B4C-Coated Copper Limiter

Similar limiter blocks have been inserted through vacuum lock systems, exposed to higher heat loads and diagnosed in detail in- and ex-situ as well. 

The surface temperature excursion during an plasma exposure is shown in Fig. 13.8. The plasma was heated auxiliary by two neutral beams of 1.5 and 1.3MW/m2. The resulting load on the test limiter amounted to 4MW/m2. The 170 pm thick B4C layer was rapidly heated up to 1300 K and cooled down, as the pyrometer signals show. The surface layer withstood such an exposure and did not detach from the copper. Increasing the deposited heating power above 8MW/m2 led to melting of the B4C coating (see Fig. 9 in [33]). 

Distinct craters developed on the coating on both limiter types down to the copper bulk and are assumed to be caused by electrical arcs. This has not 

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