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SUMMARY:Power handling of the JET ITER-like wall (limiter and divertor)
DTSTART:20130529T111500
DTEND:20130529T120000
DTSTAMP:20260916T043948Z
UID:9a8f4b95485e7494edb0d731d2bec1b17416ca8071d2fd89cff1d669
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Gilles Arnoux\, Plasma Boundary Group\, JET Diagnostics Un
 it\, Culham Science Centre\, Abingdon\, UK\nThe ITER-like wall (ILW) at JE
 T 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 b
 een designed to maximise their power handling capability. During the last 
 experimental campaign (October 2010 – July 2011) this capability has bee
 n assessed and even challenged in the case of the beryllium wall. The Be w
 all is composed of highly shaped\, castellated tiles. They are optimised f
 or 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 unexpecte
 d power loads pattern). However\, this capability has been pushed to its l
 imit leading to melt events\, both on the inner and outer limiters\, which
  revealed that the power load is toroidally asymmetric. The protection sys
 tem of the ILW has now been partially commissioned and the main chamber pr
 otection was operational. It did not prevent melt events because: 1) The s
 urface temperature of the monitored PFCs was underestimated by about 200$^
 o$C\, and 2) the protection strategy relies on the assumption that the pow
 er 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 120
 0$^o$C in order to prevent thermal fatigue. This limit has been exceeded a
 bout 300 times and no signs of damage or thermal fatigue have been observe
 d by the photogrammetric survey (post mortem analysis is underway).
LOCATION:CRPP\, PPB 019
STATUS:CONFIRMED
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