A geometric approach is used to find the threshold energies for ion orbit loss in experimental tokamak geometry, like that of ASDEX Upgrade. The effects of any pre-existing radial electric field are maintained as they nontrivially affect the calculations. The associated velocity-space loss hole is investigated using equilibria and profiles from ASDEX Upgrade discharges 30628, in the L-mode just before the L-H transition and in the resultant H-mode, and 31533, an H-mode shot with a comparably high ion temperature. We use a novel technique to calculate the shift of the passing-trapped boundary and see that the experimental radial electric field allows for upwardly bounded regions (UBRs) of the loss hole, which are now studied in detail. We further develop a new loss-hole-shape sensitive method to treat the steady-state ion orbit losses by considering relaxation processes along the border of the loss cone. Typical characteristic times of the steady-state losses in the pedestal region of an H-mode are found to be between 1 and 10 ms. The UBRs significantly enhance the steady-state losses in two ways: these velocity-space loss regions reach further into thermally accessible regions and the extensions are shaped such that they have the ability to refill under both diffusive and slowing down relaxation processes.

Brzozowski, R., Jenko, F., Bilato, R., Cavedon, M. (2019). A geometric model of ion orbit loss under the influence of a radial electric field. PHYSICS OF PLASMAS, 26(4) [10.1063/1.5075613].

A geometric model of ion orbit loss under the influence of a radial electric field

Cavedon M.
2019

Abstract

A geometric approach is used to find the threshold energies for ion orbit loss in experimental tokamak geometry, like that of ASDEX Upgrade. The effects of any pre-existing radial electric field are maintained as they nontrivially affect the calculations. The associated velocity-space loss hole is investigated using equilibria and profiles from ASDEX Upgrade discharges 30628, in the L-mode just before the L-H transition and in the resultant H-mode, and 31533, an H-mode shot with a comparably high ion temperature. We use a novel technique to calculate the shift of the passing-trapped boundary and see that the experimental radial electric field allows for upwardly bounded regions (UBRs) of the loss hole, which are now studied in detail. We further develop a new loss-hole-shape sensitive method to treat the steady-state ion orbit losses by considering relaxation processes along the border of the loss cone. Typical characteristic times of the steady-state losses in the pedestal region of an H-mode are found to be between 1 and 10 ms. The UBRs significantly enhance the steady-state losses in two ways: these velocity-space loss regions reach further into thermally accessible regions and the extensions are shaped such that they have the ability to refill under both diffusive and slowing down relaxation processes.
Articolo in rivista - Articolo scientifico
plasma;
English
Brzozowski, R., Jenko, F., Bilato, R., Cavedon, M. (2019). A geometric model of ion orbit loss under the influence of a radial electric field. PHYSICS OF PLASMAS, 26(4) [10.1063/1.5075613].
Brzozowski, R; Jenko, F; Bilato, R; Cavedon, M
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/354973
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