The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory contains a 192-beam 4.2 MJ neodymium glass laser (around 1053 nm or 1w) that is frequency converted to 351nm light or 3w. It was built to access the extreme high energy density conditions needed to support the nation’s nuclear stockpile in the absence of further underground nuclear tests, including studying Inertial Confinement Fusion (ICF) and ignition in the laboratory.
Over the last year, important results have been obtained demonstrated a fusion yield of 1.35MJ with 1.9MJ of laser energy (and 440 TW power) injected in the target, bringing the NIF to the threshold of ignition [2-3]. As the yield curve near ignition is steep, the laser performance team has focused on providing improved power accuracy and precision (better shot-to-shot reproducibility) with a high-fidelity pulse shaping system (HiFiPS), and also on extending the NIF operating power and energy space by 15% to 2.2MJ and 500TW.
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory contains a
192-beam 4.2 MJ neodymium glass laser (around 1053 nm or 1w) that is frequency converted to
351nm light or 3w. It has been designed to support the study of Inertial Confinement Fusion (ICF)
and High Energy Density Physics (HEDP). The NIF Precision Diagnostic System (PDS) was reactivated and new
diagnostic packages were designed and fielded that offer a more comprehensive suite
of high-resolution measurements. The current NIF laser performance will be presented as well as the preliminary results obtained with the various laser experimental campaigns using the new diagnostic tool suites.
KEYWORDS: Diagnostics, National Ignition Facility, Cameras, Near field, Wavefronts, Sensors, Signal to noise ratio, Calibration, Near field optics, Imaging systems
The Precision Diagnostic System (PDS) is an advanced set of laser diagnostic tools installed within the National Ignition Facility (NIF). It is capable of picking off a single, full aperture, 1053nm (1ω) beamline before the beam propagates to the target chamber and directing it to a suite of precision laser diagnostics. It was instrumental in validating the performance of the final optics 3Ω frequency conversion system design when NIF was built. The PDS has recently been recommissioned after more than a decade of non-use and enhanced to better understand laser performance limitations1 and to characterize underperforming beams. In addition to recommissioning existing diagnostics for calorimetry, power, wavefront, near-field and far-field imaging, new diagnostics have been added: two types of time-resolved near field imaging systems; higher resolution wavefront imaging; and a 1ω spectrometer. Additionally, the beam transport system was upgraded to allow PDS to select among four different 1ω beamlines to enable improved understanding of beam-to-beam variations. Two of these four beams are top-hemisphere beams, while two are bottom-hemisphere, with known performance variations. The results from NIF Shots with the new and recommissioned PDS diagnostic (spatial resolution, dynamic range, time gating, etc..) will be reviewed and data up to 14 kJ, 3.2 TW will be presented.
The National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory, is the world’s largest and highest-energy laser system. NIF’s 192 intense laser beams can deliver more energy than any previous laser system with a design point of 1.8 MJ of UV and 500 TW peak power. Efforts are currently underway to better understand the NIF performance and its limitations. One goal of recent and future campaigns is to better understand the accumulation of Bintegral within the NIF laser using existing diagnostics, as well as the Precision Diagnostic System (PDS). Among these diagnostics, the Shack-Hartmann (SH) sensor in the Output Sensor Package (OSP), a standard NIF diagnostic, and the dedicated PDS Radial Shearing Interferometer (RSI) both measure the wavefront of the beam. Using these diagnostics in concert with the NIF Programmable Spatial Shaper (PSS), which is used to tailor arbitrary spatial beam profiles, we have performed integrated experiments to study the B-Integral induced wavefront through the entire NIF main laser. We propagated a probe beam with a slowly varying spatial intensity profile through the NIF laser to produce a spatially varying B-Integral induced wavefront at the laser output, from which we obtained the magnitude of the B-Integral of the system. We present these direct measurements of the spatially resolved B-Integral induced wavefront scaled for the first time from a table-top experiment to a fusion-class laser chain. These measurements are compared to results of current simulations using Virtual Beamline (VBL) software.
The National Ignition Facility (NIF) laser produces 192 pulsed beams with transverse dimensions ∼40 cm × 40 cm and a diversity of temporal shapes with typical durations ranging from 1 to 30 ns and a total energy on target up to 2.1 MJ in the UV.1 Standard diagnostics include near-field cameras that record the spatial dependence of the time-integrated pulse fluence, as well as sensors that record the spatially integrated pulse power versus time. While these diagnostics are indispensable, beamlines and the pulses they transport may be better characterized with a diagnostic that reveals more of the spatio-temporal pulse structure, i.e., the local irradiance, especially in the presence of nonlinear optical effects. Recently, the time-resolving capability of the Icarus camera has been leveraged in the Precision Diagnostic System (PDS) at the NIF. The Icarus is a gated CMOS sensor designed to capture X-ray images in various experimental settings.2, 3 However, its sensitivity in the near-IR is sufficient for capturing time-gated images of NIF beams, thus opening the door to better characterization than is possible with standard space- and/or time-integrated diagnostics. In this work, we present the first time-gated beam profiles measured in PDS at the NIF during high-energy and high-peak-power experiments, and discuss their implications in terms of past, present, and future laser performance.
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