Ronald K. House

Description and dosimetric verification of the PEREGRINE Monte Carlo dose calculation system for photon beams incident on a water phantom.

PEREGRINE is a three-dimensional Monte Carlo dose calculation system written specifically for radiotherapy. This paper describes the implementation and overall dosimetric accuracy of PEREGRINE physics algorithms, beam model, and beam commissioning procedure. Particle-interaction data, tracking geometries, scoring, variance reduction, and statistical analysis are described. The BEAM code system is used to model the treatment-independent accelerator head, resulting in the identification of primary and scattered photon sources and an electron contaminant source. The magnitude of the electron source is increased to improve agreement with measurements in the buildup region in the largest fields. Published measurements provide an estimate of backscatter on monitor chamber response. Commissioning consists of selecting the electron beam energy, determining the scale factor that defines dose per monitor unit, and describing treatment-dependent beam modifiers. We compare calculations with measurements in a water phantom for open fields, wedges, blocks, and a multileaf collimator for 6 and 18 MV Varian Clinac 2100C photon beams. All calculations are reported as dose per monitor unit. Aside from backscatter estimates, no additional, field-specific normalization is included in comparisons with measurements. Maximum discrepancies were less than either 2% of the maximum dose or 1.2 mm in isodose position for all field sizes and beam modifiers.

Laser performance operations model

The laser performance operations model (LPOM) is developed to provide real-time predictive capabilities for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. LPOM uses diagnostic feedback from previous NIF shots to maintain accurate energetics models for each of the 192 NIF beamlines (utilizing one CPU per laser beamline). This model is used to determine the system setpoints (initial power, waveplate attenuations, laser diagnostic settings) required for all requested NIF shots. In addition, LPOM employs optical damage models to minimize the probability that a proposed shot may damage the system. LPOM provides postshot diagnostic reporting to support the NIF community. LPOM was deployed prior to the first main laser shots in NIF, and has since been used to set up every shot in NIFs first quad (four beamlines). Real-time adjustments of the code energetics parameters allow the LPOM to predict total energies within 5%, and provide energy balance within the four beamlines to within 2% for shots varying from 0.5 to 26 kJ (1.053 µm) per beamline. The LPOM has been a crucial tool in the commissioning of the first quad of NIF.

Preformance and operational modeling of the National Ignition Facility

The National Ignition Facility (NIF), currently under construction at the University of California s Lawrence Livermore National Laboratory (LLNL) is a stadium-sized facility containing a 192-beam, 1.8 Megajoule, 500-Terrawatt, 351-nm laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. NIF is being built by the National Nuclear Security Administration and when completed will be the world s largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF s 192 energetic laser beams will compress fusion targets to conditions where they will ignite and burn, liberating more energy than required to initiate the fusion reaction. The first four beamlines (a quad) are currently being commissioned, with increasingly energetic laser pulses being propagated throughout the laser system. Success on many of the NIF laser s missions depends on obtaining precisely specified energy waveforms from each of the 192 beams over a wide variety of pulse lengths and temporal shapes. A computational system, the Laser Performance Operations Model (LPOM) has been developed and deployed during NIF commissioning to automate the laser setup process, and accurately predict laser energtics. For each shot on NIF, the LPOM determines the characteristics of the injection laser system required to achieve the desired main laser output, provides parameter checking for equipment protection, determines the required diagnostic setup, and supplies post-shot data analysis and reporting.

Laser Performance Operations Model (LPOM)

The Laser Performance Operations Model (LPOM) has been developed to provide real-time predictive capabilities for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. LPOM uses diagnostic feedback from previous NIF shots to maintain accurate energetics models for each of the 192 NIF beamlines (utilizing one CPU per laser beamline). This model is used to determine the system set-points (initial power, waveplate attenuations, laser diagnostic settings) required for all requested NIF shots. In addition, LPOM employs optical damage models to minimize the probability that a proposed shot may damage the system. LPOM also provides post-shot diagnostic reporting to support NIF experimenters. LPOM was deployed prior to the first main laser shots in NIF in mid-2002 and has been used to set up the every laser shot in NIFs first quad of four laser beamlines. Real-time adjustments of the LPOM energetics parameters allows the LPOM team to predict total beam energies within 5%, and to provide energy balance among the four beamlines to within 2% for shots varying from 0.5 to 26 kJ (1w) per beamline. The LPOM has been a crucial tool in the commissioning of the first quad of NIF.

Laser performance operations model (LPOM): a computational system that automates the setup and performance analysis of the national ignition facility

The National Ignition Facility (NIF) is a stadium-sized facility containing a 192-beam, 1.8 MJ, 500-TW, 351-nm laser system together with a 10-m diameter target chamber with room for many target diagnostics. NIF will be the worlds largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. A computational system, the Laser Performance Operations Model (LPOM) has been developed and deployed that automates the laser setup process, and accurately predict laser energetics. LPOM determines the settings of the injection laser system required to achieve the desired main laser output, provides equipment protection, determines the diagnostic setup, and supplies post shot data analysis and reporting.

Laser energetics and propagation modelling for the NIF

Design, activation, and operation of modern high-energy, fusion-class lasers rely heavily on accurate simulation of laser performance. Setup, equipment protection, and data interpretation of the National Ignition Facility(1) (NIF) at Lawrence Livermore National Laboratory (LLNL) are being controlled by a Laser Performance Operations Model (LPOM) (2), which, at its core, utilizes a Virtual Beam Line (VBL) simulation code to predict laser energetics, wavefront, near- and far-field beam profiles, and damage risk prior to each shot. This same simulation tool is being used widely to understand such diverse phenomena as regenerative-amplifier saturation, damage inspection system performance, fratricide risk from small-scale flaws in large optics, converter performance, and conjugate image formation.

PEREGRINE: Bringing Monte Carlo based Treatment Planning Calculations to Today’s Clinic

Monte Carlo simulation of radiotherapy is now available for routine clinical use. It brings improved accuracy of dose calculations for treatments where important physics comes into play, and provides a robust, general tool for planning where empirical solutions have not been implemented. Through the use of Monte Carlo, new information, including the effects of the composition of materials in the patient, the effects of electron transport, and the details of the distribution of energy deposition, can be applied to the field.

Laser performance operations model (LPOM): The computational system that automates the setup and performance analysis of the National Ignition Facility

The National Ignition Facility (NIF) is a stadium-sized facility containing a 192-beam, 1.8 MJ, 500-TW, 351-nm laser system together with a 10-m diameter target chamber with room for many target diagnostics. NIF is the world’s largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. A computational system, the Laser Performance Operations Model (LPOM) has been developed that automates the laser setup process, and accurately predict laser energetics. LPOM uses diagnostic feedback from previous NIF shots to maintain accurate energetics models (gains and losses), as well as links to operational databases to provide ‘as currently installed’ optical layouts for each of the 192 NIF beamlines. LPOM deploys a fully integrated laser physics model, the Virtual Beamline (VBL), in its predictive calculations in order to meet the accuracy requirements of NIF experiments, and to provide the ability to determine the damage risk to optical elements throughout the laser chain. LPOM determines the settings of the injection laser system required to achieve the desired laser output, provides equipment protection, and determines the diagnostic setup. Additionally, LPOM provides real-time post shot data analysis and reporting for each NIF shot. The LPOM computation system is designed as a multi-host computational cluster (with 200 compute nodes, providing the capability to run full NIF simulations fully parallel) to meet the demands of both the controls systems within a shot cycle, and the NIF user community outside of a shot cycle.

Laser Performance Operations Model (LPOM): A Tool to Automate the Setup and Diagnosis of the National Ignition Facility

The National Ignition Facility (NIF), currently under construction at the University of Californias Lawrence Livermore National Laboratory (LLNL) is a stadium-sized facility containing a 192-beam, 1.8 Megajoule, 500-Terrawatt, 351-nm laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. NIF is being built by the National Nuclear Security Administration and when completed will be the worlds largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIFs 192 energetic laser beams will compress fusion targets to conditions where they will ignite and burn, liberating more energy than required to initiate the fusion reaction. The commissioning of the first four beamlines (a quad) was completed in October 2004 -- a two-year period where a wide variety of energetic laser pulses were propagated through the laser system. Success on many of the NIF lasers missions depends on obtaining precisely specified energy waveforms from each of the 192 beams over a wide variety of pulse lengths and temporal shapes. A computational system, the Laser Performance Operations Model (LPOM) has been developed and deployed during NIF commissioning to automate the laser setup process, and accurately predict laser energtics. For each shot on NIF, the LPOM determines the characteristics of the injection laser system required to achieve the desired main laser output, provides parameter checking for equipment protection, determines the required diagnostic setup, and supplies post-shot data analysis and reporting. LPOM was deployed prior to the first main laser shots in NIF, and has since been used to set up every shot in NIFs first quad (four beamlines). Real-time adjustments of the LPOM energetics model allows NIF to routinely deliver energies within 3%, of requested and provide energy balance within the four beamlines to within 2% for shots varying from 0.5 to 26 kJ (1.053 μm) per beamline. The LPOM has been a crucial tool in the commissioning of the first four beamlines (a quad) of NIF.