The beam dynamics design of the low energy DTL section of a fusion driver linac based on the IH-structure is presented. The acceleration of a 209Bi1+ beam by an IH-DTL operated at 27 MHz (54 MHz) is investigated for two specific injection energies at 60 A keV and at 200 A keV, respectively. Both cases are optimized separately, with the goal to find out the maximum achievable acceleration gradient, beam current, as well as the most attractive field strength range of the quadrupole lenses. Calculations are performed on one beamlet, but the results can be applied to build up multibeam cavities. H-mode cavities are very well suited for this purpose and provide high acceleration efficiency, especially at low particle velocity. In addition, the “Combined 0° structure” (“Kombinierte Null Grad Struktur–KONUS”) beam dynamics concept allows grouping into modular units consisting of short, simple rf cavities and of multiaperture quadrupole triplet lenses located in the intertank sections.

In the last few years, systematic studies on radiation hydrodynamics in the X-ray confining cavity and a fuel capsule have attained remarkable progress. This makes it possible to analyze quantitatively the energy transfer processes from laser to the fusion capsule and find uniform irradiation conditions of the fusion capsule driven by thermal X rays. As a result, reproducible and stable implosions were achieved. Throughout implosion experiments with the Gekko XII blue laser system (351 nm, kJ, 0.8 ns), good agreement of implosion has been obtained between the experiment and numerical simulations, assuming perfectly spherical symmetry, up to a radial convergence ratio of 15. Described are particularly the issues of (1) energy transfer processes from laser to a fuel capsule and conditions for uniform irradiation, (2) properties of the X-ray propagation through aluminum heated by X-ray radiation, and (3) dependence of the convergence ratio of Ri/Rf (where Ri and Rf are the initial and final radii) of the capsule on the initial fill pressure of D–T gas and its influence on the core parameters and fusion products to evaluate implosion sphericity.

The physics of the formation of cryogenic fuel layers with various internal structures has been studied in regard to the development of promising layering techniques for modern inertial confinement fusion (ICF) experiments. The investigations have been made with inertial confinement fusion target (ICF targets) and in a target modeling system (TMS) with the nonisochoric process of cryogenic layer formation. The results indicate that the solidlayer structure in TMS differs essentially from that obtained in ICF targets. The thermal history of a fuel layer at separation into the condensed and vapor phases is found to depend upon whether the initial gas density is more, less, or equal to the critical value for a given fuel material. The issue on the fuel-layer fabrication in the form of a long-living quasiamorphous layer is considered. A new low-temperature method to homogenize a polycrystalline cryogenic layer has been proposed and examined. The operational temperature was 4.2 K. The time to achieve the complete homogeneity of solid hydrogen was 150 s. No limitation, with respect to the thickness of a cryogenic layer, was found. The critical target is suggested as a new type of an ICF target.

A scheme for the improvement of proton beam quality by the optimized dragging field from the interaction of ultraintense laser pulse with a complex double-layer target is proposed and demonstrated by one-dimensional particle-in-cell (Opic1D) simulations. The complex double-layer target consists of an overdense proton thin foil followed by a mixed hydrocarbon (CH) underdense plasma. Because of the existence of carbon ions, the dragging field in the mixed CH underdense plasma becomes stronger and flatter in the location of the proton beam than that in a pure hydrogen (H) underdense plasma. The optimized dragging field can keep trapping and accelerating protons in the mixed CH underdense target to high quality. Consequently, the energy spread of the proton beam in the mixed CH underdense plasma can be greatly reduced down to 2.6% and average energy of protons can reach to 9 GeV with circularly polarized lasers at intensities 2.74 × 1022 W/cm2.

Spectroscopic study of plasma produced through bombardment of the 1 × 3 mm2 area on the surface of a solid Mg target with Kr+ ions is carried out. Spectral lines of Mg I and Mg II ions were observed in the visible range (200–600 nm). The plasma parameters Ne = 1.4.1017 cm−3 and Te = 0.8 eV are calculated from electron impact broadening of the 4f–3d line of Mg II and from the ratio of intensities for the 4f–3d and 4s–3p lines of Mg II. The ionic composition of the plasma is determined. The detected X-ray emission is shown to be the characteristic emission of the target.

This paper deals with the analysis of growth rate of modulation instability of a laser pulse propagating in a clustered gas. Finite pulse effects are considered to be a perturbation. Growth rates of modulation instability for 100 fs and 80 fs at the centroid as well as at the front and back of the pulses are evaluated and graphically analyzed. It has been shown that with decrease in pulse duration the growth rate of modulation instability increases at the front, back as well as at the centroid of the pulse. It is also shown that the change in growth rate of modulation instability at the front as well as at the back of the pulse in comparison to the centroid of the pulse for 80 fs pulse is less in comparison to that of 100 fs pulse.

A formalism for the analysis of the Rayleigh–Taylor instability in the multi-structured solid or shell targets is presented. The formulation covers both the plane and the curved geometry targets. A generalized eigenvalue equation for the exponential growth rate of the instability is derived along with the necessary boundary conditions. Analytical solutions for the growth rate are presented for some elementary density profiles and a comparative study is made between the plane, cylindrical and spherical targets. The solution for the step function density profile is generalized for any number Nof zones forming an arbitrary density profile. This general formulation is illustrated with the explicit calculations for N = 3 and 4. A qualitative treatment of the effects of the ablative flow is also presented. This study predicts a stabilizing effect of the ablative flow on the growth of the instability. Further, a dynamic analysis of the instability growth rate is presented for a representative inertial confinement fusion spherical solid target driven by the laser beams. This study demonstrates that an approximate analysis of the instability with the time independent initial density profile gives the conservative results for the instability growth rate.

The phenomenon of electric double layers in plasmas as a generalization of ambipolar effects and as an essential time dependent and oscillating phenomenon in the plasma interior, has emerged from studies in laser produced plasmas as well as from similar problems in space plasmas and their laboratory simulation experiments. While these results have been published occasionally in various places including the most prestigious journals and in small topical conferences, there was still a need to enter a more comprehensive presentation and overview into a referred journal.

The paper reports on a method of producing spherical targets with a light ablator layer having a density of 0·2g/cm3 and a thickness 10μm. This method for obtaining polystyrene microballoons and polyethylene microballs works for hemispheres made from plastics and metals with diameters from 600 to 1200 μm and wall thicknesses from 10 to 50 μm. It also provides a way to assemble cascade targets.

The stopping at low (V < Vth) and high (V ≤ Vth) velocity, of N strongly correlated ion debris is investigated for the case of a dense and classical electron target. The considered topologies of cluster projectile charges are taken cubic like, and circular, respectively. A specific emphasis is given to the N-dependence, and also to the topological features of the corresponding enhanced correlated stopping.

The irradiation of cylindrical targets by intense heavy ion beams was studied using a two-dimensional numerical simulation code including radiation effects on the hydrodynamical flow. Solid and hollow Aluminum targets as well as gas tubes are studied for various beam configurations with a view to identifying the characteristic features of the flow and possible observables, especially the emitted radiation from Xenon gas tubes.

The paper presents the results of statistical studies of ion beam generation in different geometry diodes with explosive emission cathode in a mode of self-magnetic insulation. The experiments were carried out using the TEMP-4M pulsed ion beam accelerator during its operation in both unipolar pulse mode (100 ns, 250–300 kV) and bipolar-pulse mode with the first negative (300–600 ns, 100–150 kV) followed by a second positive (120 ns, 250–300 kV) pulse. It is found that the standard deviation of the total energy and energy density of the beam does not exceed 10–11%, while the same shot-to-shot variation in ion current density was found to be 20–30%. The mechanism of the energy density stabilization from pulse to pulse may be associated with the charge exchange between accelerated ions and stationary molecules and formation of accelerated neutrals. We observed a high correlation between the energy density (or total beam energy) and the duration of the first voltage pulse. We performed analysis of Blumlein statistical performance when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. A characteristic feature of Blumlein operation in the double-pulse mode is an excellent reproducibility of breakdown of the preliminary spark gap, the variation in breakdown voltage is <2%. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both bipolar- and unipolar pulse mode is 3–4 times higher than that for the preliminary spark gap. To improve the statistical performance of the main spark gap we used the first voltage pulse at the output of Blumlein to trigger the main spark gap. The new trigatron-type regime of the main spark gap operation showed a better reproducibility of the first pulse duration, with the time jitter not exceeding 10 ns in a set of 50 pulses.

The inertial confinement fusion (ICF) research has remarkably developed in the last 10 years, which enables us to scope the fusion ignition and burn in the near future. Following the recent progress in the ICF, the perspectives of the inertial fusion energy (IFE) are presented. International collaboration is highly expected.

KrF and other short wavelength lasers are ideal candidates for producing hot dense plasmas since the laser energy can be absorbed with high efficiency by classical mechanisms, thereby virtually eliminating anomalous absorption and the production of non-thermal electrons. A high power KrF laser system employing optical beam multiplexing and stimulated Brillouin scattering to produce pulses as short as 1 ns and focused intensities on target of 1011−1014 W/cm2 has been developed for producing such plasmas and studying laser/plasma interaction phenomena. A variety of studies on absorption, transport, ablation, X-ray conversion and stimulated scattering instabilities have been pursued with this ¼ μm laser on single atomic number and multi-layer targets. This paper briefly describes some of the features of the KrF laser system and highlights some of the characteristics of the hot dense plasmas produced.

The contribution of different sorts of secondary particles to the preheating of thermonuclear targets driven by heavy-ion beams is analyzed. Two types of illumination geometry are considered: side-on and face-on locations of the fuel with respect to the ion beam. It is shown that a substantial preheating can be expected from (1) nuclear fission fragments for the face-on fuel position and (2) δ-electrons and low-Z nuclear fragments for the side-on fuel location. All the X-ray and gamma photons of various origin are shown to produce a negligible fuel heating.

Powerful pulse installations are usually used to produce large yields of X-ray radiation. With an increase of the stored energy up to 100 MJ, the costof a single experiment on these installations becomes comparable to the cost of a shot with explosive magnetic generators (EMG), according to expert estimates. The physical scheme of a device with a changeable mass liner forlarge soft X-ray (in the range of 0.3 to 0.5 keV) yields eneration is investigated. The scheme investigated is substantially free from difficulties connected with high precision liners and fast switches for current pulse sharpening.

Utilizing an ultraintense (1016 W cm−2) fs laser, the laser/matter interaction of the tetrahedral CH3I molecule is investigated. A mass spectrum and the angular distributions of fragment ions arising from Coulomb explosion of molecular ions, obtained with linearly polarized light, are presented. The distributions for In+ (n ≤ 7), CHm+ (m ≤ 3), Cp+ (p ≤ 4) and H+ ions are all anisotropic and maximal when the polarization lies along the spectrometer axis. The molecule hence seems to behave as a diatomic, with the fragment ions being ejected along the field direction. Also presented are mass spectra of the isomers 1- and 2-nitropropane, which are explosive species, taken for horizontal and vertical polarizations at both 375 and 750 nm. It is shown that femtosecond laser mass spectrometry (FLMS) can be used to distinguish between these two isomers through their differing dissociation patterns. Isomer identification is important for many different applications and FLMS may provide a means of achieving this for a wide range of molecules.

For the guarantee of the long-distance transport of the bunches of China Initiative Accelerator Driven System (CIADS), a new scheme is proposed that extra magnetic field is used in the accelerator-target coupling section before the windowless target to minimize the self-modulation (SM) mechanism. Particle-in-cell simulations are carried out to study the influence of the solenoidal magnetic field on the self-modulation mechanism when long proton bunches move in the background plasmas. The long proton bunches used in the simulations are similar to these in the linear accelerator of CIADS. It is found that the presence of the solenoidal magnetic field will significantly inhibit the self-modulation process. For the strong magnetic field, the longitudinal separation and transverse focusing of the long bunches disappear. We attribute these phenomena to the reason that the strong solenoidal magnetic field restricts the transverse movement of plasma electrons. Thus, there are not enough electrons around the bunch to compensate the space charge effect. Moreover, without transverse current, the longitudinal pinched effect disappears, and the long bunch can not be separated into small pulses anymore.

Dependence of quasistatic Wakefield and high harmonic generation on the pulse-shape of an ultrashort, intense, few-cycle laser in the reflected radiation from a thin dense plasma layer is investigated. The pulse envelopes considered are Gaussian, Lorentzian, and hyperbolic secant having identical full width at half maximum of intensity. The reflected radiation from the strongly driven surface plasma layer embodies a quasistatic Wakefield, which exists after the main pulse is passed over. A phase modulation is also experienced by the laser light upon reflection from plasma surface motion. As a result harmonics of center carrier frequency of the laser-pulse are generated in the reflected signal. Intensity of the laser harmonics and magnitude of the Wakefield in the reflected radiation are found to depend on the pulse-shape, number of cycles, carrier envelope phase difference, plasma density, angle of incidence, and intensity of the incident pulse.

A brief discussion of the standard theory of line broadening is presented together with an analysis of selected laser-driven implosion experiments. The effect of improved theoretical procedures on experimental analysis is discussed. In particular, we consider the combined effects of ion dynamics and opacity on line profiles used in the analysis of these plasmas. The experiments discussed were performed at the University of Rochester Laboratory for Laser Energetics (LLE). The results presented in this paper illustrate the usefulness of plasma line broadening in diagnosing hot dense plasmas and in understanding fundamental plasma processes.