Laser-beam interaction with expanding plasma was investigated using the PALS high-power iodine-laser system. The interaction conditions are significantly changing with the laser focus spot position. The decisive role of the laser-beam self-focusing, participating in the production of ions with the highest charge states, was proved.

In this article, we present the formation of an elongated plasma column by combining a laser plasma with an external magnetic field. The laser plasma is produced by irradiating solid targets with a focused Nd-glass laser. The targets were placed on the axis of the two, single-turn magnetic coils, which provided a magnetic field up to 500 kg in the target region. The expanding laser plasma is confined by the magnetic field and an elongated and uniform plasma column is formed on the axis of the coils. The plasma column emits strong, soft X-ray radiation. The pinhole photographs show that the plasma column is at least 5 mm long. To study the interaction of the expanding laser plasma with a magnetic field, the laser probing diagnostic was used.

This paper presents an investigation of self-focusing of a q-Gaussian laser beam and its effect on harmonic generation in a preformed collisionless parabolic plasma channel. In the presence of a q-Gaussian laser beam, the carriers get redistributed from high field region to low field region on account of ponderomotive force as a result of which a transverse density gradient is produced in the channel which in turn generates plasma wave at pump frequency. Generated plasma wave interacts with the incident laser beam and generate higher harmonics of the incident laser beam. Moment theory has been used to derive differential equation for the spot size of laser beam propagating through the channel. The differential equation so obtained has been solved numerically. The effect of the intensity of laser beam, deviation of intensity distribution of laser beam along its wave front from Gaussian distribution, plasma density and depth of channel on beam width of laser beam and harmonic yield has been investigated. The effect of order of higher harmonic on harmonic yield has been also investigated.

In this paper, the spectra of electron beams produced in vacuum and gas diodes were analyzed to study the capabilities and limitations of their reconstruction from beam attenuation in foils of different thickness. The electron energy distributions were calculated using the Tikhonov regularization for Fredholm integral equations on minimum a priori assumptions. The spectra reconstructed in the study were those of electron beams, including a supershort avalanche electron beam, produced in experiments on a DUET plasma-cathode electron accelerator and SLEP-150M accelerator.

Generation of high speed dense plasma blocks is well known from hydrodynamic theory and computations (PIC) with experimental confirmation by Badziak et al. (2005) since ps laser pulses with power above TW are available. These blocks may be used for fusion flame generation (thermonuclear propagation) in uncompressed solid state deuterium and tritium for very high gain uncomplicated operation in power stations. Hydrodynamic theory from computations from the end of 1970s to recent, genuine two fluid computations support the skin layer accelerations (SLA), by nonlinear (ponderomotive) forces as measured now in details under the uniquely selected conditions to suppress relativistic self-focusing by high contrast ratio and to keep plane geometry interaction. It is shown how the now available PW-ps laser pulses may provide the very extreme conditions for generating the fusion flames in solid state density DT.

An electron gun is being developed which should substantially improve the normalized current density in medium energy pulsed linacs. The gun will accelerate and pre-bunch electrons from a LaB6 cathode using the high electric field in a resonant microwave cavity.

Self-trapping, stopping, and absorption of an ultrashort ultraintense linearly polarized laser pulse in a finite plasma slab of near-critical density is investigated by particle-in-cell simulation. As in the underdense plasma, an electron cavity is created by the pressure of the transmitted part of the light pulse and it traps the latter. Since the background plasma is at near-critical density, no wake plasma oscillation is created. The propagating self-trapped light rapidly comes to a stop inside the slab. Subsequent ion Coulomb explosion of the stopped cavity leads to explosive expulsion of its ions and formation of an extended channel having extremely low plasma density. The energetic Coulomb-exploded ions form shock layers of high density and temperature at the channel boundary. In contrast to a propagating pulse in a lower density plasma, here the energy of the trapped light is deposited onto a stationary and highly localized region of the plasma. This highly localized energy-deposition process can be relevant to the fast ignition scheme of inertial fusion.

Proton-boron-11 is the clean fusion reaction par excellence, but it is very difficult to exploit it because of the very high ignition temperature of this reaction and its moderate fusion yield. In this paper, a proposal is made to induce these reactions by a heat-detonation wave that expands across a compressed target. The front of the wave has a double-layer structure, with a first front driven by electron heat conduction and a second front heated by α-particle energy deposition. Both fronts create a hot plasma where the stopping power is dominated by ions. The wave is originated by an ignitor triggered by an ultraintense lightning beam. This beam can be made of photons (laser), plasma (ramjets), or ions (proton beams, borane clusters). Proton beam shots of 1022. W/cm2 and several GA for some picoseconds would be needed for this purpose. The supersonic propagation of the fusion wave and the ignitor requirements are analyzed in this paper. The main conclusion is that the burning wave can only propagate if a substantial fraction of the radiation losses from the already burning fuel is reabsorbed in the colder fuel. It is calculated that for densities larger than few thousands g/cm3 most of the bremsstrahlung radiation created in the hot plasma can be reabsorbed by the Compton effect in a region of 1 g/cm2 optical thickness of the surrounding compressed and cold fuel.

Recently a new fast ignitor concept has been proposed by Velarde et al. (2003) that uses only one energy drive. In this concept, the ignition is induced by the collision of high velocity matter accelerated inside a conical guide. The first model used a jet produced by illuminating a conical shape with a laser or X-rays. On the other hand, in the shell impact concept, the compressed deuterium-tritium fuel is ignited by a separately imploded shell traveling in a guiding cone. In this article, we will study the first design, jet driven concept that have been developed during this year. We use for this work the Arwen code (Ogando & Velarde, 2001; Rendleman et al., 2000), with two-dimensional (2D) multi-group radiation transport. The main parameter is to analyze the specific power transmitted to the target during the collision. Problems with the designs are the guide integrity during the collapse, the radiation preheating, and the average efficiency of the process, etc. which we will address as well.

Using reductive perturbation technique, small-amplitude ion-acoustic solitary wave has been investigated in multi-component dense plasma, in which an electron beam propagates along the general streaming motion. The electrons in plasma have the q-exponential distribution. The positive and negative ions follow a regular Maxwellian distribution. It has been found that the positive and negative ion densities as well as the beam concentration have significant effect on the formation and properties of solitary structures. The streaming velocities of corresponding particles also have pronounced effect on the features of the solitons.

This paper presents an investigation of self-focusing of Gaussian laser beam in collisional plasma and its effect on second harmonic generation. Due to non-uniform heating, collisional non-linearity arises, which leads to redistribution of carriers and hence affects the plasma wave, which in turn affects the second harmonic generation. Effect of the intensity of the laser beam/plasma density on the harmonic yield is studied in detail. We have set up the non-linear differential equations for the beam width parameters of the main beam, plasma wave, second harmonic generation and second harmonic yield by taking full non-linear part of the dielectric constant of collisional plasma with the help of moment theory approach. It is predicted from the analysis that harmonic yield increases/decreases due to increase in the plasma density/intensity of the laser beam respectively.

A possibility is analyzed to use direct drive cylindrical targets in the fast ignition mode irradiated by beams of nearly relativistic heavy ions with long ranges in matter. The minimum beam energy required to compress the DT fuel in a 1-cm-long target to (ρR)DT = 0.5 g/cm2, ρDT = 100 g/cm3 is found to lie in the range 10–15 MJ. Ignition and axial burn propagation is achieved with a 0.2-ns, 0.4-MJ pulse of 100-GeV heavy ions. Thermonuclear energy gains in the range 50–150 appear to be possible.

We present the design of a single-shot third-order autocorrelator that can be used to measure optical pulse lengths of ultrashort pulses within a fixed time window on a single-shot basis. It has a number of advantages over traditional second-order autocorrelation devices, namely a more direct and accurate measurement of pulse shape, the ability to differentiate temporal activity ahead and behind the pulse, and an increased dynamic range. The design is linear and is, in principle, no more difficult to construct and operate than a second-order autocorrelator.

Neonlike ions have long been recognized as candidates for producing soft-X-ray lasers along 1s22s22p53p → 1s22s22p53s transitions. A series of experiments using exploding-foil targets driven by high-power lasers was performed at CEL-V and LLNL, and demonstrated amplified spontaneous emission in germanium, selenium, strontium, and molybdenum. We present here simulations of these experiments and discuss the importance of refraction effects on the propagation of the lasing X-rays and on the scaling of this scheme to shorter wavelengths.

We have demonstrated the acceleration of a monoenergetic electron beam by a laser-produced wakefield. Experiments were performed by focusing 2-TW laser pulses of 50 fs on supersonic gas-jet targets. The focused intensity was 5 × 1018 W/cm2 (a0 = 1.5). At an electron density of 1.5 × 1020 cm−3, the clear monoenergetic electron beam from the plasma was obtained at 7 to 15 MeV. The Stokes satellite peak in the forward scattering explained the energy spectra of electrons at various plasma densities well. Although the wakefield propagated 500 microns, which was far beyond the dephasing length, monoenergetic electron beams were obtained.

The multi-Terawatt laser system, terawatt apparatus for relativistic and nonlinear interdisciplinary science, has been recently installed in the Centre for Plasma Physics at the Queen's University of Belfast. The system will support a wide ranging science program, which will include laser-driven particle acceleration, X-ray lasers, and high energy density physics experiments. Here we present an overview of the laser system as well as the results of preliminary investigations on ion acceleration and X-ray lasers, mainly carried out as performance tests for the new apparatus. We also discuss some possible experiments that exploit the flexibility of the system in delivering pump-probe capability.

In the present paper, we have investigated self-focusing of Gaussian laser beam in relativistic ponderomotive (RP) cold quantum plasma. When de Broglie wavelength of charged particles is greater than or equal to the inter particle distance or equivalently the temperature is less than or equal to the Fermi temperature, quantum nature of the plasma constituents cannot be ignored. In this context, we have reported self-focusing on account of nonlinear dielectric contribution of RP plasma by taking into consideration the impact of quantum effects. We have setup the nonlinear differential equation for the beam-width parameter by paraxial ray and Wentzel Kramers Brillouin approximation and solved it numerically by the Runge Kutta Fourth order method. Our results show that additional self-focusing is achieved in case of RP cold quantum plasma than relativistic cold quantum plasma and classical relativistic case. The pinching effect offered by quantum plasma and the combined effect of relativistic and ponderomotive nonlinearity greatly enhances laser propagation up to 20 Rayleigh lengths.

The parameters of self-generated electron beams have been measured and correlated to the dynamics of a 60 kV, 28 kJ plasma focus. The electron beam emission occurs in two periods: the first corresponds to the initial formation and disruption of the pinched plasma and terminates with the disruption of the plasma column, and the second period occurs after the breaking up of the focus plasma. The first period is characterized by high-energy electron beams, whereas in the second period the electron beams have lower average energies but higher currents. A relativistic electron beam is found to occur around the time of first compression, when the plasma is observed to be macroscopically stable, in contrast to measurements obtained from machines with similar energies but operating at lower voltages. The plasma X-ray emission is observed to be closely related to the electron beam characteristics. Possible mechanisms for the formation of the electron beams observed are discussed.

Intense electron beams are known to produce surface plasmas when they strike typical target materials. The beam space charge then draws an ion current that can substantially affect the beam dynamics. We consider these effects for two intense-beam sources: (1) a needle-tip cathode immersed in a strong magnetic field, and (2) an induction accelerator-produced beam that is focused onto a field-free target. For the first case, the dominant effect is an electrostatic dipole instability between the beam and the ions. A sufficiently large magnetic field can keep the oscillation amplitude to a low level. For the second case, the dominant effect is that the focal length changes in time. For the “worst case” of space-charge-limited proton emission, the predicted effect is severe. The actual abundance and charge state of the target-plasma ions will need to be measured or inferred from planned experiments. Mitigation schemes also are discussed briefly.

Tesla transformers are widely used in short pulse, repetition pulsed power generators. In this paper, a high repetitive rate intense electron beam accelerator (IEBA) based on high coupling (~1) Tesla transformer, which consists of a primary charging system, coaxial pulse forming line (PFL) charged by Tesla transformer and gas spark switch is described, especially stressed on the high coupling Tesla transformer. By introducing magnetic core to enhance the coupling factor between the primary and secondary windings, the transformer is capable of producing high voltage pulse up to 1.4 MV in approximately 45 µs. A coaxial pulse forming line is closely attached to the transformer that the outer and inner magnetic cores are parts of the PFL's outer and inner conductors respectively. In addition, the parameters of the Tesla transformer and PFL are calculated, including the dimension of the PFL and Tesla transformer. Some experiment results showed that the IEBA is capable of producing electron beams of 300–700 kV/7–13 kA at repetitive rate 100 Hz, with the pulse width 35 ns. The maximal energy efficiency of the Tesla transformer is 83%.