Core plasma ion cyclotron emission driven by fusion-born ions

Abstract

Ion cyclotron emission (ICE) signals whose spectral peaks match the fundamental cyclotron frequencies of hydrogen and tritium in the plasma core, near the magnetic axis, are observed in ASDEX Upgrade deuterium plasmas. In these cases the only source of energetic (1 MeV) hydrogen and tritium ions is D-D fusion reactions between neutral beam injected deuterium ions and bulk deuterium ions. Hydrogen-matched core ICE is observed in a wide variety of ASDEX Upgrade plasmas, while tritium-matched core ICE is (so far) only observed in socalled H-mode density limit plasmas. In all cases ICE signals are detected directly using B-dot probes, which provide information on the emission frequency, the amplitude, and, in principle, the parallel wavenumber values. These observations support the idea of using an ICE-based diagnostic to monitor the presence of fusion-born alpha particles in tritium-burning fusion plasmas on devices such as JET, ITER, CFETR, or DEMO.

First observation and interpretation of spontaneous collective radiation from fusion-born ions in a stellarator plasma

“…and more recently to ICE emitted from the core of ASDEX-U [37,38,39,40]. In most contemporary ICE measurements, as in the early ICE observations in JET [10] and TFTR [41], the experimentally observed ICE spectral peaks are close to the cyclotron frequency of the energetic ions in the emitting region in the outer midplane plasma.…”

“…There may be multiple candidate energetic ion species, both fusionborn and NBI, either sub-or super-Alfvénic, furthermore ICE is detected from the core plasma [38,39], as well as from its traditional locus near the outer midplane edge [13,64]. This disambiguation is addressed in relation to contemporary ICE observations in the ASDEX-Upgrade tokamak [37,38,39,40,61]. Distinction between NBI drive and fusion-ion drive of ICE in early JET deuterium plasmas was achieved by observing ICE spectra for otherwise similar plasmas with widely dierent core density (and hence fusion reactiviy) and the same NBI power, see Fig.…”

Tokamak research at the Ioffe Institute

“…In contrast to other experiments, where ICE was found to originate mostly from the low field side (LFS) periphery, ICE in TUMAN-3M comes from the core plasma region. A rare example of core ICE can be seen in the recent ASDEX Upgrade experiments [37]. ICE frequency in TUMAN-3M was found to follow toroidal magnetic field evolution and to be insensitive to changes in plasma density.…”

Origin of ion cyclotron emission at the proton cyclotron frequency from the core of deuterium plasmas in the ASDEX-Upgrade tokamak

“…Strongly suprathermal radiation known as ion cyclotron emisison (ICE) is widely observed in magnetic confinement fusion (MCF) plasmas [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. Its intensity is typically orders of magnitude greater than that of black-body radiation from thermal ions, and its spectral peak frequencies correspond to multiple cyclotron harmonics of one or more energetic ion species at a specific radial location.…”

“…Most of the early ICE observations were localised to the outer midplane edge region of the MCF plasmas [1,2,3,4,5,6,7,11,19,20], but recently ICE has also been detected from the core plasmas of ASDEX-Upgrade [8,9,10] and DIII-D [12,13,14]. Figure 5a of Ref.…”