Andrzej Igielski

A 14?MeV neutron generator as a source of various charged particles produced in fusion reactions

Measuring the energy of ions from the thermonuclear reaction in future energetic tokamaks (like ITER) is important in order to obtain information on the energetic balance in a plasma toroidal column. Detectors made of synthetic diamond can be used for the spectrometry of ions which accompany burning plasma. A fast neutron (14?MeV) generator, which is a linear accelerator of deuterons, is based on the nuclear reaction T(d,n)? in a tritium target. The energy of alpha particles produced in the D?T reaction in the neutron generator is the same (maximum 3.5?MeV) as the energy of alpha particles present in the hot D?T plasma in tokamaks. Other reactions in the target also occur and the energy spectra of various created ions can be also measured. The experiments have been performed with an ion spectrometry made possible with the use of scCVD diamond detectors at the fast neutron generator (IGN-14) at the Institute of Nuclear Physics in Krak?w, Poland.

Thermal neutron diffusion parameters for plexiglass

Abstract Thermal neutron diffusion and absorption parameters for plexiglass have been measured in the spherical geometry using the pulsed method. The results obtained are: νΣ a = (4120 ± 30) s −1 , D 0 = (36 882 ± 314) cm 2 s −1 , C = (7149 ± 615) cm 4 s −1 (at 19.5°C).

The effective absorption cross-section of thermal neutrons in a medium containing strongly or weakly absorbing centres

The structure of a heterogeneous system influences diffusion of thermal neutrons. The thermal-neutron absorption in grained media is considered in the paper. A simple theory is presented for a two-component medium treated as grains embedded in the matrix or as a system built of two types of grains (of strongly differing absorption cross-sections). A grain parameter is defined as the ratio of the effective macroscopic absorption cross-section of the heterogeneous medium to the absorption cross-section of the corresponding homogeneous medium (consisting of the same components in the same proportions). The grain parameter depends on the ratio of the absorption cross-sections and contributions of the components and on the size of grains. The theoretical approach has been verified in experiments on prepared dedicated models which have kept required geometrical and physical conditions (silver grains distributed regularly in Plexiglas). The effective absorption cross-sections have been measured and compared with the results of calculations. A very good agreement has been observed. In certain cases the differences between the absorption in the heterogeneous and homogeneous media are very significant. A validity of an extension of the theoretical model on natural, two-component, heterogeneous mixtures has been tested experimentally. Aqueous solutions of boric acid have been used as the strongly absorbing component. Fine- and coarse-grained pure silicon has been used as the second component with well-defined thermal-neutron parameters. Small and large grains of diabase have been used as the second natural component. The theoretical predictions have been confirmed in these experiments.

High-Dose TL Dosimetry of Reactor Neutrons

Radiation dose was measured with set of TL dosimeters during checkout of neutron radiation hardness of the ORTEC preamplifier type 142A in the experiment at the MARIA nuclear reactor at the National Centre for Nuclear Research (NCBJ), Otwock-Świerk, Poland. Different types of LiF-based TL detectors have been used for measurements in order to evaluate neutron and non-neutron components of the radiation field in the reactor channel during exposure and to check their relevancy for dose measurements in the reactor environment. For high-dose evaluation a new Ultra-High-Temperature Ratio (UHTR) method established for highly sensitive LiF:Mg,Cu,P detectors has been applied. Neutron fluence evaluated from TL measurements was in good agreement with one calculated using neutron flux data during the experiment.

EXPERIMENTAL AND MONTE CARLO INVESTIGATIONS OF BCF-12 SMALL‑AREA PLASTIC SCINTILLATION DETECTORS FOR NEUTRON PINHOLE CAMERA

Plastic organic scintillators such as the blue-emitting BCF-12 are versatile and inexpensive tools. Recently, BCF-12 scintillators have been foreseen for investigation of the spatial distribution of neutrons emitted from dense magnetized plasma. For this purpose, small-area (5 mm × 5 mm) detectors based on BCF-12 scintillation rods and Hamamatsu photomultiplier tubes were designed and constructed at the Institute of Nuclear Physics. They will be located inside the neutron pinhole camera of the PF-24 plasma focus device. Two different geometrical layouts and approaches to the construction of the scintillation element were tested. The aim of this work was to determine the efficiency of the detectors. For this purpose, the experimental investigations using a neutron generator and a Pu-Be source were combined with Monte Carlo computations using the Geant4 code.

Influence of granulation of the sample on the thermal neutron Σa measurement

Abstract The theoretical approach to the influence of granulation of samples on the measured thermal neutron absorption cross-section has been verified in an experiment on samples containing irregular grains. The neutron absorption heterogeneity effect is defined as the ratio G of the absorption cross-section of the grained sample to the cross-section of the corresponding homogenised medium. The parameter G=1 when the heterogeneity of a material does not influence the thermal neutron transport, otherwise G