V.I. Zhuravlev , T.S. Fetisova
№ 6 The sky distribution of radio sources with flat spectra
Скачать препринт |Аннотация|
Extragalactic radio sources with flat spectra (a<0.5) from two NRAO surveys at 4.85 and 1.4GHz covering most of the northern hemisphere (about 6sr) have been analysed by the angular correlation function versus flux densities. Excesses over the random expectation were concentrated in the supergalactic plane in the range of 400н-800т.Ту and high (>10°) supergalactic latitudes in the range of 150-ь400т.Гу. The shift of the correlation interval for the sources which are away from the supergalactic plane to fainter flux densities as well as the shift of the distribution of correlating pairs to less angular sizes for these sources probably reflect the sky distribution of radio sources for more distant rich clusters.
---------------------------
V.I. Bujakas , S.N. Pyshkin , N.I. Snopok , V.F. Troitsky
№ 17 Radioastron space antenna: low-noise amplifiers cooling during ground-based radio-engineerring tests
Скачать препринт |Аннотация|
During ground — based radio — engineering tests of the RADIOASTRON space antenna the low — noise amplifiers must operate at the temperature 80° — 100° K. To solve this problem a new design of the cooling system was proposed. The functioning principle, the design and the results of cryogenic tests of the cooler for ground -based radio — engineering tests are described in the paper.
---------------------------
A.. Caruso , C.. Strangio , S.Yu. Gus’kov , N.N. Demchenko , V.B. Rozanov
№ 18 Interaction of nanosecond laser pulses with plastic foams
Скачать препринт |Аннотация|
Some results of the researches on the interaction of laser pulses with plastic foams performed by the ENEA Frascati ICF Physics and Technology group in the framework of a collaboration with the P.N. Lebedev Physical Institute (Moscow, Russia) are presented. This paper includes the description of some theoretical considerations, as well as the presentation of preliminary ABC laser facility experiments performed by irradiating plastic foams. The ABC facility was built by the Frascati Inertia! Physics and Technology Group which had the entrusted task to maintain a critical evaluation capability on energy oriented ICF, in the context of ENEA-EURATOM Association. Experimental results includes the measurement of the velocity of hydrodynamic process propagation, which was initiated in foam target under action of laser pulse with intensity of q ~ 210 W/cm , the measurement of distribution function of plasma ions on velocities, which are characterized by two peaks, and also the time-integrated spectroscopic measurements of an intense red-shifted signal at 2ю, and a broad line corresponded to a red-shifted signal of (5/2) a. A self-consistent model of the foam target’s laser plasma formed in a hydro-mode regime was built in a frames of the two main assumptions that the momentum of the displaced material is produced by the ablation pressure and that the isothermal plasma’s density and temperature in the formed cavity are so, that to make the inverse bremsstrahlung absorption distance match the size of the cavity. The predictions of this model corresponds to the experimental results. The model of a micro-processes of laser plasma formation in a structured material also was constructed. That model indicates two factors of more slower thermal conductivity process in a structured media in comparison with homogeneous one: the first, relatively long stage of the electron-ion energy exchanging in low density, high temperature homogeneous plasma and , the second, considerable part of the energy of the plasma of an initially structured media consisted in a form of thermal and kinetic energy of plasma ions. The results of the numerical simulations by ID and 2D computer codes also presented in the paper.
---------------------------
V.Yu. Bychenkov , W.. Rozmus , V.T. Tikhonchuk , A.V. Brantov
№ 21 Nonlocal hydrodynamics and electron transport in a plasma
Скачать препринт |Аннотация|
We have developed an analytical nonlocal perturbation theory of electron transport in unmagnetized plasmas with arbitrary electron collisionality in the limit of large ion charge. We have found nonlocal expressions for electron transport coefficients: the electric conductivity, thermoelectric coefficient, heat conductivity, electron viscosity, friction, and ion flux coefficients. We demonstrate that our theory quantitatively describes the transition from the strongly collisional, hydrodynamics! regime into the collisionless, free-stream limit. Remarkably, the thermoelectric coefficient changes its sign when the perturbation wavelength is comparable to the electron-ion mean free path. Electron and ion susceptibilities and the damping rate of ion acoustic waves are derived from our nonlocal hydrodynamics and the problem of the correct definition of the electron heat conductivity is also discussed. PACS numbers: 52.25.Fi, 52.25.Dg
---------------------------
V.N. Ochkin , S.Yu. Savinov , S.N. Tskhai , U.. Czarnetzki , V.. Schulz-von der Gathen , H.F. Dobele
№ 22 Nonlinear optical techniques for plasma diagnostics
Скачать препринт
O.. Arzhatkina , S.. Batygov , M.. Belov , E.. Devitsin , L.. Dmitruk , Y.. Efimov , V.. Fedorov , O.. Khorozova , N.. Kirikova , V.. Kozlov , V.. Makhov , L.. Popov , S.. Potashov , A.. Provorova , N.. Vasiljeva , N.. Vinogradova
№ 24 Further progress in R&D of scintillating fluoride glasses
Скачать препринт |Аннотация|
In the present work the detailed studies on improving scintillat?ing properties of heavy fluoride glasses by verification of its compo?sition and casting technology modification are described. An affect of raw material impurities on scintillating characteristics and radi?ation hardness of the glasses were studied also. It was found that significant levels of the impurities are tolerable indicating that the raw material purification can be simplified. New fluoride glasses having fluoride-chloride(oxide) lattice have been produced. The emission spectra of these glasses are shifted to longer wavelenghts where the sensitivity to radiation damage was less pronounced. It is demonstrated that Ce-doped hafnium fluoride glasses are good candidates for electromagnetic calorimeter medium at high energies.
---------------------------
S.N. Andreev , V.N. Ochkin , S.Yu. Savinov , N.V. Slobozhanov , V.L. Stakhusky
№ 28 IR molecular spectral lines pressure broadening dependence on the relative velocity of colliding particles
Скачать препринт |Аннотация|
The IR linewidth of CO2 molecules has been measured by means of tunable diode laser spectroscopy technique in wide field of a gas temperature and rotational quantum numbers. It has been found that there are no existing semiclassical models of pressure broadened linewidths to describe satisfactorily our and other published experimental results. A new cutoff-free semiclassical model of pressure broadening of rotation-vibration spectra in gases was provided. It corresponds to ail experimental results quite well. The model lakes into account: 1. trajectory bend of moving particles by intermolecular forces, and 2. increasing of optical cross section for molecules with low relative energy of translation motion due to orbiting collisions. It takes not so much computing time to calculate the impact broadened linewidths by our method (only slightly more time than calculations by Anderson-Tsao-Curnutc theory). It enables us to compute the shape of IR spectral lines with correct averaging over a disbibution of relative velocities. The important role of particles collisions with low relative energy of translation motion Ец (liu/e < 0.8. where e is constant of Lennard-Jons itermolecular potential) even imder room temperature has been shown. This role is increased essentially at lower temperature It has been found that ordinary applied calculation scheme of average linewidths over a Maxwell-Boltzuiann distribution of relative velocities leads to essential systematic errors. The above features make our results attractive for its usage for determinations of exact linewidths in molecular infrared spectra.
---------------------------
V.M. Grishin , A.P. Kostin , S.K. Kotelnikov , B.N. Lomonosov , M.A. Negodaev , S.V. Rusakov
№ 29 Monte-Carlo simulation of a micro-strip gas chamber
Скачать препринт|Аннотация|
An algorithm is given to simulate the performance of a micro-strip gas chamber (MSGC). It includes calculation of the electric field configuration, of ionization energy loss of a primary parti?cle, and of transport processes for secondary electrons inside the gas volume. Simulation results are presented for a MSGC proto?type developed in Lcbcdev Physical Institute (LPI).
---------------------------
V.V. Nikishin , V.F. Tishkin , N.V. Zmitrenko , I.G. Lebo , V.B. Rozanov , A.P. Favorsky
№ 30 Numerical simulations of nonlinear and transitional stages of richtmyer-meshkov and rayleigh-taylor instabilities
Скачать препринт |Аннотация|
The report presents the results from studying the nonlinear stage of the development of Richtmayer-Meshkov and Rayley-Taylor instabilities. The simulations have been made with the help of 2D and 3D code «NUT» [1]. The report gives a brief description of the methods used in the solution of the gas dynamics equations in Euler coordinates. The «NUT» code makes use of the nonlinear quasimonotonic conservative difference schemes of the high order of approximation, and this makes possible the modeling of the instability development up to the late nonlinear stage (the formation and overlapping of »mushroom» like structures). We have performed the modeling of the single-mode and multimode perturbations at the non?linear stage up to the formation of the turbulent mixing zone. The criteria for the transition to the turbulence in accordance with different values of the Atwood and Mach numbers and the initial parameters of the perturbations (amplitude and shape) have been found basing on the performed simulations. We have also found the temporal dependences of the amplitude and mass growth and the perturbation circulation. The results have been compared with the experimental data obtained from the shock tubes at Krzhizhanovsky Power Institute [2] and the simulations made by Dr. D. Youngs (AWE Aidermaston, UK) and Dr. R.Holmes (New York University, USA).
---------------------------
I.G. Lebo , V.B. Rozanov , V.F. Tishkin , V.V. Nikishin
№ 31 Computational modeling of the hydrodynamic instability development in shock tube and lazer driven experiments
Скачать препринт |Аннотация|
А 2D and 3D Euler codes «NUTfl] and «NUT-СУ»(cylindrical 2D geometry), and a 2D Lagrangian-Euler code «ATLANT» [2] have been used in studying the laws of the develop ment of the instabilities in two cases: 1) the shock waves are passing through the contact interface of two gases (the initial density of the gases is similar, and the adiabtic indices 7 differ), 2) the laser acceleration of thin foils. The computer simulations have been made for concrete experiments to be held with the shock tubes at the Kizhizhanovsky Power Institute (Moscow), and those being performed with the laser facilities «MISHEN» (Nd-laser, the pulse energy up to 50 J, and the duration и 2 ns) [3] and «GARPUN» (KrF-laser, the energy up to 100 J and duration и 100 ns) [4].
---------------------------
Yu.P. Shitov , V.D. Pugachev
№ 33 Radio pulsar Geminga
Скачать препринт |Аннотация|
We report our results of searches of pulsed radio emission from Geminga carried out in 1992, 1993 and 1996 at 102.5 MHz using BSA radiotelescope of Pushchino Ra-dioastronomy Observatory. Geminga radio pulsar (PSR J0633+1746) was detected in all three epochs of observations. With the best signal to noise ratio Geminga was detected in records made in 1993, when the maximum passband of radiotelescope was used for searches. Main criterion of detection of radio pulsar was the presence in amplitude spectra of records of the dominate spectral line on the frequency of pulsar rotation ft = 4.22 Hz. Method of averaging of amplitude spectra, obtained for many days during February — June in 1993 was used for determination of mean flux density of Geminga radio emission at 102.5 MHz. We report the main parameters of pulsar PSR .10633+1746, obtained from our observations. Mean flux 5ш2 = 8(-t-3, ~2)rnjy. Average pulse profile is very wide and has a Shape like in X- rays (Halpern and Holt 1993). Profile width on 0.5 level Whs cz 120ms, i.e. about 180°. Dispersion measure value DM ? 3.2i0.3pc-cm~3. Timing analysis, which was made for the best profiles, obtained during 1992 — 1996 yields the values of period P and derivative P, which are in error limits agree with the data, published by Mayer-Hasselwander 1994. We discuss the possible reasons of extremely low radio luminosity of Geminga pulsar.
---------------------------
A.V. Smirnov
№ 34 Analytic continuation of a many channel scattering wave function to a bound state pole
Скачать препринт |Аннотация|
The simple formulas connecting bound state and extrapolated to the bound state pole scattering wave functions, obtained recently by Faldt and Wilkin for a single-channel two-body system, are generalized for a coupled chan?nel problem. The practically important particular case ? pn-system ? is considered in detail. It is proved that the formulas pointed out remain ap?proximately valid, even if pro-scattering wave function is taken at a physical (real) nearthreshold value of relative momentum. In contrast to previous considerations the present results allow to incorporate not only the pure S-wave component of pn-wave functions, but also the D-wave for deuteron and the «mixed» 3Di-3Si-componcnt for pn-scattering wave function. This fact enables to extend the applicability range of the obtained earlier ap?proximate relations between the differential cross sections of deuteron and unbound nearthreshold triplet (pn)rpair production at large momentum transfer.
---------------------------
A.V. Agaponov , V.M. Fedorov , V.P. Tarakanov
№ 37 Dynamics of magnetic insulation violation in smooth-bore magnetrons
Скачать препринт |Аннотация|
The efficiency of large and high-power magnetrons of GW power levels is less than 30% and an inherent pulse-length and repetition rate limitations seems to exist because of use of explosive field emission. Another approach is the development of low voltage high-efficiency magnetrons utilizing a secondary emission magnetron array with high repetition rate. The numerical model of nonstationary nonuniform secondary electron emission from a cathode surface has been developed. The results of the first steps in computer simulations of an electron cloud formation inside a smooth-bore magnetron under the condition of the back-bombardement instability (BBI) are presented. A mechanism of the violation of the magnetic insulation are considered. Calculations have been performed for a coaxial smooth-bore magnetron and for magnetrons with different types of azimuthal inhomogeneities which could help the grow of BBI, and for magnetrons of different aspect ratios. The results of computer simula?tion are compared with experimental data. The main calculations of the beam dynamics were carried out with PIC-code KARAT.
---------------------------
A.V. Agaponov , E.G. Krastelev
№ 38 Double-sided relativistic manetron
Скачать препринт |Аннотация|
A new scheme of a symmetricaly powered relativistic magnetron and several methods of localized electron flow forming in an interaction region are proposed to increase an efficiency of relativistic magnetrons. As will be shown, a very important reason is the effect of nonsymmetric feeding of power from one side of a magnetron, which is typical for experiments. One-sided powering leads to the axial drift of electrons, to the transformation of transverse velocities of electrons to longitudinal one and to the generation of a parasitic e-beam which does not take part in energy exchange between electrons and waves at all. A special driver was designed for double-sided powering of relativistic magnetrons. The proposed system is compact, rigid and capable of reliable operation at high repetition rates, which is advantageous for many applications. Several smooth?bore magnetrons were tested by means of computer simulations using PIC code KARAT. The results showed a dramatical difference between the dynamics of electron flow for one- and two-sided power feeding of a structure under test. Design of a driver and computer simulation results are presented.
---------------------------
A.V. Agafonov , V.S. Voronin
№ 39 Brillouin flow in a magnetron diode as the kinetic model limit
Скачать препринт |Аннотация|
Two classes of approaches that have received the most attention to describe the important space charge dynamics in a magnetron are Briliouin now and the double-stream kinetic model. It is supposed that in the first case electrons move parallel to the electrode surfaces and in the second case they move in cycloidal orbits performing a single turn. Precise analysis of electron dynamics in fully selfconsistent kinetic equilibria in a smooth-bore magnetron shows that for a given external magnetic field and a voltage there exists a multiplicity of natural equilibrium states, differing as to structure of electron trajectories and emission current density. The value of emission current density differs from one to another type of equilibrium and can aspire to zero under the same condition of space charge limited flow due to a large number of revolutions of electrons around the cathode. The greater the number of revolutions the closer the main parameters of the kinetic flow to the Briliouin one. The comparison of analytical calculations and the results of computer simulation of transient processes of Briliouin flow formation from initially kinetic flow are presented.
---------------------------
V.M. Kolybasov
№ 42 Monzero orbital momenta in triangle graphs and the pictureof moving singularities
Скачать препринт |Аннотация|
It is shown that nonzero orbital momenta in nuclear vertex and in the vertex of secondary interaction in the triangle graph lead to more distinct picture corresponding to the moving complex singularity com?pared with the case of zero momenta and constant vertices. Peak in the distribution with respect to the invariant mass of the group of final particles becomes narrower and its shift with momentum trans?fer becomes more distinct. It gives possibility to observe this picture experimentally. The formula is obtained for the triangle graph for nuclear reactions with account of nontrivial nuclear and secondary interaction vertices. It has a form of one-fold integral in coordinate space including some new function corresponding to the rescattering vertex. Properties of this function are described for various kinds of the vertex.
---------------------------
J.. Becker , J.Y. Gesland , N.Yu. Kirikova , J.C. Krupa , V.N. Makhov , M.. Runne , M.. Queffelec , T.V. Uvarova , G.. Zimmerer
№ 43 Vuv emission of Er3+ and Tm3+ in fluoride cfystals
Скачать препринт |Аннотация|
VUV emission of several fluoride crystals doped with Er3+ and Tm3+ has been studied under pulsed synchrotron radiation excitation. It was shown that emission spectra of these ions in the 150-190 nm spectral range consist of both fast emission bands (decay constant in the range from a few to tens nanoseconds) and slow ones (decay constant in the microsecond range). The former bands are due to parity-allowed interconfiguration 4f»»15d ?> 4f radiative transitions while the latter ones — to parity-forbidden intraconfiguration 4f -> 4f» transitions. Depending on the relative position of the lowest level of the excited 4f_15d configuration and corresponding level of the ground 4f configuration both fast and slow emissions, or only slow, or only fast emission are observed.
---------------------------
A.N. Lebedev
№ 45 Self-field pinch diodes
Скачать препринт |Аннотация|
Self-consistent steady-state distributions of electron and ion flows in a high-current plane diode with space charge current limitations are investigated. A problem of electron flow transition to the super-pinch regime is discussed taking into account a counter-stream ion flow. Л selfconsistent theory of crossed flows is presented with evaluations of ion generation efficiency in a self-field pinch diode. The results are compared with available experimental data.
---------------------------
A.V. Agaponov , V.A. Bogachenkov , V.A. Papadichev , V.M. Fedorov , V.P. Tarakanov
№ 46 Relativistic magnetron: simulation and experiment
Скачать препринт |Аннотация|
The development of high-power magnetron-type microwave generator is described. The 10-cm wavelength band and the 200 ns, 500 kV high voltage pulse are used. An axial magnetic field of about 0.5 T is produced by solenoid in a pulse with 3.0 ms rise time. To reduce breakdown phenomena, a 1-cm cathode-anode gap was employed. A long anode configuration was chosen to increase microwave power. The radiation of gigawatt range was extracted in the axial direction using a coaxial converter. First type of set-up contains the anode resonant structure with 16 resonators (8 rising-sun and 8 slit types). Prelimi?nary experiments show that breakdown in resonant structure restricts extracted microwave power. Computer simulation is made by 2&3 D PIC relativistic fully electromagnetic code KARAT. Cold RF measurements of the magnetron are in good agreement with simulation results. PIC simulation of the magnetron shows storage of electrons inside resonator cavities of high power magnetrons because of larger resonator slit width. The influence of back bombardment pro?cesses on a cathode electron emission was investigated in oscillating and non oscillating regimes. Work supported in part by RFFI under grant 96-02-19215a. Presented at 11th IEEE International Pulsed Power Conference, Baltimore, Maryland, USA, June 29 — July 2, 1997.
---------------------------
V.V. Andreyanov , A.A. Borisov , I.A. Knorin
№ 55 Radioastron data format & observation modes
Скачать препринт |Аннотация|
To transmit radio astronomical and auxiliary data from space telescope to ground tracking station (and then to correlator) through radio link it is necessary to use special data format, coding and decoding. Such data format for Radioastron mission is considered in detail. Different scientific tasks require different observation modes which are described here also. This information is needed for the observers, for tracking stations (including data decoder) designers, for compatibility tests (simulation of data stream from satellite) and for further processing.
---------------------------
A.A. Berezin , V.A. Shcheglov
№ 56 Some aspects of principle in problem of neural physics
Скачать препринт |Аннотация|
A qualitative model of a neuron has been theoretically and experimentally studied. A coupled system of nonlinear Schrodingei (NLS) and sine-Gordon equations was used for mathematical description of the complex Fermi-Pasta-UIam (FPU) recurrence, interpreted as a principal memory carrier in the model. Computer and analog experiments have been developed to verify the proposed concept
---------------------------
V.G. Bakaev , V.Yu. Korol` , I.G. Lebo , N.N. Mel`nik , G.E. Metreveli , A.G. Molchanov , V.V. Nikishin , V.B. Rozanov , G.V. Sychugov , V.F. Tishkin , V.D. Zvorykin
№ 69 Lazer-taget interactions on KrF «Garpun» facility
Скачать препринт |Аннотация|
Multi-stage, e-beam-pumped, 100 J-class KrF laser installation «GARPUN» is described with the emphases to high-power laser beam control and target irradiation experiments. The ablation pressures in the megabar range were measured and hydrodynamic flow was investigated both experimentally and by numerical simulations for laser intensities up to Sx 10n W/cm2, pulse duration of 100 ns, and focal spot diameter 150 pm. Graphite-diamond phase transfonnation under laser loading was observed by dynamic and Raman scattering methods. Some approaches to the fast ignition inertia! confinement fusion, using the simultaneous amplification of long and short laser pulses in KrF drivers are considered.
---------------------------
