Reviewers Comments on the 5th Symposium and the Status of Fusion Research 2003

Better to understand the status of fusion research in the year 2003 we will first put the research in its historical context. Fusion power research, now beginning its sixth decade of continuous effort, is unique in the field of scientific research. Unique in its mixture of pure and applied research, unique in its long-term goal and its promise for the future, and unique in the degree that it has been guided and constrained by national and international governmental policy. Though fusion research's goal has from the start been precisely defined, namely, to obtain a net release of energy from controlled nuclear fusion reactions between light isotopes (in particular those of hydrogen and helium) the difficulty of the problem has spawned in the past a very wide variety of approaches to the problem. Some of these approaches have had massive international support for decades, some have been pursued only at a ''shoestring'' level by dedicated groups in small research laboratories or universities. In discussing the historical and present status of fusion research the implications of there being two distinctly different approaches to achieving net fusion power should be pointed out. The first, and oldest, approach is the use of strong magneticmore » fields to confine the heated fuel, in the form of a plasma and at a density typically four or five orders of magnitude smaller than the density of the atmosphere. In steady state this fusion fuel density is still sufficient to release fusion energy at the rate of many megawatts per cubic meter. The plasma confinement times required for net energy release in this regime are long--typically a second or more, representing an extremely difficult scientific challenge --witness the five decades of research in magnetic fusion, still without having reaching that goal. The second, more recently initiated approach, is of course the ''inertial'' approach. As its name implies, the ''confinement'' problem is solved ''inertially,'' that is by compressing and heating a tiny pellet of frozen fusion fuel in nanoseconds, such that before disassembly the pellet fuses and releases its energy as a micro-explosion. The first, and most thoroughly investigated means to create this compression and heating is to use multiple laser beams, with total energies of megajoules, focused down to impinge uniformly on the pellet target. To illustrate the extreme difference between the usual magnetic confinement regime at that of inertial fusion, there are twenty orders of magnitude in fusion power density (ten orders of magnitude in plasma density) between the two regimes. In principle fusion power systems could operate at any density between these extremes, if means were to be found to exploit this possibility.« less