Time- and space-integrated emission spectra measurements have been performed in plasma produced by 308 nm wavelength XeCl laser radiation (IL = (4–10)·1012 W/cm2, τ = 10 ns) and by 248 nm wavelength KrF laser pulse train radiation (IL = 5·1015 W/cm2, τ = 7 ps, 16 pulses in train) on CF2 plane target. Theoretical modelling of Lyman series and He-like ion resonance series of fluorine and its fit of experimental data show considerable differences in the absorption of laser radiation in the two plasmas.

Two-photon absorption (TPA) of Au-ion irradiated glasses in the femtosecond regime has been analyzed by an open-aperture Z scan technique. Three types of glasses, namely GIL49, BK7, and Glass B were irradiated by using 1700 keV Au+ ion beams. Samples were post-annealed at 600°C for 5 h. Penetration depth and distribution of Au+ ions having 1700 keV energy within glass substrates were estimated by transport of ions in matter (TRIM) simulations. Detailed calculations with full-damage cascades were performed for each sample, taking into account the chemical composition of glass substrates. TRIM results reveal that there is no significant change in ion range, straggling, and ion distribution with the change in the substrate composition. However, Z scan results showed a difference in TPA coefficients for all three glasses. Extent of crosslinking within each of irradiated sample, owing to its chemical composition, may have affected their TPA coefficients.

For the future, we have to develop new sources of energy. These new sources may be based on nuclear fusion with magnetic confinement (as with the ITER experiment) or with a new concept based on inertial confinement. The European community plans to build a facility (HiPER project) which is dedicated to reaching high gain with cryogenic targets, and to test the concepts of target mass production and rep rate shots. The cryogenic system for the 1st phase experiments in HiPER is based on the cryogenic system developed for the French facility Laser MegaJoule (LMJ). The latter must be modified and upgraded for direct drive targets. In particular the target must be protected from the radiation flux from the vacuum vessel by a thermal shroud. In addition, the LMJ system must be equipped with a thermal system to allow layering of the fusion fuel to take place. The new developments concern a leak tightness thermal shroud for direct drive and a fast shroud retractor able to allow the laser shot within few milliseconds.

We survey the present status and potentialities of diagnostics for arbitrary magnetized plasmas of inertial confinement fusion concern. These diagnostics include: Faraday rotation, inverse Faraday effect, Thomson scattering, Stark–Zeeman line broadening as well as proton stopping for any ratio, of the particles plasma frequency to cyclotron frequency. This presentation is timely motivated by recent experiments highlighting laser-produced kilo Teslas and nearly steady magnetic fields in inertial fusion plasmas. Positive synergies due to diagnostics combinations are also addressed.

Volume 23, Number 2, Pages 177–182, 2005

Below is the complete Reference citation for Limpouch et al. (2005).

Limpouch, J., Demchenko, N.N., Gus'kov, S.Yu., Gromov, A.I., M. Kalal, Kasperczuk, A., Kondrashov, V.N., Krousky, E., Masek, K., Pfeifer, M., Pisarczyk, P., Pisarczyk, T., Rohlena, K., Rozanov, V.B., Sinor, M. & J. Ullshmied, J. (2005). Laser interactions with low-density plastic foams. Laser Part. Beams23, 321.

Below is the complete Reference citation for Neumayer et al. (2005).

Neumayer, P., Bock, R., Borneis, S., Brambrink, E., Brand, H., Caird, J., Campbell, E.M., Gaul, E., Goette, S., Haefner, C., Hahn, T., Heuck, H.M., Hoffmann, D.H.H., Javorkova, D., Kluge, H.-J., Kuehl, Th., Kunzer, S., Merz, T., Onkels, E., Perry, M.D., Reemts, D., Roth, M., Samek, S., Schaumann, G., Schrader, F., Seelig, W., Tauschwitz, A., Thiel, R., Ursescu, D., Wiewior, P., Wittrock, U. & Zielbauer, B. (2005). Status of PHELIX laser and first experiments. Laser Part. Beams23, 87–93.

An ion diode, where the insulating magnetic Bθ-field is produced by the diode current itself, has been investigated. Using a novel Thomson-parabola spectrometer that is capable of detecting up to 41 beam traces at a single shot and a carbon activation diagnostic the ion beam has been analyzed. The diode, operating at “KALIF”, delivers ion beams of 750 kA at energies of about 0·7 MeV. The focusing version of the diode shows a focus size of 1 cm2, the beam is neutralized to 98–99%, the proton content is about 60%.

Determining the cryogenic target parameters with high precision calls for the development of a new direction in the area of target characterization based on microtomography methods of data processing. In this report we present our first results in this area.

Kα radiation from low charge chlorine is examined for cold dense plasma diagnostics. A relativistic atomic structure calculation shows that the transition energies of Kα lines are slightly shifted to a higher-energy side according to the degree of M-shell ionization. Total spectral shift from Cl+ Kα lines up to those with a fully stripped M-shell is about 10 eV. With an assumption that collisional-radiative-equilibrium is valid, spectral calculations were carried out for a C2H3Cl-plasma heated by an ion beam, and clear deformation among spectral line-shapes is found in the range of the electron temperatures of ≤~ 30 eV. Contribution to the composite spectra of Kα lines with an excited electron in the outer-shell is also briefly discussed. Cl-Kα lines with M-shell electrons can be expected to give us distinct understandings for energy deposition by an ion beam in cold dense plasma.

The recombination X-ray laser scheme is considered in the case of recombining plasmas produced by laser pulses which are short to such a degree that the condition for inversion in X-ray transitions of the ions is essentially time-dependent. Using an analytic four-level model, applicable for H-like and Li-like ions, we calculate the inversion conditions for the 4→3, 3→2, and 2→l transitions in H-like ions as functions of time. As we have already shown, a drastic change occurs, especially for the 3→2 transition. To achieve inversion, for short times the free-electron density as a function of the temperature Te, Neinv(Te), must be greater than a critical density Nesh (Te), Neinv(Te) > Nesh(Te), whereas for longer times in the quasi-steady state, Neinv(Te) must be smaller than a critical density Neqv(Te), Neinv(Te) < Nequ(Te). We also consider the evolution of the inversion condition in the intermediate time domain. The time duration of the existence of the short-time 3→2 inversion condition–in the time interval from the initial state with unoccupied lower levels to the quasi-steady state—is in the main determined by t α 1/A21; for example, one has t ≈ 730 fs for Na.

In a plasma produced in particular by optical-field ionization, during the initial cascade populating the excited levels, an inversion may be possible in the 2→1 resonance line transition in the transient regime. The inversion in this transition is of interest especially because of the arising possibility to achieve X-ray gain at shorter wavelengths. In the transient case, an inversion occurs for a small time depending on the temperature Te and the density N.

In addition, we discuss generally the time behavior of the population densities (especially of N3) and show that an optimal population density occurs, on the one hand, for very short times (fs region, depending on Z). On the other hand, however, the optimal (ion-)density-temperature relation is determined via a time of the optimal population density required with regard to the experimental conditions.

Theoretical treatments of the stopping power are reviewed and problems necessary to extend these treatments to high temperature and high density materials are discussed. Physically important parameters which govern the stopping power properties are indicated. The average equilibrium charge for a gaseous medium is one of the important parameters in the stopping power and the charge-exchange processes involved are discussed. The effective charge is described in terms of a relation between the average equilibrium charge and the effective charge. The atomic energy levels for high density and high temperature matter are also included in the stopping power formula.

Actual calculations of the stopping power are made for Pb ions passing through the HIBLIC-target. Range profiles are estimated for Xe and U ions in an ionized Al target for temperatures T = 0 to T = 1290 eV using the Brueckner, Senbetu & Metzler (1982) theory based on a dielectric response function. Results are compared with those of Northcliffe & Schilling (1970), Ziegler (1980), and Hubert et al. (1980). In order to include dynamic local-field corrections in the dielectric function, a model is proposed similar to a two component plasma.

A large, high density, high temperature plasma has been produced by using a high power laser with a capillary electrical discharge. The laser beam is synchronized with the discharge to reach the plasma after it emerges several hundred microns from the capillary.

A new technique to achieve smooth laser irradiation profiles on laser fusion targets is evaluated numerically and experimentally. In this technique, smoothing is obtained by using a spectral dispersing optic and a random-phase plate placed in front of a focusing lens employing the broad-bandwidth of KrF lasers. Experimental results and numerical calculations agree well, verifying that this simple optical system is effective for smooth irradiation on targets.

In this paper the results of numerical computations of rippling smoothing basing on the broad-band laser irradiation method for the laser intensity range 1016−1017 W/cm2 and short-pulse (<10 ps) interaction with plasma are described.

The development activity of a new experimental technique for the study of the fast electron transport in high density matter is reported. This new diagnostic tool enables the X-ray 2D imaging of ultrahigh intensity laser plasmas with simultaneous spectral resolution in a very large energy range to be obtained. Results from recent experiments are discussed, in which the electron propagation in multilayer targets was studied by using the Kα. In particular, results highlighting the role of anisotropic Bremsstrahlung are reported, for the sake of the explanation of the capabilities of the new diagnostics. A discussion of a test experiment conceived to extend the technique to a single-shot operation is finally given.

High-power relativistic magnetrons operating in both S-Band and X-Band (4 GHz) and 8·5 GHz) have been developed with a variety of extraction methods. Using a six window radial extraction scheme, the S-Band magnetron produces ∼3·6 GW. The X-Band magnetron produces 0·05 GW with one radial extraction window. Axial extraction from all six vanes produced power in excess of 0·3 GW. Enhanced erosion and gap closure occur in the smaller X-Band resonator.

Chromatin is the complex of deoxyribonucleic acid (DNA) with proteins that exists in eukaryotic cell nuclei. Chromatin was extracted from livers of Wistar rats and subjected to a 248-nm excimer laser radiation, in doses of 0.5–3 MJ/m2. An UV excimer laser Iofan 1701, with 40-mJ dose/pulse and frequency of 30 Hz was used. The radiolysis of chromatin was analyzed by (1) 1H-NMR spectroscopy, (2) steady-state fluorescence, (3) time-resolved fluorescence, and (4) fluorescence resonance energy transfer (FRET) methods. The laser action on chromatin determines bigger values of the transverse relaxation time (T2), which indicates less bound water in the chromatin structure, therefore a more injured one. The chromatin intrinsic fluorescence decreases on laser action, proving the destruction of the chromatin protein structure. By the time-resolved fluorescence we established that the relative contribution of the excited state lifetime of bound ethidium bromide to chromatin DNA diminishes with the laser dose. This denotes single- and double-strand breaks produced in DNA structure. By the FRET method, the energy transfer efficiency and the distance between dansyl chloride and acridine orange coupled at chromatin were determined. The distance increases with laser action. The determination of the chromatin structure modification in an excimer laser field can be of real interest in medical applications.

The differential imaging technique is particularly suitable for the detection of small concentrations of contrasts agents for biological and medical applications in samples using X-ray radiography. In this paper, we present an application of this technique using a laser-plasma soft X-ray source combined with a bent crystal. Using a Fresnel plate as a test object, we were able to obtain spatial resolutions of the order of a few tens of microns. The use of our configuration to perform differential imaging of a test-sample at the L2 edge of Br at 1,596 eV is finally demonstrated.

This article describes the design of a laser setup excited by 3He(n, p)3H reaction products and intended for investigations of the laser characteristics of 3He mixtures with metal vapors or other gases at temperatures up to 800˚C. This setup could also be used to study the effect of the medium heating on the characteristics of nuclear-pumped gas lasers.

The effect of surface deformations on laser absorption and transport in overdense plasma targets is investigated with 2D Vlasov simulations. Fractional absorption increases strongly with the deformation depth and scales weakly with density or intensity. Fast electrons generated in the skin layer have high tangential velocity directed toward the deformation center. In the case of a single, smooth deformation, they may be collimated by magnetic fields into a single jet which penetrates deeply into the plasma. Small-scale surface corrugations are able to destroy the collimation of a single jet leading to multiple jets or diffuse electron sprays.

Results are presented for a theoretical model, known as the ion model (IM), recently elaborated to calculate the radiative opacity of a hot dense plasma. The density functional theory is used to obtain the general set of self-consistent field equations that describe the state of the whole ensemble of plasma atoms and ions. Theoretical features of the Hartree–Fock–Slater model, the detail configuration account, and the IM are considered. The IM is used for optimal selections of compound chemical compositions for laser and heavy ion target designs.