Runaway electrons in a tokamak: A free-electron maser
- Max-Planck-Institut fuer Plasmaphysik, Euratom-IPP Association, D-85748 Garching (Germany)
In ohmic divertor plasma discharges of the ASDEX upgrade tokamak containing a small population of runaway electrons, fluctuating emission in the microwave region with a very narrow bandwidth is observed. The radiation can be explained by relativistic runaway electrons, which are captured in a ripple resonance of the tokamak and are thus made monoenergetic enough that they can undergo the collective instability of a free-electron maser. From the frequency of the maser, the energy of the runaway electrons, and from the linewidth and energy per radiation pulse, the particle density of the runaway electrons is determined locally. Observing this maser radiation is thus a different diagnostic for runaway electrons in tokamaks. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 491642
- Journal Information:
- Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 55, Issue 4; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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