Browsing by Author "Dworak, Dominik"
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Item Budowa modeli geochemiczno-mineralogicznych na podstawie danych uzyskiwanych z zaawansowanych metod geofizyki jądrowej. Część 1(Institute of Nuclear Physics Polish Academy of Sciences, 2007) Woźnicka, Urszula; Cywicka-Jakiel, Teresa; Drabina, Andrzej; Dworak, Dominik; Tracz, Grzegorz; Drozdowicz, Krzysztof; Zorski, Tomasz; Ossowski, Andrzej; Środoń, Jan; Kawiak, Tadeusz; Bakowska, Dorota; Zielińska, Małgorzata; Zalewska, JadwigaAn extensive set of conventional and special core analysis measurements, complemented by additional chemical and mineralogical analyses was performed, forming the basis for the evaluation of the complex thin bedded gas-bearing shaly-sand formations of Miocene age in the Carpathian Foredeep region of Southern Poland. Mineralogy was established by using full elemental composition, XRD method, total surface area and cation exchange capacity (CEC). The analysis showed that the most important clay component is illite – smectite mixed layer. Statistical multivariate analysis of all data helped to set up a comprehensive general petrophysical model. For the notoriously difficult CEC information for the rock matrix we could establish a reliable correlation (corr. coefficient r2 around 0.95) between thermal neutron absorption cross section SIGMA and total natural radioactivity GR with CEC, with boron and rare earth elements the two most important SIGMA contributors in the rock matrix. This good correlation permits a continuous on-line CEC determination and therefore a reliable application of the Waxman-Smits water saturation model to properly take into account the clay mineral effects in evaluating water saturation.Item Numeryczne modelowanie wpływu niejednorodności otoczenia odwiertu poziomego na odpowiedź sondy gęstościowej gamma-gamma(Institute of Nuclear Physics Polish Academy of Sciences, 2009) Zorski, Tomasz; Woźnicka, Urszula; Wiącek, Urszula; Kowalik, Krzysztof; Dworak, DominikThe response of the spectrometric gamma-gamma density tool in borehole conditions has been numerically simulated. A transport of gamma rays from a point source situated in a borehole tool through the rock medium to the detectors has been simulated using the MCNP code. An influence of heterogeneity of a rock medium surrounding the borehole on the response of detectors in the probe has been examined. The heterogeneity results from the presence of the interface between two different geological layers parallel to the borehole axis. Such conditions happen in horizontal logging practice when the borehole is drilled along the boundary of geological layer. It is possible to assess the distance from the boundary on the basis of the response of the gamma-gamma density tool, using the classic interpretation procedure “spine&ribs. We take advantage of the effect of different densities of the bordered layers. When the boundary is far-away the response of the probe fits to the “spine” curve and when the boundary is close – the response fits to the “rib”. The presented examples show the wide possibilities of numerical modeling of the complex borehole geometry and of applications to solve difficult interpretation problems of the nuclear borehole logging.Item Preliminary study of a target-moderator assembly for a linac-based neutron source(Institute of Nuclear Physics Polish Academy of Sciences, 2005) Bartalucci, Sergio; Drozdowicz, Krzysztof; Dworak, Dominik; Tracz, Grzegorz; Angelov, VladimirThe report concerns a design of a future pulsed neutron source at an electron linac. A massive target is irradiated with an electron beam and the neutrons are generated mainly by collisions of the bremsstrahlung photons. A first step of the work, related to the optimization of the target materials and geometry using numerical simulations, is presented. The Monte Carlo FLUKA and MCNP codes are used. The water-cooled tantalum target is investigated: 0.41 cm Ta slices separated with 0.15 cm H2O layers. Two different sizes of the cylindrical target are assumed: 5 or 2.5 cm in diameter. The 1 GeV and 1.5 GeV electron beams are tested. The outgoing neutron angular-energy spectra are presented. The angular space 0°÷180° is divided in 10-degree intervals. The neutron emission in the direction perpendicular to the originated electron beam has been observed in the particularly narrow (2°) interval. The FLUKA results of a comparison of the neutron currents in main directions (0° – forward, 90° – perpendicular, 180° – backward) are as follows. For the 5 cm target the distribution is quite uniform: at 1 GeV input electrons – n(180°)/n(0°) = 1.00, n(90°)/n(0°) = 1.04, and at 1.5 GeV electrons – n(180°)/n(0°) = 0.91, n(90°)/n(0°) = 1.00. For the 2.5 cm target the relative neutron current in the perpendicular direction is significantly higher: at 1 GeV electrons – n(180°)/n(0°) = 1.02, n(90°)/n(0°) = 1.53, and at 1.5 GeV electrons – n(180°)/n(0°) = 0.93, n(90°)/n(0°) = 1.45. In the cases when the FLUKA and MCNP simulation results can be compared, a high similarity of the neutron energy distributions is stated although a possible discrepancy of the values reaches 20 %. Spectra of the accompanying radiation (photons, electrons, positrons, protons, charged pions) have been also obtained. The angular distributions of photons, electrons, and positrons are strongly peaked up towards the beam direction. Their emission at 90° is significantly lower, which means a decrease of the background in this direction. The energy deposition in the target is estimated on a simplified model with no cooling system. About 63 % of energy is then stored in the space at ca. 20÷40 % target length along the initial electron beam axis.Item Study of the mutual dependence between Lower Hybrid current drive and heavy impurity transport in tokamak plasmas. Part 1. Preparatory work and theoretical background(Institute of Nuclear Physics Polish Academy of Sciences, 2020) Jardin, Axel; Bielecki, Jakub; Król, Krzysztof; Peysson, Y.; Mazon, D.; Dworak, Dominik; Scholz, MarekThis document reports the activities performed during the year 2019-2020 in the framework of the HARMONIA 10 project entitled “Study of the mutual dependence between Lower Hybrid current drive and heavy impurity transport in tokamak plasmas” as well as the preliminary results obtained during the first year of project execution. The project is founded by the Polish National Science Centre (NCN) and carried out in a close collaboration with the foreign partner - Institute for Magnetic Fusion Research (IRFM) of the French Alternative Energies and Atomic Energy Commission (CEA).Item Symulacja Monte-Carlo odpowiedzi otworowej sondy geofizycznej gamma-gamma w ceramicznym ośrodku modelowym stanowiska kalibracyjnego w Zielonej Górze(Institute of Nuclear Physics Polish Academy of Sciences, 2015) Dworak, DominikResponses of the spectrometric gamma-gamma density tool in borehole were numerically simulated by means of the MCNP code. The rock medium has been modelled as a few layers of some ceramic materials with well-known chemical composition and mudstones of 2, 5, 9 and 15 % porosity.Item Symulacja Monte-Carlo odpowiedzi spektrometrycznej sondy geofizyki otworowej sPNG w ośrodku modelowym stanowiska kalibracyjnego w Zielonej Górze(Institute of Nuclear Physics Polish Academy of Sciences, 2016-07) Dworak, Dominik; Wiącek, UrszulaThe MCNP model of the spectrometric well-loging tool, sPNG, was designed and coded. Responses of the sPNG probe were simulated,and obtained gamma spectra compared with measurements performed at Zielona Góra calibration facility. Good agreement of the calculated and measured spectra seams to confirm correctness of the modelling.Item Symulacje numeryczne odpowiedzi głębokościowej sondy NNTE w formacjach cienkowarstwowych nachylonych do osi odwiertu. Założenia i obliczenia wstępne metodą Monte Carlo(Institute of Nuclear Physics Polish Academy of Sciences, 2011) Woźnicka, Urszula; Dworak, Dominik; Wiącek, Urszula; Zorski, TomaszBasic assumptions for calculation of well-logging profiles, expected from measurements of the neutron logging tools (type of NNTE) are presented. The report includes also results of the first tests and calculations. The NNTE tool responses were simulated using MCNP - the well-known Monte Carlo code. The general model consists of a huge rock, intersected by a borehole. A thin, flat rock layer of different lithology crosses that huge rock under an angle to the borehole. Numerous combinations of the model parameters - various porosities and neutron absorption cross-sections of the rocks as well as different layer thicknesses and angles - have been considered. The final results should be instantly useful for elaboration of the well-logging interpretation procedures for directional drillings, where the rock layers are usually sloped, or even highly inclined to the borehole axis.Item Using X-ray measurements to assess uncertainties in plasma temperature and impurity profiles in tokamaks(49th European Physical Society (EPS) Conference on Plasma Physics, 2023-07) Jardin, Axel; Krzysztof, Król; Mazon, Didier; Bielecki, Jakub; Dworak, Dominik; Guibert, Denis; Peysson, Yves; Scholz, Marek; Walkowiak, JędrzejIn tokamaks, the local X-ray plasma emissivity is a complex quantity resulting from the contribution of several plasma parameters, i.e. electron temperature, density and concentration of impurities in multiple ionization states. In particular, the impurity core concentration can be estimated from the emissivity in the soft X-ray (SXR) range 0.1 – 20 keV, while information about the superthermal electron population can be obtained in the hard X-ray (HXR) range 20 keV – 200 keV. The estimation of the tungsten concentration profile is subject to many uncertainties, in particular it requires accurate knowledge of plasma temperature, magnetic equilibrium, atomic processes leading to its cooling factor and the spectral response of the diagnostic. A global W concentration can, for example, be inferred with integrated simulation codes in order to match the total radiated power. When all other plasma parameters are well-known, the impurity density profile can be reconstructed in the core with the help of SXR tomographic tools. Nevertheless, in the case of a significant fraction of superthermal electrons e.g. due to RF heating, accurate estimation of electron temperature from ECE measurements can become a challenging task. Therefore, the goal of this contribution is to establish a methodology to assess the uncertainty in the core electron temperature and impurity concentration profiles based on X-ray measurements. The proposed strategy is to define a grid of candidates (Te, cW) scenarios and identify the ones having the highest consistency with respect to multiple line-integrated measurements. In order to determine the capabilities and limitations of such an approach, the method is first tested on well-known synthetic profiles in an arbitrary tokamak geometry. In a second step, first experimental tests are presented for some selected WEST discharges.