Diatlov, A. V.

Lomaev, Mikhail I.

Tarasenko, Viktor Fedotovich

English

Tomsk State University Repository

PULSED LASERS AND LASER APPLICATIONSTHE 15th  INTERNATIONAL CONFERENCEThe 15th International Conference AMPL-2021 PULSED LASERS AND LASER APPLICATIONS September 12–17, 2021 Tomsk, Russia ABSTRACTS GENERAL SPONSOR Special Systems. Photonics, St. Petersburg, Russia CONFERENCE ORGANIZERS Institute of Atmospheric Optics SB RAS Institute of High Current Electronics SB RAS Tomsk State University Tomsk Polytechnic University CONFERENCE SPONSORS Ministry of Education and Science of Russian Federation, Russia Russian Academy of Sciences, Russia Siberian Branch of Russian Academy of Science, Russia Laser Association, Russia  CONFERENCE SPONSORS TOPAZ Research and Inculcation Enterprise, Tomsk, Russia Young Scientists Counsil IAO SB RAS, Tomsk, Russia SP Equipment, Novosibirsk, Russia Azimut Photonics, Moscow, Russia LOTIS TII, Minsk, Belarus Special Systems. Photonics, St.-Petersburg, Russia CLZ Ltd, Moscow, Russia Leningrad Laser Systems, St.-Petersburg, Russia MEDIA SPONSORS Atmospheric and Oceanic Optics Journal, Tomsk, Russia Photonics Journal, Moscow, Russia  Tomsk, 2021  128  GAS DISCHARGES FOR LASERS AND NON-COHERENT RADIATION SOURCES SESSION H  In this study, we present the data on these parameters in the plasma of a high voltage nanosecond discharge in gas filled gaps with a high overvoltage measured by methods of the optical emission spectroscopy (OES): Stark broadening and Stark shift methods [4] for Ne, a method based on the radiation collisional plasma model [5] for Te and E/N, as well as the Boltzmann method [6] for Ttr and the vibrational temperature Tvib. Based on the data obtained, it was established that the impemented plasma is highly non-equilibrium (there is a significant difference between Te (several eV) from Ttr (hundreds of K)), and, in addition, has high electron density at the level of 1014–1016 cm–3. The proofs of the use of these methods for measuring the plasma parameters of the object being implemented are presented. The studies were performed in the framework of the State Task for IHCE SB RAS, Project No. FWRM-2021-0014.  1. Tarasenko V.F. (ed.). Runaway Electrons Preionized Diffuse Discharges. USA. NY: Nova Science Publishers Inc. 2014. 613 p. 2. Sorokin D.A., Tarasenko V.F., Beloplotov D.V., and Lomaev M.I. Features of streamer formation in a sharply non-uniform electric field // J. Appl. Phys. 2019. V. 125, Is. 4. 143301 (7 p.). 3. Adamovich I., Baalrud S.D.,  Bogaerts A. et al. The Plasma Roadmap. Low temperature plasma science and technology // J. Phys. D: Appl. Phys. 2017. V. 50. Art. No. 323001. 4. Chernichowsky A. and Chapelle J. Use of the 447 nm He I line to determine electron concentration // J. Quant. Spectr. and Rad. Transfer. 1985. V. 33, No. 5. P. 427–436. 5. Nassar H., Pellerin S., Musiol K.,  Martinie O., Pellerin N., and Cormier J.-M. // J. Phys. D: Appl. Phys. 2004. V. 37, No. 14. P. 1904–1916. 6. Phillips D.M. Determination of gas temperature from unresolved bands in the spectrum from a nitrogen discharge // J. Phys. D: Appl. Phys. 1976. V. 9, No. 3. P. 507–521. H-7 SELF FOCUSING MECHANISMS OF AN ELECTRON BEAM FORMED IN A HIGH VOLTAGE NANOSECOND LOW PRESSURE DISCHARGE M.I. Lomaev1,2, A.V. Diatlov2 and V.F. Tarasenko1 1Institute of High Current Electronics, 2/3 Akademichesky Ave., 634055, Tomsk, Russia contact@hcei.tsc.ru; 2Tomsk State University, 36 Lenin Ave., 634050, Tomsk, Russia, rector@tsu.ru From a practical point of view, the effect of self-focusing of an electron beam attracts, first of all, by the possibility of increasing the beam current density and, accordingly, increasing the power density in the cumulation zone. This can be used to generate highly ionized plasma and powerful  X-ray radiation, in the study of  matter at elevated pressure and thermonuclear research, in the fields of radiation chemistry and solid state physics, to generate powerful radiation in the terahertz frequency range, excite luminescence of artificial and synthetic crystals, and in others applications. It was found that at currents of tens to hundreds of kA, the beam is focused by its own  magnetic field. At the same time, the effect of self focusing of the beam at currents of no more than  2 kA is interpreted in different ways. Among the reasons for this effect in various publications, indicate the electrostatic repulsion of electrons, the formation of conductive plasma jets from cathode spots formed at the early stage of the discharge, breakdown on the runaway electrons, and others. This study aims to study the effect of self focusing of an electron beam formed during a high-voltage nanosecond discharge in gas filled and vacuum diodes. It was found that in both cases the distribution of the beam current density in the plane of the grounded anode is nonuniform. The highest beam current density is achieved in the axial part of the anode. It is found that, in the case of a gas diode at a pressure of 0.2 Torr,  2 ns after the onset of the beam current pulse, the self-focusing effect is enhanced. From the obtained experimental data and the performed estimate of the time required to reach the density of positive nitrogen ions equal to the density of electrons, it follows that the most probable cause of additional self focusing of the beam is the compensation of the electron charge of the beam by the positive charge of ions arising in the process of air ionization in the diode.  129  GAS DISCHARGES FOR LASERS AND NON-COHERENT RADIATION SOURCES SESSION H    The studies were performed in the framework of the State Task for IHCE SB RAS, Project No. FWRM-2021-0014. H-8 EFFICIENT LASING IN THE VUV RANGE IN HIGH PRESSURE DIFFUSE DISCHARGES A.N. Panchenko, V.F. Tarasenko and V.V. Kozhevnikov Institute of High Current Electronics SB RAS, 2/3 Akademichesky Ave., 634055, Tomsk, Russia, alexei@loi.hcei.tsc.ru Formation and emission features of run-away electron preionized diffuse discharge formed in sharply non uniform electric field by run away electrons in different experimental conditions are studied. The VUV radiation spectra of diffuse discharges in various high pressure gas mixtures have been measured. It is shown that the sufficient homogeneity of diffuse discharges  makes it possible to use it as a source of excitation of lasers based on various gas mixtures at an elevated pressure. This is evidenced by the continuation of the VUV laser pulses during several current oscillations in the gap. VUV lasing was obtained on ArF* (193 nm) and F*2 (157 nm) molecules. The total duration of the laser pulses is as long as 30 ns. The radiation energy of a molecular fluorine laser increased linearly with the active mixture pressure. The  maximum lasing energy at He pressure of 8.5 atm is as high as 3 mJ. In this case, a further increase in the generation energy is possible. The electrical efficiency of the F*2 laser reached 0.15%, which corresponds to the parameters of F*2 lasers obtained upon excitation by a transverse discharge with UV preionization.  The possibility of reaching VUV lasing in mixtures of pure inert gases pumped by diffuse discharges is considered, as well. The work was performed within the framework of the State assignment of the HCEI SB RAS, Project No. 0291-2021-0014. H-9 MULTICHANNEL DIFFUSE PLASMA AS A STABLE FORM OF DISCHARGE COMBUSTION AT HIGH SPECIFIC PUMP POWERS Yu.N. Panchenko, M.V. Andreev, A.V. Puchikin, S.A. Yampolskaya, V.F. Losev Institute of High Current Electronics SB RAS, 2/3 Akademichesky Ave., 634055, Tomsk, Russia, ypanchenko@sibmail.com The studies were carried out on a discharge XeCl laser developed at the HCEI SB RAS, Tomsk. When the laser was operating in the free running mode, the output radiation energy was 0.2 J. The pump generator used a C–C electric circuit with automatic spark preionization. The storage and discharge capacitors were 36.5 and 22.4 nF, respectively. The volume of the active medium was  70 cm3. The  maximum pump power reached 315 MW, and the  maximum radiation power was 5.6 MW. The duration of the lasing pulse, measured in the experiment and obtained in a numerical calculation, was  100 ns. It is noted that the  main condition for the ignition of a stable discharge is to ensure the growth rate of the current density dj/dt more than 6  1010 A/cm2  s.  When using a Ne–Xe–HCl gas mixture at Xe/HCl ratios ≥ 12/1 and Ne/HCl ≤ 800/1 and a specific pump power of P ≥ 3 MW/cm3, the volume discharge transforms into a stable structured diffuse discharge consisting of  many current  macrochannels  0.5 mm diameter. In this case, the properties of the active medium are preserved during the entire duration of the pump pulse, which has an oscillatory shape of the discharge current. This work has been supported by the RFBR Project Nos. 20-08-00371_à and 20-58-00008 Bel_à. 

Self focusing mechanisms of an electron beam formed in a high voltage nanosecond low pressure discharge

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Self focusing mechanisms of an electron beam formed in a high voltage nanosecond low pressure discharge

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