Compressional Alfven and ion-ion hybrid waves in tokamak plasmas with two ion species
2014 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 56, no 12, 125017- p.Article in journal (Refereed) Published
Compressional Alfven and ion-ion hybrid waves excited by energetic beam ions are studied in plasmas with two ion species. In our experiment, a hydrogen-deuterium (H-D) plasma is used to produce instabilities similar to those likely to be present in the burning deuterium-tritium plasmas of future tokamaks. Modes are suppressed in the deuterium cyclotron frequency range with increasing hydrogen gas puffing. In plasmas with H/D concentrations of 2.57 or higher, short-lived modes with small and predominantly negative toroidal mode numbers are observed at frequencies omega/omega(beta D0) approximate to 2.25, where omega(beta D0) = omega(beta D0)(R-0) is the on-axis deuterium cyclotron frequency. These are the highest mode frequencies yet detected in the ion cyclotron range in a spherical tokamak. Modeling of the transparency regions and plasma resonances using the cold plasma dispersion relation explains the observed features. Mode conversion at ion-ion hybrid resonances and subsequent kinetic damping is believed to be responsible for mode suppression. The high frequency modes are present due to excitation by wave-particle resonances within the transparency region for high hydrogen concentrations. The absence of other wave-particle resonances explains significant features of our experiment. This technique has possible applications in plasma heating, current drive and real-time diagnosis of relative ion concentration in the plasma core.
Place, publisher, year, edition, pages
2014. Vol. 56, no 12, 125017- p.
alfven waves, tokamaks, multi-component and negative-ion waves
IdentifiersURN: urn:nbn:se:uu:diva-243061DOI: 10.1088/0741-3335/56/12/125017ISI: 000346926300028OAI: oai:DiVA.org:uu-243061DiVA: diva2:787752