Azimuthal surface waves during plasma production in large tokamaks

Summary form only given. Our report is devoted to studying the dispersion properties of SW in large tokamaks (a/spl middot/B/sub 0/>3 10/sup 6/, here a is the small radius of plasma column in cm, B/sub 0/ in G) during plasma production in addition to that accomplished for small devices (a/spl middot/B/sub 0/<2/spl middot/10/sup 3/) with dense plasma. It is shown that the phase of SW varies strongly in the vacuum layer that is why their eigenfrequencies mostly depend upon the vacuum layer width. These waves cannot be considered as potential as the B/sub z/ component is quite significant. The dependence of SW frequency and their field topology upon tokamak parameters, vacuum layer width, a, B/sub 0/, plasma density n and azimuthal wave number m value and sign is analyzed both numerically (for the devices with JET parameters) and analytically. Slots between two dispersion curves are more sufficient at the lower boundary of the frequency range, they are greater for the waves with the negative m. The results reported can be useful for the fusion experimental data analysis and the suppression of the undesirable tokamak edge plasma heating.