Synthetic NPA diagnostic for energetic particles in JET plasmas

J. Varje*, P. Sirén, H. Weisen, T. Kurki-Suonio, S. Äkäslompolo, J. E.T. Contributors

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


Neutral particle analysis (NPA) is one of the few methods for diagnosing fast ions inside a plasma by measuring neutral atom fluxes emitted due to charge exchange reactions. The JET tokamak features an NPA diagnostic which measures neutral atom fluxes and energy spectra simultaneously for hydrogen, deuterium and tritium species. A synthetic NPA diagnostic has been developed and used to interpret these measurements to diagnose energetic particles in JET plasmas with neutral beam injection (NBI) heating. The synthetic NPA diagnostic performs a Monte Carlo calculation of the neutral atom fluxes in a realistic geometry. The 4D fast ion distributions, representing NBI ions, were simulated using the Monte Carlo orbit-following code ASCOT. Neutral atom density profiles were calculated using the FRANTIC neutral code in the JINTRAC modelling suite. Additionally, for rapid analysis, a scan of neutral profiles was precalculated with FRANTIC for a range of typical plasma parameters. These were taken from the JETPEAK database, which includes a comprehensive set of data from the flat-top phases of nearly all discharges in recent JET campaigns. The synthetic diagnostic was applied to various JET plasmas in the recent hydrogen campaign where different hydrogen/deuterium mixtures and NBI configurations were used. The simulated neutral fluxes from the fast ion distributions were found to agree with the measured fluxes, reproducing the slowing-down profiles for different beam isotopes and energies and quantitatively estimating the fraction of hydrogen and deuterium fast ions.

Original languageEnglish
Article numberC11025
Pages (from-to)1-6
JournalJournal of Instrumentation
Issue number11
Publication statusPublished - 22 Nov 2017
MoE publication typeA1 Journal article-refereed
EventEuropean Conference on Plasma Diagnostics - Bordeaux, France
Duration: 18 Apr 201721 Apr 2017
Conference number: 2


  • Analysis and statistical methods
  • Nuclear instruments and methods for hot plasma diagnostics
  • Simulation methods and programs

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