Data analysis for particle balance studies on the axially symmetric divertor experiment

Throughput of H2 or D2 fueling gas during and after a plasma discharge is a strongly time‐dependent quantity. Various data, such as divertor pressure and integral fueling rate, are used in a computer routine to investigate the particle balance on the axially symmetric divertor experiment (ASDEX). It is seen that the dominant portion of the gas required to fuel the plasma is reversibly pumped by the walls. This is due to the dissociation of molecules and subsequent strong wall adsorption of the resulting atoms. The amount of gas lost to the wall increases with plasma density. After the discharge most of the gas is released depending somewhat on the preconditioning of the walls by previous discharges and the time interval in between discharges.