HIGH-BETA DISCHARGES WITH NEUTRAL BEAM INJECTION IN CHS

High beta plasmas with a volume averaged equilibrium beta value of 2.1 % were produced in CHS using tangential neutral beam injection. This b eta value was achieved with the confinement improvement (reheat mode) observed after turning off strong gas puffing. Wall conditioning with titanium gettering was used to make high density operation ((n) over b ar(e) less than or equal to 8 x 10(19) m(-3)) possible for low magneti c fields (B-t = 0.6 T). The discharges start with the magnetic hill co nfiguration (in vacuum) and finally achieve Mercier stable equilibrium owing to the self-stabilization effect given by the magnetic well whi ch is produced by the plasma pressure. The Shafranov shift was about 4 0% of a plasma minor radius. Magnetic fluctuations did not increase wi th increasing plasma pressure when the beta value exceeded 1%. Dynamic poloidal field control was applied to suppress the outward plasma shi ft with increasing plasma pressure. Such operation gave an additional increase of beta value compared with the constant poloidal field opera tion.