Model-based impurity emission front control using deuterium fueling and nitrogen seeding in TCV

Abstract This paper presents the first result using nitrogen-seeded exhaust feedback control of NII impurity emission front in TCV. The position is consistently located below its commonly used CIII counterpart, indicating representative a colder plasma region. We demonstrate for two cases: (a) nitrogen seeding as sole actuator, and (b) deuterium fueling an actuator while injecting small amount that remains trace impurity. For actuation, peak target current density significantly reduced when approaches x-point (?50% at halfway point). When actuating with deuterium, less affected, which explained by changes engendering different scrape-off-layer density. Perturbative (system identification) experiments show actuation induces stronger, but slower, response than actuation. Moving back to after pushing it towards has proven difficult, where both total radiated power do not reach pre-seeding conditions within discharge time following termination injection. highlights need account retention such seeded discharges strategies.