Long pulse H-mode operation in JET-ITER Like Wall

In the last experimental campaign of the JET tokamak in December 2023, long duration discharges in deuterium plasmas were performed to assess the sustainment of the plasma performance over many resistive time scales and to address plasma-wall interaction physics in a full metallic environment with the ITER-like wall (ILW), featuring a W divertor and a Be first wall [1,2]. Two types of long duration discharges were developed: (i) a 30s flat-top ELMy H-mode with combined 12-14MW neutral beam injection (NBI) and 2MW of ion-cyclotron resonance heating (ICRH) and (ii) a 60s long pulse with 4-6MW of NBI during the entire flat-top and 2MW of ICRH for about 40s. The pulses were stationary from the radiation point of view without sign of core impurity accumulation and featured regular type-I ELMs with roughly equilibrated ion and electron temperatures in most cases. The discharges required significant technical adjustments in many subsystems, ranging from plasma shape control, machine protection and diagnostic settings [3]. The experiments achieved the maximum energy ever injected in a single pulse in JET (EIN=450MJ) and challenged the operational domain of the inertially cooled divertor limits. An overview of the main properties of these discharges in terms of plasma stationarity, ELM behaviour, plasma-wall interaction and overall performance will be presented and the contribution of these unprecedented JET-ILW results to the multi-machine CICLOP (Coordination on International Challenges on Long duration OPeration) database [4] will be highlighted.