AC Susceptometer User Instrumentation
AC Coil Sets
An AC susceptometer is available to measure the susceptibility of samples. Due to the nature of the measurement, this instrument is mainly used for the detection of transitions in the magnetic properties rather than obtaining absolute values of susceptibility. The available temperature range so far is 35 mK to 500 mK in magnetic fields up to 18 T. An AC-probe for the temperature range between 300 mK and 300 K in fields up to 33 T has been developed. This probe also features a sample rotator so that oriented samples can be measured at a number of angles without having to remove the probe from the dewar.
Developed in conjunction with a user, Prof. Art Hebard of the University of Florida, the two-position susceptometer has been used to measure the susceptibility of samples with signals as low as 10-6 emu in fields up to 10 T. Samples with larger susceptibilities have been measured up to 30 T. This instrument can be used in a helium-3 fridge.
A version of the two-position susceptometer is available for use in the dilution refrigerator (SCM1). To date test samples have been measured at temperatures as low as 50 mK with this probe.
Thin Film Coils
A coil specially designed for 3 mm diameter, circular thin films is available. The specifications for TFC1 are supplied in the following table.
Thin Film Coils
|
|
TFC1
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Wire Type
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Number of Turns
|
|
Drive
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#34 Cu
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1,543
|
|
Balance
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#50 Cu
|
2,784
|
|
Sample
|
#50 Cu
|
2,784
|
|
Background measurements at room temperature for TFC1 are shown in the figure below.
Non-translating AC Susceptibility Coils
For applications where one needs to detect a transition temperature or field, the non-translating AC susceptibility coils provide an easy and sensitive measure method. The following diagrams show the dimensions of one of the non-translating AC coil systems.
This side cutaway shows the form on which the astatic pair will be wound. Standard coils are wound with 50-gauge copper wire. Note that all of these coils mount to standard probes with a 4-40 thread. The small holes are for anchoring the twisted pair leads.
A standard drive coil has approximately 1,000 turns of 34-gauge copper wire.
For more information about the magnetometry facilities, contact Eun Sang Choi. For information about scheduling magnet time and submitting facility requests, contact Interim DC Program Director Tim Murphy.
