Simulation of afterglow plasma evolution in an inertial fusion energy chamber

Frolov, B. K.; Pigarov, A. Yu.; Krasheninnikov, S. I.; Petzoldt, R.W.; Goodin, Dana

doi:10.1016/j.jnucmat.2004.10.061

Cited by 3 publications

(2 citation statements)

References 5 publications

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“…In the 1D diffusion model used here, the radial neutral diffusion coefficients are calculated from first principles, from the first-order expansion of Chapman-Enskog theory [23], but an empirical correction factor (applied equally all neutral diffusion coefficients) is used to approximate the enhancement resulting from large-scale convective cells. Numerical simulations made for low pressure gas in inertial confinement fusion chambers suggest an enhancement factor D 0 = 2.3 [24]. However, better matching of observed DIII-D and JET recombination time scales is typically obtained here using slightly higher values D 0 ≈ 3 − 9, so a higher value D 0 = 5 is used in this work for extrapolating to ITER and SPARC.…”

Section: Recombination Time Scalementioning

confidence: 72%

Trends in runaway electron plateau partial recombination by massive H₂ or D₂ injection in DIII-D and JET and first extrapolations to ITER and SPARC

et al. 2023

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Experimental trends in thermal plasma partial recombination resulting from massive D_2 injection into high-Z (Ar) containing runaway electron (RE) plateaus in DIII-D and JET are studied for the purpose of achieving sufficiently low electron density (n_e≈10^18/m^3) to increase RE final loss MHD levels. In both DIII-D and JET, thermal electron density n_e is found to drop by ~ 100× when the thermal plasma partially recombines, with a minimum at a vacuum vessel-averaged D_2 density in the range 10^20-10^21/m^3. RE effective resistivity also drops after partial recombination, indicating expulsion of the Ar content. The n_e level after partial recombination is found to increase as RE current is increased. The amount of initial Ar in the RE plateau is not observed to have a strong effect on partial recombination. Partial recombination timescales of order 5 ms in DIII-D and 15 ms in JET are observed. These basic trends and timescales are matched with a 1D diffusion model, which is then used to extrapolate to ITER and SPARC tokamaks. It is predicted that ITER will be able to achieve sufficiently low n_e values on time scales faster than expected RE plateau vertical drift timescales (of order 100 ms), provided sufficient D_2 or H_2 is injected. In SPARC, it is predicted that achieving significant n_e recombination will be challenging, due to the very high RE current density. In both ITER and SPARC, it is predicted that achieving low n_e will be easier with Ar as a background impurity (rather than Ne).

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Section: Recombination Time Scalementioning

confidence: 72%

Trends in runaway electron plateau partial recombination by massive H₂ or D₂ injection in DIII-D and JET and first extrapolations to ITER and SPARC

et al. 2023

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“…Modeling of cooling mechanisms for gas within the chamber, the temperature of the gas during target injection, recombination of the plasma after the shot, and the heat flux the target will experience has been initiated. 18 Preliminary results show that heat fluxes of 0.6 to 0.7 W/cm 2 can be obtained only with extremely low gas densities (< 10 20 m -3 ), whereas thermally insulated targets could withstand modest gas densities (~10 20 -10 21 m -3 ). A large-scale convective motion induced within the chamber was found to be an effective way to speed up the plasma cooling and recombination, by effectively bringing hot particles closer to the wall.…”

Section: Laser Fusionmentioning

confidence: 88%

Demonstrating a Target Supply for Inertial Fusion Energy

Goodin

Alexander

Brown

et al. 2005

Fusion Science and Technology

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A central feature of an Inertial Fusion Energy (IFE) power plant is a target that has been compressed and heated to fusion conditions by the energy input of the driver. The technology to economically manufacture and then position cryogenic targets at chamber center is at the heart of futureIFE power plants. For direct drive IFE (laser fusion) energy is applied directly to the surface of a spherical CH polymer capsule containing the deuterium-tritium (DT) fusion fuel at approximately 18 K. For indirect drive (heavy ion fusion, HIF) the target consists of a similar fuel capsule within a cylindrical metal container or "hohlraum" which converts the incident driver energy into xrays to implode the capsule. For either target, it must be accurately delivered to the target chamber center at a rate of about 5-10 Hz, with a precisely predicted target location. Future successful fabrication and injection systems must operate at the low cost required for energy production (about $0.25/target, about 10 4 less than current costs).Z-pinch driven IFE (ZFE) utilizes high current pulses to compress plasma to produce x-rays that indirectly heat a fusion capsule. ZFE target technologies utilize a repetition rate of about 0.1 Hz with a higher yield This paper provides an overview of the proposed target methodologies for laser fusion, HIF, and ZFE, and summarizes advances in the unique materials science and technology development programs

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Observation of D2 molecule line emission after massive D2 injection into runaway electron plateaus in DIII-D

Hollmann,

Herfindal,

McLean

et al. 2023

Physics of Plasmas

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Molecular deuterium line emission is observed in both the visible and ultraviolet (UV) wavelength ranges after massive (> 100 Torr-L) injection of D2 gas into post-disruption runaway electron (RE) dominated plasmas in the DIII-D tokamak. D2 UV line emission is found to be the dominant source of radiated power, surpassing D Lyα. Interpretive modeling with a collisional-radiative model (CRM) indicates that D2 radiation surpasses D radiation because Lyα is strongly trapped, while D2 UV lines are mostly untrapped. The CRM also indicates that the D2 line emission is completely dominated by RE impact (rather than thermal electron impact), so the D2 line emission can serve as a good diagnostic for the spatial localization of REs. Analysis of D2 visible lines indicates that the D2 molecules in the plasma are thermally equilibrated with the background plasma, with vibrational, rotational, and kinetic temperatures all near 0.3 eV. D2 spectroscopy therefore serves as a convenient diagnostic of background plasma temperature. Measurement of D2 radiated power also appears to serve as a useful diagnostic for constraining neutral transport modeling.

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Simulation of afterglow plasma evolution in an inertial fusion energy chamber

Cited by 3 publications

References 5 publications

Trends in runaway electron plateau partial recombination by massive H₂ or D₂ injection in DIII-D and JET and first extrapolations to ITER and SPARC

Trends in runaway electron plateau partial recombination by massive H₂ or D₂ injection in DIII-D and JET and first extrapolations to ITER and SPARC

Demonstrating a Target Supply for Inertial Fusion Energy

Observation of D2 molecule line emission after massive D2 injection into runaway electron plateaus in DIII-D

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Simulation of afterglow plasma evolution in an inertial fusion energy chamber

Cited by 3 publications

References 5 publications

Trends in runaway electron plateau partial recombination by massive H2 or D2 injection in DIII-D and JET and first extrapolations to ITER and SPARC

Trends in runaway electron plateau partial recombination by massive H2 or D2 injection in DIII-D and JET and first extrapolations to ITER and SPARC

Demonstrating a Target Supply for Inertial Fusion Energy

Observation of D2 molecule line emission after massive D2 injection into runaway electron plateaus in DIII-D

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Trends in runaway electron plateau partial recombination by massive H₂ or D₂ injection in DIII-D and JET and first extrapolations to ITER and SPARC

Trends in runaway electron plateau partial recombination by massive H₂ or D₂ injection in DIII-D and JET and first extrapolations to ITER and SPARC