Performance of direct-drive cryogenic targets on OMEGA

Goncharov, V. N.; Sangster, T. C.; Radha, P. B.; Betti, R.; Boehly, T. R.; Collins, T. J. B.; Craxton, R. S.; Delettrez, J. A.; Epstein, R.; Glebov, V. Yu.; Hu, S. X.; Igumenshchev, I. V.; Knauer, J.P.; Loucks, S. J.; Marozas, J.A.; Marshall, F. J.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Regan, S. P.; Seka, W.; Skupsky, S.; Smalyuk, V. A.; Soures, J. M.; Stoeckl, C.; Shvarts, D.; Frenje, J. A.; Petrasso, R. D.; Li, C. K.; Sèguin, F. H.; Manheimer, Wallace M.; Colombant, D.

doi:10.1063/1.2856551

Cited by 97 publications

(43 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…LILAC includes a nonlocal electron thermal conduction model [21], a CBET model [16], and a new CH first-principles equation of state [22]. The 1D simulations match the experimental observables throughout the implosion, including the scattered laser light energy and spectrum [23], shell trajectories [24], and neutron bang time [13].…”

Section: =3mentioning

confidence: 99%

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Regan¹,

Goncharov²,

Igumenshchev³

et al. 2016

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

A record fuel hot-spot pressure P hs ¼ 56 AE 7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition [A. Bose et al., Phys. Rev. E 93, LM15119ER (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laserdrive nonuniformity and target-positioning error reduces target performance. DOI: 10.1103/PhysRevLett.117.025001 The spherical concentric layers of a direct-drive inertial confinement fusion (ICF) target nominally consist of a central region of a near-equimolar deuterium and tritium (DT) vapor surrounded by a cryogenic DT-fuel layer and a thin, nominally plastic (CH) ablator. The outer surface of the ablator is uniformly irradiated with multiple laser beams having a peak overlapped intensity of <10 15 watts=cm 2 . The resulting laser-ablation process causes the target to accelerate and implode. As the DT-fuel layer decelerates, the initial DT vapor and the fuel mass thermally ablated from the inner surface of the ice layer are compressed and form a central hot spot, in which fusion reactions occur. ICF relies on the 3.5-MeV DT-fusion alpha particles depositing their energy in the hot spot, causing the hotspot temperature to rise sharply and a thermonuclear burn wave to propagate out through the surrounding nearly degenerate, cold, dense DT fuel, producing significantly more energy than was used to heat and compress the fuel. Ignition is predicted to occur when the product of the temperature and areal density of the hot spot reach a minimum of 5 keV × 0.3 g=cm 2 [1-3]. Currently, the 192-beam, 351-nm, 1.8-MJ National Ignition Facility (NIF) [4] is configured for indirectdrive-ignition experiments using laser-driven hohlraums to accelerate targets via x-ray ablation. Approximately 26 kJ of thermonuclear fusion energy has been recorded on the NIF using indirect-drive ICF targets [5], where alpha heating has boosted the fusion yield by a factor of ∼2.5 from that caused by the implosion system alone [6,7]. The indirect-drive NIF implosions have achieved over 60% of the Lawson parameter Pτ required for ignition, where P is the pressure and τ is the confinement time [6]. Here P and τ are estimated without accounting for alpha heating to assess the pure hydrodynamic performance. The goal of achieving laboratory fusion and progress made with direct-drive ICF over the last decade motivate direct-drive implosions on NIF [8,9]. Hot-spot formation for spherically symmetric, direct-drive, DT-layered implosions is st...

show abstract

Section: =3mentioning

confidence: 99%

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Regan¹,

Goncharov²,

Igumenshchev³

et al. 2016

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Differences between diffusion and more detailed modeling of electron conduction have long been known and have motivated the development of physics-based non-local heat transport models. [27][28][29][30][31][32] Two of these models (Refs. 30 and 31) have recently been shown to improve the modeling of hohlraum energetics 33 and shock timing.…”

Section: Calculation Setupmentioning

confidence: 99%

The effects of laser absorption on direct-drive capsule experiments at OMEGA

et al. 2012

Self Cite

View full text Add to dashboard Cite

The yield of an inertial confinement fusion capsule can be greatly affected by the inclusion of high-Z material in the fuel, either intentionally as a diagnostic or from mixing due to hydrodynamic instabilities. To validate calculations of these conditions, glass shell targets filled with a D 2 and 3 He fuel mixture were fielded in experiments with controlled amounts of pre-mixed Ar, Kr, or Xe. The experiments were fielded at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using 1.0 ns square laser pulses having a total energy 23 kJ and direct drive illumination of shells with an outer diameter of $925 lm and a thickness of $5 lm. Data were collected and compared to one-dimensional integrated models for yield and burn-temperature measurements. This paper presents a critical examination of the calculational assumptions used in our experimental modeling. A modified treatment of laser-capsule interaction improves the match to the measured scattered laser light and also improves agreement for yields, burn-temperatures, and the fuel compression as measured by the ratio of two yields. Remaining discrepancies between measurement and calculation will also be discussed. V C 2012 American Institute of Physics. [http://dx

show abstract

“…Adiabat control is critical to achieving the desired R at peak compression [1,2]. Shock mistiming was an important cause of R degradation in direct-drive, cryogenic implosions on OMEGA and a subject of intensive research [5,6]. Another area of concern to ICF is the unstable growth of target modulations caused by hydrodynamic instabilities [1,2].…”

mentioning

confidence: 99%

Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

et al. 2010

Self Cite

View full text Add to dashboard Cite

Direct-drive implosions with 20-m-thick glass shells were conducted on the Omega Laser Facility to test the performance of high-Z glass ablators for direct-drive, inertial confinement fusion. The x-ray signal caused by hot electrons generated by two-plasmon-decay instability was reduced by more than $40Â and hot-electron temperature by $2Â in the glass compared to plastic ablators at ignition-relevant drive intensities of $1 Â 10 15 W=cm 2 , suggesting reduced target preheat. The measured absorption and compression were close to 1D predictions. The measured soft x-ray production in the spectral range of $2 to 4 keV was $2Â to 3Â lower than 1D predictions, indicating that the shell preheat caused by soft x-rays is less than predicted. A direct-drive-ignition design based on glass ablators is introduced. DOI: 10.1103/PhysRevLett.104.165002 PACS numbers: 52.57.ÀzThe goal of inertial confinement fusion (ICF) [1,2] is to implode a spherical target to achieve high compression of the fuel and high temperature in the hot spot to trigger ignition and maximize the thermonuclear energy gain. To achieve high compression, the shell entropy and temperature must remain low because it is easier to compress the fuel at a low temperature than at a high temperature [2]. The entropy is defined [3] by adiabat ¼ PðMbÞ=½2:2 ðg=ccÞ 5=3 , the ratio of the plasma pressure to the Fermi pressure of a fully degenerate electron gas [3]. In direct-drive spherical implosions, the target is driven by direct illumination with overlapped laser beams. To ignite DT fuel on the National Ignition Facility (NIF) [2] with a laser energy of E L ¼ 1:5 MJ and to achieve a gain of $40 to 50 will require high fuel compression with a total target areal density ( R) of $1500 mg=cm 2 [4]. As shown in Ref.[3], Rðmg=cm 2 Þ % 2600E L ðMJÞ 1=3 À0:6 so high areal densities require low-adiabat, 3 implosions. The fuel adiabat is determined by shocks launched at the beginning of the implosion [2]. The shock waves must be precisely tuned to set the inner portion of the shell on a low adiabat. Adiabat control is critical to achieving the desired R at peak compression [1,2]. Shock mistiming was an important cause of R degradation in direct-drive, cryogenic implosions on OMEGA and a subject of intensive research [5,6]. Another area of concern to ICF is the unstable growth of target modulations caused by hydrodynamic instabilities [1,2]. While the areal densities at peak compression have been shown to be relatively insensitive to hydrodynamic instabilities, the fusion neutron yields are very sensitive [7]. Shell preheat, another source of compression degradation, is caused by hot electrons generated by two-plasmon-decay (TPD) instability [8,9]. This preheat was shown to be virulent in DT and D 2 ablators [6,10] and was reduced by using plastic ablators [6,11]. The highest ignition-relevant areal densities with a shell R of $200 mg=cm 2 were achieved in cryogenic D 2 -ice implosions with plastic ablators, when the hotelectron preheat was suppressed, at a moderate laser-dr...

show abstract

Performance of direct-drive cryogenic targets on OMEGA

Cited by 97 publications

References 24 publications

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

The effects of laser absorption on direct-drive capsule experiments at OMEGA

Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

Contact Info

Product

Resources

About