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Browsing by Author "Scholz, Marek"

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    Assumptions for the design of a neutron pinhole camera dedicated to the PF-24 device
    (Institute of Nuclear Physics Polish Academy of Sciences, 2014) Scholz, Marek; Bielecki, Jakub; Wójcik-Gargula, Anna; Wiącek, Urszula; Drozdowicz, Krzysztof; Igielski, Andrzej; Kulińska, Agnieszka; Tracz, Grzegorz; Woźnicka, Urszula
    The report presents main assumptions on the design of the neutron pinhole camera dedicated to the PF-24 (Plasma Focus) device. The pinhole camera will be used for the investigation of the spatial and temporal distributions of DD neutrons from the PF-24 source. It makes use of principles of the optical geometry adopted for neutron imaging. In the report the evaluation of pinhole geometrical layout has been made on the basis of principles of the geometrical optics. A further optimization of the pinhole geometry has been carried out by means of neutron transport calculations (the MCNP code). The main aim of this report is to provide information on technical solutions for the neutron pinhole.
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    Beryllium neutron activation counter for pulsed D-D fusion sources
    (Institute of Nuclear Physics Polish Academy of Sciences, 2013) Bieńkowska, Barbara; Prokopowicz, Rafał; Scholz, Marek
    The fusion reaction occurring in DD plasma is followed by emission of 2.45 MeV neutrons, which carry out information about fusion reaction rate and plasma parameters and properties as well. Neutron activation of beryllium has been chosen for detection of DD fusion neutrons. The cross-section for reaction 9Be (n, α) 6He has a useful threshold near 1 MeV, which means that undesirable multiply-scattered neutrons do not undergo that reaction and therefore are not recorded. The product of the reaction, 6He, decays with half-life T1/2 = 0.807 s emitting β– particles which are easy to measure. Large area gas sealed proportional detector has been chosen as a counter of β– particles which leave activated beryllium plate. The plate with optimized dimensions adjoins the proportional counter entrance window. Such set-up is also equipped with appropriate electronic components and forms beryllium neutron activation counter. The density of neutron flux on beryllium plate can be determined from the number of counts. Therefore, a proper calibration procedure needs to be performed to establish such a relation. The measurements with the use of known β– source have been done. In order to determine the detector response function such experiment has been modelled by means of MCNP5 – the Monte Carlo transport code. It has allowed a proper application of results of the transport calculations of β– particles emitted from the radioactive 6He and reaching the proportional detector active volume. In order to test the counter system and measuring procedure a number of experiments have been performed on PF-6, PF-1000 and PF-4 devices. The experimental conditions have been simulated by means of MCNP5. The correctness of simulation outcome have been proved by measurements with known radioactive neutron source. The results of the DD fusion neutrons measurements have been compared with other neutron diagnostics.
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    Calculations of the neutron-induced activity in air inside the Cuboid 2 of the High-Resolution Neutron Spectrometer for ITER
    (Institute of Nuclear Physics Polish Academy of Sciences, 2017-01) Wójcik-Gargula, Anna; Tracz, Grzegorz; Scholz, Marek; Drozdowicz, Krzysztof
    This report presents results of the calculations performed in order to predict the neutron - induced activity in air inside the second Cuboid in the ITER equatorial port cell #1 where the Time of Flight detectors of the High Resolution Neutron Spectrometer are planned to be installed. Based on the neutron spectra generated by 2.45 MeV and 14 MeV neutron sources, calculated with the MCNP code, it was possible to determine the activity of the dominant radionuclides using the FISPACT-II Transmutation - Activation Inventory Code and the EAF - 2010 nuclear data library. The results show that although long - lived isotopes such as e.g. H-3 or C-14 are produced following neutron irradiation, their activity will not be significant since they will not exceed the maximum permissible levels.
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    Fast electron dynamics in tokamak plasmas with high-Z impurities
    (Institute of Nuclear Physics Polish Academy of Sciences, 2021) Król, Krzysztof; Scholz, Marek; Mazon, Didier; Jardin, Axel; Słabkowska, Katarzyna; Rzadkiewicz, Jacek
    Na drodze do energii termojądrowej, tokamaki stanowią obecnie najbardziej obiecującą metodę przeprowadzenia kontrolowanej reakcji termojądrowej. Aby uniknąć problemu retencji trytu, jaki ma miejsce w przypadku ścian tokamaka wykonanych z komponentów węglowych, divertor Międzynarodowego Eksperymentalnego Reaktora Termojądrowego (ITER) będzie wykonany z wolframu (W). W związku z tym małe stężenia domieszek wolframu będą obecne w plazmie ITER-a. Niewielkie stężenia wolframu są wystarczające, aby znacząco wpłynąć na działanie tokamaka, a mogą nawet prowadzić do zakończenia wyładowania plazmowego. W szczególności krytycznym zagadnieniem, które musi być zbadane, jest wpływ domieszek o wysokiej liczbie atomowej Z na dynamikę szybkich (supratermalnych) elektronów. Zagadnienie to jest ważne z ze względu na dwa aspekty. Po pierwsze konieczne jest rozwijanie metod tłumienia wiązek elektronów uciekających w plazmie po zerwaniu sznura plazmowego. Po drugie domieszki wolframowe mają negatywny wpływ na efektywność generowania prądu szybkich elektronów w plazmie tokamakowej. Jak dotąd, główny nacisk kładziono na badania dotyczące domieszek o niskiej liczbie atomowej Z, takich jak węgiel, azot czy argon. Jednak obecnie konieczne jest rozszerzenie metod badania dynamiki szybkich elektronów na cięższe domieszki, takie jak krypton, molibden czy wolfram. W związku z tym niezbędne jest uwzględnienie efektu częściowego ekranowania podczas oddziaływania pomiędzy jonami domieszek a szybkimi elektronami w plazmie. Cel ten został osiągnięty poprzez konsekwentne włączenie teorii częściowego ekranowania do obliczeń kinetycznych. Wykorzystany w pracy łańcuch kodów numerycznych C3PO/LUKE/R5-X2 jest standardowym narzędziem do modelowania LHCD w tokamaku Tore Supra, ostatnio zmodernizowanym do tokamaka WEST. W przedstawionej pracy szczególny nacisk został położony na konsekwencje obecności nie w pełni zjonizowanych domieszek o wysokiej liczbie atomowej Z na generowanie przepływu prądu za pomocą fal LH oraz intensywność promieniowania hamowania emitowanego przez szybkie elektrony dla przypadku tokamaka WEST.
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    Plasma-Focus and controlled nuclear fusion
    (Institute of Nuclear Physics Polish Academy of Sciences, 2016) Scholz, Marek
    The dependence of the binding energy per nucleon on the nucleus mass number known in nuclear physics shows that nuclear energy can be produced (emitted) not only in the fission reactions of heavy nuclei, but also in the fusion reactions of light nuclei. In both cases, the production (emission) of energy is equal to the increment of the total binding energy. Thus nuclear fusion reactions, in addition to fission reactions, may be the second major source of energy production on Earth.
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    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, Marek
    This 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).
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    The Plasma-Focus device at IFJ PAN Kraków: Status and Perspectives
    (Institute of Nuclear Physics Polish Academy of Sciences, 2020) Scholz, Marek; Kulińska, Agnieszka
    The report presents the principle of operation of the Plasma Focus (PF) device and a description of the phenomena in the generation of hot, dense magnetized plasma. Here is a brief outline of its history and the current state of research conducted on these systems in various laboratories around the world. Against this background, the specification and operating parameters of PF-24, operating at the Laboratory of Neutron Sources (IFJ PAN) since 2014, have been described. The current state of the diagnostic systems used was presented as well as the main research objectives illustrated by the results obtained. Plans and perspectives for future experiments as well as related topics of doctoral dissertations were presented.
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    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, Jędrzej
    In 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.