Alignment and wavefront control systems of the National Ignition Facility

Zacharias, R.; Beer, Neil Reginald; Bliss, Erlan S.; Burkhart, Scott C.; Cohen, Simon J.; Sutton, Steven B.; Atta, Rinki; Winters, Scott; Salmon, J. Thaddeus; Latta, M. R.; Stolz, Christopher J.; Pigg, D.; Arnold, Timothy

doi:10.1117/1.1815331

Cited by 81 publications

(41 citation statements)

References 2 publications

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“…The image plane for this sensor is the last of the four tiled gratings inside the compressor. The Hartmann-Shack sensor is also used at National Ignition Facility (NIF) [2] for phase measurements, where the beam passes though a micro-lens array and is focused on a CCD. A hexagonal lens array of 77 micro-lenses is used to form the focal spot array and a measurement accuracy of 0.1λ is achieved at 1.053 mm in the offline test.…”

Section: Hartmann-shack Wavefront Sensormentioning

confidence: 99%

“…High power solid-state laser facilities for Inertial Confinement Fusion (ICF) employ thousands of large optical components, including amplifiers, polarizing films, electro-optical switches, lenses, and mirrors [1][2][3] . These components usually possess large sizes and weights; some of them have diameters larger than half a meter and weigh up to hundreds of kilogram.…”

Section: Introductionmentioning

confidence: 99%

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Wavefront measurement techniques used in high power lasers

Wang

Liu

et al. 2014

High Pow Laser Sci Eng

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Section: Hartmann-shack Wavefront Sensormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Wavefront measurement techniques used in high power lasers

Wang

Liu

et al. 2014

High Pow Laser Sci Eng

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“…Like NIF, the laser is an image-relayed, four-pass-amplifier design; the pulses propagate to the target area through a system of transport optics; and each beam is precisely aligned to a specific point on the target. 50,51 However, there are also some important differences: LIFE operates continuously at 16Hz, while NIF is a single shot system; pump light as well as the pulsed beam must be aligned; the output from the fusion engine places new limitations on the location of control electronics; and finally, each pulse must hit a moving target. It is important to note that shooting this small target is not outside demonstrated commercial capabilities.…”

Section: Beam Controlmentioning

confidence: 99%

“…50 LIFE requires a similar capability, but its amplifiers introduce significantly more thermal distortion at the beam edges. This occurs because the size of the pumped footprint is closely matched to the beam size for maximum efficiency and produces large index gradients at the edge.…”

Section: Xb Wavefront Correctionmentioning

confidence: 99%

Compact, Efficient, Low-cost Lasers (CELL) Project: Final Report

Deri¹,

Bayramian²,

Erlandson³

2012

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PROJECT MOTIVATION and SCOPEDevelopment of clean, sustainable and affordable energy sources is a national and international challenge. Inertial Fusion Energy (IFE) may provide a transformational solution that is scalable, proliferationresistant, and that generates negligible nuclear waste. To produce energy economically competitive with alternative power plants, the IFE laser drive must operate at a high repetition rate (>10 Hz) with high efficiency (>10%), while maintaining beam quality suitable for focusing to a small spot suitable for compressing the fusion target. The NIF laser system meets the beam quality requirements using a solidstate gain medium pumped by flashlamps. Scaling from NIF to IFE requires increases of ~10 5 in rep rate and ~20X in efficiency, which adds significant challenges to the laser design. The increased repetition rate results in much more waste heat generated in the system, and the prevention of thermal beam quality degradation (through phenomena such as thermally-induced birefringence) becomes a critical issue. While thermal issues are mitigated by increasing the system volume, a major size increase renders the system less economical and less easy to site. LIFE laser efficiency targets can be achieved at high rep rate without reliability degradation by using diode lasers as pumps. An IFE plant requires ~10 8 diode laser bars. At current costs the diodes dominate the overall laser cost and render IFE less cost-effective. Thus, designing a compact and cost-effective laser system with the repetition rate, efficiency, and beam quality required for IFE presents a significant technical challenge.The goal of the CELL strategic initiative was to develop new laser architectures to address these challenges by leveraging recent advances in optical technology. New laser design options have become potentially feasible due to improvements in laser gain media, diode pumps, large aperture nonlinear optics, and damage-resistant optics that have occurred since NIF's conception. The project investigated designs that take advantage of these advances, combining them with advanced and novel subsystem concepts to achieve laser designs with significantly improved performance, size, and cost. APPROACHA primary objective of this project was to rapidly evaluate a variety of beamline concepts and architectures, to ascertain their suitability for IFE applications. This is best done in simulation, due to the time and expense associated with prototyping such systems, even at significantly reduced scale. These evaluations were performed rapidly using a laser energetics code ("LPM") specifically developed for this project. This tool tracks all system inefficiencies from wallplug power to the final optic, includes the power consumed by cooling systems, and captures the behavior of different laser materials. In particular, it is suitable for simulating both four-level (e.g.; Nd-based) and three-level (e.g.; Yb-based) gain media. In order to achieve fast run-times, LPM abstracts away details of optical diffraction and ...

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“…The key functions of the NIF laser such as specifying pulse shape, alignment, amplification and beam control are managed by the integrated computer control system (ICCS) in order to produce proper timing, high-energy density and pressure leading to a controlled fusion reaction [4][5][6][7]. ICCS divides alignment, optics inspection and shot planning, etc.…”

Section: Introductionmentioning

confidence: 99%

Image processing and control of a programmable spatial light modulator for spatial beam shaping

et al. 2013

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Programmable spatial shapers using liquid-crystal-based spatial-light-modulators in the National Ignition Facility lasers enable spatial shaping of the beam profile so that power delivered to the target can be maximized while maintaining system longevity. Programmable spatial shapers achieve three objectives: Introduce obscurations shadowing isolated flaws on downstream optical elements that could otherwise be affected by high fluence laser illumination; Spatial shaping to reduce beam peak-to-mean fluence variations to allow the laser to operate at higher powers so that maximum power can be delivered to the target; And finally gradually exposing the optical regions that have never seen laser light because they have always had shadowing from a blocker that is no longer needed. In this paper, we describe the control and image processing algorithms that determine beam shaping and verification of the beam profile. Calibration and transmittance mapping essential elements of controlling the PSS are described along with spatially nonlinear response of the device such as scale and rotation.

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Alignment and wavefront control systems of the National Ignition Facility

Cited by 81 publications

References 2 publications

Wavefront measurement techniques used in high power lasers

Wavefront measurement techniques used in high power lasers

Compact, Efficient, Low-cost Lasers (CELL) Project: Final Report

Image processing and control of a programmable spatial light modulator for spatial beam shaping

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