Runaway electrons in a tokamak: A free-electron maser
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.
Bibliographic Reference: Article: Physics Review E, Vol. 55 (1997) No. 4, pp. 4608-4616
Record Number: 199710971 / Last updated on: 1997-08-14
Original language: en
Available languages: en