Use of the chemical Fricke dosimeter and its modifications for dosimetry of gamma neutron radiation of a pulsed reactor

The paper investigates the characteristics of the chemical Fricke dosimeter (with the standard composition (D1), without NaCl addition to the solution (D2), without NaCl but with a tenfold increased concentration of Fe2+ (D3)) under continuous and pulsed irradiation with an ultra-high dose rate of the BARS-6 reactor with unshielded metallic cores. The dosimeter radiosensitivity had a linear dependence on the gamma neutron radiation dose in a range of 25 to 750 Gy and was respectively 1.96 ± 0.05 μGy–1 (D1), 2.04 ± 0.05 μGy–1 (D2), and 2.08 ± 0.5 μGy–1 (D3) in the continuous irradiation mode, and 1.24 ± 0.05 μGy–1, 2.00 ± 0.05 μGy–1, and 1.94 ± 0.05 μGy–1 in the pulsed irradiation mode. This makes ≈ 60% of their sensitivity to the 60Со gamma radiation (3.40 ± 0.02 μGy–1), and 36%, 1.6 times as less, for a standard Fricke dosimeter irradiated in the pulsed mode. The experimental value of the radiation chemical yield, Gn(Fe3+), for all solution modifications and both irradiation modes varied slightly and was 0.84 ± 0.11 μM/J on the average, except for the standard solution in the pulsed mode (0.66 ± 0.07 μM/J). The neutron doses determined by chemical and activation dosimeters coincided within the error limits, but the chemical dosimeter readings were systematically higher, by about 20%. Therefore, in the fission spectrum neutron dose rate range of 0.4 to 7×108 Gy/min, there is no dose rate effect both in the standard Fricke dosimeter version (without NaCl) and in the modified version, which makes it possible to use modified Fricke dosimeters to assess the physical and dosimetry characteristics of mixed gamma neutron radiation beams.

Amorphization and Nano-Crystallization of Ni-Nb Coating on GH3039 Alloys by High Current Pulsed Electron Beam

In this paper, the Ni-Nb coatings were successfully prepared onto the GH3039 alloys by High current pulsed electron beam (HCPEB). The transmission electron microscopy (TEM) results confirmed that the Ni-Nb layer of 10-pulsed samples exhibited partial amorphization, which was consisted of γ-Ni particles, rod-like Ni3Nb particles and nano Ni3Nb with 30 nm in size. After 20-pulsed irradiation, the results show that only Ni3Nb clusters with around 3 nm in size were dispersed in fully amorphization layer. With increased pulse number to 30, the nano-particles embedded into the amorphous layer were grown up, the size of which was about 8 nm. The microstructure evolution during HCPEB irradiation was from the partial amorphous to fully amorphous and then to nano-crystallization. The 20-pulsed samples possessed the best hardness and corrosion resistance. The ultrafine clusters uniformly embedded into amorphous layer were main reason for improving properties.

Plasmonic carriers responsive to pulsed laser irradiation: a review of mechanisms, design, and applications

This review focuses on interactions which govern release from plasmonic carrier systems including liposomes, polymersomes, and nanodroplets under pulsed irradiation.

The efficiency of ablation of metals by scanning beam of pulsed irradiation with nanosecond-range fiber Yb:YAG laser

The results of experiments on ablation of targets made of stainless steel and aluminum by a scanning beam of nanosecond pulses at intensity up to 109 W/cm2 are presented. It was found that the overlap of the impact zones during irradiating leads to an increase in the ablation depth in proportion to the area of overlap of the irradiation spots. This is due to increase in overlap irradiation spots degree, zones with a large number of pulse effects are formed on surface, which increases the depth of the melt bath and leads to the ejection of larger particles. An increase in ablation depth of aluminum increase with increase of the interval between pulses up to 10 ms and overlapping of the irradiation spots. The shape of the ejected particles changes from spherical, when formed from a melt, to an irregular shape, when the target is mechanically destroyed by an internal shock wave. The size and velocity distribution of the ejected particles was determined, and on the basis of these data, the laser radiation shielding coefficients were calculated depending on the degree of overlapping of the irradiation spots. It was found that the main mechanism for the decrease in the efficiency of ablation by a scanning beam of radiation is the backflow of microparticles deposited on the target surface. The analysis of the energy balance of the aluminum ablation process is carried out.

Численное моделирование миграции фотонов в однородных и неоднородных цилиндрических фантомах

The specific features of photon diffusion of low-coherence pulsed irradiation in phantoms of soft biological tissues (blood-saturated tissues of the brain, breast, etc.) are described. The results of photon migration simulation using the Diffusion Approximation to the Radiation Transfer Equation (RTE) are compared with ones of the Monte Carlo simulations. It has been confirmed that the Photon Density Normalized Maximum (PDNM) moves towards the center of the investigated object in case of relatively uniform and strongly scattering media. In the presence of inhomogeneities, type of the PDNM motion changes drastically. Presence of an absorbing inhomogeneity in the medium directs trajectory of the PDNM motion of towards the point symmetric to the inhomogeneity relative to the geometric center of the investigated object. In case of scattering the PDNM moves toward the direction of the center of the scattering inhomogeneity.