Systematic Fuel Cavity Asymmetries in Directly Driven Inertial Confinement Fusion Implosions

Shah, Rahul; Haines, Brian; Wysocki, F. J.; Benage, J.F.; Fooks, J. A.; Glebov, V. Yu.; Hakel, P.; Hoppe, M.; Igumenshchev, I. V.; Kagan, Grigory; Mancini, Roberto; Marshall, F. J.; Michel, D. T.; Murphy, T. J.; Schoff, M. E.; Silverstein, K.; Stoeckl, C.; Yaakobi, B.

doi:10.1103/physrevlett.118.135001

Cited by 26 publications

(11 citation statements)

References 23 publications

(27 reference statements)

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“…The experimental evidence of low-mode asymmetries includes the x-ray self-emission imaging from a tracer Ti layer embedded into CH shell [36]. This technique shows significant low-mode nonuniformities developed during deceleration.…”

Section: D Simulation Resultsmentioning

confidence: 99%

National direct-drive program on OMEGA and the National Ignition Facility

Goncharov

Regan

Campbell

et al. 2016

Plasma Phys. Control. Fusion

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A major advantage of the laser direct-drive (DD) approach to ignition is the increased fraction of laser drive energy coupled to the hot spot and relaxed hot-spot requirements for the peak pressure and convergence ratios relative to the indirect-drive approach at equivalent laser energy. With the goal of a successful ignition demonstration using DD, the recently established national strategy has several elements and involves multiple national and international institutions. These elements include the experimental demonstration on OMEGA cryogenic implosions of hot-spot conditions relevant for ignition at MJ-scale energies available at the National Ignition Facility (NIF) and developing an understanding of laser-plasma interactions and laser coupling using DD experiments on the NIF. DD designs require reaching central stagnation pressures in excess of 100 Gbar. The current experiments on OMEGA have achieved inferred peak pressures of 56 Gbar (Regan et al 2016 Phys. Rev. Lett. 117 025001). Extensive analysis of the cryogenic target experiments and two-and three-dimensional simulations suggest that power balance, target offset, and target quality are the main limiting factors in target performance. In addition, cross-beam energy transfer (CBET) has been identified as the main mechanism reducing laser coupling. Reaching the goal of demonstrating hydrodynamic equivalence on OMEGA includes improving laser power balance, target position, and target quality at shot time. CBET must also be significantly reduced and several strategies have been identified to address this issue.

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Section: D Simulation Resultsmentioning

confidence: 99%

National direct-drive program on OMEGA and the National Ignition Facility

Goncharov

Regan

Campbell

et al. 2016

Plasma Phys. Control. Fusion

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“…Shifts in the mean neutron energy were then interpreted as bulk collective fluid motion with the use of Eqs. (1) and (2).…”

Section: Measurementsmentioning

confidence: 99%

Calibration of a neutron time-of-flight detector with a rapid instrument response function for measurements of bulk fluid motion on OMEGA

Mannion

Glebov

Forrest

et al. 2018

Review of Scientific Instruments

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A newly developed neutron time-of-flight (nTOF) diagnostic with a fast instrument response function has been fielded on the OMEGA laser in a highly collimated line of sight. By using a small plastic scintillator volume, the detector provides a narrow instrument response of 1.7 ns full width at half maximum while maintaining a large signal-to-noise ratio for neutron yields between 10 10 and 10 14. The OMEGA hardware timing system is used along with an optical fiducial to provide an absolute nTOF measurement to an accuracy of ∼56 ps. The fast instrument response enables the accurate measurement of the primary deuterium-tritium neutron peak shape, while the optical fiducial allows for an absolute neutron energy measurement. The new detector measures the neutron mean energy with an uncertainty of ∼7 keV, corresponding to a hot-spot velocity projection uncertainty of ∼12 km/s. Evidence of bulk fluid motion in cryogenic targets is presented with measurements of the neutron energy spectrum.

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“…challenges to ICF ignition. [16][17][18] These low-mode asymmetries induce flows in the burning fuel and can manifest as T ion asymmetries. nTOF measurements of the primary DT neutron spectrum at OMEGA show evidence of such asymmetries, 19 which are important to control and understand.…”

Section: Introductionmentioning

confidence: 99%

Measurement of apparent ion temperature using the magnetic recoil spectrometer at the OMEGA laser facility

Johnson

Katz

Forrest

et al. 2018

Review of Scientific Instruments

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The Magnetic Recoil neutron Spectrometer (MRS) at the OMEGA laser facility has been routinely used to measure deuterium-tritium (DT) yield and areal density in cryogenically layered implosions since 2008. Recently, operation of the OMEGA MRS in higher-resolution mode with a new smaller, thinner (4 cm 2 , 57 µm thick) CD 2 conversion foil has also enabled inference of the apparent DT ion temperature (T ion) from MRS data. MRS-inferred T ion compares well with T ion as measured using neutron time-of-flight spectrometers, which is important as it demonstrates good understanding of the very different systematics associated with the two independent measurements. The MRS resolution in this configuration, ∆E MRS = 0.91 MeV FWHM, is still higher than that required for a high-precision T ion measurement. We show how fielding a smaller foil closer to the target chamber center and redesigning the MRS detector array could bring the resolution to ∆E MRS = 0.45 MeV, reducing the systematic T ion uncertainty by more than a factor of 4.

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Systematic Fuel Cavity Asymmetries in Directly Driven Inertial Confinement Fusion Implosions

Cited by 26 publications

References 23 publications

National direct-drive program on OMEGA and the National Ignition Facility

National direct-drive program on OMEGA and the National Ignition Facility

Calibration of a neutron time-of-flight detector with a rapid instrument response function for measurements of bulk fluid motion on OMEGA

Measurement of apparent ion temperature using the magnetic recoil spectrometer at the OMEGA laser facility

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