Diagnostics for experimental thermonuclear fusion reactors

The book Diagnostics for experimental thermonuclear reactors gathers together the papers presented at the Workshop on Diagnostics for ITER organized by the International School of Plasma Physics in Varenna, Italy, in August 1995. The authors had clearly done an enormous amount of work in preparation for the Workshop, and this book will serve as an excellent tutorial for anyone involved in diagnostic design for any future fusion device, let alone one with the complex design issues of ITER. This book has three very important strengths. The first is in the focus in meeting requirements for the measurements of plasma parameters set down by the ITER organization. These measurements appear formidable, but the standards of physics studies and code development on the current devices require such localization and accuracy. In the descriptions of the diagnostic equipment, there is little detail about the physics of the measurement of the specific techniques presented, but a great deal about the practical implementation of such techniques. For example, there is considerable discussion about microwave reflectometry for measurement of electron density profiles, a rapidly evolving technique but one which requires special consideration in the flattish profiles and high electron temperatures anticipated for ITER. Another case is spectroscopy where measurements in the core of such parameters as the density of the helium ash, left in the core of the plasma after the alpha-particles have given up their energy to the surrounding plasma, for which a seed beam is essential. There is extensive treatment of neutron spectroscopic techniques to benefit from the production of copious neutrons for new and better plasma measurement. The second strength is in its summation of the state of the art of diagnostics on the currently operating devices. It is seldom possible to find summarized so conveniently the experience of some of the most able diagnostic physicists in the world. While some of the measurements are explicitly described, elsewhere the quality of measurement is implicit and the publications making use of those measurements are referenced. There is significant information about the capability of magnetic diagnostics for providing plasma control capability. The section on diagnostics of the divertor plasmas brings together well the measurements needed for this very important region. It is a very rapidly growing area of measurement, and very important in the near term for qualifying computer code predictions of the behaviour of divertor plasmas. Spectroscopy and total radiation in the divertor are very well treated and it is clear that vacuum ultraviolet measurement will be an important tool. The third strength is in its comprehensiveness, covering the whole range of diagnostics from the most sophisticated newly developed techniques down to Langmuir probes and pressure gauges (though the reader will find that these last two become fairly sophisticated in an ITER-like environment). There is good coverage of the measurement of the confined alpha particles using collective scattering, not yet fully demonstrated on an operating tokamak, and also discussion of the use of laser-induced fluorescence in divertor measurements, particularly of the neutral species, which could be very important with a highly radiating divertor plasma. As in any such collection of papers the referencing and figures are not always of the highest quality, but nevertheless, the overall presentation is surprisingly good. The book will be extremely valuable for graduate students and for anyone looking for a perspective on the best possible ways to measure the plasmas in high temperature magnetic fusion devices, including stellarators as shown in two of the closing papers on the diagnostics for the W7-X and LHD stellarators, both now under construction.