Effect of limiter biasing on electron temperature in IR-TWOW AW1 Tokamak

In this paper, the effect of limiter biasing on the plasma parameters as floating potential, ion and electron saturation currents, plasma potential and electron temperature has been investigated. The measurements have been done by the Langmuir-ball pen probe in IR-T1 plasma edge. For this purpose, this probe has been constructed and installed on IR-T1. In this work, the biased limiter voltages are V = +200V, V = 0 and V = -200V. The results show that ion and electron saturation currents have decreased when the collector retracts inside the tube. The negative biased voltage has reduced the ion and electron saturation currents while the positive voltage has increased them. The ratio R = I^-_sat - I⁺_sat is very close to one at a certain collector position. The results show that this position changes with the applying limiter biasing. The results show that the ratio R is very close to one at h = 0-1.1mm, h = -0.7mm and h = -0.6mm for VRbiasing R= +200V, V_biasing R= 0 and V_biasing R= -200V, respectively. In this collector position, the plasma potential that is close to floating potential is about 54V, 45V and 39V for V_biasing R= +200V, V_biasing R= 0 and V_biasing R= - 200V respectively, in plasma edge. The biased limiter with V_biasing R= +200V causes to the increase of plasma potential (>20%) and electron temperature (>30%) in plasma edge. But the plasma potential and electron temperature decrease (<;15%) and (>40%) due to applying the negative biased voltage (V_biasing R= -200V).