When an extremely high pressure gas is irradiated by an intense laser light, a dense plasma produced at the focal spot moves towards the focusing lens with a high velocity. Making use of this phenomenon, a new plasma-bridged gap switch is proposed and its switching characteristics is experimentally examined. From the experiments, it is confirmed that the switching time is almost constant with the applied voltage only when the focal spot is just on the positive electrode, indicating that the bridging of gap is caused by the laser light.

Lithography techniques hold the key to achieving ultra large-scale integration (ULSI) and they have been a major research subject. For fabrication of ULSI devices, a quarter micron or smaller pattern delineation with nanometer scale accuracy is required. Various techniques using electron, ion and photon beams have been investigated to fulfill these requirements. The present paper discusses the characteristics of several key lithography techniques and their limitations.

Strong ionization in metal vapors is known to be very readily produced by a variety of pulsed and CW lasers. Particularly well known is ‘resonance’ ionization by pulsed or CW dye lasers operated at the atomic resonance lines (e.g. Na 3s → 3p). We also have experimental results for two other forms of ionization: ‘quasiresonant’ ionization using a CW dye laser (e.g. at the Na 3p → 4d transitions), and ‘two-photon resonance’ ionization using a pulsed dye laser (e.g. at the Na 3s → 4d two-photon resonances). Both new forms are visually characterized by bright ‘white sparks’ and correspond to reasonably high electron densities of ∼1014−1015 cm3 and low electron temperatures of ∼0·1−0·2 eV. The ‘quasiresonant’ ionization is remarkable in that it occurs even with a very low power 1 mW focused CW laser in 10 torr of Na. A variety of interesting atomic and molecular spectroscopic features have been observed and analyzed.

Preliminary experimental results are shown on the production of plasmas by low frequency helicon waves. At constant rf frequency and power, the results show a maximum in density as the dc magnetic field is varied. The measurements confirm the theoretical expectation that the plasma is ionized by Landau damping of the radiofrequency waves.

Powerful lasers have the potential to be used for power sources of the high energy particle accelerators. However, we have to convert the transverse wave into a longitudinal one which can trap the charged particles in the wave trough to accelerate them. In order to obtain a high field-gradient in an accelerator, several new concepts have been proposed. One of them is a beat wave accelerator (BWA) which uses a nonlinear optical mixing of two laser beams. Another concept is a Cross Field Acceleration (or a Vp × B acceleration) scheme, in which the trapped particles in the wave trough are accelerated along the wavefront and across the static magnetic field applied externally. An overview is presented including some new results.

An effective potential and an associated electron density in a partially ionized high-Z ion are evaluated within the framework of the Thomas–Fermi–Dirac–Weizsäcker statistical model of atoms. The results are then injected as an initial input into the one-electron Schrödinger equation, a procedure based on the density functional theory. The self-consistency between the two approaches is examined. For a partially ionized ion at zero and finite temperatures, a number of bound electrons is counted by a sum over the principal quantum number, which diverges due to the contribution from shallow bound (Rydberg) levels. A truncation of this sum is devised by application of the Planck–Larkin scheme to the Fermi distribution

The laser ablated plasma flow and subsequent plasma density profile in steep plasma temperature gradient in spherical geometry are studied. Using local flux-limited model of heat flow the effect of flux-inhibition on the hydrodynamics of plasma ablation zone is investigated. The radial variation of thermal flux through local flux-limited model with recently accepted numerical range of flux-limit ≈ 10% of the free streaming is in close agreement with Spitzer's classical thermal conduction reduced by about an order of magnitude which may be attributed to the presence of megagauss level self-generated magnetic fields as predicted earlier to interpret experimental observations on X-rays emission spectra.

Two complementary models invoking ion heating are presented which, together with pump depletion, quantitatively account for the principal observations (reflectivity, spectral shape, saturation) of stimulated Brillouin scattering (SBS) in a CO2 laser/plasma interaction experiment. A simple energy balance model, which incorporates ion heating and includes a consistent calculation of ion wave damping, is applicable for steady state convective growth of the ion waves (long interaction times). A more refined model, which includes a calculation of the trapped ion fraction (along with heating), is applicable for SBS in a transient regime. Strong ion wave damping has been consistently observed in both cases in our high intensity CO2 laser/plasma scattering experiments. A variety of measurements have been made to investigate the basic features of SBS and associated density fluctuations for both long pulse (40 ns) and short pulse (2 ns) CO2 laser irradiation. Measured parameters reported here include plasma density, temperature, density scalelength, SBS reflectivity, and spectral characteristics. Together with previous measurements of density fluctuations (amplitude, wavenumber spectra, spatial and temporal information), the observed behavior confirms that Brillouin scattering is dominated by strong ion trapping, heating and ion wave damping for the laser/plasma parameters prevailing in these experiments.

We describe the operation of a repetitive semiconductor opening switch in conjunction with inductive energy storage systems. Different materials and switch configurations are examined. A new method of generating square pulses of nanosecond duration is implemented. It utilizes the opening switch and a current charged transmission line.

Refractive smoothing of weak non-uniformities in the illumination of laser targets is analyzed, assuming absorption at the critical density and restricting conduction to a thin layer, and using results from thermal smoothing, which is uncoupled from the refraction. Magnetic effects are included. Non-uniformity wavelengths comparable to the thickness of the conduction layer are considered; efficient smoothing exists at both short and long wavelengths in this range. Thermal focusing could make the ablated plasma unstable.

Ionospheric acceleration of high energy particles by a short wavelength microwave pulse is discussed. The intense electromagnetic waves in an ionospheric (F2) or magnetospheric plasma can be self-trapped above a threshold power. The self-binding property and the consequent self-induced transparency of the triple soliton structure of two electromagnetic waves and a plasma wave allow the propagation of an intense electromagnetic pulse without the severe and wasteful distortion that accompanies low power pulse propagation. The effects of magnetospheric fluctuations on the particle beam transport are considered. The fluctuation-induced transport seems to be within the margin of tolerance for useful beam transport. Orbits of negatively charged particles are stable. While synchrotron radiation loss for electrons is prohibitive, that of muons and antiprotons is negligible. A corresponding terrestrial application is also suggested.