LLNL, Livermore, California, USA
The National Ignition Facility (NIF) is the world’s most energetic laser capable of delivering 2.05MJ of energy with peak powers up to 500 terawatts on targets a few mms in diameter. This enables extreme conditions in temperature and pressure allowing a wide variety of exploratory experiments from triggering fusion ignition to emulating temperatures at the center of stars or pressures at the center of giant planets. The capability enabled the groundbreaking results of December 5th, 2022 when scientific breakeven in fusion was demonstrated with a target gain of 1.5. A key aspect of supporting various experiments at NIF is the ability to custom shape the pulses of the 48 quads independently with high fidelity as needed by the experimentalists. For more than 15 years, the Master Oscillator Room’s (MOR) pulse shaping system has served NIF well. However, a pulse shaping system that would provide higher shot-to-shot stability, better power balance and accuracy across the 192 beams is required for future NIF experiments including ignition. The pulse shapes requested vary drastically at NIF which led to challenging requirements for the hardware, timing and closed loop shaping systems. In the past two years, a High-Fidelity Pulse Shaping System was designed, and a proof-of-concept system was shown to meet all requirements. This talk will discuss design challenges, solutions and how modernization of the pulse shaping hardware helped simple control algorithms meet the stringent requirements set by the experimentalists.
LLNL Release Number: LLNL-ABS-848060
LLNL, Livermore, California, USA
This last year we achieved an important milestone by reaching fusion ignition at Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF), a multi-decadal effort involving a large collaboration. The NIF facility contains a 192-beam 4.2 MJ neodymium glass laser (around 1053 nm) that is frequency converted to 351 nm light. To meet stringent laser performance required for ignition, laser modeling codes including the Virtual Beamline (VBL) and its predecessors are used as engines of the Laser Operations Performance Model (LPOM). VBL comprises an advanced nonlinear physics model that captures the response of all the NIF laser components (from IR to UV and nJ to MJ) and precisely computes the input beam power profile needed to deliver the desired UV output on target. NIF was built to access the extreme high energy density conditions needed to support the nation’s nuclear stockpile and to study Inertial Confinement Fusion (ICF). The design, operation and future enhancements to this laser system are guided by the VBL physics modeling code which uses best-in-class standards to enable high-resolution simulations on the Laboratory’s high-performance computing platforms. The future of repeated and optimized ignition experiments relies on the ability for the laser system to accurately model and produce desired power profiles at an expanded regime from the laser’s original design criteria.
LLNL Release Number: LLNL-ABS-847846