Search

In this study we present the experimental differential cross sections of natO(p,p0) elastic scattering, determined via the relative measurement technique, in the proton beam energy range Elab=4-6 MeV with a varying step (from 5-15 keV), at six backscattering detector angles between 120o and 170o (every 10o). A thin, self-supporting target manufactured in the lab was used in this experiment and the determination of its stoichiometry was carried out according to the currently existing evaluation, which has also been benchmarked recently. The measurements were performed using the Van de Graaff Tandem 5.5 MV Accelerator of N.C.S.R. “Demokritos” in Athens, Greece. The differential cross-section datasets obtained in the present work and already existing ones in literature for this extended proton beam energy range are shown and the observed peculiarities and discrepancies are discussed and analyzed.

A simulation code was developed using the GEANT4 [1] toolkit in order to determine the behavior of the neutron production beams generated by proton induced reactions while applying the cross section biasing technique [2]. As the application of the biasing technique can cause a change in the physical processes occurring during the simulation, the specific implemented technique was tested via control simulations to determine any deviations of the results from the theoretically expected ones. Different materials, geometries and biasing factors were used in order to qualify and quantify the discrepancies between the unbiased and the biased simulations. One of the main reactions used for the production of the neutron beam at the Tandem accelerator laboratory of N.C.S.R. “Demokritos” [3] is the 3H(p,n)3He one. In the geometry of the main tritiated target, elements such as molybdenum, copper and titanium are included. During the interaction of the proton beam with them, it is possible to produce neutrons that will “contaminate” the main neutron beam. These neutrons are called parasitic and their quantification is necessary in order to avoid obtaining erroneous results in cross section measurements on the various targets under study.[4] By constructing the proper geometry and using the GEANT4 code mentioned above, the determination of the parasitic neutrons is achieved with optimal statistical results in short computational times, while the discrepancies between the unbiased and the biased results remain minimal.

Accurate neutron flux measurements in fusion reactors are essential, in order to determine the feasibility and progress of the reaction as well as for safety issues. Semiconductor neutron detectors exhibit promising characteristics for operation in the extreme environmental conditions of fusion reactors. Silicon, Diamond and Silicon Carbide are the most studied and anticipated materials for constructing detectors with high efficiency and irradiation resistance. The ITER fusion reactor is expected to run D-D plasma measurements in the near future, so the detection of 2.45 MeV neutrons with appropriate detectors is of great and immediate importance. In the present work the study of 2.45 MeV neutrons interactions with a silicon, diamond and silicon carbide detector was made, using GEANT4 [1] simulations, in order to compare their response. An experimental study will follow at the neutron production facility of the TANDEM accelerator of the I.N.P.P. of the NCSR “Demokritos”, with detectors provided by CIVIDEC Instrumentation GmbH, so the geometry of the simulations was built accordingly. A quasi-monoenergetic neutron beam of 2.45 MeV was produced through 3H(p,n) reactions in a TiT target. Due to the low cross section of the reaction, biasing techniques were implemented in the simulation to increase the counting rate and thus producing realistic results. These biasing techniques were studied, with various tests and the parameters affecting the choice of the biasing factor are shown and discussed.

In this study we present the experimental cross sections of the natO(p,p0) elastic scattering, determined via the relative measurement technique, in the proton energy range Elab=4-6 MeV, at six backscattering detector angles between 120o and 170o, with a 10o step. The measurements were performed using the Van de Graaff Tandem 5.5 MV Accelerator of N.C.S.R. “Demokritos” in Athens, Greece and a high precision goniometer.

The differential cross section values of the natSi(p,p0) elastic scattering were determined in the energy range of Ep,lab = 3000–5000 keV at 6 backscattering detection angles (120°, 130°, 140°, 1 50°, 160° and 170°). The target was a self-supported thin Si3N4 foil. In addition, a thick crystalline silicon wafer was irradiated on its unpolished side with protons at energies Ep,lab = 3200, 3400, 3600, 3850, 4100, 4300, 4500, 4740, 5000 keV, in order to validate the results of the first experiment. On top of both targets a thin layer of 197Au was evaporated for normalization purposes. Both measurements were performed in parallel, using the 5.5 MV TN11 HV Tandem Accelerator and the high precision goniometer of N.C.S.R. ‘Demokritos’, Athens, Greece. The experimental and data analysis processes are presented in detail, as well as, comparisons between the obtained differential cross sections and already existing datasets in literature, along with the benchmarking results.