Historical research guide · 0919 · 2005
TW-ps laser driven blocks for light ion beam fusion in solid density DT
Heinrich Hora · Frederick Osman · Y. Cang · Jan Badziak · S. Jablonski · S. Glowacz · George H. Miley · Peter X. Hammerling · Jerzy Wolowski · Karel Jungwirth · Karel Rohlena · Xiao-ping He · Hansheng Peng · JingJuan Zhang
In one minute
Fire an intense laser at a solid target and the usual result is a mess: the beam bores into the plasma cloud it has already made, breaks up and self-focuses, and no simple theory describes it. Heinrich Hora and thirteen colleagues from Australia, Poland, the United States, the Czech Republic and China report the exception. Use a pulse of about a picosecond or shorter, above a terawatt, and clean enough that no plasma cloud forms first, and the light stops behaving like a drill and starts behaving like a flat wave pushing on the target’s skin — the very thin surface layer light can penetrate. The push drives two slabs of plasma apart, one flying back at the laser and one driven into the target, and the inward slab carries an ion current density above ten billion amperes per square centimetre. Hora’s group say they have that block both in theory and in the laboratory, and propose it as the spark for fusion in solid-density deuterium-tritium, and as a new class of ion source for accelerators.
Connection
Chapter 12 is about lowering the price of admission to fusion, and this is the cleanest statement of the alternative route: do not compress the fuel a thousandfold, drive a dense directed block of ions straight into it. Chapter 9 needs the mechanism by which a laser makes a self-organised, directed slab of plasma at all, and the skin-layer picture is where that mechanism is at its simplest.
From the source
The observations of plane-wave-geometry interaction within the skin depth of a laser-irradiated target — the thin surface layer the light actually penetrates — are very unique exceptions from the broad stream of the usual experiments of laser-plasma interaction, and the paper sets out why.Abstract, sentence 1; Proceedings of SPIE 5627, page 51
For laser pulses of about a picosecond or shorter and powers above a terawatt, this regime permits a much more simplified description by plane-wave interaction theory and correspondingly simpler computation, in contrast to the usual cases where relativistic self-focusing dominates.Abstract, sentence 2
The generation of highly directed plasma blocks with ion current densities above ten billion amperes per square centimetre has been established both theoretically and experimentally, with blocks moving against the laser light and into the target.Abstract, sentence 3
The application proposed for those blocks is fusion: a light ion beam driven into solid-density deuterium-tritium, which is a different architecture from the spherical compression of a fuel capsule that laser fusion normally requires.Title; Abstract, final sentence
The same skin-layer block is offered as a completely new improvement of ion sources for the next generation of accelerators, because the current density it delivers is orders of magnitude above what conventional sources reach.Abstract, final sentence
What to watch: the measurement that decides this architecture is whether a block driven into uncompressed solid fuel actually ignites it and returns more energy than the pulse delivered. Hora carried the same block-ignition idea forward from deuterium-tritium to proton-boron-11, where the products are charged particles rather than neutrons, and that later line is where the experiments now sit.Title and abstract, read against Hora and colleagues, Road map to clean energy using laser beam ignition of boron-hydrogen fusion
The way in
https://doi.org/10.1117/12.570492How to cite it
Heinrich Hora, Frederick Osman, Y. Cang, Jan Badziak, S. Jablonski, S. Glowacz, George H. Miley, Peter X. Hammerling, Jerzy Wolowski, Karel Jungwirth, Karel Rohlena, Xiao-ping He, Hansheng Peng, JingJuan Zhang (2005) TW-ps laser driven blocks for light ion beam fusion in solid density DT doi:10.1117/12.570492