Conditioners for cryogenic sensors
In order to ensure accuracy, all temperature sensors must be cabled with 4 wires to an accurate
conditioner, using a low measuring current (self heating). The conditioning signal device must provide
adjustment for offset and span. Located at a long routing distance, the way that this low-level signal is
transported and analyzed is certainly an issue (R&D).
4.2.16.4.3.4 Cryogenic sensor packaging & installation:
As some unsticking could appear during the life of the Tokamak due to differential contraction, it is
recommended to prefer canisters set up in a package with a calibrated hole rather than a bare chip for a
thermal sensor installed in place of difficult access. The package used to mount the sensor could be
welded, soldered or bolted on the pipe for the thermal anchoring. The sensor canister will be mounted
with Apiezon grease. This kind of mounting would allow disassembly.
If there are packages or sensors attached to a pipe, particular care must be taken to clean the pipe
surface. Thermal anchoring will be carried out downstream at closest temperature of spot measurement
and at 80 K on a nearby thermal shield. The anchoring will take into account possible movement of
cables during operation due to Lorentz force and thermal contraction. This movement should not break
the insulation of cables or their insulation.