Towards energy discretization for muon scattering tomography in GEANT4 simulations: A discrete probabilistic approach

In this study, by attempting to eliminate the disadvantageous complexity of the existing particle generators, we present a discrete probabilistic scheme adapted for the discrete energy spectra in the GEANT4 simulations. In our multi-binned approach, we initially compute the discrete probabilities for each energy bin, the number of which is flexible depending on the computational goal, and we solely satisfy the imperative condition that requires the sum of the discrete probabilities to be the unity. Regarding the implementation in GEANT4, we construct a one-dimensional probability grid that consists of sub-cells equaling the number of the energy bin, and each cell represents the discrete probability of each energy bin by fulfilling the unity condition. Through uniformly generating random numbers between 0 and 1, we assign the discrete energy in accordance with the associated generated random number that corresponds to a specific cell in the probability grid. This probabilistic methodology does not only permits us to discretize the continuous energy spectra based on the Monte Carlo generators, but it also gives a unique access to utilize the experimental energy spectra measured at the distinct particle flux values. Ergo, we initially perform our simulations by discretizing the muon energy spectrum acquired via the CRY generator over the energy interval between 0 and 8 GeV along with the measurements from the BESS spectrometer and we determine the average scattering angle, the root-mean-square of the scattering angle, and the number of the muon absorption by using a series of slabs consisting of aluminum, copper, iron, lead, and uranium. Eventually, we express a computational strategy in the GEANT4 simulations that grants us the ability to verify as well as to modify the energy spectrum depending on the nature of the information source in addition to the exceptional tracking speed.Comment: 9 pages, 5 figures, 4 tables, ACAT 202

Particle generation through restrictive planes in GEANT4 simulations for potential applications of cosmic ray muon tomography

In this study, by attempting to resolve the angular complication during the particle generation for the muon tomography applications in the GEANT4 simulations, we exhibit an unconventional methodology that is hinged on the direction limitation via the vectorial construction from the generation location to the restriction area rather than using a certain angular distribution or interval. In other words, we favor a momentum direction that is determined by a vector constructed between an initial point randomly chosen on a generative point/plane and a latter point arbitrarily selected on a restrictive plane of the same dimensions with the basal cross section of the volume-of-interest (VOI). On account of setting out such a generation scheme, we optimize the particle loss by keeping an angular disparity that is directly dependent on the VOI geometry as well as the vertical position of the restrictive plane for a tomographic system of a finite size. We demonstrate our strategy for a set of target materials including aluminum, copper, iron, lead, and uranium with a dimension of 40$\times$10$\times$40 $\rm cm^{3}$ over three restrictive planes of different positions by using a discrete energy spectrum between 0.1 and 8 GeV and we compute the scattering angle, the number of absorption, and the particle loss. Upon our simulation outcomes, we show that the particle generation by means of restrictive planes is an effective strategy that is flexible towards a variety of computational objectives in the GEANT4 simulations.Comment: 7 pages, 2 figures, 9 tables, ACAT 202

Investigation of deflection angle for muon energy classification in muon scattering tomography via GEANT4 simulations

In muon scattering tomography, the investigated materials are discriminated according to the scattering angle that mainly depends on the atomic number, the density, and the thickness of the medium at a given energy value. The scattering angles at different initial energies also provide the opportunity to classify the incoming muons into a number of energy groups. In this study, by employing the GEANT4 code, we show that the deflection angle exponentially decays as a function of energy, and the numerical values for the current configuration are below the detector accuracy except the initial energy bins owing to the low-Z, low density, and low thickness of the current plastic scintillators. This implies the necessity of additional components that provoke the muon scattering. Therefore, we introduce stainless steel surfaces into the top and bottom sections in order to amplify the deflection angle as well as to reduce the uncertainty, thereby improving the detector performance

14C emission from Swedish nuclear power plants and its Eeffect on the 14C levels in the environment

The radionuclide 14C is produced in all types of nuclear reactors mainly by neutron-induced reactions in oxygen (17O), nitrogen (14N) and carbon (13C). Part of the 14C created is continuously released during normal operation as airborne effluents in various chemical forms (such as CO2, CO and hydrocarbons) to the surroundings. Because of the biological importance of carbon and the long physical half-life of 14C, it is of interest to measure the releases and their incorporation into living material. The 14C activity concentrations in annual tree rings and air around two Swedish nuclear power plants (Barsebäck and Forsmark) as well as the background 14C activity levels from two reference sites in southern Sweden during 1973-1996 are presented in this report. In order to verify the reliability of the method some investigations have been conducted at two foreign nuclear sites, Sellafield fuel reprocessing plant in England, and Pickering nuclear generating station in Canada, where the releases of 14C are known to be substantial. Furthermore, results from some measurements in the vicinity of Paldiski submarine training centre in Estonia are presented. The results of the 14C measurements of air, vegetation and annual tree rings around the two Swedish nuclear power plants show very low enhancements of 14C, if at all above the uncertainty of the measurements. Even if the accuracy of the measurements of the annual tree rings is rather good (1-2%) the contribution of 14C from the reactors to the environment is so small that it is difficult to separate it from the prevailing background levels of 14C. This is the case for all sampling procedures: in air and vegetation as well as in annual tree rings. Only on a few occasions an actual increase is observed. However, although the calculations suffer from rather large uncertainties, the calculated release rate from Barsebäck is in fair agreement with reported release data. The results of this investigation show that the effective doses to man related to the releases of 14C from the Swedish light-water reactors at Barsebäck and Forsmark are very low, especially compared to the situation at other nuclear installations, such as the fuel reprocessing plant at Sellafield, England, and the heavy-water reactors at Pickering nuclear generating station, Canada. Lund/Malmö February 200

Improvement of the AMS-technique and applications to 3H and 59Ni Measurements

Accelerator mass spectrometry (AMS) is a highly sensitive technique for counting atoms. Its main advantage in comparison with radiometric methods is the smaller amount of sample required (by a factor of a thousand). The method has a high efficiency and requires only some ten mg of sample material. The radioisotope 59Ni is of great importance in nuclear waste management in the nuclear industry. This isotope is produced by the neutron activation of the stable 58Ni, close to the core of nuclear reactors. Due to its long half-life, it is necessary to determine its activity concentration in the various construction materials in connection with classification and storage considerations. In this thesis, further development of the 59Ni detection technique, using the small 3 MV tandem accelerator in Lund, is presented. Some results of measurements on 59Ni samples from nuclear power plants are presented. Improvements of the detection and chemical purification methods of the stainless steel samples, to reduce the content of the interfering isobar 59Co have been made. In order to make heavy ion AMS feasible at the Lund accelerator facility, new improvements on the AMS technique and in the detection technique have been developed. The performance and the improvements of the new gas stripper with terminal pumping are presented. Charge state distributions for various isotopes used in AMS analysis have been measured. Characteristic X-ray cross-sections have been measured for Fe, Ni and Cu ions in connection with the 59Ni project. The radioisotope 3H is the most frequently utilized isotope in biomedicine, and has numerous applications, e.g. determination of total body water, metabolism studies, dosimetry measurements, etc. The development of tritium AMS is expected to have a great impact in biomedical research for two reasons: tritium is the most widely used radioisotope in biomedicine, and secondly, used in conjunction with 14C, it allows low-level, double-labelling experiments. In this thesis, development of the chemical procedure for sample preparation and of the tritium detection technique using a 3 MV tandetron accelerator at the Rossendorf Research Centre, Germany, are presented. The first measurements of the blood samples from patients after administration of tritiated water are presented

AMS with heavy ions at a small tandem accelerator

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DOME: Discrete Oriented Muon Emission in GEANT4 Simulations

The simulation of muon tomography requires a multi-directional particle source that traverses a number of horizontal detectors of limited angular acceptance that are used to track cosmic-ray muons. In this study, we describe a simple strategy that can use GEANT4 simulations to produce a hemispherical particle source. We initially generate random points on a spherical surface of practical radius by using a Gaussian distributions for the three components of the Cartesian coordinates, thereby obtaining a generating surface for the initial position of the particles to be tracked. Since we do not require the bottom half of the sphere, we take the absolute value of the vertical coordinate, resulting in a hemisphere. Next, we direct the generated particles into the target body by selectively favoring the momentum direction along the vector constructed between a random point on the hemispherical surface and the origin of the target, thereby minimizing particle loss through source biasing. We also discuss a second scheme where the coordinate transformation is performed between the spherical and Cartesian coordinates, and the above-source biasing procedure is applied to orient the generated muons towards the target. Finally, a recipe based on restrictive planes from our previous study is discussed. We implement our strategies by using G4ParticleGun in the GEANT4 code. While we apply these techniques to simulations for muon tomography via scattering, these source schemes can be applied to similar studies for atmospheric sciences, space engineering, and astrophysics where a 3D particle source is a necessity

A modified method for the sequential determination of Po-210 and Pb-210 in Ca-rich material using liquid scintillation counting

WOS: 000392075200039This research describes methods for the sequential determination of Pb-210 and Po-210 activity concentrations in Ca-rich ash samples collected from oil shale-fired power plants in Estonia. The procedure involves digestion of Ca-rich ash samples in a microwave digestion system, radiochemical separation of Pb-210 and Po-210 and their measurements. All samples, blanks and standards were measured by liquid scintillation counting (Quantulus 1220). The method was tested using IAEA (International Atomic Energy Agency) RGU-1 and IAEA-444 reference materials. Spectral calibration/peak identification which included the optimization of alpha/beta discrimination system (pulse shape analyser), and recovery have been made by Po-209 and Pb-210 standard solutions.Estonian Research Council ETF grant [ETF9304]This work was supported by the Estonian Research Council ETF grant (award number ETF9304). The authors also would like to thank Kaja Orupold from the Estonian University of Life Sciences, Tartu for her cooperation and support in the laboratory