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22-27 October 2018
Mahatma Mandir Conference Centre
Asia/Kolkata timezone
CONFERENCE MATERIAL NOW AVAILABLE!

Active conditioning of ASDEX-Upgrade tunsgten PFCs through boron particulate injection

25 Oct 2018, 15:00
20m
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Oral FIP - Fusion Engineering, Integration and Power Plant Design FIP/2, MPT/1, SEE/1 In Vessel Components & Plasma Interface

Speaker

Dr Robert Lunsford (Princeton Plasma Physics Laboratory)

Description

The injection of boron (B) and boron nitride (BN) powders into ASDEX-Upgrade (AUG) H-mode discharges have shown the ability to effectively control tungsten influx in low density/collisionality operational regimes, similar to conventional boronization methods. A newly designed impurity powder dropper was installed onto AUG with 5m diameter BN powder, and 50 m B powder (99%+ purity) loaded into separate dropper assemblies. The sub-mm powder particles are gravitationally accelerated into the upper edge of a lower single null H-mode plasma. Discharges with IP = 800 kA, ne = 6x1019 m-3, PNBI = 10 MW , and a conformal boundary shape were used for the conditioning sequences. These were followed by different discharges to evaluate the effects of the conditioning.
The first experiment was performed with five BN conditioning discharges, in which injected B was varied from ~4x1018 atoms/discharge to ~4x1020 atoms/discharge. Visible spectroscopy measurements at the outer limiter showed increases in both boron and nitrogen signal levels, well as elevated boron levels in the divertor and an increase in PRAD by greater than a factor of 2. Globally the BN injection also improved energy confinement by 10-20%, similar to gaseous N2 injection. Discharges with increasing B injection rates were also performed. Injecting, 9.2x1021 atoms of pure B resulted in minimal impact on plasma performance and up to 50% increase in radiated power. To test the conditioning effect of B powder, a sequence of discharges with magnetic perturbations for ELM suppression were conducted afterwards. Historically these discharges are very sensitive to wall conditions. However, following the B conditioning discharges, all three attempts to run low density discharges with ELMs suppressed by magnetic perturbations were successful. These preliminary results suggest that the application of B containing powders can be used to both improve plasma performance in real-time, and improve wall conditions. Furthermore the injection system is capable of injecting a wide number of impurities (B, BN, B4C, Li, C, Sn, Mo, W, …) for a range of studies. Similar systems are being installed on the EAST and DIII-D devices. Results from these and forthcoming studies on AUG, and possibly other devices, will be reported. The U.S. authors supported by U.S. Dept. of Energy contract DE-AC02-09CH11466.

Country or International Organization United States of America
Paper Number FIP/2-3

Primary author

Dr Robert Lunsford (Princeton Plasma Physics Laboratory)

Co-authors

Dr Albrecht Herrmann (Max-Planck_Institut für Plasmaphysik, Garching, Germany) Dr Alessandro Bortolon (PPPL) Dr Alex Nagy (Princeton Plasma Physics Laboratory) Dr Arne Kallenbach (Max-Planck-Institut f. Plasmaphysik) Dr Dennis Mansfield (Princeton University Plasma Physics Laboratory) Dr Elisabeth Wolfram (Max-Planck-Institut f. Plasmaphysik) Dr Rachael McDermott (Max Planck Institut für Plasmaphysik) Dr Rajesh Maingi (Princeton Plasma Physics Laboratory) Dr Ralph Dux (Max-Planck-Institut für Plasmaphysik, Garching, Germany) Dr Rudolf Neu (Max-Planck-Institut f. Plasmaphysik) Dr Volker Rohde (Max-Planck-Institut f. Plasmaphysik)

Presentation Materials

Paper