The liquid 3He is essential for good thermal contact. The device is a modification of a standard mutual inductance bridge with counter-wound secondary coils with only one containing the sample and one excitation coil as shown below. The components are selected to optimize thermalization and high sensitivity at ultra-low temperatures. Each electrical lead passes through a “sock” of sintered Ag to thermalize the electrons in the electrical leads.
A mutual inductance bridge is used to read the difference in inductance of the two pick-up coils and illustrated below. The transformer is wound form very fine annealed Ag wire (5μm φ) and no ferrite core is used at these temperatures.
Instrumentation
- Andeen Hagerling Capacitance Bridge 2700A
Images
Click on images for details.
-
Cell filled with liquid 3He.
Cell filled with liquid 3He.
-
Mutual inductance bridge.
Mutual inductance bridge.
https://nationalmaglab.org/user-facilities/high-b-t-facility/high-b-t-measurement-techniques/ac-magnetic-susceptibility-in-high-bt?tmpl=component&print=1#sigProId41013853ce
Related Publications
L. Yin et al., Magnetic Susceptibility Measurements at Ultra-Low Temperatures, J. Low Temp. Phys., 158, 710-715 (2010) Read online