We analyze experimental results of the acceleration of protons at the rear side of an aluminum target under the action of a picosecond laser pulse (an intensity of 2 · 1018 W/cm2 and a wavelength of 1.06 μm). The picosecond pulse has two prepulses, picosecond and nanosecond (a prepulse of amplified spontaneous emission of 8 ns duration). We examine a target of thickness 10 μm, at which the energy of protons is maximum. The decrease in the energy of protons with increase in the target thickness is due to the increase in ionization losses of the energy of fast electrons in passing from the region of their generation to the rear side of the target. A drop in energy of protons at target thicknesses less than 10 μm is due to the breakdown of the target rear side owing to a split-off phenomenon at the exit of the shock wave to the surface. We consider various cases of the target rear side breakdown depending on the aggregate state of the target material behind the front of the shock wave (solid, liquid, and gaseous states).

Серия экспериментов по модификации ионосферы радионагревом в КВ диапазоне, проведенных на базе стенда “СУРА” совместно с оптическими измерениями на борту международной космической станции (МКС), показали эффективность таких воздействий на ионосферу при рабочей частоте стенда выше критической плазменной (для основного слоя F2 ионосферы). Эксперименты сопровождались поддержкой измерений средствами наземных обсерваторий, МКС, спутников Demeter и GPS. В работе приводятся результаты анализа всего комплекса данных. Проведены расчеты лучевого КВ радиотрассирования для эксперимента 02 октября 2007 г. и показано, что за счет рефракции на градиенте критических частот слоя F2 пучком стенда засвечивалась ионосфера (эффекты перераспределения и перефокусировки лучей) к северу от стенда вплоть до широт 60–62° N. В итоге получено, что результаты анализа наземных и спутниковых измерений (как в окрестности нагревного стенда, так и в магнитносопряженной области) свидетельствуют о возможности триггерирования суббури в экспериментах с нагревным стендом “СУРА”.

It is proposed to use a high rate of collisional ionization in a superdense laser plasma to generate incoherent femtosecond X-ray pulses. The calculations indicate that the use of picosecond laser pulses with a contrast of about 10(10) will allow the generation of an X-ray pulse with a duration of about 10 fs. The adequacy of the proposed model of the excitation of linear X-ray radiation from the plasma has been tested in the experiments with a picosecond laser of a moderately high contrast.

The results of work on choosing and substantiating promising lines of research in the realms of laboratory astrophysics with the aid of powerful lasers are presented. These lines of research are determined by the possibility of simulating, under laboratory conditions, problematic processes of presentday astrophysics, such as (i) the generation and evolution of electromagnetic fields in cosmic space and the role of magnetic fields there at various spatial scales; (ii) the mechanisms of formation and evolution of cosmic gamma-ray bursts and relativistic jets; (iii) plasma instabilities in cosmic space and astrophysical objects, plasma jets, and shock waves; (iv) supernova explosions and mechanisms of the explosion of supernovae featuring a collapsing core; (v) nuclear processes in astrophysical objects; (vi) cosmic rays and mechanisms of their production and acceleration to high energies; and (vii) astrophysical sources of x-ray radiation. It is shown that the use of existing powerful lasers characterized by an intensity in the range of 1018–1022 W/cm2 and a pulse duration of 0.1 to 1 ps and high-energy lasers characterized by an energy in excess of 1 kJ and a pulse duration of 1 to 10 ns makes it possible to perform investigations in laboratory astrophysics along all of the chosen promising lines. The results obtained by experimentally investigating laser plasma with the aid of the laser facility created at Central Research Institute of Machine Building (TsNIIMash) and characterized by a power level of 10 TW demonstrate the potential of such facilities for performing a number of experiments in the realms of laboratory astrophysics.

A series of experimental modifications of the ionosphere in the HF range, performed at the SURA facility base, together with optical measurements onboard the International Space Station (ISS), indicated that such impacts on the ionosphere are effective when the facility operational frequency is higher than the critical plasma frequency (for the main ionospheric F2 layer). The experimental measurements were supported by measurements at ground-based observatories, ISS, and the Demeter and GPS satellites. The analysis results of the entire data set are presented. The ray HF radio tracing for the experiment of October 2, 2007, has been calculated, and it has been indicated that the ionosphere to the north of the facility up to 60°–62° N latitudes was irradiated by the facility beam (the effects of ray redistribution and refocusing) due to refraction on the gradient of the F2 layer critical frequencies. An analysis of the ground-based and satellite measurements (both in the vicinity of a heater and in the magnetically conjugate region) indicates that it is possible to trigger a substorm in experiments with the Sura heating facility.

Представлены результаты работы по выбору и обоснованию перспективных направлений исследований в области лабораторной астрофизики с использованием мощных лазеров. Эти направления определяются возможностью моделирования в лабораторных условиях проблемных процессов современной астрофизики, таких, как: 1) генерация и эволюция электромагнитных полей в космосе, роль магнитных полей в космосе на разных пространственных масштабах; 2) космические гамма-всплески и релятивистские джеты, механизмы их образования и эволюции; 3) плазменные неустойчивости в космосе и астрофизических объектах, плазменные струи, ударные волны; 4) взрывы сверхновых, механизмы взрыва сверхновых с коллапсирующим ядром; 5) ядерные процессы в астрофизических объектах; 6) космические лучи, механизмы генерации и ускорения до высоких энергий; 7) астрофизические источники рентгеновского излучения. Показано, что использование существующих мощных лазеров с интенсивностью в диапазоне 10 –10 Вт/см и длительностью импульса 0.1–1 пс и высокоэнергетических лазеров с энергией более 1 кДж и длительностью импульса 1–10 нс позволяет проводить исследования в области лабораторной астрофизики по всем выбранным перспективным направлениям. Представленные результаты экспериментальных исследований лазерной плазмы, полученные с помощью созданной в ЦНИИмаш лазерной установки с уровнем мощности 10 ТВт, показывают возможности и перспективность подобных установок для проведения ряда экспериментов в области лабораторной астрофизики.

The shape of the X-ray pulse generated by picosecond laser plasma is experimentally studied. The unusual phenomenon was experimentally observed for the first time for targets made of moderate-heavy chemical elements, namely, the pulse of hard X-ray radiation generated by laser plasma at the laser radiation flux of similar to 10(18) W cm(-2) had a longer duration than the pulse of softer X-ray radiation. A simple kinetic model is suggested for explaining this fact. We have suggested a method for controlling the temporal shape of X-ray pulse emitted by laser plasma by varying the contrast of laser pulse.

We present the results of analysis of helio-geophysical conditions for the experiments performed in 2007–2010 to study modification of the ionosphere by high-power radio emission of the “Sura” heating facility. The feature of the experiments is that the operating frequency of the facility exceeded the upper-hybrid frequency for the F2 layer maximum in the ionosphere. All the experiments were performed in the local-time sector of the Harang discontinuity (i.e., from 21:00 to 00:00, local time) to ensure the most probable influence of the facility operation on the onset of natural processes in the subauroral region of the ionosphere. At least two experiments were found to demonstrate that the observed substorm activity in the region of the modification produced by the facility could be stimulated by its operation. The results of the ground- and satellite-based measurements, both in the vicinity of the “Sura” facility and in the magnetically conjugate region, confirm the conclusion about the possibility of substorm localization by this facility.

A quantitative analysis is presented of the data on modification of the ionosphere by high-power radio emission from the SURA heating experiment run on October 2, 2007 (18:40 - 19:00 UT). The Sura facility was working in the mode of periodic heating at the radio frequency (RF) of 4.30 MHz. The modulation frequency was close to the frequency of natural Alfven oscillations of plasma in the local magnetic flux tube. The effects of modification were observed onboard the Russian Segment of the International Space Station (RS ISS). The observations have provided more than 1500 images of a bright local glow, which appeared within the field of view of the TV camera as the ISS was passing close to the location of the Sura facility. The brightness of aurora reached some hundreds of kiloRayleighs. The compact bright aurora appeared North-East of the heating facility and was moving East in the image plane. The analysis of helio-geophysical conditions did not reveal any significant anomalies during the experiment. A low power of the heating RF emission and high intensity of the observed aurora suggest that the local glow wasn't due directly to HF heating of ionosphere, but rather might be caused by the particle precipitation artificially stimulated by the heating effects, such as modification of the ionosphere over the SURA heating facility, which forms the base of the magnetic flux tube (and the standing wave node) whose natural Alfven oscillations have a period close to the modulation period of the heating HF emission. The Alfven mode of the magnetic tube could be intensified during the experiment by a short (less than 1 min) and weak (amplitude of about 2 nT) pulse in the planetary geomagnetic field that occurred at 18:47:30 UT.

Results of two space experiments on observation of the radiation caused by interaction of a spacecraft thruster exhaust with rarified Earth atmosphere are compared with modeling results. Traditional radiation models based on single-collision chemical reactions between the exhaust molecules with atmospheric oxygen atoms were found unable to explain spatial distribution of the radiation observed one of the experiments. Satisfactory agreement between modeling and the experiment has been achieved when multi-step reaction of water molecule with oxygen atoms was taking into account. Effective values for the cross-sections of elastic scattering of oxygen atoms in the exhaust flow σe,eff ≈ 9⋅10 -16 cm 2 and for the reaction between water molecules with oxygen atoms σr,eff ~ 0.5-0.6⋅10 -16 cm 2 at collision energy Ec~ 5 eV have been evaluated basing on the experimental data. The cross-section values may be utilized for verification of collisional models at hypervelocity conditions.

The paper is dedicated to development and validation of a real time optical diagnostic method for monitoring of the Hall effect thruster erosion rate variation from one operating regime to another. A convenient semi-empirical formula has been utilized for relation of the thruster erosion rate with intensities of the impurity and xenon emissions. The formula was verified in a number of dedicated experiments. In particular, the erosion rate predictions based on the optical diagnostic data were compared with results of the thruster ware tests. Good agreement has been found. Additional verification of the method was achieved through measurements of variation of the erosion rate coefficient of metallic samples placed inside the ionic beam in the Hall thruster plume. The method was found to be appropriate for measuring of the erosion rate variation in a wide range of the thruster operating parameters. However, some limitations of the method have been manifested. In particular, evaluation of the erosion rate variation becomes less accurate, when electron temperature in the thruster plasma varies from one operating regime to another. In this case formula for the erosion rate variation must be generalized to include dependence of the emission excitation functions on the electron temperature.

Implementation of a simple non-intrusive optical diagnostic method to determine local erosion rates within Hall thrusters has been shown to be an extremely sound approach for thrusters of anode layer type. The development of probabilistic failure analysis tools to estimate thruster lifetime is critical in the space program today with highly cost and time constrained missions. These tools with experimental data are required to optimize the configuration of the thrusters, thruster materials, and operating conditions to maximize lifetime and optimize performance. These tools also improve our understanding of the accelerating capabilities of these thrusters so that we can better model their performance. Possibility of the anode layer thruster erosion rate evaluation through analysis its optical emissions and methods is demonstrated in present paper. The ability to quantify and identify erosion rates using a relatively inexpensive diagnostic method could lead to a very significant reduction in the development and flight validation cost of these thrusters. To date these methods after careful consideration are improved at TsNIIMASH. Based on these new methods of investigation data processing equipment was improved, several experiments with TAL D-80 were conducted and described. New experimental data which verify the method were obtained in various condition of the TALs operation and discussed. Erosion rate of the anode layer thruster was monitored through measuring of emissions of chrome and iron atoms sputtered from the thruster body. Despite the difference between excitation functions of these atoms, time dependence of the erosion rate appeared to be almost identical in both cases indicating the method reliability. The new diagnostic method could be widely implemented at many different laboratories where optical diagnostics is used.. Results discussed in the paper, will definitely contribute to the successful development of a Hall thruster erosion properties diagnostics.

Ultraviolet radiation from hydrazine spacecraft thruster plumes interacting with ambient atomic oxygen is modeled forlow-Earth-orbit conditions. Two numerical techniquesthatemploy the direct simulation MonteCarlo method are applied for the e rst time to the modeling of space plume radiation transient and three-dimensional e ows. These efe cient procedures allow one to analyze the effect of atomic oxygen penetration of the thruster plume, which is a key factor in modeling raree ed space plume radiation. The overlay technique is used to model thetransiente owevolutionduringthee rstseveralsecondsaftermotorignition.Goodagreementbetweenmodeling and experiment are obtained before 1-s motor burn time. The sensitivity of the plume radiation to the molecular total collision model is analyzed using the overlay technique, and the radiation spatial distribution was found to be strongly dependent on the temperature exponent of the coefe cient of viscosity. Three-dimensional computations are conducted for different angles between the plume axis and the freestream directions, and the radiation maps forOH(A)andNH(A)arepresented.Signie cantdifferencebetween OH (A)andNH(A)radiatione eldsasafunction of the angle of attack is shown.

Modeling and calculations are presented with the goal of elucidating possible mechanisms of ultraviolet radiation from a Soyuz-TM spacegraft plume interacting with the ambient gas at altitudes of about 380 km, observed during the Mir experiment. The studies were performed with the direct simulation Monte Carlo method. The results presented include sensitivity studies of the simulation to various numerical parameters and an investigation of different radiation mechanisms. Among the mechanisms considered was the formation of OH(A) due to water dissociation by atomic O, collisional excitation of OH(X), and the formation of NH(A) by the reaction of atomic O with hydrazine fragments. The simulations are found to overpredict the data by approximately a factor of 5-70, depending on the parameters of the chemistry model for water dissociation. However, the simulations are in close agreement with the near-field plume intensity profile.

A semi-empirical method has been developed that allows to evaluate variation of a xenon Hall thruster erosion rate with changing of its operating conditions. Instead using the results of a long duration life-time test the method is based on the analysis of the thruster emission spectra. That provides a unique opportunity to monitor variation of the thruster erosion rate in the real time during ordinary performance tests. Simple relation has been derived that reduces the erosion rate determination to measurement of intensity of particular lines of xenon ions and eroded atoms. Despite that method is not completely perfect so far, it will be very useful for quick look estimate of the erosion intensity and material sputtering rate in the Hall thrusters operating at varying conditions.

The results on an investigation of nonequilibrium uv radiation in the systems of molecular hands NO and N-2(+)(1-) in a shock layer in air are presented. The studies included the experiments on a measurement of the nonequilibrium radiation behind a strong shock wave in an electric are-driven shock tube within the range of shock-wave velocity change V-s = 5 to 10 km/s at the initial air pressure P-1 = 0.1 torr, and numerical simulation of radiation processes behind the shock wave and in a hypersonic viscous shock layer, where the now was Simulated on the basis of Navier-Stokes equations. A numerical model of the radiation behind the strong shock wave has been used to verify a kinetic scheme of radiation processes by comparison with experimental results. Examples of emission calculations in the NO and N-2(+)(1-) systems for the conditions of a flight test are presented.