Browsing by Author "Igielski, Andrzej"
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Item 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, UrszulaThe 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.Item Feasibility study of experimental detection of the hydrogen content in rock material by a pulsed neutron method(Institute of Nuclear Physics Polish Academy of Sciences, 2003) Drozdowicz, Krzysztof; Drabina, Andrzej; Dąbrowska, Joanna; Gabańska, Barbara; Igielski, Andrzej; Janik, Władysław; Krynicka, Ewa; Kurowski, Arkadiusz; Wiącek, Urszula; Woźnicka, UrszulaTheoretical principles of a pulsed neutron method to measure the water or hydrogen content in a rock material have been tested on the experimental set-up at the fast neutron generator in the INP. The time decay constant of the thermal neutron flux in the samples has been measured as a function of the hydrogen content. Dry crumbled granite has been used as a rock sample. The hydrogen content has varied due to addition of a defined amount of polyethylene (0 to 20 %). A few arrangements (neutron source + sample) have been tried. A dedicated pulsed thermal neutron source has been designed and built. The measuring set-up has been chosen for a final elaboration of the method.Item Measurements of the effective thermal neutron absorption cross-section in multi-grain model(Institute of Nuclear Physics Polish Academy of Sciences, 2005) Drozdowicz, Krzysztof; Gabańska, Barbara; Igielski, Andrzej; Krynicka, Ewa; Schneider, Krystyna; Woźnicka, UrszulaThe effective macroscopic absorption cross-section Σaeff of thermal neutrons in a grained medium differs from the corresponding cross-section Σahom in the homogeneous medium consisting of the same components, contributing in the same amounts. The ratio of these cross-sections defines the grain parameter, G, which is a measure of heterogeneity of the system for neutron absorption. Heterogeneous models have been built as two- or three-component systems (Ag, Cu and Co3O4 grains distributed in a regular grid in Plexiglas, in various proportions between them). The effective absorption cross-section has been measured and the experimental grain parameter has been found for each model. The obtained values are in the interval 0.34 < G < 0.58, while G = 1 means the homogeneous material.Item Physical assumptions for a design of the DET-12 chamber for detection of delayed neutrons(Institute of Nuclear Physics Polish Academy of Sciences, 2014) Bieńkowska, Barbara; Drozdowicz, Krzysztof; Gabańska, Barbara; Igielski, Andrzej; Prokopowicz, Rafał; Wiącek, Urszula; Woźnicka, UrszulaPhysical assumptions have been outlined to design a new device (DET-12) for measurements of delayed neutron emitted from samples of fissionable materials activated with neutrons at big fusion-plasma devices. The aim is to support in this way a classic neutron activation method used as one of the hot plasma diagnostics at tokamaks or stellarators. Physical fundamentals of generation of the delayed neutrons are mentioned and a resulting concept of the measuring chamber is presented. A general size and dimensions of particular constituent material layers, and a number and placement of neutron detectors are optimized by means of Monte Carlo modelling of the neutron transport. Recommendations for a technical design of the measuring chamber are formulated.Item Preliminary test of the scintillator with optical fiber (SOF) detector in a pulsed thermal neutron experiment(Institute of Nuclear Physics Polish Academy of Sciences, 2006) Igielski, Andrzej; Janik, Władysław; Kurowski, ArkadiuszA scintillator with an optical fiber detector (SOF) consists of a small amount of the ZnS(Ag) scintillator mixed with a transparent adhesive material and a thermal neutron converter (6LiF). It is tightly connected to the tip of an optical fiber. The other tip is optically coupled with a small photomultiplier. The SOF detector was assembled and checked in Institute of Nuclear Physics (IFJ PAN). A preliminary test has been done to compare the SOF detector and the 3He proportional counter which has been used for a long time in the pulsed neutron experiments carried out in the Neutron Transport Physics Laboratory (IFJ). It was find that the SOF detector may be used successfully instead of the 3He proportional detector. Small dimmensions of the detector (diameter is about 2 mm) allow to obtain accurate information on the spatial distribution of the thermal neutron flux inside a small investigated system.Item Principles of a method to use CVD diamond detectors for spectrometric measurements of particles in mixed radiation field emitted by D-D and D-T fusion plasmas(Institute of Nuclear Physics Polish Academy of Sciences, 2014) Drozdowicz, Krzysztof; Dankowski, Jan; Igielski, Andrzej; Jaskóła, Marcin; Korman, Andrzej; Kurowski, Arkadiusz; Marczewska, Barbara; Nowak, Tomasz; Wiącek, Urszula; Woźnicka, Urszula; Gabańska, BarbaraFuture thermonuclear reactors for needs of power plants will operate with the deuterium-tritium fuel. Neutron, alpha particle, and energy are created in the fusion reaction between these isotopes. Measurement of energy of the reaction products is important to control energetic balance in the thermonuclear plasma. Fast neutrons (14 MeV) should deliver energy outside the tokamak. Alpha particles are the ash of the reaction but they should also leave their energy (3.6 MeV) in the plasma to maintain the fusion reaction. Therefore, knowledge of the energy of alpha particles escaping from plasma (the lost alpha particles) is essential. Because of a short range of alpha particles the measurement has to be performed inside the tokamak, in harsh surrounding (high temperature and high particle fluxes). Diamond seems to be a proper material for use it as a semiconductor detector under those conditions. A diamond detector (synthetic high purity CVD monocrystal) was tested in aspect of its potential application for spectrometric diagnostic of the ions in tokamaks. The energy calibration of the diamond detectors of the different thickness was performed using isotopic sources: energies around 5 MeV from the 239Pu + 241Am + 244Cm source, and 6.8 and 8.7 MeV from the 212Bi + 212Po source. Additionally, monoenergetic ions beams (alpha particles and protons) were obtained from a van de Graaff accelerator in the 0.4 – 2 MeV energy range. A very good linearity of the amplitude signal vs. energy was obtained. At any working tokamak, a mixed radiation field is present consisting of various particles, like n, α, γ, p, d, t. Their contributions fluctuate depending on a regime of tokamak work and on plasma instabilities. Thus, the CVD diamond detector response in a mixed radiation field can be properly studied only in well-defined conditions of a laboratory experiment. Detection of ions and neutrons was performed at our 14 MeV neutron generator, IGN-14, where (i) the same nuclear reaction as in the D-T plasma occurs and (ii) also other types of radiation similar as at tokamaks are observed (owing to a number of different reactions on the generator target). A new measuring chamber at IGN-14 was designed and built to make possible observation of responses of detectors placed symmetrically or at different angles in respect to the primary ion beam. Two identical or different type detectors can be compared at the same time. A complex spectrograms were obtained and analysed to distinguish signals from various particles.Item Sensitivity of the Thermal Neutron Time Decay to the Hydrogen Content in a Rock Sample(Institute of Nuclear Physics Polish Academy of Sciences, 2004) Drozdowicz, Krzysztof; Dąbrowska, Joanna; Gabańska, Barbara; Igielski, Andrzej; Janik, Władysław; Krynicka, Ewa; Kurowski, Arkadiusz; Niedźwiedź, K.; Wiącek, Urszula; Woźnicka, UrszulaA pulsed neutron method to measure the water or hydrogen content in a rock material has been tested on the experimental set-up at the fast neutron generator in the IFJ PAN. A dedicated pulsed thermal neutron source has been designed, built and added to this set-up. The test experiments have been done using dry crumbled granite as the rock matrix. The hydrogen content in samples has varied due to an addition of a defined amount of polyethylene. The time decay constant of the pulsed thermal neutron flux has been measured as a function of polyethylene content in granite+polyethylene samples. The experimental results have been supplemented with Monte Carlo simulations of the experiments. Analytical estimations of the time decay constant in the examined geometry have also been done. Difficulties of the proposed experimental method at low values of the hydrogen content are discussed. The proposed method using the pulsed neutron source to determine the hydrogen content which is less than 10 %, can be applied for rock samples of volume about 30 dm3. For higher hydrogen content the volume of the sample can be lower – about 7 dm3.Item Spectrometric properties of the CVD diamond detector for measurement of the ‘lost alpha particles’(Institute of Nuclear Physics Polish Academy of Sciences, 2010) Wodniak, Iwona; Dankowski, Jan; Drozdowicz, Krzysztof; Gabańska, Barbara; Igielski, Andrzej; Kurowski, Arkadiusz; Maczewska, Barbara; Nowak, TomaszMeasurement of energy of the ‘escaping alpha particles’ from the thermonuclear reaction in the tokamak is important to get information on the energetic balance in future thermonuclear reactors producing electrical energy. Detectors will work in a harsh environment (high fluxes of particles, high temperature). Synthetic (CVD) diamond can be used in this case as a semiconductor detector. Tests with such a detector are described. Energy calibration has been carried out with a triple alpha particle isotopic source, 239Pu, 241Am, 244Cm (PAC), with the α energy peaks at ca. 5.2, 5.5 and 5.8 MeV. A very good energy resolution has been obtained, comparable with the resolution of the classic silicon detector. Energy response has been also investigated with the use of monoenergetic alpha particle beams (0.4 to 2 MeV) from the Van de Graaf accelerator. The amplitude linearity of the signal is very good, including besides results of measurements with the PAC source.Item Technical design and operation tests of the DET-12 device for detection of delayed neutrons(Institute of Nuclear Physics Polish Academy of Sciences, 2014) Bieńkowska, Barbara; Drozdowicz, Krzysztof; Gabańska, Barbara; Igielski, Andrzej; Janik, Władysław; Kurowski, Arkadiusz; Tracz, Grzegorz; Wiącek, Urszula; Dankowski, JanA technical design of the device for detection of delayed neutrons emitted from neutron-activated fissionable material samples has been performed according to physical assumptions which were earlier elaborated. The DET-12 device was constructed. The detection system was composed, consisting of twelve 3He neutron detectors, related electronics lines, and the data acquisition and recording system. The detectors were adjusted to work in groups by three connected to one preamplifier, considering a weak intensity of emission of the delayed neutrons. Laboratory measurement tests of the device operation were made with use of an isotopic neutron source. A total efficiency of neutron detection in DET-12 was experimentally determined and a relative benchmark calculation was made by means of a Monte Carlo modelling of the neutron transport in the device from the source to detectors.Item The SOF detectors in pulsed neutron measurements(Institute of Nuclear Physics Polish Academy of Sciences, 2009) Igielski, Andrzej; Gabańska, Barbara; Drozdowicz, Krzysztof; Janik, Władysław; Kurowski, ArkadiuszThe time decay of the pulsed thermal neutron flux has been measured with quasi-point SOF detectors (scintillator with the optical fiber). The detectors have been placed at three positions in a 12 cm cube of polyethylene. The time decay constants of the fundamental exponential mode of the thermal neutron flux have been determined and compared with results of a reference measurement using 3He neutron detectors at the cube surface and with a theoretical result from the thermal neutron diffusion theory.