Since 18 of December 2019 conferences.iaea.org uses Nucleus credentials. Visit our help pages for information on how to Register and Sign-in using Nucleus.
4-7 November 2019
IAEA Headquarters, Vienna, Austria
Europe/Vienna timezone
Meeting Material is now available and accessible from the left-menu

Radiative Power Exhaust Research at DIII-D - From Divertor Science to Core-Edge Integration of High Performance Plasmas

6 Nov 2019, 10:00
20m
Board Room C (C Building, 4th Floor) (IAEA Headquarters, Vienna, Austria)

Board Room C (C Building, 4th Floor)

IAEA Headquarters, Vienna, Austria

Oral (Plenary Session) Radiative Power Exhaust Core-Boundary Plasma Compatibility

Speaker

Aaro Jaervinen (Lawrence Livermore National Laboratory)

Description

Power exhaust research at DIII-D is addressing the need for fusion reactors to integrate high $\beta_N$, high confinement plasmas with a radiating mantle and divertor that are compatible with stringent requirements on fuel dilution, high confinement mode power threshold, plasma stability, and wall heat flux limits. This research program encompasses studies from diagnostic optimized divertor science to compatibility of power exhaust with high performance pedestal and core plasmas [1, 2, 3].

Interaction of radiative divertor with high performance, peeling limited pedestals have been investigated in the super H-mode regime in DIII-D, reaching 2$p_\text{e,ped}$ > 20 kPa. By using a highly shaped configuration with a particular density trajectory, a peeling limited pedestal can be maintained at density levels where ballooning modes would typically reduce the achievable $p_\text{e,ped}$. Using 3D coils to control $n_\text{e,ped}$ while increasing gas fueling, $n_\text{e,sep}$ close to 50% of $n_\text{e,ped}$ were achieved without compromising $p_\text{e,ped}$. With N$_2$ injection, the radiative power fraction, $f_\text{RAD}$, was increased from 40% to 65%, providing a factor of 3 reduction of the outer target electron temperature while $p_\text{e,ped}$ was maintained. However, increasing $f_\text{RAD}$ to 85% was observed to lead to strong divertor detachment with a highly localized radiation at the X-point, and about a factor 2 reduction in $p_\text{e,ped}$.

In hybrid plasmas at high $\beta_N$ > 3.0, divertor peak heat fluxes could be reduced by about 40% with either neon or argon injection. However, fuel dilution and the emergence of harmful tearing modes significantly compromised the performance of these plasmas, in contrast to previous observations at lower $\beta_N$ operation. These findings highlight the need to control impurity transport and tearing mode stability when integrating mantle radiation to a DEMO relevant plasma core.

To test the scaling of impurity densities required for divertor detachment and its compatibility with a high performance core plasma, diagnostic capability to directly measure divertor radiating impurity densities has been developed on DIII-D. By combining divertor Thomson scattering with vacuum ultraviolet spectroscopy, the local emitting ion density can be measured directly.

Work supported by the US DOE under DE-FC02-04ER54698 and DE-AC52-07NA27344,
and LLNL LDRD project 17-ERD-020.

[1] A. E. Jaervinen, et al. Nucl. Mat. Ene. 19 (2019) 230-238
[2] P. B. Snyder, et al. Accepted to Nucl. Fusion 2019
[3] T. W. Petrie, et al. Submitted to Nucl. Fusion 2019

Country or International Organization United States of America

Primary author

Aaro Jaervinen (Lawrence Livermore National Laboratory)

Co-authors

B.A. Grierson (Princeton Plasma Physics Laboratory) Thomas W. Petrie (General Atomics) Philip B. Snyder (General Atomics) Francesca Turco (Columbia University) Dr Steve Allen (Lawrence Livermore National Laboratory) John Canik (Oak Ridge National Laboratory) Max Fenstermacher (LLNL @ DIII-D) Mathias Groth (Aalto University) Dr Matthias Knolker (General Atomics) Dr Charlie Lasnier (Lawrence Livermore National Laboratory) Anthony W. Leonard (General Atomics) Jeremy Lore (ORNL) Adam McLean (Lawrence Livermore National Laboratory) Dr Gary Porter (Lawrence Livermore National Laboratory) Dr Thomas Rognlien (Lawrence Livermore National Laboratory) Dr Cameron Samuell (Lawrence Livermore National Laboratory) Dr Jonathan Watkins (Sandia National Laboratory) Dr Huiqian Wang (General Atomics, San Diego, CA 92186 USA) Theresa Wilks (UsMIT)

Presentation Materials