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

Recent upgrades in H-1 power supplies have enabled the operation of the H-1experiment at higher heating powers than previously attainable. A heating powerscan in mixed hydrogen/helium plasmas reveals a change in mode activity withincreasing heating power. At low power (<50 kW) modes with beta-induced Alfveneigenmode (BAE) frequency scaling are observed. At higher power modesconsistent with an analysis of nonconventional Global Alfven Eigenmodes (GAEs)are observed, the subject of this work. We have computed the mode continuum,and identified GAE structures using the ideal MHD solver CKA and thegyrokinetic code EUTERPE. An analytic model for ICRH-heated minority ions isused to estimate the fast ion temperature from the hydrogen species. Lineargrowth rate scans using a local flux surface stability calculation, LGRO, areperformed. These studies demonstrate growth from circulating particles whosespeed is significantly less than the Alfven speed, and are resonant with themode through harmonics of the Fourier decomposition of the strongly-shapedheliac magnetic field. They reveal drive is possible with a small, hotenergetic tail of the hydrogen species. Local linear growth rate scans are alsocomplemented with global calculations from CKA and EUTERPE. These qualitativelyconfirm the findings from the LGRO study, and show that the inclusion of finiteLarmor radius effects can reduce the growth rate by a factor of three, but donot affect marginal stability. Finally, a study of damping of the global modewith the thermal plasma is conducted, computing continuum, and the dampingarising from parallel electric fields. We find that continuum damping is oforder 0.1% for the configuration studied. The inclusion of resistivity liftsthe damping to 19%. Such large damping is consistent with experimentalobservations that in absence of drive the mode decays rapidly (~0.1 ms).

Global Alfven Eigenmodes in the H-1 heliac