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Vol. 17/2012SECTION 3 The Concept of Cascade Reactors Developed in VNIIEF N. V. Zavyalov, V. F. Kolesov, V. T. Punin The paper informs about the calculated/theoretical, design and experimental activities performed in RFNC-VNIIEF referring to cascade reactors: two-sectional reactors with unilateral neutron link between sections. The unique capabilities, demonstrated by these devices as far as pulsed reactors and electric-nuclear facilities go, explain the substantial interest, the scientific community shows to them. A short description of both facility types is provided as well as the story of the first experiments in RFNC-VNIIEF, based on laboratory models of cascade reactors. Experiments confirmed the theoretical conclusions about advantageous properties of cascade reactors. SECTION 4 Improved Effectiveness of Transmission of High-Current Pulsed Electron Beam A. I. Gerasimov, S. A. Gornostay-Polsky, V. P. Gritsyna, A. V. Grishin, B. I. Model When high-current pulsed electron beam is accelerated and/or transported through the linear vacuum path, the radial and/or longitudinal high-frequency oscillations can be excited in it. It was assumed, that should such a beam be sunk in the cavity of the additional external tube-type electron beam, the amplitude of which is 0.1–0.3 of the amplitude of the principal beam, the amplitudes of the developing in the principle beam high-frequency radial oscillations will be eased or suppressed. This has to improve stability of the dynamics of the principal beam, when it is laid through the path, with the facility operating in a sequential mode, as well as to reduce electron loss in the path and to increase the dose rate of bremsstrahlung at the facility outlet. The concept was experimentally verified in the course of tests involving metal-free linear inductive electron accelerator LIU-30 (40 MeV, 100 kA, 25 ns). Composite Target to Generate Bremsstrahlung from A. I. Gerasimov, S. A. Gornostay-Polsky, A. V. Grishin, V. P. Gritsyna, In metal-free LIU accelerators the pulsed magnetic field, transmitting the beam in the path, induces eddy current in the metal target, the current deviating the field lines away from the path axis. As a result, the angle, with which electrons of the beam enter the target, grows, which, in its turn, increases the angle of divergence of bremsstrahlung quanta and downgrades the dose of bremsstrahlung, thus mitigating the spectrum of its quanta. The facility is described and the method is presented, in which composite targets made of tungsten and epoxy compound are used in LIU accelerator. Meshes made of stainless wire and fabric made of carbon-graphite filaments are incorporated into the target to rapidly remove electrons onto the reverse current distributor of the beam, as well to increase target mechanical strength. The targets designed in such a manner upgrade the dose of bremsstrahlung and make the accelerator easy to operate. SECTION 5 Measurements of Plasma Temperature in Indirect Drive Targets from the Shock Wave Velocity in Aluminum in the «Iskra-5» Facility V. V. Vatulin, N. V. Zhidkov, A. G. Kravchenko, P. G. Kuznetsov, D. N. Litvin, V. V. Misko, A. V. Pinegin, N. P. Pleteneva, A. V. Senik, K. V. Starodubtsev, G. V. Tachaev Results are presented from the development of a method for measuring plasma temperature in indirect (X-ray) drive targets by recording the shock wave velocity in the Iskra-5 facility. The samples under investigation were irradiated by X-rays in a converter box, and the shock wave velocity was determined from the time at which the wave reached the back surface of the sample and the surface began to emit visible radiation. This emission, in turn, was detected by a streak camera. The results of experiments on the interaction of X radiation with a hot dense plasma, as well as the accompanying gas-dynamic processes in aluminum samples, are analyzed both theoretically and numerically. In experiments with Al and Pb samples, the shock wave velocity was measured to vary in the range U = 8–35 km/s, and the range of variation of the temperature of the box walls was measured to be Te = 140–170 eV. SECTION 6 developing the Adaptive system: results of Experimental setup at luch laser facility S. G. Garanin, M. O. Koltygin, S. M. Kulikov, A. N. Manachinskiy, S. P. Smyshlyaev, S. A. Sukharev An adaptive system to compensate
for aberrations of the wave front of amplification path in LUCH laser facility
is considered. With the adaptive system introduced into the facility design,
the aberrations of the wave front were reduced down to RMS = 0.12 mm, whereas radiation divergence was
reduced down to q = 0.9×10–4rad. Laser system emitting 100 mJ in Laguerre – Gaussian modes Yu. V. Dolgopolov, A. V. Kopalkin, F. A. Starikov, V. Kh. Bagdasarov, S. V. Garnov, N. N. Denisov, A. A. Malyutin The optical scheme and radiation parameters of a neodymium glass laser system emitting high-power 40-ns pulses in the first-third-order Laguerre-Gaussian modes of energy up to 100 mJ are described. Laser Tests Bed for Target Irradiation by Pulses with 100 MHz Repetition Frequency at «Iskra-5» Facility V. I. Annenkov, S. G. Garanin, V. A. Yeroshenko, N. V. Zhidkov, A. V. Zubkov, S. V. Kalipanov, N. A. Kalmykov, V. P. Kovalenko, V. A. Krotov, S. G. Lapin, S. P. Martynenko, V. I. Pankratov, V. S. Faizullin, V. A. Khrustalev, N. M. Khudikov, V. S. Chebotar’ The mode of operation was implemented at the «Iskra-5» laser facility, in which a sequence of several dozens of powerful subnanosecond pulses with a time distance of 10 ns between them follow at the facility output. The train of laser pulses has the energy of 300 J, and comprises up to 40 pulses at the level of 0.15 of maximal. The duration of single pulse in the train is approx 0.5 ns. The results of the experiment on the conversion of laser pulses train into x-ray pulses train are presented. Irradiation of a tungsten target resulted in the generating of x-ray pulses train, with the envelop in the 0.18–0.28 keV spectral range, similar to the laser pulses train envelop. The duration of a single x-ray pulse in the train is the same as the duration of laser pulse. Nano- and sub-nanosecond laser pulses of the controllable time shape and spectral composition of radiation S. G. Garanin, B. G. Zimalin, V. V. Romanov, N. N. Rukavishnikov, S. V. Sokolovsky, S. A. Sukharev, O. V. Trikanova A laser system, generating nano and
sub-nanosecond laser pulses with time and spectral profiling was developed. The
system operates on the basis of selection of spectral components involving a device,
used to stretch femtosecond laser pulses up to several nanoseconds and to
spectrally ordered radiation (stretcher). Experiments yielded laser pulses with
steep frontal and trail edges (less than 100 ps due to instrumental function of
measuring hardware). Amplification of these pulses was studied using
regenerative amplifier with a physical gain factor ~ 6×1017 (up to ~5 mJ energy level). High-Power Electric-Discharge HF Laser with Solid State Pump Oscillator S. D. Velikanov, S. G. Garanin, A. P. Domazhirov, V. M. Efanov, M. V. Efanov, S. Yu. Kazantsev, Yu. N. Komarov, I. G. Kononov, S. V. Podlesnykh, A. A. Sivachev, K. N. Firsov, V. V. Shurov, P. M. Yarin A possibility of creation of high-power nonchain electric-discharge laser with solid-state pump oscillator is shown. Maximal energy, stored in capacitors of pumping source on the basis of solid-state FID-keys, is 990 J at open-circuit voltage of 240 kV. The radiant energy in a pulse (W = 30 J) at electrical efficiency ≈ 3 % is received on SF6 mix with hydrogen. Simulation of X-Ray Laser in Transient Mode Under the Effect of Gain Saturation F. A. Starikov, V. A. Volkov, P. D. Gasparyan, V. I. Roslov Three-D calculations of amplified spontaneous radiation (ASR) in X-ray lasers were performed using TRANS code for 3p-3s transition of Ne-like Ge (l = 19,6 nm) and Ti (l = 32.6 nm) for the transient mode of flat target pumping by the focused into the line radiation of a high-power picosecond laser featuring one or two nanosecond pre-pulses. To calculate hydrodynamics and kinetics of the populated active X-ray laser medium the code named SS-9M was used. The resulting pulse duration, gain factor, spatial beam structure and the character, with which the «progressive pumping wave» effects ASR brightness are in good concordance with experimentally observed behavior. With the progressive pumping wave applied not only the brightness of APS grows, but its angular divergence significantly drops down. Investigation of Two Laser Channels Parallel Composition at Ar/Xe (1.73 mm) and He/Ar/Xe (2.03 mm) Mixtures Excitation by Uranium-235 Fission Fragments V. M. Tsvetkov, A. A. Pikulev, P. V. Sosnin The results of experimental and analytical investigations of two laser channels parallel composition scheme at nuclear-pumped laser setup LUNA-2M are presented. Investigations were conducted for two laser-active media: 1) He/Ar/Xe (380:380:1, pressure 1 bar), wavelength is 2.03 mm and 2) Ar/Xe (380:1, pressure 0.5 bar), wavelength is 1.73 mm. For active medium He/Ar/Xe maximal power and energy of lasing amounted to 1.94 J and 870 W. Lasing energy 1.94 J is the record one for LUNA-2M setup. At maximum of lasing pulse the efficiency of composition equaled to 95 % by energy and 89 % by power. For active medium Ar/Xe maximal power and energy of lasing amounted to 1.72 J and 980 W. At maximum of lasing pulse the efficiency of composition equaled to 92 % by energy and about 100 % by power. The calculations have shown that these lasing parameters may be increased by using divi-ding mirrors with reflectance coefficient about 30–50 %. |
