The Laser Performance Operations Model (LPOM) is an integrated computational system designed to accomplish multiple NIF operations functions.
- LPOM automates the calculation of the laser setup required to achieve experimental goals. LPOM is built around a physical optics propagation code, the Virtual Beamline (VBL). VBL code, using a detailed NIF laser model, does a back solve to come up with a required pulse shape needed to deliver the requested 3ωpulse shape by the user. This is an essential step that enables NIF to deliver high precision pulse shapes for experiments (such as those shown in Figure 4-6). A shot setup for a 192 beam NIF experiment can be completed in approximately 20 minutes.
- The LPOM suite of codes completes a laser post shot data analysis to assess the delivered energy, power, etc. to the expected values. Additionally, near-field contrasts, power accuracy and power balance are calculated. Deviations between the measured and the expected quantities are used to update the laser models to improve future performance. Periodic adjustments of the code’s energetics parameters have allowed LPOM to predict total energies within 2–3%, and provide beam-to-beam energy balance better than 5% for full system shot with energies and power as high as 1.8 MJ and 500 terawatts (TW).
- LPOM also manages the equipment protection on the NIF laser. It uses the data gathered from the Final Optics Damage Inspection (FODI) measurements to determine where to place the Programmable Spatial Shaper (PSS) blockers to block the damage sites from further growth. For a given laser setup the LPOM package uses the built-in rules to assess the risk of damage to optics throughout the laser chain (front end, Injection Laser System (ILS), the main amplifier, and the final optics).
- LPOM can also be used in a stand-alone mode to conduct exploratory studies to enable new, safer laser configurations and design new experimental operational platforms.
Together with the optics loop tools, LPOM is a valuable asset for designing NIF experiments.
In order to maintain an accurate model of each beamline, LPOM requires feedback at the conclusion of each shot from each diagnostic. A suite of laser diagnostics provides data on the performance of NIF. The measured data from individual beams are processed to determine the total power and energy on target and the power and energy balance for any given shot. When the predictions of the model begin to deviate from measured data, LPOM uses a set of measured data to recalibrate its models of the laser. Revisions and upgrades to VBL and LPOM occur at frequent intervals as new features are added to the facility and new configurations must be modeled.
In addition to the ILS settings, LPOM also predicts the energies and powers at each of the laser diagnostic locations in NIF, thereby ensuring that each diagnostic is configured to accurately measure the results of the shot.