LLE Review 103

Review 103


This volume of the LLE Review, covering April—June 2005, features the design and optimization of targets for fast-ignition inertial confinement fusion relevant to direct-drive inertial fusion energy. It is shown that a 750-kJ laser can assemble fuel with VI = 1.7 × 107 cm/s, α = 0.7, ρ = 400 g/cc, ρR = 3 g/cm2, and a hot-spot volume of less than 10% of the compressed core. If fully ignited, this fuel assembly can produce energy gains of 150.

Recent OMEGA experiments have studied the fuel assembly of gas-filled, cone-in-shell, fast-ignition targets. Using both fusion products and backlit images, an areal density of ~60-70 mg/cm2 was inferred for the dense core assembly. The results are promising for successful integrated fast-ignition experiments on the OMEGA EP Facility, scheduled for completion in 2007.

Additional research developments presented in this issue include the following:

  • A high-performance "planar" Cryogenic Target Handling System has been added to LLE's OMEGA Laser Fusion Facility. The system has demonstrated a shot-to-shot cycle interval of less than two hours and has fielded more than 125 experiments using several distinct target types. An overview of the cryogenic capabilities at LLE and a comparison of operational requirements of LLE's spherical and planar cryogenic systems is given.
  • Nonlinear growth measurements of 3-D broadband nonuniformities near saturation using x-ray radiography in planar foils accelerated by laser light have been made. The initial target modulations were seeded by laser nonuniformities and later amplified during acceleration by the Rayleigh—Taylor instability.
  • The significant developments in tritium-capture technology that have occurred over the past two decades are described. The merits and drawbacks of the various technologies that have been developed for both air and inert gas streams are discussed.
  • An all-solid-state, diode-pumped Nd:YLF laser system has been developed and tested. It produces fiducial timing signals at three wavelengths (fundamental, second, and fourth harmonics) and will be used as a primary timing reference for the OMEGA facility diagnostics. Performance results of the new OMEGA fiducial laser are reported.
  • Extended x-ray absorption fine structure (EXAFS) measurements have been used to demonstrate the phase transformation from body-centered-cubic (bcc) to hexagonal-closely-packed (hcp) iron due to nanosecond, laser-generated shocks. This is a direct, atomic-level, and in-situ proof of shock-induced transformation in iron.

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