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Title: Quantifying Fusion Born Ion Populations in Magnetically Confined Plasmas using Ion Cyclotron Emission

Abstract

Ion cyclotron emission (ICE) offers unique promise as a diagnostic of the fusion born alpha-particle population in magnetically confined plasmas. Pioneering observations from JET and TFTR found that ICE intensity P ICE scales approximately linearly with the measured neutron flux from fusion reactions, and with the inferred concentration, n /n i , of fusion-born alpha-particles confined within the plasma. We present fully nonlinear self-consistent kinetic simulations that reproduce this scaling for the first time. This resolves a longstanding question in the physics of fusion alpha particle confinement and stability in MCF plasmas. It confirms the MCI as the likely emission mechanism and greatly strengthens the basis for diagnostic exploitation of ICE in future burning plasmas.

Authors:
 [1];  [2];  [3];  [4];  [3];  [3];  [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. (United Kingdom)
  3. Warwick Univ., Coventry (United Kingdom)
  4. (United Kingdom). Culham Centre for Fusion Energy (CCFE)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1347308
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 118; Journal Issue: 10; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Carbajal, L., Warwick Univ., Coventry, Dendy, R. O., Culham Science Centre, Abingdon, Chapman, S. C., Cook, J. W. S., and First Light Fusion Ltd., Oxfordshire. Quantifying Fusion Born Ion Populations in Magnetically Confined Plasmas using Ion Cyclotron Emission. United States: N. p., 2017. Web. doi:10.1103/PhysRevLett.118.105001.
Carbajal, L., Warwick Univ., Coventry, Dendy, R. O., Culham Science Centre, Abingdon, Chapman, S. C., Cook, J. W. S., & First Light Fusion Ltd., Oxfordshire. Quantifying Fusion Born Ion Populations in Magnetically Confined Plasmas using Ion Cyclotron Emission. United States. doi:10.1103/PhysRevLett.118.105001.
Carbajal, L., Warwick Univ., Coventry, Dendy, R. O., Culham Science Centre, Abingdon, Chapman, S. C., Cook, J. W. S., and First Light Fusion Ltd., Oxfordshire. Tue . "Quantifying Fusion Born Ion Populations in Magnetically Confined Plasmas using Ion Cyclotron Emission". United States. doi:10.1103/PhysRevLett.118.105001. https://www.osti.gov/servlets/purl/1347308.
@article{osti_1347308,
title = {Quantifying Fusion Born Ion Populations in Magnetically Confined Plasmas using Ion Cyclotron Emission},
author = {Carbajal, L. and Warwick Univ., Coventry and Dendy, R. O. and Culham Science Centre, Abingdon and Chapman, S. C. and Cook, J. W. S. and First Light Fusion Ltd., Oxfordshire},
abstractNote = {Ion cyclotron emission (ICE) offers unique promise as a diagnostic of the fusion born alpha-particle population in magnetically confined plasmas. Pioneering observations from JET and TFTR found that ICE intensity P ICE scales approximately linearly with the measured neutron flux from fusion reactions, and with the inferred concentration, n /n i , of fusion-born alpha-particles confined within the plasma. We present fully nonlinear self-consistent kinetic simulations that reproduce this scaling for the first time. This resolves a longstanding question in the physics of fusion alpha particle confinement and stability in MCF plasmas. It confirms the MCI as the likely emission mechanism and greatly strengthens the basis for diagnostic exploitation of ICE in future burning plasmas.},
doi = {10.1103/PhysRevLett.118.105001},
journal = {Physical Review Letters},
number = 10,
volume = 118,
place = {United States},
year = {Tue Mar 07 00:00:00 EST 2017},
month = {Tue Mar 07 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 2works
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  • Magnetically confined plasmas can contain significant concentrations of nonthermal particles, arising from neutral beam injection, fusion reactions, shock heating, or wave-driven acceleration of resonant plasma species. The associated distribution functions can depart significantly from Maxwellians, which may impact the propagation and absorption of radio frequency waves. The potential effect of these particles has been investigated using a full-wave code that has been extended to handle gyrotropic, but otherwise arbitrary distribution functions. This code has been used to numerically simulate ion cyclotron resonance heating (ICRH) in magnetic fusion plasmas in which coresonant neutral beam injection (NBI) heating may also be applied.more » The presence of nonthermal ion populations generated by the NBI can alter the ICRH characteristics. Two situations involving ion cyclotron range of frequency waves are presented: fast wave to ion Bernstein wave mode conversion and high harmonic fast wave electron heating. In both cases, the adequacy of an equivalent Maxwellian-based description is discussed. Results indicate that the absorption profiles are more strongly affected than the wave fields by the presence of nonthermal species.« less
  • The magnetoacoustic cyclotron instability (MCI) probably underlies observations of ion cyclotron emission (ICE) from energetic ion populations in tokamak plasmas, including fusion-born alpha-particles in JET and TFTR [Dendy et al., Nucl. Fusion 35, 1733 (1995)]. ICE is a potential diagnostic for lost alpha-particles in ITER; furthermore, the MCI is representative of a class of collective instabilities, which may result in the partial channelling of the free energy of energetic ions into radiation, and away from collisional heating of the plasma. Deep understanding of the MCI is thus of substantial practical interest for fusion, and the hybrid approximation for the plasma,more » where ions are treated as particles and electrons as a neutralising massless fluid, offers an attractive way forward. The hybrid simulations presented here access MCI physics that arises on timescales longer than can be addressed by fully kinetic particle-in-cell simulations and by analytical linear theory, which the present simulations largely corroborate. Our results go further than previous studies by entering into the nonlinear stage of the MCI, which shows novel features. These include stronger drive at low cyclotron harmonics, the re-energisation of the alpha-particle population, self-modulation of the phase shift between the electrostatic and electromagnetic components, and coupling between low and high frequency modes of the excited electromagnetic field.« less
  • It is shown that during ion-Bernstein--wave heating experiments, nonlinear ion Landau damping absorbs efficiently the incident Bernstein waves in present-day tokamak and tandem-mirror plasmas. Further, this nonlinear absorption will dominate absorption by minority (impurity) ions.
  • The existence of suprathermal ion populations gives rise to significant broadening of and modifications to the fusion neutron spectrum. We show that when this population takes the form of a power-law at high energies, specific changes occur to the spectrum which are diagnosable. In particular, the usual Gaussian spectral shape produced by a thermal plasma is replaced by a Lorentz-like spectrum with broad wings extending far from the spectral peak. Additionally, it is found that the full width at half maximum of the spectrum depends on both the ion temperature and the power-law exponent. This causes the use of themore » spectral width for determination of the ion temperature to be unreliable. We show that these changes are distinguishable from other broadening mechanisms, such as temporal and motional broadening, and that detailed fitting of the spectral shape is a promising method for extracting information about the state of the ions« less
  • Abstract not provided.