Tomographic reconstruction of the runaway distribution function in TCV using multispectral synchrotron images

Abstract

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Resonant interaction between runaway electrons and the toroidal magnetic field ripple in TCV

“…with rest mass m e , speed of light c, magnetic field ripple mode amplitudes δB nm /B, a resonance width function H nm (p ∥ ) and parallel RE velocity v ∥ . The pitch angle diffusion term, added to the kinetic equation ( 1), is given by: (7) For the width function H nm we assume a Gaussian shape…”

“…RE sensitive diagnostics on present-day tokamaks can be used to validate physics models of their velocity distribution and generation. Filtered camera imaging [4] of visible light synchrotron radiation observed in Tokamak à Configuration Variable (TCV) [5] was recently used to reconstruct the part of the RE distribution dominating the synchrotron emission in the visible-light [6,7]. The inferred ratio between RE momenta perpendicular (p ⊥ ) and parallel (p ∥ ) to the magnetic field B, also described by the pitch angle θ p = arctan(p ⊥ /p ∥ ), was found inconsistent with a kinetic model describing RE electric field acceleration and plasma collisions [6].…”

Overview of the TCV tokamak experimental programme

“…Further experiments aim at understanding and controlling runaway electrons (REs), whether created during start-up or by disruptions, as they can cause severe damage in larger devices Filtered imaging for multiple wavelength ranges, avoiding in particular contributions from strong line radiation using TCV's MULTICAM diagnostic, provided the first measurements of synchrotron radiation emitted by an RE beam on TCV and even allowed the detection of pre-disruption seed distributions, figure 13(a), [78]. The versatility of TCV and its control system allowed the beam to be vertically displaced, altering the diagnostic viewing angle, and thereby test the synthetic synchrotron diagnostic SOFT, figure 13(b).…”

Full conversion from ohmic to runaway electron driven current via massive gas injection in the TCV tokamak

“…The post-disruption RE beam vertical position sometimes requires adjustment during the I RE decay. In addition, displacing the RE beam vertically can optimize diagnostic coverage and/or provide a scan of plasma profiles [25,26].…”

“…The tokamak à configuration variable (TCV) [19] is contributing to this effort [20][21][22][23][24][25][26]. With extended shaping capabilities, advanced real-time plasma control, a proven ability to sustain very low density discharges, and a wide set of diagnostics investigating fast electron physics, TCV is particularly well suited for RE experimental studies.…”