Although the region of the TFTR vacuum vessel wall which is susceptible to damage by neutral beam strike is armored with a mosaic of TiC-olad POCO graphite tiles, at power deposition levels above 2.5 kW/cm 2 the armor surface temperature exceeds 1200° C within 250 ms and itself becomes susceptible to damage. In order to protect the wall armor, a neutral beam interlock system based on infrared pyroraetry measurement of the armor surface temperature was installed on TFTR. For each beamline, a

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... e-fiber-optic telescope views three areas of -30 cm diameter centered on the armor hot spots for the three ion sources. Each signal is fiber-optic coupled to a remote 900 nm pyrometer which feed3 analog signals to the neutral beam interrupt circuits. The pyrometer interlock system is designed to interrupt each of the twelve ion sources independently within 10 ms of the temperature exceeding a threshold settable in the range of 500-2300° C.