Electron pumping is a method by which the electron population in a mirror plug cell can be driven from the trapped region of momentum space into the passing region. The driving mechanism is an electric field parallel to the axial magnetic field and resonant with the bounce motion of the trapped electrons. Detrapping the electrons lowers the electron density of the plug cell, thereby raising the electric potential of the cell (Φp). The author has developed a particle-tracking code which simulates the effect of a bounce resonant electric field on the electron distribution in a mirror reactor. It is found that electron pumping is an efficient mechanism for adding parallel momentum to the plug electron distribution. A thermal barrier is needed, however, so as to avoid strongly coupling the pumping power to the centre-cell electrons. The author has found that a thermal-barrier potential (Φb) of 3.2 , ( = centre-cell electron temperature) is necessary to reduce the pumping power requirements to an economical level (63 MW of absorbed power in each plug). A comparison with ECRH heating showed that ECRH heating with the same potential barrier depth required an amount of power that is higher by more than an order of magnitude.
Modeling very high electron heating by radio frequency waves on EAST
Slide-away distributions and relevant collective modes in high-temperature plasmas