Primary Ionization Density Produced by Charged Fragments in the Working Volume of the Fission Chambers

The question of the spatial distribution of ion pairs created by 235U fission fragments in the active volume of the fission chamber has been studied. The formulas of the spatial distribution of ion pairs in cylindrical fission chambers are proposed, which allows you to evaluate correctly the density of ion pairs in any point in the sensitive volume of the fission chamber

Measurements of Scintillation Light Yield Non-proportionality in NaI(Tl) Detector

The SABRE (Sodium-iodide with Active Background Rejection) experiment consists of 50 kg of ultrapure NaI(Tl) crystal contained within a 10.5 ton liquid scintillator (LS) veto detector, and will search for dark matter interactions in the inner NaI(Tl) detector. The relative scintillation light yield in NaI(Tl) scintillator for different incident particle energies is not constant and is important for characterizing the detector response. The relative scintillation light yield in two different NaI(Tl) scintillators was measured with a 10 µCi 137Cs radioactive source using the Compton coincidence technique (CCT) for scattering angles 30? - 135? using electron energies ranging from 60 to 500 keVee, and these measurements are compared to the previously published results. Light yield was proportional within 3.5% at energies between 60 and 500 keVee, but non-proportionality increases drastically below 60 keVee which might be due to the non-uniform ionization density and multiple Compton scattering background events in the scintillator. An improved experimental setup with ultrapure NaI(Tl) scintillator and proper coincidence timing of radioactive events could allow scintillation light yield measurement at lower electron recoil energy. The obtained light yield non-proportionality results will be useful for the SABRE dark matter detector experiment.

Features of modifying properties of chemicals under the action of radiation of different quality: UV light, gamma-radiation and alfa-particles

Modification of the action of ionizing radiation by chemicals, used both to enhance its action and to weaken it’s known and is widely used in medical radiology. The article presents a comparative analysis of the modifying properties of three chemical radioprotectors (cysteamine, cysteine and cysteamine) when they are simultaneously act with to gama-rays, alpha-particles and ultraviolet radiation on yeast cells. The aim of the study was to compare the features of the manifestation of the properties of chemicals in relation to the protection of cells from UV-like damage when exposed to ionizing radiation or from damage caused by ultraviolet radiation. It was demonstrated that the cysteamine protects cells both from the damaging effects of gama-rays and from ultraviolet radiation, unlike cysteamine and cysteine, which protect cells exclusively from the effects of ionizing radiation. Moreover, cystamine does not change the effect of alpha-particles, which have a high ionization density of the substance, but practically do not cause excitation processes in biological objects. The obtained data indicate that cystamine realizes its protective properties against damage caused by ultraviolet radiation and UV-like damage resulting from the action of gama-rays due to the excitation of molecules or, more precisely, the ultraviolet component of Vavilov-Cherenkov luminescence accompanying the action of ionizing radiation.

DEMONSTRATION OF THE POTENTIAL AND DIFFICULTIES OF COMBINED TL AND OSL MEASUREMENTS OF TLD-600 AND TLD-700 FOR THE DETERMINATION OF THE DOSE COMPONENTS IN COMPLEX NEUTRON-GAMMA RADIATION FIELDS

The results reported herein demonstrate the potential application of combined optically stimulated luminescence/thermoluminescent (OSL/TL) measurements in neutron-gamma discrimination dosimetry. The advantages of OSL/TL are two-fold: (i) The OSL and TL readout can be carried out on the same sample and (ii) the greater efficiency of OSL to high ionization density radiation due to F 2 and F3 excitation. The gamma/electron calibration coefficients for LiF:Mg, Ti (TLD-600 and TLD-700) were measured using a 90Sr/90Y source calibrated at the SARAF-SSDL nuclear facility. The estimation of the neutron calibration coefficients was carried out by irradiation with broad-spectrum beam of fast neutrons with median energy 5 MeV at the Radiological Research Accelerator Facility (RARAF) of Columbia University. Naturally cooled samples of TLD-600 and TLD-700 were dosed to levels of 29.8 Gy neutrons and 6.1 Gy gammas in air and KERMA calculations employed to transfer the levels of dose to6,7LiF. A figure of merit for fast-neutron/gamma ray discrimination was determined at 10.6 for TLD-700 in the current measurements. The use of combined TLD-600/TLD-700 allowed, as well, the determination of a considerable and somewhat unexpected thermal neutron component of 116 Gy in TLD-600.

Super star cluster feedback driving ionization, shocks and outflows in the halo of the nearby starburst ESO 338-IG04

Context. Stellar feedback strongly affects the interstellar medium (ISM) of galaxies. Stellar feedback in the first galaxies likely plays a major role in enabling the escape of LyC photons, which contribute to the re-ionization of the Universe. Nearby starburst galaxies serve as local analogues allowing for a spatially resolved assessment of the feedback processes in these galaxies. Aims.We aim to characterize the feedback effects from the star clusters in the local high-redshift analogue ESO 338-IG04 on the ISM and compare the results with the properties of the most massive clusters. Methods. We used high quality VLT/MUSE optical integral field data to derive the physical properties of the ISM such as ionization, density, shocks, and performed new fitting of the spectral energy distributions of the brightest clusters in ESO 338-IG04 from HST imaging. Results.We find that ESO 338-IG04 has a large ionized halo which we detect to a distance of 9 kpc. We identify four Wolf-Rayet (WR) clusters based on the blue and red WR bump. We follow previously identified ionization cones and find that the ionization of the halo increases with distance. Analysis of the galaxy kinematics shows two complex outflows driven by the numerous young clusters in the galaxy. We find a ring of shocked emission traced by an enhanced [O I]/Hα ratio surrounding the starburst and at the end of the outflow. Finally we detect nitrogen enriched gas associated with the outflow, likely caused by the WR stars in the massive star clusters. Conclusions. Photoionization dominates the central starburst and sets the ionization structure of the entire halo, resulting in a density bounded halo, facilitating the escape of LyC photons. Outside the central starburst, shocks triggered by an expanding super bubble become important. The shocks at the end of the outflow suggest interaction between the hot outflowing material and the more quiescent halo gas.