Initiation of high-energy material ignition by nanosecond high-current electron beam

Results of experiments on the initiation of ignition in high-energy materials with a broad range of physicochemical parameters by high-current electron beams of nanosecond duration are presented. It is shown that ignition of these materials can be initiated even at relatively low energy parameters of the electron beam, provided that the ignition temperature does not exceed 200°C.     

Transport of a high-current relativistic electron beam by magnetic multipoles

With the aid of moments of the distribution function a system of differential equations is obtained to describe the dynamics of a Gaussian high-current electron beam in magnetic fields with quadrupole and octupole symmetries. Results of its numerical solution are reported. Research Institute for Nuclear Problems at the Belarusian State University, Minsk, Belarus; Institute of Mathematics of the Academy of Sciences of Belarus, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 5, pp. 776–782, September-October, 1997.     

Copper spall fracture under sub-nanosecond electron irradiation

Ultra-short powerful electron beam is a suitable tool for producing of high rate deformation in substance. In paper we present a new model of high rate fracture and use this model for numerical investigation of fracture of copper target at irradiation by sub-nanosecond electron beam. In this model, fracture is considered as a time-dependent process of nucleation and growth of opening mode cracks. The nucleation and growth rates are controlled by specific free energy of crack surface which is sole fitted parameter. Plastic deformations, both in cracks vicinity and total in substance, are described in frames of dislocation theory. For verification of the model, we performed simulations of spall fracture at plate impact and at irradiation by high-current electron beam with pulse duration of tens of nanoseconds, and reasonable agreement with experimental data has been demonstrated. Simulations of the sub-nanosecond electron beam action on target indicate that spall fracture of the irradiated target surface is possible. This fracture takes place at the enclosed energy density slightly below the value, which is sufficient for melting of irradiated substance. Fracture threshold energy density does not depend on the origin dislocation density and it increases with the increase of pulse duration. As a result, at long pulse durations (more than ten nanoseconds) the substance melts before fracture.     

Induction self-acceleration of a high-current electron beam

Computer modeling using the particle-in-cell method confirmed that self-acceleration by induction of a high-current relativistic electron beam predicted by G. A. Askar’yan [At. énerg. 6, 658 (1959)] may occur when this beam passes through a thick diaphragm containing an aperture. Pis’ma Zh. Tekh. Fiz. 25, 52–56 (July 26, 1999)     

Melting of porous silicon under the action of a nanosecond pulsed high-power ion beam

We have studied the melting of porous silicon (por-Si) layers under the action of a nanosecond pulsed high-power proton-carbon ion beam. Dimensions of ellipsoidal silicon particles formed as a result of this processing have been determined. The threshold energy density necessary for the melting of por-Si with a porosity of ～50% is experimentally evaluated.     

Low-energy high-current electron beam heating of target with second-phase microinclusions

The temperature field generated by microsecond pulsed low-energy high-current electron beam (LEHCEB) in the surface layer of a stainless-steel target containing second-phase (manganese sulfide, MnS) microinclusions has been numerically simulated. The results of calculations show that the temperature is nonuniformly distributed over the target surface. By the end of the LEHCEB pulse, the temperature in the regions of MnS inclusions significantly exceeds that of the steel matrix. This nonuniformity is related to (i) markedly greater thermal conductivity of steel compared to that of MnS and (ii) the pulsed character of the electron-beam-induced heating of the target surface. It is also established that LEHCEB-induced melting begins at the inclusion-steel interface and then involves the inclusion and spreads over the entire irradiated surface. The dependence of the characteristics of the irradiation-induced temperature field on the parameters of the pulsed electron beam has been studied.     

Explosion initiation of furazanotetrazine dioxide by a high-current electron beam

Results of investigations of physicochemical processes which develop in furazanotetrazine dioxide under irradiation by a high-current electron beam with an energy density varied in a range of 0.05–0.3 J/cm² are represented. The spectral-kinetic characteristics of pulse cathodoluminescence are measured, and thresholds of the mechanical failure and explosive decomposition of samples are determined. A strong effect of the energy density of the electron beam on kinetics of the explosive transformation (induction period and duration of explosive glow) is revealed. The dimensional effect of the explosion initiation is found.

     

Surface structuring of polycrystalline magnesium under the action of high-power ion beam of nanosecond duration

The formation of periodic structures and micro- and nanoparticles on the surface of polycrystalline magnesium under the action of a high-power proton-carbon ion beam of nanosecond duration have been studied. Spatial parameters of the observed structures and dimensions of particles are determined and possible mechanisms of their formation are considered.     

Structural phase transformations in tin dioxide under the action of a nanosecond high-power ion beam

Structural phase transformations in polycrystalline tin dioxide under the action of a nanosecond high-power ion beam with a current density of 50–150 A/cm² are studied. It is found that the effect of a beam with a current density of 150 A/cm² on SnO₂ leads to the formation of submicron particles of tetragonal SnO with an average size of 210 nm on the exposed surface. The particles have a pronounced crystallographic facet pattern. Possible mechanisms of the observed transformations are discussed.     

Luminescence of crystals under the action of a subnanosecond electron beam

Subnanosecond avalanche electron beams formed in air at atmospheric pressure ensure intense luminescence of synthetic ruby and natural spodumene crystals.     

Application of a model of a quasiequlibrium plasma and methods of lie algebra to calculations of parameters of a transported high-current relativistic electron beam

A method for calculation of the parameters of an intense beam of charged particles transported by the magnetic field of the focusing elements is described, and the results of numerical modeling are presented. Scientific Research Institute for Nuclear Problems, Belarusian State University, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 1, pp. 33–38, January–February, 1996.     

Formation of surface structures on single-crystalline silicon under the action of nanosecond high-power ion beam pulses

We have studied the formation of surface structures on single-crystalline silicon surface under the action of a nanosecond pulsed high-power proton-carbon ion beam. Morphological features of the structures that appear as a result of this processing are described and possible mechanisms of their formation are considered.     

Emissive characteristics of electric discharge initiated by high-current electron beam in atmosphere

Spectral and kinetic characteristics of electric discharge induced by a high-current electron beam in air at atmospheric pressure have been experimentally studied. The luminescence spectrum of a volume (diffuse) discharge generated under the conditions studied displayed emission bands due to the second positive system of nitrogen molecules. The cathode region of discharge exhibited bright cathode spots, which emitted short-term (nanosecond) pulses with continuous spectrum and long-term line radiation from atoms entering into the cathode material composition.     

Removal of acrolein vapor from air by a nanosecond electron beam

Results are presented of an experimental investigation of the decomposition of small quantities of acrolein vapor in air irradiated by a pulsed electron beam. It is shown that the reduction in the impurity concentration as a function of the energy deposited in the gas is satisfactorily approximated by an exponential law. An empirical expression is derived to predict the energy consumption for a given initial acrolein concentration and required degree of purification. Pis’ma Zh. Tekh. Fiz. 24, 35–39 (August 26, 1998)     

Specific features of high-power nanosecond ion beam action on polycrystalline bismuth

Specific features of surface relief formation on a polycrystalline bismuth target under the action of a high-power proton-carbon ion beam of nanosecond duration have been studied. Local melt extrusion from subsurface layers and its crystallization on the surface is observed, which is explained by a significant (3.35%) thermal expansion of bismuth during the transition from liquid to solid state.     

Virtual anode as a source of low-frequency oscillations of a high-current electron beam

We have studied the transport of a relativistic electron beam with supercritical current in a cylindrical drift chamber in the presence of an ion flux. A theoretical analysis of the electron-ion flux dynamics was based on the coarse particle PIC method (code SOM). Simultaneous injection of a supercritical electron beam and a weak-current low-energy ion beam may result in the formation of a virtual anode in addition to the electron virtual cathode in a drift chamber. The virtual anode exhibits periodic pulsations. Numerical results obtained for hydrogen and nitrogen ions show that the ratio of the frequencies of these pulsations is inversely proportional to the square root of the ion mass ratio. These oscillations of the virtual anode lead to temporal modulation, at the same frequency, of both electron and ion currents at the drift chamber output.     

Ion accelerator with space-time modulation of a relativistic electron beam

An analysis is made of a possible method of collective ion acceleration by combining spatial modulation of the electron beam potential with temporal modulation of the current. A conceptual design is proposed. Pis’ma Zh. Tekh. Fiz. 24, 74–78 (September 26, 1998)