In a triple plasma device, the injection of electron current from the source chamber to the target chamber causes the formation of a potential double layer. At a low current density, the space charge of the injected current produces a virtual cathode-type potential double layer. This double layer is stable and various wave instabilities are observed to associate with this double layer. As the current density is increased, the double layer becomes unstable and a moving double layer results. As the current density is increased further, the enhanced ionization causes the neutralization of the space charge of the electron beam and the ‘beam plasma discharge’ is ignited.

To control an input energy for a load, an impedance control with a gap distance of an electron beam diode was studied using an intense pulsed-power generator. The output current of the pulsed-power generator as a function of the gap distance of electron beam diode was measured. It indicated that the behaviors of the experimentally obtained peak current and the theoretically obtained space-charge limited current were found to decrease with an increase in the gap distance. The input energy for the load was estimated from the output current, which decreased with an increase in the gap distance. It also revealed the space-charge limited current suppresses the input energy for the load with a decade.

Rotating motion of a propagating LIB is analyzed in order to suppress the mixed mode of the Kelvin-Helmholtz instability, the tearing instability and the sausage instability by the action of a self-induced magnetic field in the axial direction. The beams are assumed to be charge-neutralized but not current-neutralized. The steady-state solutions of a propagating LIB with rotation are first obtained numerically. Through the dispersion relation with respect to the ikonal type of perturbations, which are added to the steady-state solutions, the growth rates of instabilities appearing in an LIB are obtained. It is concluded that if the mean rotating velocity of an LIB is comparable to the propagation velocity, in other words, if the induced magnetic field intensity in the axial direction is comparable to the magnetic field intensity in the azimuthal direction, the instability disappears in the propagating ion beam.

The radiation hydrodynamics of a 125-μm thin carbon layer illuminated by thermal radiation of Trad = 200 eV temperature is studied within a multigroup radiation model. Whereas a major part of the incident photons deposit their energy by K-shell absorption close to the surface, soft photons below the K edge and hard photons (hv > 800 eV) penetrate deeper into the material and drive a heat wave with a sharp front. A nonablated mass fraction of 20% is accelerated with a hydrodynamic efficiency of 11%. About half of the incident radiation flux is reemitted by the heated carbon plasma. The heat front trajectory can be reproduced by the analytical heating wave model when effective opacity parameters corresponding to the most penetrating components are used.

Absorption of electrical energy provided to a metal wire in an exploding wire system is thought to be terminated or greatly diminished when the plasma is formed, after the joule heating of the metallic wire by the electrical current. Accordingly, it is common to account for the electrical energy delivered to the wire that the integration of current and voltage signals is halted when the voltage peak changes its slope. Usually, this moment is synchronized with the plasma appearance, as detected by optical sensors. In this work, experimental evidence of a two-step electrical energy absorption in an exploding wire surrounded by atmospheric air is presented. During the first step of the energy absorption the plasma is not formed, indicating that the delivered energy is not enough for ionizing the wire, giving place to a dark pause that lasts until a second energy absorption produces a plasma. The delay between the two steps can reach ≈2.2 µs for copper wires of 50 µm diameter charged at an initial voltage of 10 kV. Experimental investigation of variation of the delay between the two steps with different metals, charging voltages, and wire diameters are presented. A relation of the current density with the initial kinetic energy of the plasma and the electrical current rate is devised as a possible explanation of the observed phenomena.

A multiwire screw pinch, a variant of a z-pinch load, is proposed as a means for further improvement of load performance for high-current 100-ns pulsed-power generators used for terawatt X-ray radiation. Wires twisted along a curved load surface are suggested to be an effective way to create an axial magnetic field and to generate and to maintain rotation of the subsequently formed plasma shell due to conservation of angular momentum. A multiwire screw pinch is predicted to mitigate the growth of the magneto-Rayleigh–Taylor instabilities, to provide a higher pinch compression ratio and more effective X-ray generation compared to classical z-pinch loads. A model based on the self-consistent simulation of the dynamics of a twisted plasma shell and the development of Rayleigh–Taylor (R-T) perturbations on a plasma surface is proposed to quantitatively study the effect of various physical factors on the generation of X rays. The model provides us with a tool for the analysis of processes that occur during the implosion of the plasma-shell–wire-core system. We plan for the R-T perturbations to break through the plasma shell at the moment when the internal radius of a shell becomes zero, where the greatest possible values of kinetic energy and X-ray radiation power ought to be obtained. The results of numerical simulations for the Sandia National Laboratories' Z generator are presented and discussed.

A comparison of the recombination and photo-pumping approaches for producing X-ray lasing on the hydrogen-like Balmer alpha line is presented. An approximate analytic expression for the ratio of the populations of the n = 3 and 2 quantum states of the hydrogen-like ion is derived and used to delineate the plasma parameter space where Balmer alpha gain can occur in a recombining plasma. The photo-pumping intensities required to produce Balmer alpha gain for plasmas initially in the steadystate are calculated using a collisional-radiative code and compared to intensities required to produce the initial plasmas for a recombination Balmer alpha laser with comparable gain. The recombination approach becomes relatively more efficient compared to the photo-pumping approach with increasing atomic number Z of the hydrogen-like ion with an estimated break-even at approximately Z = 16.

The Pseudospark is an axially symmetric, high-voltage gas discharge operating at pressures below 100 Pa. It is capable of producing pinched high current ion beams. Streak camera photographs of the operation of this discharge reveal that a pinch with a diameter of ∼1 mm occurs in the diode. The beam then expands to about 1 to 10 mm in a distance of 12 cm. The beam-target interaction shows a UV-emitting plasma corresponding to protons with a main energy of 100 keV and a current density of about 16 kA/cm2. Initial theoretical results for the pseudospark are given.

This paper discusses the principles of reduction of quantum noise in optical radiation. The dynamics of photon number fluctuations in direct and cascade two-photon processes is investigated. The paper considers the cases of absorption and emission for the fields originally prepared in coherent and thermal states. It is shown that photon antibunching and bunching should occur for the passed radiation. The photon antibunching effect is only in definite time intervals of field interaction with resonance absorbing or emitting systems.

The possible cases of accumulation of photon antibunching effects are considered.

In preparation for an experiment with a laser-generated intense proton beam at the Laser Fusion Research Center at Mianyang to investigate the 11B(p,α)2α reaction, we performed a measurement at very low proton energy between 140 keV and 172 keV using the high-voltage platform at the Institute of Modern Physics, Lanzhou. The aim of the experiment was to test the ability to use CR-39 track detectors for cross-section measurements and to remeasure the cross-section of this reaction close to the first resonance using the thick target approach. We obtained the cross-section σ = 45.6 ± 12.5 mb near 156 keV. Our result confirms the feasibility of CR-39 type track detector for nuclear reaction measurement also in low-energy regions.

A comparative analysis of a fast atom beam and ion beam effect on a metal target in the binary collision model is performed. Irradiation by fast atoms has been shown to more closely correspond to neutron radiation in a nuclear reactor, in terms of the primary knocked-on atom spectrum and the efficiency and mechanism of the radiation defect formation. It was found that upon irradiation by fast carbon atoms with an energy of 0.2-0.3 MeV, the average number of radiation defects in the displacement cascade of one atom is four to five times higher than the calculated values using the SRIM program for ions with the same energy. It is shown that during penetration in the target, the probability of ionization of atoms with energies less than 0.4 MeV is negligible.

The experimental results of the activation spectra, dose rate measurements, and the residual nuclide production cross sections obtained after the irradiation of the NatCu and 59Co targets by 12C ion beams at ITEP and GSI are presented in this paper. These results are compared with simulations by the CASCADE and LAQGSM codes.

This paper considers the heating of a target in a shock wave created in a planar geometry by the ponderomotive force induced by a short laser pulse with intensity higher than 1018 W/cm2. The shock parameters were calculated using the relativistic Rankine–Hugoniot equations coupled to a laser piston model. The temperatures of the electrons and the ions were calculated as a function of time by using the energy conservation separately for ions and electrons. These equations are supplemented by the ideal gas equations of state (with one or three degrees of freedom) separately for ions and electrons. The efficiency of the transition of the work done by the laser piston into internal thermal energy is calculated in the context of the Hugoniot equations by taking into account the binary collisions during the shock wave formation from the target initial condition to the compressed domain. It is shown that for each laser intensity there is threshold pulse duration for the formation of a shock wave. The explicit calculations are done for an aluminum target.

The interaction of electromagnetic radiation with plasmas is studied in relativistic four-vector formalism. A gauge and Lorentz invariant ponderomotive four-force is derived from the time dependent nonlinear three-force of Hora (1985). This four-force, due to its Lorentz invariance, contains new magnetic field terms. A new gauge and Lorentz invariant model of the response of plasma to electromagnetic radiation is then devised. An expression for the dispersion relation is obtained from this model. It is then proved that the magnetic permeability of plasma is unity for a general reference frame. This is an important result since it has been previously assumed in many plasma models.

The paper reviews a number of X-ray streak cameras developed at AWRE. These cameras are used to provide temporal and one-dimensional spatial or spectral information on X-rays emitted from laser produced plasmas. Two of these cameras have been designed to be combined with other diagnostic instrumentation; one with a Wolter X-ray microscope (×22 magnification) and the other with a Bragg diffraction crystal spectrometer. This latter instrument provides a few eV spectral resolution and ∼15 ps temporal resolution; a typical experimental application at the AWRE HELEN laser facility will be described. The paper describes the circuitry of the bipolar avalanche transistor ramp generator used to drive the streak plates of the cameras. Improvements to this include: (a) increasing the fastest streak rate to ∼10 ps mm−1 by a distributed capacitance network across each of the bipolar stacks of transistors, and (b) reducing the trigger jitter to approximately ±10 ps by the use of a new mix of transistors in the stack and a Raytheon RS 3500 avalanche transistor. Additional improvements have now been added. These include a ‘half-scan’ user facility to aid initial camera timing and direct switching to select the sweep rate of the camera.

The results of an experimental investigation of iodine laser interaction with Al targets obtained on the laser system PERUN (λ = 1.315 μm, E < 50 J, τ ∼ 350 ps) by means of corpuscular diagnostics, are presented. Ion velocity distributions, angular distributions, and electron temperature were determined. The plasma electron temperature Te ∼ 550 ± 100 eV was weakly dependent on laser intensity in the range Iλ2 ∼ 1014-1015 Wcm-2 μm2. Maximal velocity (energy) for the Al ions was estimated as V ∼ 9 × 107 cm/s (∼ 110 keV) and the maximal measured charge state was z = 13. It was shown that the diameter of the area emitting high energy ions is a few times larger than the focus diameter (80 μm), which indicates a strong influence of lateral heat transport on plasma parameters. The hot electron temperature Te.h was estimated to be in the range 6–10 keV. On the basis of Langmuir probe measurements, the electron temperature of expanded Al plasma at a distance of about 100 cm was estimated to be Te ∼ 3 eV

Experimental study of the radiation scattered at the laser heating of low-density foam targets and transmitted through the targets is presented. The scattered and transmitted radiations were investigated using spectrometers and streak cameras providing spatial, angular, spectral and temporal resolutions that enabled us to study the dynamics of the process of burning-through of the thick foam targets, the velocities of the plasma critical density motion as well as mass velocity of the plasma.

A heavy ion fusion (HIF) system, named HIBLIC (Heavy Ion Beam and LIthium Curtain) is conceptually designed. The driver system consists of RF linacs (RFQ linacs, IH linacs and Alvarez linacs), storage rings (one accumulator ring and three buncher rings) and beam transport lines with induction beam compressors. This accelerator complex provides 6 beams of 15 GeV208Pb1+ ions to be focused simultaneously on a target. Each beam carries 1·78 kA current with 25 ns pulse duration, i.e., the total incident energy on the target is 4 MJ, 160 TW per shot. Superconducting coils are used in most parts of the magnet system to reduce power consumption.

Hot-spot path in the thermodynamic space $({\rm \rho} R,T_{\rm i} )_{{\rm hs}} $ is investigated for direct-drive scaled-target family covering a huge interval of kinetic energy on both sides of kinetic threshold for ignition. Different peak implosion velocities and two initial aspect ratios have been considered. It is shown that hot spot follows almost the same path during deceleration up to stagnation whatever the target is. As attended, after stagnation, a clear distinction is done between non-, marginally-, or fully igniting targets. For the last, ionic temperature can reach very high values when the thermonuclear energy becomes very high.

The X-ray image of a compressed shell (enhanced by high-Z doping) was used in recent experiments to diagnose the effect of shell-fuel mixing. The emission ring (due to the limb effect) moves toward smaller radii due to mixing. We show here that using backlighting imaging can greatly enhance future imaging experiments. In addition to the emission ring, a backlighting absorption ring can appear around it. The absorption ring is virtually unaffected by mixing. Thus, the relative position of the two rings constitutes a mixing signature. In other words, the absorption ring delineates the colder part of the shell and is a true signature of the compression, whereas the emission ring reflects the shell material motion due to mixing.