Operational challenges for long pulses on JET-ILW

The typical pulse on the JET tokamak is ∼10 s during the main phase of the discharge, however long discharge operation (>30 s) is possible with sufficient preparation and care. During the last period of JET operation in 2023 long pulses in deuterium plasmas were developed to assess the sustainment of the plasma performance over several times the current resistive time scale and to address plasma-wall interaction physics in a full metallic environment with the ITER-like wall, with a W divertor and a Be first wall. To prepare for the long pulse operation an analysis of heatloads was required to ensure the pulse was safe for the machine, this defined a number of choices on toroidal field and plasma configuration. While the 30 s pulse was within the control and protection systems commissioned operating envelope the target 60 s pulse was beyond the normal operation of the control and protection systems. These systems were adapted and tested as far as possible to ensure they would work in the real pulse and a number of issues resolved over a series of tests. Significant modifications were required to carry out the experiment which had to be reversed before going back to standard operations. Even with these extensive preparations issues were found and resolved leading to the success of the 60 s pulse. The technical details of these preparations and their implementation will be discussed in detail.