S. Yu. Savinov

X-pinch source of subnanosecond soft X-ray pulses based on small-sized low-inductance current generator

For the first time, the regime of a micrometer-size hot spot formation is impemented for an X-pinch in a plasma, which is fed from a current generator based on low-inductance capacitors and rapid current switches. The configurations of X-pinches, which can be used effectively as point sources of soft X-rays with this type of current generator, are determined. A prototype of a small-size radiation source for high-resolution point projection X-ray radiography has been constructed. The main parameters of X-pinch as a radiation source are analyzed and compared with X-pinch parameters in high-voltage setups with shaping lines. An analysis of the data on the operation of X-pinches in generators with different parameters has led to simple relations that can be used to select optimal initial X-pinch parameters.

Experimental verification of the method for detection of water microleakages in plasma vacuum chambers by using the hydroxyl spectrum

Experimental determination of the sensitivity of the method for detection of water microleakages in the cooling systems of the plasma vacuum chambers of complex electrophysical devices (such as tokamaks, fuel elements of nuclear reactors, and plasmachemical reactors) is considered. It was shown that the spectroscopic method for detection of water microleakages by using the hydroxyl radiation spectrum makes it possible to detect leakages at a level of 10−5 Pa m3 s−1. The spatial resolution of the method allows one to localize defects with an accuracy of several centimeters.

High-resolution X-ray projection radiography of a pin cathode in a high-current vacuum diode using X-pinch radiation

To study processes in a high-current vacuum diode with a cathode in the form of a single pin made of a metallic wire 20–30 μm in diameter, the method of high-resolution projection X-ray radiography with an X-pinch as a source has been used. A strong inhomogeneity of the energy contribution to the wire has been revealed. The smallest energy release has been observed near the end of the pin, where the electric field strength is maximal. Hard X rays, as well as the ejection of matter from the anode, have been observed, indicating the generation of an electron beam with the parameters characteristic of explosive electron emission in the diode with this configuration. The data obtained indicate complex processes occurring in the diode. Possible scenarios of their development have been considered.

Ordering of the flame track in the ring mode of the Trichel pulse negative corona discharge

The ring mode of the Trichel pulse negative corona discharge was studied in atmospheric air. The localization of the discharge flame track in the stable self-organized regular pattern of 3, 4, 5 and 6 – pointed star was found at the cathode surface. This phenomenon was observed at mean currents in the range 100-115 μA at the conditions of the experiment, when the modes with one or two rings are not stable. The conclusion was made that the ring mode of the discharge, which is caused by the symmetrical distribution of the volumetric charges in the conditions of the symmetrical electric field, may be unstable. This instability results in the spatial self-organization of these parameters and causes the organization of the discharge flame track at the cathode surface in the regular patterns.

The airflow effect on a negative corona discharge

The effect of the airflow on the negative corona discharge is studied. It is shown by use of telemicroscopy that the localization of the discharge torch on the cathode surface can be significantly affected by the aerodynamic action on the discharge gap region.

Erosion cell formation in the pulseless negative corona discharge

Graphite cathode surface erosion in the pulseless negative corona discharge in air is studied in the point-plane electrode configuration at a pressure of 0.3–1 atm. The formation of erosion craters in the form of orderly arranged erosion cells shaped as regular polygons on the cathode tip is detected. The cell size coincideswith the negative glow diameter of the discharge torch. The formation of orderly arranged cells is associated with features of the discharge torch dynamics in the pulseless discharge type.

Generation of Intense UV Radiation during High-Current Breakdown over a Ferrite Surface

The dynamics and emission characteristics of pulsed breakdown over a ferrite surface at a current amplitude of 270 kA and current rise time of 80 ns were studied experimentally. It is shown that the characteristic transverse size of the discharge region in visible radiation is ~3 mm, while that in vacuum UV (VUV) radiation is ~200 μm. The duration of the VUV pulse with an average power of ≈0.275 GW is about 80 ns.

Growth and Study of Scintillation Properties of Orthovanadate Crystals Ca:GdVO4 and Ca:YVO4

New scintillation orthovanadate crystals Ca:GdVO4 and Ca:YVO4 featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the 137Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO4 and Ca:GdVO4 crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.

Influence of defects on scintillation properties of oxyorthosilicate crystals Ce:Sc:LFS

New scintillation crystals Ce:Sc:Li:LFS and Ce:Sc:Ca:LFS based on lutetium oxyorthosilicate are grown. Optical characteristics and the decay time of new scintillators are studied. For Ce:Sc:Ca:LFS crystals, it is shown that oxygen vacancies dominate in the energy transfer in the matrix transmission range of 3.46–6.26 eV. It is found that the high density of oxygen vacancies at the lower part of the Ce:Sc:Ca:LFS crystal leads to a decrease in the scintillation time to 22–26 ns.

The study of radiation degradation of optical properties of non-stoichiometric Lu3.01−xYxAl4.99O12 crystals doped with Ce3+, Cr3+, and Sc3+ ions under the action of gamma radiation

The spectra of pulsed cathodoluminescence (PCL) and optical transmission (OT) of crystals grown from Lu3.01−xYxAl4.99O12 melts doped with Cr3+, Ce3+, and Sc3+ ions before and after irradiation with gamma radiation of a 60Co radioactive source are studied. The gamma radiation dose absorbed by samples was 45 Mrad. The maximum gamma-radiation-induced absorbance in the range of 525–700 nm was 0.48 cm−1. Changes in the PCL and OT spectra of all samples after irradiation were detected. It was found that the relative intensity of Cr3+ bands increased after irradiation in relation to the Ce3+ band intensity by a factor of 1.6–8; the OT spectra of all samples after irradiation lost specific features and became identical. The results obtained are qualitatively explained. According to the explanation, the induced absorption is controlled first of all by optically active Frenkel defects formed after irradiation, which include an oxygen vacancy and an interstitial oxygen ion.