LLE's High-Pressure DT-Fill Process Control System

The OMEGA laser at the University of Rochester's Laboratory for Laser Energetics (UR/LLE) implodes fusion targets that contain cryogenic solid deuterium-tritium (DT) ice layers. These ICF targets are fabricated in a high-pressure DT-fill process. This paper describes the integration and control of this DT-fill process. The appropriate safety-control response during the DT-fill process depends on the location of the tritium inventory and where the containment alarm is detected A control response that is deemed appropriate earlier in the fill process could be a dangerous action at a later point in the fill process. The control system must adapt as the DT inventory moves through the process train. This is achieved by defining eight "fill states" in the fill process. The control system transitions to the appropriate fill state as the DT fill progresses. The fill state reflects the tritium location, pressure, and temperature. Steps are taken to ensure that the tritium location and the fill state are in agreement. The control system monitors the containment system's integrity and will take the appropriate action, based on the tritium location and the type of containment failure. This approach not only ensures process safety, but also maximizes the productivity by executing process pauses (in lieu of aborts) when conditions allow.