Simultaneous visualization of wall motion, beam propagation, and implosion symmetry on the National Ignition Facility (invited)

Izumi, N.; Meezan, N. B.; Johnson, S.; Woodworth, B. N.; Woods, D. T.; Jones, O. S.; Landen, O. L.; Kroll, J. J.; Vonhof, S.; Nikroo, A.; Jaquez, J.; Kangas, K. W.; Bailey, C. G.; Hardy, Mike; Ehrlich, R.; Ralph, J. E.; Town, R. P. J.; Bradley, D. K.; Hinkel, D. E.; Moore, A. S.; Divol, L.; Young, C. V.; Moody, J. D.

doi:10.1063/1.5039364

Cited by 17 publications

(2 citation statements)

References 12 publications

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“…The attenuation of equatorial laser drive causes the T e to fall. Indeed, recent measurements to quantify inner beam transport give support to this explanation [27].…”

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confidence: 89%

Developing an Experimental Basis for Understanding Transport in NIF Hohlraum Plasmas

et al. 2018

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We report on the first multilocation electron temperature (T_{e}) and flow measurements in an ignition hohlraum at the National Ignition Facility using the novel technique of mid-Z spectroscopic tracer "dots." The measurements define a low resolution "map" of hohlraum plasma conditions and provide a basis for the first multilocation tests of particle and energy transport physics in a laser-driven x-ray cavity. The data set is consistent with classical heat flow near the capsule but reduced heat flow near the laser entrance hole. We evaluate the role of kinetic effects, self-generated magnetic fields, and instabilities in causing spatially dependent heat transport in the hohlraum.

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“…The attenuation of equatorial laser drive causes the T e to fall. Indeed, recent measurements to quantify inner beam transport give support to this explanation [27].…”

mentioning

confidence: 89%

Developing an Experimental Basis for Understanding Transport in NIF Hohlraum Plasmas

et al. 2018

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“…The principal challenge is propagation of the inner cone laser beams to the waist of the hohlraum. As shown in figure 3(a), expansion of the gold plasma ablated from the hohlraum by the laser pointed just inside the laser entrance holes, known as the 'gold bubble', begins to block the path of the inner cone beams [47,48]. Material ablated from the surface of the capsule also blows-off into the path of the inner cone beams.…”

Section: Low Modementioning

confidence: 99%

Progress of indirect drive inertial confinement fusion in the United States

Kline¹,

Batha²,

Benedetti³

et al. 2019

Nucl. Fusion

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Indirect drive converts high power laser light into x-rays using small high-Z cavities called hohlraums. X-rays generated at the hohlraum walls drive a capsule filled with deuterium–tritium (DT) fuel to fusion conditions. Recent experiments have produced fusion yields exceeding 50 kJ where alpha heating provides ~3× increase in yield over PdV work. Closing the gaps toward ignition is challenging, requiring optimization of the target/implosions and the laser to extract maximum energy. The US program has a three-pronged approach to maximize target performance, each closing some portion of the gap. The first item is optimizing the hohlraum to couple more energy to the capsule while maintaining symmetry control. Novel hohlraum designs are being pursued that enable a larger capsule to be driven symmetrically to both reduce 3D effects and increase energy coupled to the capsule. The second issue being addressed is capsule stability. Seeding of instabilities by the hardware used to mount the capsule and fill it with DT fuel remains a concern. Work reducing the impact of the DT fill tubes and novel capsule mounts is being pursed to reduce the effect of mix on the capsule implosions. There is also growing evidence native capsule seeds such as a micro-structure may be playing a role on limiting capsule performance and dedicated experiments are being developed to better understand the phenomenon. The last area of emphasis is the laser. As technology progresses and understanding of laser damage/mitigation advances, increasing the laser energy seems possible. This would increase the amount of energy available to couple to the capsule, and allow larger capsules, potentially increasing the hot spot pressure and confinement time. The combination of each of these focus areas has the potential to produce conditions to initiate thermo-nuclear ignition.

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Approaching a burning plasma on the NIF

et al. 2019

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The locus of National Ignition Facility (NIF) inertial confinement fusion (ICF) implosion data, in hot-spot burn-average areal density (ρR) and Brysk temperature (T) space, is shown and illustrates that several implosions are nearing a burning plasma state, where α-heating is the dominant source of plasma heating. A formula for diagnosing a burning plasma using measured/inferred data from ICF implosion experiments is given with the underlying derivation. Plotting ICF implosion performance against inferred hot-spot energy illustrates the key need to maximize the delivery of energy to an implosion hot-spot. A very compact analytical equation for α-heating is given, which shows that fundamentally, α-heating provides a discrete “boost” to pVγ of an implosion hot-spot. It is then shown numerically that the analytical expression for the amplification of pVγ is simply related to yield amplification and to other more famous metrics used for inferring yield amplification in experiments. Interestingly, the argument of the pVγ boost equation appears to provide a fundamental ignition condition that implicitly includes the effects of asymmetry, and it also exposes the origin of why there is uncertainty in defining single ignition criteria. The resulting analysis of NIF implosion data indicates that an increase in burn-average hot-spot temperature will be needed in order to ignite, and the strategy being pursued to achieve this goal is outlined.

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Simultaneous visualization of wall motion, beam propagation, and implosion symmetry on the National Ignition Facility (invited)

Cited by 17 publications

References 12 publications

Developing an Experimental Basis for Understanding Transport in NIF Hohlraum Plasmas

Developing an Experimental Basis for Understanding Transport in NIF Hohlraum Plasmas

Progress of indirect drive inertial confinement fusion in the United States

Approaching a burning plasma on the NIF

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