Operational experience of the JET neutral beam actively cooled duct liner and implications for ITER operations

Abstract We describe the operational experience of the JET actively cooled duct liner and compare it with the previous inertially cooled duct. The paper discusses the initial conditioning of the duct liner during restart commissioning and subsequent high power performance. The new duct was conditioned in 48 plasma pulses during its first time commissioning in only 35 plasma pulses in the following restart. The inertial duct liner conditioning typically required 100 plasma pulses. In a well conditioned beamline for a 15 MW beam pulse the duct liner temperature and pressure were observed to establish an equilibrium 5 s into the pulse and remain in a steady state to the end of the pulse. The observed behaviour is compared with the design basis predictions.