Direct-drive laser fusion has one potential advantage over all other approaches to fusion energy. The hot plasma can be kept near or below the various plasma instability thresholds, if one uses purely spherical targets, with a short wavelength, large bandwidth and optically smoothed excimer laser. Instead of trying to manage laser–plasma instabilities, one avoids them. There is a path to complete the evaluation and development of this energy option, with moderate costs and a moderate time scale. Glass lasers, with their longer wavelength and narrower bandwidth, are no longer useful to evaluate fusion targets.

Two transmission curved crystal spectrometers are designed to measure the hard x-ray emission in the laser fusion experiment of Compton radiography of implosion target on ShenGuang-III laser facility in China. Cylindrically curved ${\it\alpha}$-quartz (10–11) crystals with curvature radii of 150 and 300 mm are used to cover spectral ranges of 10–56 and 17–100 keV, respectively. The distance between the crystal and the x-ray source can be changed over a broad distance from 200 to 1500 mm. The optical design, including the integral reflectivity of the curved crystal, the sensitivity, and the spectral resolution of the spectrometers, is discussed. We also provide mechanic design details and experimental results using a Mo anode x-ray source. High-quality spectra were obtained. We confirmed that the spectral resolution can be improved by increasing the working distance, which is the distance between the recording medium and the Rowland circle.

The effect of laser intensity on characteristics of the plasma ablated from a low-Z (CH) planar target irradiated by a 250 ps, 0.438 µm laser pulse with the intensity of up to 1016 W/cm2 as well as on parameters of the laser-driven shock generated in the target for various scale-lengths of preformed plasma was investigated at the kilojoule Prague Asterix Laser System (PALS) laser facility. Characteristics of the plasma were measured with the use of 3-frame interferometry, ion diagnostics, an X-ray spectrometer, and Kα imaging. Parameters of the shock generated in a Cl doped CH target by the intense 3ω laser pulse were inferred by numerical hydrodynamic simulations from the measurements of craters produced by the shock in the massive Cu target behind the CH layer. It was found that the pressure of the shock generated in the plastic layer is relatively weakly influenced by the preplasma (the pressure drop due to the preplasma presence is ~10–20%) and at the pulse intensity of ~1016 W/cm2 the maximum pressure reaches ~80–90 Mbar. However, an increase in pressure of the shock with the laser intensity is slower than predicted by theory for a planar shock and the maximum pressure achieved in the experiment is by a factor of ~2 lower than predicted by the theory. Both at the preplasma absence and presence, the laser-to-hot electrons energy conversion efficiency is small, ~1% or below, and the influence of hot electrons on the generated shock is expected to be weak.

The new possibility of side-on laser ignition of p-11B with negligible radioactivity encouraged to study the fusion of solid state p-7Li fuel that again turns out to be only about 10 times more difficult than the side-on ignition of solid deuterium-tritium using petawatt-picosecond laser pulses at anomalous interaction conditions if very high contrast ratio. Updated cross sections of the nuclear reaction are included.

The anomaly at laser plasma interaction at laser pulses of TW to PW power and ps duration led to a very unique generation of quasi-neutral plasma blocks by a skin layer interaction avoiding the relativistic self-focusing. This is in contrast to numerous usual experiments. The plasma blocks have ion current densities above 1011 A/cm2 and may be used for a fast ignition scheme with comparably low compression of the deuterium tritium (DT) fuel. The difficulty is that a very high energy flux density E* of the ions is necessary according to the hydrodynamic theory (Bobin, 1971, 1974; Chu, 1972). This theory did not include the later discovered collective effect for the stopping power of the alpha particles. One problem is being discussed, whether the Bethe-Bloch binary collision theory or the collective collision theory of Gabor has to be applied. The inclusion of the collective effect results in a reduction of the threshold value of E* for ignition by a factor of about fife.

A feasibility of a new approach of laser fusion in plasma without implosion has been proposed and discussed using an intense laser. The cross-section of nuclear reaction is increased by the enhanced penetrability of nuclei through the Coulomb barrier. In this approach, an intense laser field of more than 10 EW was required to distort the Coulomb barrier to obtain enough penetrability. In the new improved model, a nuclear potential with meson attractive force is considered. Enhancement is observed for penetrability around EW or less power laser due to a nuclear potential. Energy gain even with Deuterium-Deuterium reaction can be obtained on this scheme in Deuterium plasma with energetic nucleon theoretically.

An approach to an alternative laser fusion in a magnetic field with an intense laser of exa watt level will be discussed. Such a strong field in an exa watt laser will induce enhanced nuclear tunneling through the propagation in plasma. This causes an enhanced nuclear reaction for fusion. We discuss the possibilities to apply this to nuclear fusion energy and to obtain break even in a 100 kJ laser.

Laser fusion requires very high energy/power output with high repetition rate over 10 Hz, which is very difficult with the current laser technologies. However, the recent research work on the phase controlling of the stimulated Brillouin scattering wave enables the realization of this kind of laser fusion driver. The recent progress of controlling the phase has been successfully demonstrated by the self-generated density modulation method proposed by one of the authors (Kong). Nevertheless, it showed a long-term fluctuation of the phase because of the long-term fluctuation of the density of the SBS medium due to the thermal fluctuation. This long-term thermal fluctuation is inevitable a fact in nature. The authors used a specially designed stabilizing system for the phase controlling system, which has the PZT control of the mirror for phase controlling SBS-PCM (the so-called feedback mirror). This system stabilizes the phase controlling system very well for more than 1 h. This technique will help the laser fusion driver to be realized sooner than expected. In addition, we propose a similar scheme to be applied to the ultra-fast pulse laser system, which must operate at high repetition rate for the laser fusion energy power plant.

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.

Inertial confinement fusion (ICF) has developed remarkably in the last 30 years. In the 21st century, we can expect fusion energy for civilian use. After the cold war era, the value of ICF has shifted from defense demands to peaceful applications. The megajoule laser systems are under construction expecting the development of spark ignition. However there are many problems to solve in science and technology. One alternative way is to use a petawatt short-pulse laser aiming for fast ignition. On the way to the final goal, we would like to contribute for various applications of high power lasers such as laboratory astrophysics, X-ray lasers, laser-induced lightning as well as laser processing.