A broad range of Alfv\u00e9n eigenmodes (AEs) was destabilized by fast ions in JET D-3He plasmas heated with the three-ion ICRF scenario [1, 2], see Fig. 1. The observed modes include the toroidicity-induced AEs (TAEs), ellipticity-induced AEs (EAEs), as well as reversed-shear AEs (RSAEs), originating from the presence of a local minimum of the safety factor qmin. Two different types of centrally localized RSAEs were regularly observed during the long-period sawtooth phases in this series of JET experiments [3]. In addition to the low-frequency RSAEs with frequencies below the TAE frequency (f ? 80-180 kHz), also RSAEs with frequencies above the TAE frequency (f ? 330-450 kHz) were destabilized. The high-frequency RSAEs feature the temporal decrease of their frequency as the value of qmin decreases (cf. Fig. 1), opposite to the dynamics of the more often observed low-frequency RSAEs. Such high- frequency RSAEs were previously reported in reversed-shear plasmas in JT-60U heated with negative-ion-based NBI, injecting a large number of passing ions with energies ~400 keV [4]. In this contribution, we report the characteristics of the high-frequency RSAEs in JET experiments, investigated in detail using HELENA, CSCAS and MISHKA codes. The computed radial mode structure is consistent with the experimental mode measurements, using an X-mode reflectometer, a multiline interferometer and soft X-ray diagnostics. Our analysis also shows that the high-frequency RSAE destabilization is mostly caused by passing fast ions with energies of several hundred keV [3]. Although the high- frequency RSAEs are not often seen on JET, these modes could be highly relevant for future ITER and fusion reactors dominated by ~MeV-range energetic ions, including a significant population of passing fast ions.<\/p>\n","protected":false},"excerpt":{"rendered":"
Dreval M.; Sharapov S.E.; Kazakov Ye.O.; Ongena J.; Nocente M.; Calado R.; Coelho R.; Ferreira J.; Figueiredo A.; Fitzgerald M.; Garcia J.; Giroud C.; Hawkes N.C.; Kiptily V.G.; Nabais F.; Nave M.F.F.; Weisen H.; Craciunescu T.; Salewski M.; Stancar Z.<\/p>\n","protected":false},"featured_media":1294,"comment_status":"closed","ping_status":"open","template":"","meta":[],"product_cat":[704],"product_tag":[822,1182,2387,4362],"class_list":["post-9499","product","type-product","status-publish","has-post-thumbnail","hentry","product_cat-conference-proceedings","product_tag-jet","product_tag-fast-ions","product_tag-alfven-eigenmodes","product_tag-high-frequency","prodpage-style2"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/product\/9499","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/types\/product"}],"replies":[{"embeddable":true,"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/comments?post=9499"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/media\/1294"}],"wp:attachment":[{"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/media?parent=9499"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/product_cat?post=9499"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.istp.cnr.it\/it\/wp-json\/wp\/v2\/product_tag?post=9499"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}