Loss of relativistic electrons when magnetic surfaces are broken
Relativistic runaway electrons in ITER could be confined in a broad annulus of stochastic magnetic field lines bounded by an annulus of magnetic surfaces. The outer confining annulus can be broken by either an evolution of the magnetic field or by the drift of the plasma into the walls. Both possibilities are studied, and in both cases, the relativistic electrons in the stochastic region are lost to the walls in a short pulse of length $$\tau$$ℓ along a narrow tube, which carries a flux fψst, where f ~ 10-3 and ψst is the toroidal flux in stochastic annulus. Both $$\tau$$ℓ and f are determined by two parameters: the time it takes for a toroidal transit of a relativistic electron $$\tau$$t = 2πR/c, which is approximately 0.1 μs in ITER, and the evolution time $$\tau$$ev, which is of order 100 ms in most conditions of interest for ITER. The concept of turnstiles in Hamiltonian mechanics is then used to obtain the relation between $$\tau$$ℓ and f and $$\tau$$t and $$\tau$$ev. The turnstile concept is also important in the theory of divertors for stellarators.
- Research Organization:
- Columbia Univ., New York, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Contributing Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
- Grant/Contract Number:
- FG02-03ER54696; FG02-04ER54793; AC02-05CH11231
- OSTI ID:
- 1465170
- Alternate ID(s):
- OSTI ID: 1330119
- Journal Information:
- Physics of Plasmas, Vol. 23, Issue 10; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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