Direct-drive cryogenic target implosion performance on OMEGA

Abstract

Layered and characterized cryogenic D2 capsules have been imploded using both low- and high-adiabat (α, the ratio of the electron pressure to the Fermi-degenerate pressure) pulse shapes on the 60-beam OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at the Laboratory for Laser Energetics (LLE). These experiments measure the sensitivity of the direct-drive implosion performance to parameters such as the inner-ice-surface roughness, the adiabat of the cryogenic fuel during the implosion, the laser power balance, and the single-beam nonuniformity. The goal of the direct-drive program at LLE is to demonstrate a high neutron-averaged fuel ρR at a significant fraction of the predicted one-dimensional (1-D) neutron yield using an energy-scaled, low-adiabat (α∼3) ignition pulse shape driving a hydrodynamically scaled deuterium–tritium ignition capsule. New results are reported from implosions of ∼920-μm-diam, thin (∼5 μm) polymer shells containing 100 μm D2-ice layers with characterized inner-surface ice roughness of 3–12 μm rms. These capsules have been imploded using ∼17–23 kJ of 351 nm laser light with a beam-to-beam rms energy imbalance of less than 5% and full beam smoothing [1 THz bandwidth, two-dimensional (2-D) smoothing by spectral dispersion and polarization smoothing]. Near-1-D performance has been measured for a high-adiabat (α∼25) drive pulse, and the implosion performance with a low-adiabat (α∼4) pulse is in agreement with 2-D hydrocode predictions.

Cryogenic Hydrogen Fuel for Controlled Inertial Confinement Fusion (Review of World Results)

“…-в Лаборатории лазерной энергетики США действует лазерная установка OMEGA UPGRADE. Энергия лазера 30 кДж в 60 пучках лазерного излучения [26,27,57,99]; -в России, в РФЯЦ-ВНИИЭФ действуют установки ИТС ИСКРА-5 (12 пучков лазерного излуче-ния) и ЛУЧ (4 пучка лазерного излучения) [100,101]. Энергия лазера в этих установках составляет 12-15 кДж.…”

An accelerator based fusion-product source for development of inertial confinement fusion nuclear diagnostics

“…They feature many improvements, including the ability to detect protons with energies as low as 3 MeV, and therefore probe denser plasmas that are created in low-adiabat cryogenic implosions. 17 An absolute calibration of these spectrometers is currently underway using the accelerator. Using two filters of aluminum in front of the WRF, a discrete 3-line proton spectrum is being generated and used for the calibration (Fig.…”

Effects of Nonuniform Illumination on Implosion Asymmetry in Direct-Drive Inertial Confinement Fusion

“…(3) is useful for estimating behavior in future experiments. On OMEGA, the performance of cryogenic implosions has been shown to be diminished when target offsets cause low-mode asymmetries [19,20]. Another example is cone-capsule, fastignition experiments on OMEGA [25], where there is no laser illumination on part of the capsule (essentially an ℓ = 1 mode).…”

“…The room-temperature capsules had plastic (CH) shells with nominal thickness 20 µm, and were filled with 18 atm of D 3 He or 15 atm of D 2 gas. Each imploded cryogenic capsules had a 80-100 µm D 2 ice layer inside a ~ 5µm CH shell [19,20]. The primary [21] or secondary protons [10] generated from D 3 He reactions (D+ 3 He→α+p) were measured.…”