English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Conditions for net fast ion drive are derived for beam-driven, sub-cyclotroncompressional (CAE) and global (GAE) Alfv\'en eigenmodes, such as thoseroutinely observed in spherical tokamaks such as NSTX(-U) and MAST. Both co-and counter-propagating CAEs and GAEs are investigated, driven by the ordinaryand anomalous Doppler-shifted cyclotron resonance with fast ions. Whereas priorresults were restricted to vanishingly narrow distributions in velocity space,broad parameter regimes are identified in this work which enable an analytictreatment for realistic fast ion distributions generated by neutral beaminjection. The simple, approximate conditions derived in these regimes for beamdistributions of realistic width compare well to the numerical evaluation ofthe full analytic expressions for fast ion drive. Moreover, previous results inthe very narrow beam case are corrected and generalized to retain all terms in$\omega/\omega_{ci}$ and $k_\parallel/k_\perp$, which are often assumed to besmall parameters but can significantly modify the conditions of drive anddamping when they are non-negligible. Favorable agreement is demonstratedbetween the approximate stability criterion, simulation results, and a largedatabase of NSTX observations of cntr-GAEs.

physics of plasmas

Analytic stability boundaries for compressional and global Alfv\'en  eigenmodes driven by fast ions. I. Interaction via ordinary and anomalous  cyclotron resonances