Investigation of the angular distribution and energy spectrum of fast ions produced during irradiation of targets by short laser pulses in the SOKOL-P facility

Results are presented from experimental investigations of the angular distributions and energy spectra of fast ions produced in deuterium polyethylene targets under irradiation by picosecond laser pulses with intensities of up to 2 × 10¹⁸ W/cm² in the SOKOL-P facility. The parameters of ion fluxes were measured by time-of-flight spectrometers based on semiconductor detectors.     

Methods of spatiotemporal measurements of line X radiation generated in laser plasmas on the Iskra-5 facility

The methods are described that were devised for spatiotemporal measurements of line X radiation generated in Al and Fe plasmas inside a 2-mm-diameter hollow spherical target whose inner surface was coated with a thin layer of the material to be investigated and which was irradiated by the second harmonic of the laser radiation in the Iskra-5 laser facility. The results of measurements are presented.     

Diagnostics of jet structures formed in the plasma corona during the irradiation of porous targets by intense laser pulses

Jet structures formed during laser irradiation of porous targets with an average density of ?? = 1?30 mg/cm³ were studied experimentally by using the diagnostic complex of the Mishen facility. To study complicated plasma structures, the experimental data were processed using specially elaborated mathematical methods. The probability of the emergence of jet plasma structures in plane open-pore triacetate cellulose targets was studied as a function of the parameter ??d, where ?? is the average mass density and d is the target thickness. Analysis of the experimental results and their comparison with the existing data on the jet structures formed during laser irradiation of solid-density targets allowed the authors to reveal the characteristic features and mechanisms of the development of large-scale plasma jets.     

Ultrastructural study of lens fiber damages after laser irradiation

Summary Lens fiber lesion after laser irradiation were studied in the albino rats. Lose of cytoplasmic contrast, pulling apart of intercellular cell junctions and increase of intracellular vesicles were observed.     

Repair of chromosome damage in human lymphocytes after fractionated irradiation with fast neutrons

The frequency of chromosome aberrations in nonstimulated lymphocytes of the peripheral human blood was shown to change after fractionated neutron irradiation of mean energy of 6.0 MeV. At a 2-hour interval between exposures, the number of aberrations exceeded, and at 5-6-hour interval was less than that induced by a single exposure at the same dose.     

Microcinematographic study of the lengthening of the cell cycle after x-ray and fast neutron irradiation

The median cycle duration of unirradiated EMT6 cells is equal to 9.68 +/- 0.20 h. It reaches 10.77 +/- 0.42 h, 12.95 +/- 0.62 h, 14.95 +/- 1.10 h, 16.15 +/- 1.87 h and 20.25 +/- 2.25 h after 250 kV X-rays doses of 1 Gy, 2 Gy, 4 Gy, 6 Gy and 8 Gy respectively and 11.23 +/- 1.03 h, 13.40 +/- 0.53 h and 15.13 +/- 1.15 h after p(65) + Be neutron doses of 0.75 Gy, 1.5 Gy and 2.5 Gy respectively. The corresponding mitotic delay (Tc irradiated - Tc controls) may be evaluated equal to congruent to 1.15 h per Gy for X-rays and to congruent to 2.30 h per Gy for neutrons.     

Histophysiology of tissue basophils of the cerebral dura mater after laser irradiation

By means of the histochemical and morphometric methods the reaction of the tissue basophils of the brain dura mater has been studied to the one-time and varying-duration (0.5 sec.-3 hr.) irradiation by a helium-neon laser of the wave length 632.8 nm, power density 0.76 mvt/sm2. It has been found, that the laser irradiation had a biostimulating effect upon the tissue basophils; the first peak of activity is in the case of a 3-second continuous irradiation; the second--from 15 min. to 1 hr. In symmetrical parts of the right (irradiated) and left (nonirradiated) regions of the dura very similar changes of the functional activity of the tissue basophils activity were seen.     

Photon emission and changes in fluorescent properties of bone after laser irradiation

Laser scalpels used in medical surgery concentrate light energy, heating the tissues. Recently, we reported thermoluminescence emission from laser-treated soft tissues. Here we investigated the thermo-optical effects caused by a laser operating at 808 nm on animal bones (beef ribs) through luminescence and fluorescence imaging, thermal imaging and scanning electron microscopy. Laser-induced artificial lesions emitted luminescence peaking around 650 nm, with a half-life of almost 1 hour. As concerns fluorescence, 24 hours after laser treatment we observed an increase of the emission and a shift from 500 (untreated) to 580 nm (treated). Recrystallization observed by SEM indicates that the temperature in the artificial lesions is over 600°C. We can conclude that laser treatment induces specific luminescent and fluorescent emissions due to heating of the bone and modification of its components. Monitoring these emissions could help prevent tissue overheating and its potential damages during laser-assisted medical procedures.     

Interaction of laser plasmas with noble gases

The interaction of a noble gas jet (Xe, Kr, He) with a laser plasma at a distance of ～1 cm from a solid target (Mg, (CH₂)_n, LiF, or CF₄) was studied for the first time. The line spectra that were excited in the course of charge exchange of multicharged ions with noble gas atoms in the interaction region were recorded. A clean (debris-free) soft X-ray source excited by laser pulses focused into a xenon jet was designed and investigated.     

Present status of the medical irradiation facility at the Musashi reactor

Boron neutron capture therapy (BNCT) of malignant brain tumors has been efficiently performed since March 1977, and the first human case of malignant melanoma was also successfully treated on July 1987 in our reactor (Musashi reactor, TRIGA-II, 100 kW). To obtain both good irradiation field characteristics and a better irradiation facility, some tests and developments have been continued in accordance with the study of medical and biological irradiations. The results of these evaluations and a new approach are presented.     

Microwave irradiation and instrumental behavior in rats: Unitized irradiation and behavioral evaluation facility

A facility for the exposure of small animals to pulse-modulated microwave radiation ( PM MWR ) concurrent with their performance of operant behavioral tasks is described. The computer-managed facility comprises an array of 32 individual waveguide exposure cells, each enclosing instrumental conditioning apparatus within a plastic subhousing. The distribution of the microwave electric field intensity within the waveguide was measured by a nonperturbing probe and the modifications induced by the behavioral apparatus and animal within the waveguide determined. Input and interior voltage standing wave ratios are presented to characterize the design of the chambers and to demonstrate the suitability of the chambers for whole-body irradiation of rat. The specific absorption rate (SAR) is presented utilizing data derived from incremental thermometric examination of saline loads and of selected sites in rat carcasses. This is compared with the whole-body SAR derived from the input/ output energy balance equation for the waveguide. The results of continuous monitoring of the SAR by the latter method, while unrestrained rats were engaged in operant and exploratory behavior within the waveguide, are utilized to derive a relationship between chamber input power and the dose rate for adult rats behaviorally active within the waveguide. From these data, we conclude that the experimental array provides a practical method for exposing a large number of animals to PM MWR for long periods of time and coincident with the establishment and/or performance of complex operant behavior.     

Diagnostics of soft X-ray emission from the plasma of a fast capillary discharge

Results are presented from time-resolved measurements of the soft X-ray emission in the 10-to 40-eV spectral range from the plasma of a pulsed capillary discharge in argon at current pulse amplitudes of up to 26 kA and a current rise time of ～10¹² A/s. The experiments were carried out with 0.3-cm-diameter 15.7-cm-long ceramic capillaries filled with argon at a pressure of 0.25–0.5 Torr in the SIGNAL electrophysical facility. The experimental data are interpreted via computer simulations of the magnetohydrodynamics and level-by-level ion kinetics of an argon plasma. The results obtained indicate that soft X-ray laser pulses with a photon energy of 26.4 eV and duration of 1–2 ns are generated ≈33 ns after the beginning of the discharge current pulse.