Status of the ATF program

Technical progress during the last year has led to increased confidence in ATF performance. The ATF 1 = 2 torsatron, scheduled to operate in October 1986, will have R = 2.1 m, a = 0.3 m, B = 1 T steady state and B = 2 T for 5 -10 seconds. A wide range of magnetic configurations are accessible on ATF by varying the relative currents in the three sets of poloidal field coils and in the two separate helical windings. In the transport area, modest electric fields (eΦ ∼ >T) of either sign dramatically reduce direct orbit losses and improve confinement (χi ∼ υ*) at intermediate values of υ* (∼ < 10). ATF plasma heating will use: ECH - 0.2 MW, 53.2 GHz CW with an additional 0.2 MW at 53.2 GHz CW or 0.4 MW, 28 GHz CW as backup; ICRF - 0.4 MW, 5 - 30 MHz CW with 1.5 MW, 40 - 80 MHz CW as backup; and NBI - 4.5 MW, 40 - 50 kV, 0.3 - 0.5 s pulse with 30 s injection at lower power as backup. Collisionless particle orbit studies with the accurate ATF wall geometry show that trapped particles do not hit the ATF wall (no collisionless loss cone) and that the closest approach is in a helical strip between helical coils on the small major radius side where ports are conveniently located