Inertial fusion energy (IFE) research indicates that the energy generation by means of cryogenic fuel target compression requires that targets must be injected to the target chamber center at a rate of about 6 Hz. This requirement can be fulfilled only if the targets are free-standing. The most interesting results concerning the activity of the Lebedev Physical Institute in the area of free-standing targets (FST) fabrication, characterization and delivery are presented.

A pulsed power generator by inductive voltage adder, versatile inductive voltage adder (VIVA-I), which features a high average potential gradient (2.5 MV/m), was designed and is currently in operation,. It was designed to produce an output pulse of 4 MV/60 ns by adding 2 MV pulses in two-stages of induction cells, where amorphous cores are installed. As a pulse forming line, we used a Blumlein line with the switching reversed, where cores are automatically biased due to the presence of prepulse. Good reproducibility was obtained even in the absence of the reset pulse. Within ∼40% of full charge voltage, pulsed power characteristics of Marx generator, pulse forming line (PFL), transmission line (TL), and induction cells were tested for three types of loads; open-circuit, dummy load of liquid (CuSO4) resistor, and electron beam diode. In the open-circuit test, ∼2.0 MV of output voltage was obtained with good reproducibility. Dependences of output voltage on diode impedances were evaluated by using various dummy loads, and the results were found as expected. An electron-beam diode was operated successfully, and ∼18 kA of beam current was obtained at the diode voltage of ∼1 MV.

A new kind of high power tunable microwave radiation source is studied theoretically and experimentally. Following the previous works presented by Dorranian et al. (2003, 2004) in this paper more details about the radiation is presented. The theory of the radiation is developed to calculate the radiation spatial distribution, and more discussion on radiation behavior and characteristics is done. In this radiation scheme, a part of large amplitude electrostatic plasma wake, generated by an intense laser pulse or a relativistic electron bunch, are converted to electromagnetic oscillations by applying a modest dc magnetic field perpendicular to the wake propagation direction. A direct one-dimensional (1D) analytic procedure for calculating the magnetized plasma wake equations is developed and the properties of the radiation are investigated theoretically. The effects of the ramp plasma-vacuum boundary in coupling the radiation from plasma to vacuum is noticed and solved by employing a gas jet flow to generate a sharp boundary. Wakefield is excited by TW-100 fs Ti:sapphire laser beam operating at 800 nm wavelength. The neutral density of gas jet flow is measured with a Mach-Zehnder interferometer. The frequency of the emitted radiation with the pulse width of 200 ps (detection limitation) is in the millimeter wave range. Radiation is polarized perpendicularly to the dc magnetic field lines and propagates in the forward direction and normal direction with respect to the laser pulse propagation direction, both perpendiculars to the direction of the applied magnetic field. Intensity of the radiation in different plasma densities and different magnetic field strengths has been observed.

Physics of Inertial Fusion: Beam Plasma Interaction, Hydrodynamics, Hot Dense Matter, Stafano Atzeni and Jürgen Meyer-ter-Vehn, Clarendon Press, 2004, 458 pages, ISBN: 0198562640

This book has several remarkable highlights summarized on laser produced plasmas and particle beam driven fusion energy. In contrast to the usual books, the nuclear fusion reactions are presented with very detailed experience, including pycnonuclear reactions, spin polarization, and mentioning the 25 orders of magnitude less probable weak force pp-reaction than DT. There is a rather comprehensive collection of the conditions of confinement, spherical implosion, ignition burn, and gain. Hydrodynamics is based on a one fluid model, not Schlüter's space charge quasi-neutral two-fluid model nor the genuine two-fluid treatment. Hohlraum targets are covered and the fast ignition (FI) contains the forte of the authors' own achievements though the entire problems shown experimentally or theoretically (Mulser et al., 2004) are not discussed nor the new aspects on FI known before finishing the book (Hora, 2004). The 36 pages for the entire physics of (laser- and particle-) beam-target interaction are used to sketch at least the most important aspects.

(This article appeared in Volume 23, Number 3, Pages 297–302, 2005)

Author Index