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/

Zendy Plus

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

Zendy Tools

Zendy Open

Characterizing the gap eigenmode of shear Alfv\'{e}n waves (SAW) and itsinteraction with energetic ions is important to the success of magneticallyconfined fusion. Previous studies have reported an experimental observation ofthe spectral gap of SAW on LAPD (Zhang et al 2008 Phys. Plasmas 15 012103), alinear large plasma device (Gekelman et al 1991 Rev. Sci. Instrum. 62 2875)possessing easier diagnostic access and lower cost compared with traditionalfusion devices, and analytical theory and numerical gap eigenmode using idealconditions (Chang 2014 PhD Thesis at Australian National University). To guideexperimental implementation, the present work models the gap eigenmode of SAWusing exact LAPD parameters. A full picture of the wave field for previousexperiment reveals that the previously observed spectral gap is not global butan axially local result. To form a global spectral gap, the number of magneticmirrors has to be increased and stronger static magnetic field makes it moreclear. Such a spectral gap is obtained for the magnetic field of$B_0(z)=1.2+0.6\cos[2\pi (z-33.68)/3.63]$ with $7.74$~m magnetic beach. Byintroducing two types of local defects (corresponding to $E_\theta(z_0)=0$ and$E_\theta'(z_0)=0$ respectively), odd-parity and even-parity discreteeigenmodes are formed clearly inside the gap. The strength of these gapeigenmodes decreases significantly with collision frequency, which isconsistent with previous studies. Parameter scans show that these gapeigenmodes can be even formed successfully for the field strength of$B_0(z)=0.2+0.1\cos[2\pi (z-33.68)/3.63]$ and with only $4$ magnetic mirrors,which are achievable by LAPD at its present status. This work can serve as astrong motivation and direct reference for the experimental implementation ofthe gap eigenmode of SAW on LAPD and other linear plasma devices.

Preliminary computation of the gap eigenmode of shear Alfv\'{e}n waves on LAPD