Montana Instruments Cryostation s Series - Sample Chamber Wiring; Types of Wiring; Thermal Lagging Techniques

System User Manual
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4.5 Sample Chamber Wiring
4.5.1 Types of Wiring
Various applications require different types of wiring. Always select the optimal wire for the application
with the appropriate diameter (between 32-40 gauge). Longer wires are ideal -- the length of wiring
between stages should be at least 2 in (5 cm).
• 40 AWG Manganin wire: very low thermal conductivity and good for low power signal
transmission
o Recommended use: Wiring the platform heater or for user heaters
o Raises temperature ~0.5 mK per wire
• 32 AWG Phosphor Bronze wire: low thermal conductivity and good for moderate power
transmission
o Recommended use: Building additional wiring harnesses
o Raises temperature ~5 mK per wire
• Copper wire: high thermal conductivity and good for high power transmission
o Recommended use: Wiring harness for high power transmission when high base
temperatures are acceptable
o Raises temperature ~0.3 K per wire
» NOTE
See the Cryogenic Wiring Guide for more information: www.montanainstruments.com/help/Wiring-
Guide/
4.5.2 Thermal Lagging Techniques
To minimize the effects of wiring heat loads on the base temperature, all incoming wiring (including
coax cables) must be properly thermally lagged to Stage 1 of the cryocooler.
Select cryostat models (s100 & s200) provide “pre-lagged” connections for some user inputs and wiring.
These wires, which plug directly into the 4 K circuit board “wedge” inside the sample space, do not need
additional thermal lagging.
Wiring where pre-lagged connections are not available must route under the thermal clamp locations:
1. Unscrew the two M2.5 screws on the top of the thermal clamp. Remove the top cover.
2. Wrap a small piece of Kapton® tape around the wires to help prevent electrical shorts.
3. Place the wires on the felt pad. Wires should not cross or touch one another under the clamp.
4. Replace the top cover of the clamp and replace the two screws. Do NOT overtighten.
5. Check to ensure wires do not touch the inside of the radiation shield.
» NOTE
Ensure there are a few inches of wire before and after the thermal clamp. A 10-inch (25 cm) wire
should be thermally lagged such that 5 inches (12.5 cm) is outside of the thermal clamp and the
remaining 5 inches (12.5 cm) is inside of the 4K sample space.