Around the Lab
Control Room Operations at LLE
November, 2011The word “shot” can suggest an informal attempt, a try, or something upon which to bet. That casual attitude is far removed from the control, coordination, and caution built into all aspects of OMEGA and OMEGA EP shot operations. The atmosphere surrounding Control Room operations at LLE before a laser shot is fired feels measured, quietly assured, and cautiously anticipatory. Highly trained experienced scientists, engineers, and technicians “stand watch” at computer workstations to ensure operations move forward safely and as planned.
At the core of the exercise is a Shot Director (SD) who is responsible for the overall operational performance of the respective laser facility during shot operations as well as during maintenance periods. The SD oversees the operational control of all laser and target systems, equipment, and ancillary support systems. This includes
- coordinating the shot sequence and cadence with the Principal Investigator (PI)
- coordinating the completion of pre-operational checks, alignments, and preparations required to fulfill the system or experimental requirements,
- directing the completion of actual system and experimental shots, and
- ensuring that the requisite system and experimental shot data are collected.
In addition, the SD operates the software applications that control facility access and safety interlocks, and the Shot Executive. During the time from establishing “closed access” until a shot is completed, the SD maintains a constant vigil in the Control Room.
Shot director controlling the shot sequence
Laser System Scientists monitor laser performance and ensure critical parameters are correctly configured
However, the successful operation of the OMEGA Laser is a collaborative effort of the SD and several other individuals. The Laser Drivers/Sources Operator (LDO/LSO) for OMEGA and OMEGA EP ensures that the necessary laser driver/source control, pulse shaping, and diagnostic functions are provided. This operator has overall responsibility for verifying that the laser driver/sources equipment is configured to support the planned shot operations. The Power Conditioning Operator (PCO) is the watchstander in charge of the Power Conditioning Executive, which ensures that the correct amplifiers are armed and that the charge voltages are consistent with operational limits and beam-balance requirements. The Beamlines Operator (BO) takes responsibility for the operation of the Beamline Executive–a software package used to align and control the optical path from the driver/sources to the target prior to shot operations–to ensure the proper functioning of laser diagnostics at shot time, and to assess the results between shots. The Experimental System Operator oversees the use of the Experimental System Executive to insert, view, and position targets; operate experimental diagnostics; and control target chamber vacuum systems. Finally, control room operations are supported by a Laser System Scientist who monitors and checks critical parameters to ensure the laser stays within the design operational envelope.
The control system architecture reflects the hierarchical subsystem configuration of OMEGA. Four autonomous consoles in the Control Room make it possible for each subsystem to be controlled by mission-specific operators. During shot operations, the Shot Director, who uses a fifth supervisory control station, coordinates the subsystem functions. The five Control Room workstations are arranged to allow the operators to work efficiently together with minimal distraction. The PI and shot crew use an adjacent conference room for briefings, data assessment, and planning. The SD, adhering to a strict set of guidelines, also controls and coordinates access to the Target and Laser Bays.
The control system provides the operational infrastructure to maintain the overall laser system, prepare it for a shot, execute the shot, and record the shot results. Computer network communication coordinates actions requiring synchronization to within ~1 sec. The Hardware Timing System (HTS) enables the subnanosecond precision timing required to execute and diagnose a shot. A “handoff” between the two levels of timing control takes place in the final 20 sec before the firing of a shot.
The OMEGA Control Room: Experimental Operations (left), Shot Director (center foreground), Beamlines Operator (center background), and Laser Drivers (right)
The OMEGA shot cycle encompasses a sequence of system states. While in the “active” state, the system is not formally preparing for a specific shot but makes it possible for all of the subsystems to be operated independently for maintenance or setup. The combination of the pre-shot/shot/post-shot states represents the sequence that is repeated for each shot attempt. The system remains in the “active” state until preparations for a specific target shot are initiated, which represents the transition to the “pre-shot” phase. The system progresses through the shot preparations and remains in this phase, completing several necessary tasks, including establishing that the diagnostics are set up per the PI’s instructions and are ready for the shot. At this point the system enters directly into the shot state. Once the shot crew has driven the software and hardware sequence through the issuing of the shot triggers, the system then enters the “post shot” state. Here, each of the system elements that have acquired shot-related data automatically proceed to log that data into the system database. As the logging is completed, each element effectively reverts to its “active” state. When all of the elements complete this process, the system formally transitions to the active state and is ready to begin another shot cycle.
Unforeseen events can factor into the normal shot cycle, which can be interrupted by either a “stand-down” or an “abort.” If a problem arises or a change of plans occurs prior to the system entering the “shot state,” the system can stand-down directly to the active state. When the situation is resolved, a new shot cycle can then commence. Since a stand-down occurs prior to the post-shot phase, shot data is not logged back to the system and, as such, the “shot number” is not incremented. If a critical problem arises after charging has begun, the abort process stops the shot. Each of the operators has an ABORT button that can be used to initiate the process. The Shot Director also has the option of de-energizing the electrical power substation that powers the laser “Power Conditioning Units” through a large red “dump” button.
Because of the remarkable planning, exactitude, and coordination in operation of the Control Room, an impressive number of experiments have taken place during 2011. The Omega Facility conducted 1348 target shots on OMEGA and 457 target shots on OMEGA EP for a total of 1805 target shots in FY11. OMEGA averaged 10.3 target shots per operating day with Availability and Experimental Effectiveness averages of 93.3% and 96.2%, respectively. OMEGA EP was operated extensively in FY11 for a variety of internal and external users. A total of 401 target shots were taken into the OMEGA EP target chamber and 56 joint target shots were taken into the OMEGA target chamber. OMEGA EP averaged 5.5 target shots per operating day with Availability and Experimental Effectiveness averages of of 85.6% and 95.1%, respectively.
Recognizing nuclear fusion as tomorrow’s energy source, and acknowledging LLE as one of the most prominent nuclear fusion centers in the world, Control Room Operations at LLE will most certainly continue to provide a robust environment that is innovative, purposeful, responsible, and relevant for research and education directed to science and technology.