PHYSICS: Fast Track for Fusion

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Science  01 Dec 2006:
Vol. 314, Issue 5804, pp. 1357b
DOI: 10.1126/science.314.5804.1357b

The search for controlled nuclear fusion for energy production has been hindered by substantial engineering and fundamental physical challenges. One approach has been to confine a hot plasma with magnetic fields in a device called a Tokamak and then to heat the plasma until nuclear reactions become self-sustaining. As the plasma is heated, however, the highest-velocity ions can drive wave motions and instabilities that disrupt its integrity. Worse yet, the fast ions can escape with their energy rather than contributing to the heating process. Bindslev et al. report a diagnostic technique in which beams of electromagnetic waves at frequencies of ∼110 GHz are scattered off the ions in the TEXTOR (Tokamak Experiment for Technology-Oriented Research) reactor in Germany. The energy spectrum of the scattered photons from this collective Thomson scattering process reveals the velocity distribution of the fast ions. By acquiring spectra at different times during the heating of the plasma, the authors can uncover the evolution of the fast ion dynamics. Diagnostic tools such as this are expected to be especially important when ITER (the International Thermonuclear Experimental Reactor) commences operation in 2016. — DV

Phys. Rev. Lett. 97, 205005 (2006).

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