The role of energetic particles in fusion plasmas

Pinches, S. D.; Berk, H. L.; Borba, D.; Breǐzman, B. N.; Briguglio, S.; Fasoli, A.; Fogaccia, G.; Gryaznevich, M.; Kiptily, V.; Mantsinen, M.; Sharapov, S. E.; Testa, D.; Vann, R. G. L.; Vlad, G.; Zonca, F.; Contributors, Jet‐Efda

doi:10.1088/0741-3335/46/12b/017

Cited by 84 publications

(107 citation statements)

References 54 publications

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“…Also TAE and tornado mode activities affecting fast ion power deposition profiles were found on DIII-D [14,15] and on TFTR [16]. The fast particle redistribution/losses similar to those observed on JT-60U were found on JET as a significant (by a factor of 2) decrease of γ-ray emission coming from the nuclear reaction 12 C(p,p'γ) 12 C during the combined activity of tornado modes (inside the q = 1 radius) and TAE (outside the q = 1 radius) [17,18]. Also core-localized TAE modes were observed to cause significant fast ion redistribution in the plasma core and enhanced losses in AT plasma discharges [19].…”

Section: Fast Ion Interaction With Tornado Modessupporting

confidence: 67%

“…7 that at around t = 15.5 s the observed TAE activity is abruptly terminated by the occurrence of a monster sawtooth crash, which may have been triggered by the loss of fast ion stabilization due to the tornado modes [14][15][16][17][18]. A burst of fast ion losses during the sawtooth crash is clearly seen in Fig.…”

Section: Fast Ion Interaction With Tornado Modesmentioning

confidence: 81%

“…Another energy window related to the neutron induced γ-ray emission was used for assessments of the background component recorded in the 3.09-MeV window. Measurements of confined fast particles with the 2D γ-ray camera made it possible to distinguish the energy ranges of fast D-ions using γ-ray emission from the 12 C(D,pγ) 13 C reaction threshold deuteron energy E D ≈ 0.5 MeV [3], a much lower threshold than the 4.5-MeV proton threshold of the 12 C(p,p'γ) 12 C reaction in [17,18]. In addition DD neutron data from the TOFOR provides information on high energy deuterons E D > 0.5 MeV [5].…”

Section: Fast Ion Interaction With Tornado Modesmentioning

confidence: 99%

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Study of Interaction between Fast Ions and MHD Instabilities by Fusion Product Measurements in Joint European Torus

Kiptily

Sharapov

Gaßner

et al. 2013

Plasma and Fusion Research

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Fast ion redistribution and losses caused by plasma disruptions, Toroidal Alfvén Eigenmodes (TAE) and fishbones are measured with a suite of improved gamma-ray diagnostics, Neutral Particle Analyser (NPA), neutron spectrometry, Faraday Cups and a Scintillator Probe (SP). Fast ion populations in the MeV energy range were generated in fusion reactions and were also produced by 3rd harmonic Ion Cyclotron Resonance Heating (ICRH). Significant fast ion losses preceding plasma disruptions were often detected by SP in discharges with high β N . These losses were caused by the m = 2 / n = 1 kink mode and typically occurred at the time of thermal quench, before the current quench. Core-localised TAE modes inside the q = 1 radius causing redistribution of the fast ions in the resonance energy range were directly measured for the first time with the gamma-ray camera, confirming that the TAE instability expels fast ions from inside the q = 1 radius and triggers the monster sawtooth crashes. Energy and pitch angle resolved SP measurements of lost fusion products in the MeV energy range were found to correlate with low-frequency fishbone oscillations driven by 100 keV beam ions. The origin and amplitude of these non-resonant losses are investigated.

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Section: Fast Ion Interaction With Tornado Modessupporting

confidence: 67%

Section: Fast Ion Interaction With Tornado Modesmentioning

confidence: 81%

Section: Fast Ion Interaction With Tornado Modesmentioning

confidence: 99%

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Study of Interaction between Fast Ions and MHD Instabilities by Fusion Product Measurements in Joint European Torus

Kiptily

Sharapov

Gaßner

et al. 2013

Plasma and Fusion Research

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“…Time traces of the total NBI power and the magnetic fluctuations due to the (m=2,n=1) and the (m=3,n=2) NTM for a typical discharge (#21089) are shown in the bottom of Fig.2. An NBI power ramp in the period [1][2]s excites a (2,1) NTM, which changes strongly in frequency and resonance location during the NBI modulation phase [2][3]s. Between t = 3 s and t = 5 s the mode reaches a plateau phase in which it maintains constant its main features i.e.…”

mentioning

confidence: 99%

NTM induced fast ion losses in ASDEX Upgrade

et al. 2007

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The loss of fast (i.e. suprathermal) ions from a magnetically confined fusion plasma due to the interaction with magnetohydrodynamic instabilities has been experimentally characterized and interpreted by means of a numerical model. It is found that for a special class of instabilities, the so-called Neoclassical Tearing Modes, fast ions losses are increased and modulated at the same frequency of the mode. This new experimental finding is explained as a result of the drift islands formed by energetic ions in particle phase space. An eventual overlapping of these drift islands leads to an orbit stochasticity and therefore to an enhancement of the fast ion losses. This explanation is confirmed by statistical analysis of simulations of fast ions trajectories performed with the ORBIT code. The mechanism is of general importance for understanding the interaction between MHD modes and fast particles in magnetic confinement experiments. A significant fraction of plasma pressure in a magnetized fusion experiment is carried by suprathermal (fast) ions, which are produced either by fusion reactions (like α particles), injected through energetic beams, or by RF heating. In general, these fast particles play an important role in the energy balance of a fusion plasma, either for the heating and/or for current drive processes [1], [2] and [3]. The confinement of fast particles is therefore an issue of great importance, since significant losses of these ions may drastically reduce the heating as well as the current drive efficiency. In addition, an intense and localized loss of fast ions may cause damage to plasma facing components. Due to their high energy, the dynamics of fast ions in a magnetized plasma is rather different than that of thermal ions and, in many aspects, still experimentally unexplored. Several issues are still open, for example, about the interplay between a population of fast particles and a key player of magnetized fusion plasmas, like the Magnetohydrodynamic (MHD) instabilities.In this Letter we present the first measurements of fast ion losses with simultaneous high time, energy and, pitch angle resolution due to Neoclassical Tearing Modes (NTMs). We explain the measurements on the basis of drift islands and their overlap, which leads to orbit stochasticity. The main experimental phenomenology is in fact reproduced by a model simulating the guiding center orbits of fast ions. The results reported here are important for next-step fusion devices like ITER where a significant population of α-particles and of NBI and ICRH generated fast ions will be present.NTMs are metastable modes driven by the missing bootstrap current within a preexisting seed magnetic is- * Electronic address: Manuel.Garcia-Munoz@ipp.mpg.de land, provided that the plasma poloidal beta, β pol , is larger than a threshold value [4]. When a NTM grows in the plasma, global confinement is severely affected. NTMs set the limit to the maximum β pol achievable in conventional scenarios. While the NTM impact on the global confinement is rather w...

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“…In the absence of external electromagnetic fields, the free energy associated with energetic α particles can feed numerous plasma instabilities, which can, in turn, transport energy to background plasma species [28][29][30][31][32]. The energy conversion rate in such processes was estimated [29] to be approximately 25%.…”

Section: Introductionmentioning

confidence: 99%

Waves for alpha channeling in mirror machines

Zhmoginov

Fisch

2009

Physics of Plasmas

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Alpha-channeling can, in principle, be implemented in mirror machines via exciting weaklydamped modes in the ion cyclotron frequency range with perpendicular wavelengths smaller than the alpha particle gyroradius. Assuming quasi-longitudinal or quasi-transverse wave propagation, we search systematically for suitable modes in mirror plasmas. Considering two device designs, a proof-of-principle facility and a fusion rector prototype, we in fact identify candidate modes suitable for alpha-channeling.

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The role of energetic particles in fusion plasmas

Cited by 84 publications

References 54 publications

Study of Interaction between Fast Ions and MHD Instabilities by Fusion Product Measurements in Joint European Torus

Study of Interaction between Fast Ions and MHD Instabilities by Fusion Product Measurements in Joint European Torus

NTM induced fast ion losses in ASDEX Upgrade

Waves for alpha channeling in mirror machines

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