Power handling of the JET ITER-like wall (limiter and divertor)
Event details
| Date | 29.05.2013 |
| Hour | 11:15 › 12:00 |
| Speaker | Dr. Gilles Arnoux, Plasma Boundary Group, JET Diagnostics Unit, Culham Science Centre, Abingdon, UK |
| Location |
CRPP, PPB 019
|
| Category | Conferences - Seminars |
The ITER-like wall (ILW) at JET is a unique opportunity to study the combination of material (beryllium and tungsten) that will be used for the plasma facing components (PFC) in ITER. Both the limiters (Be) and divertor (CFC W coated and bulk W) have been designed to maximise their power handling capability. During the last experimental campaign (October 2010 – July 2011) this capability has been assessed and even challenged in the case of the beryllium wall. The Be wall is composed of highly shaped, castellated tiles. They are optimised for a range of scrape-off layer (SOL) power decay length $5 < \lambda_{q,design} < 20$ mm. Its power handling capability, predicted with a simple model, has been proven to be robust by the experiments (despite unexpected power loads pattern). However, this capability has been pushed to its limit leading to melt events, both on the inner and outer limiters, which revealed that the power load is toroidally asymmetric. The protection system of the ILW has now been partially commissioned and the main chamber protection was operational. It did not prevent melt events because: 1) The surface temperature of the monitored PFCs was underestimated by about 200$^o$C, and 2) the protection strategy relies on the assumption that the power load is toroidally symmetric. Operations on the bulk W divertor target were constrained by: 1) an energy load limit of 60MJ per stack (~60MJ/m2), and 2) the limited number of cycles of the surface temperature above 1200$^o$C in order to prevent thermal fatigue. This limit has been exceeded about 300 times and no signs of damage or thermal fatigue have been observed by the photogrammetric survey (post mortem analysis is underway).
Practical information
- Expert
- Free
Organizer
- Prof. P. Ricci
Contact
- Prof. P. Ricci