Effect Of High Ion Temperature On The Polytropic Coefficient In The End Region Of Gamma 10/Pdx

The effect of high ion temperature on the ion polytropic coefficient (gamma) was experimentally investigated in the end region of the GAMMA 10/PDX tandem mirror. The ion temperature parallel to the magnetic field (T-i parallel to) was varied using the ion cyclotron range of frequencies (ICRF) waves, which heat the plasma in the central cell, and by applying an additional gas puff in the central cell. Assuming the ion sound speed, gamma T-i parallel to was evaluated by a Langmuir probe, and T-i parallel to was evaluated in an ion energy analyzer. These parameters were combined to evaluate gamma. The time evolutions of gamma T-i parallel to obtained from the probe and T-i parallel to obtained from the energy analyzer were similar. The plasma in the end region can be regarded as collisionless, but gamma was lower with ICRF heating than without the heating. A high T-i parallel to component was identified in the heated case. As mentioned in a previous numerical study [B. Lin et al., Phys. Plasmas 23, 083508 (2016)], it is experimentally suggested that. can be reduced by the high T-i parallel to component resulting from the ICRF heating. (C) 2019 The Japan Society of Plasma Science and Nuclear Fusion Research