power ratio curves between muscle (ICRP and ICRU) and water material extracted using other Monte Carlo software, EGSnrc.
关键词： stopping power,Monte Carlo,mass attenuation coefficient,Geant4,GAMOS,muscle
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Null Technique for Precision RF Phase Shift Measurements
摘要： A dual channel IF substitution null system is developed for precision phase shift measurements and standards in frequency ranges of 1 MHz to 1 GHz. A particular programmable IF phase shifter equipped with a calibrated phase monitor is used as a phase reference standard. High sensitivity nature of the null technique provides accurate measurements to the DUT even with large attenuation. Measurement resolutions of 0.002 deg., 0.006 deg., and 0.023 deg. were obtained for DUT with attenuation of 20 dB, 40 dB, and 60 dB, respectively, at 1 GHz.
关键词： Phase measurement,uncertainty,radio frequency,precision measurements,attenuation measurement,phase shifters
更新于2025-09-10 09:29:36
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Evaluation of the shielding parameters of alkaline earth based phosphate glasses using MCNPX code
摘要： Glass systems of composition 16XO–3Al2O3–6CuO–20Na2O–55P2O5 (where X=Sr, Ca, Mg and Ba mol%) have been investigated to check its potential utilize as gamma ray shielding material. Different shielding quantities namely mass attenuation coefficient (μ/ρ), effective atomic number (Zeff), half value layer (HVL) and mean free path (MFP) have been evaluated using MCNPX code and XCOM program at different photon energies between 0.015-10 MeV. The obtained data revealed good agreement between the μ/ρ values derived from XCOM and MCNPX code (version 2.6.0). It is found that the mass attenuation coefficients of BaO-doped phosphate glass are higher than those of the other alkaline earth elements–doped glasses, whereas MgO possess the lowest values. This indicates that the BaO-doped phosphate glass is the superior gamma radiation attenuator among the studied glass samples. The gamma shielding performance of the glasses under study has been compared to some commercial glasses and different concrete samples in terms of MFP.
关键词： MCNPX,effective atomic number,attenuation coefficients,radiation,Phosphate glass,XCom
更新于2025-09-10 09:29:36
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Modeling of effective path-length based on rain cell statistics for total attenuation prediction in satellite link
摘要： ITU-R recommends a global rain-attenuation prediction model for satellite link, but it lacks a physical meaning because it is an empirical model and the effective path-length model is frequency dependent. In this paper, a global effective path-length model, which can be used for total attenuation prediction in satellite link, is proposed. The proposed model is a physical model based on rain-cell concept. The test for the proposed model was performed against the data in the ITU-R SG3 DB, using the procedures in the recommendation ITU-R P. 311 and the Fascicle. The test results show that the prediction error of the proposed model is less than the existing ITU-R model. In addition, the proposed model is a physical model and simple compared to the current ITU-R model.
关键词： Total attenuation,Effective path length,Rain cell,Satellite link
更新于2025-09-10 09:29:36
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Application of the Beer-Lambert Model to Attenuation of Photosynthetically Active Radiation in a Shallow, Eutrophic Lake
摘要： Models of primary production in aquatic systems must include a means to estimate subsurface light. Such models often use the Beer–Lambert law, assuming exponential attenuation of light with depth. It is further assumed that the diffuse attenuation coef?cient may be estimated as a summation of scattering/absorbing constituent concentrations multiplied by their respective speci?c attenuation coef?cients. While theoretical deviations from these assumptions have been documented, it is useful to consider the empirical performance of this common approach. Photosynthetically active radiation (PAR) levels and water quality conditions were recorded weekly from six to eight monitoring stations in western Lake Erie between 2012 and 2016. Exponential PAR extinction models yielded a mean attenuation coef?cient of 1.55 m (interquartile range = 0.74–1.90 m). While more complex light attenuation models are available, analysis of residuals indicated that the simple Beer–Lambert model is adequate for shallow, eutrophic waters similar to western Lake Erie (R2 > 0.9 for 96% of samples). Three groups of water quality variables were predictive of PAR attenuation: total and nonvolatile suspended particles, dissolved organic substances (dissolved organic carbon and chromophoric dissolved organic matter), and organic solids (volatile suspended solids and chlorophyll). Multiple regression models using these variables predicted 3–90% of the variability in PAR attenuation, with a median adjusted R2 = 0.86. Explanatory variables within these groups may substitute for each other while maintaining similar model performance, indicating that various combinations of water quality variables may be useful to predict PAR attenuation, depending on availability within a model framework or monitoring program.
关键词： water quality,Lake Erie,PAR attenuation,photosynthetically active radiation,Beer–Lambert law
更新于2025-09-09 09:28:46
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HIGH FREQUENCY ELECTRICAL CHARACTERIZATION OF 3D SIGNAL/GROUND THROUGH SILICON VIAS
摘要： 3D integration using through-silicon-vias (TSVs) is gaining considerable attention due to its superior packaging e?ciency resulting in higher functionality, improved performance and a reduction in power consumption. In order to implement 3D chip designs with TSV technology, robust TSV electrical models are required. Speci?cally, due to the increase of signal speeds into the gigahertz (GHz) spectrum, a high frequency electrical characterization best describes TSV behavior. In this letter, 5 × 50 μm TSVs are manufactured using a via-mid integration scheme and characterized using S-parameters up to 65 GHz. At 50 GHz, the measured attenuation constant is 0.35 dB/via with a time delay of 0.7 ps/via.
关键词： time delay,3D integration,attenuation constant,through-silicon-vias (TSVs),S-parameters,high frequency electrical characterization
更新于2025-09-09 09:28:46
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - SPECT Reconstruction and Analysis for the Inspection of Spent Nuclear Fuel
摘要： A gamma-emission-tomography (GET) system for the inspection of spent nuclear fuel (SNF) has been developed and tested on multiple fuel types. This tool can be used for verification of the integrity of an assembly and consistency with fissile-material content. Parallel-beam line integrals are measured by a discrete array of CdZnTe detectors that view the fuel through a 1.5mm wide by 100mm thick tungsten collimator. Detectors and electronics are on a rotating platform within a watertight stainless steel torus. During operation, the system is underwater and fuel is lowered through the center of the torus and held stationary as data are collected. Tomographic data collection requires a time on the order of minutes. In field experiments, data with count rates in the range of 50kcps to >500kcps per pixel have been recorded. In the reconstructed images, missing or replaced pins in all assembly types can be visually discriminated in the lattice of fuel pins. Automated detection of missing/replaced pins is the metric used for determination of optimal processing steps. Effectiveness of reconstruction and data-processing tools is measured by a tools ability to improve performance on the pin-discrimination task. This paper describes the data preprocessing, image reconstruction, image analysis, and performance evaluation of this system.
关键词： gamma-ray emission tomography,image quality metrics,safeguards,attenuation correction,image reconstruction,spent nuclear fuel
更新于2025-09-09 09:28:46
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In vitro assessments of white-spot lesions treated with NaF plus tricalcium phosphate (TCP) toothpastes using synchrotron radiation micro computed tomography (SR micro-CT)
摘要： Synchrotron radiation micro-computed tomography (SR micro-CT), considered superior to standard polychromatic micro-CT techniques, was used to assess the densities of bovine enamel white-spot lesions (WSL) treated in a 10-day pH cycling model with either: (A) Clinpro Tooth Crème (0.21% NaF plus TCP), (B) Clinpro 5000 (1.1% NaF plus TCP) or (C) Tom’s of Maine (0% NaF) dentifrice. Each day consisted of four 2 min treatments, one 4 h acid challenge (pH=5.0), and immersion in artificial saliva (pH=7.0) between these events. After 10 days, WSL specimens were evaluated for lesion depth using confocal microscopy and lesion density using SR micro-CT with depths ranging from 2.76 to 113.16 μm, in 2.76 μm slice increments. Statistical analyses (Student’s t-test) were performed at the 95% confidence level. SR micro-CT analyses revealed the NaF plus TCP dentifrices improved WSL densities relative to the fluoride-free toothpaste, and is consistent with an earlier study utilizing polychromatic micro-CT. In contrast to previous findings, SR micro-CT analyses also revealed significant differences in WSL densities treated with the two NaF dentifrices at enamel depths of 13.80, 16.56, and 19.32 μm. These findings suggest SR micro-CT may be especially suited for detecting density differences in lesions sensitive to fluoride-driven remineralization processes.
关键词： X-ray linear attenuation coefficient (X-ray LAC),synchrotron radiation micro computed tomography (SR micro-CT),density,Toothpaste,monochromatized X-ray beams,fluoride,remineralization
更新于2025-09-09 09:28:46