Plasma behaviour with molecular beam injection in the HL-1M tokamak

摘要

A new method of gas fuelling has been introduced in the HL-1M tokamak. The method consists of a pulsed high speed molecular beam formed by a Laval type nozzle. The velocity of the well collimated hydrogen beam is about 500 m/s. About 6×10~19 molecules pass through the nozzle and into the vacuum chamber in each pulse. A series of helium pulses was injected into the HL-1M low density(n_e=4×10~18 m~-3)hydrogen plasma. With penetration depth up to 12 cm, the Ramp-up rate of the electron density, dn_r/dt, was as high as 3.1×10~20.s~-1 at steady state, and The resulting plasma density reached n_e = 5.6×10~19 m~-3. The profile peaking factor of the electron Density, Q_n=n_e(0)/of about 100 ms after helium molecular beam injection(MBI)reached a Maximum value of more than 1.51.