Cabling

As part of the CRESST II readout system we required cables to read out the SQUID sensors; supply the bias and heater signals to the detectors; and connect the SQUIDs to the detectors. We achieved this using woven cables supplied by Tekdata, made to our design.  The cables are designed to minimise the heat load, while ensuring that crosstalk and susceptibility to external electromagnetic interference remained very low. Some of the wires need to have a low resistance, thereby presenting a significant heat load to the helium main bath.

The woven cables consist of twisted wire pairs woven with an insulating thread; the pairs are twisted in alternate directions (clockwise or anticlockwise) and single wires (connected to ground) run between them to reduce the crosstalk between channels. Inside the cryostat the cables are clamped in heatsinks to ensure there is no heatload on the detectors. The cables running inside evacuated tubes to the top of the cryostat (at room temperature) are clamped inside baffles to ensure a gradual reduction in the temperature, minimising the heatload.

To compare the crosstalk in different cable designs, we developed software to model the crosstalk between wires. The results, shown below, confirm that our woven cable design was best. However due to the high cost of supplying woven cables to readout the 1000+ detectors required for EURECA, we started investigating alternative designs, such as Kapton cables - metals tracks deposited on Kapton foil. In this case the design is even more critical to ensure the crosstalk is kept within acceptable limits.