Designing an AC Magnetic Susceptometer Measurement 

Technique in Conjunction with High Pressures and Low 

Temperatures in Neutron Beam Experiments

Presenter: Paul Neves

Mentors: Nicholas Butch & Juscelino Leão

NIST Center for Neutron Research

Summer Undergraduate Research Fellowship

1
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Outline

• Background

• Methodology

• Results
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Currently, users can:

• Load their sample in a 

pressure cell

SAMPLE

https://www.ncnr.nist.gov/

equipment/Pressure.html
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Currently, users can:

• Load their sample in a 

pressure cell

• Bring that sample to 

low temperatures in a 

cryostat

https://www.ncnr.nist.gov/

equipment/displex.html

SAMPLE

https://www.ncnr.nist.gov/

equipment/Pressure.html
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https://www.ncnr.nist.gov/

equipment/displex.html

SAMPLE

https://www.ncnr.nist.gov/

equipment/Pressure.html

Currently, users can:

• Load their sample in a 

pressure cell

• Bring that sample to 

low temperatures in a 

cryostat

• Then look at it with a 

beam of neutrons

N N

N N

N

N

N
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What is an AC Susceptometer and 

Why Do We Need One Here?

• Measures magnetic susceptibility

• Tells you about the magnetic phase

• In situ with neutrons
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What it Measures

• M = χH

• Diamagnets, paramagnets, 

ferromagnets, 

superconductors, etc

No Field

With Field
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What it Measures

• M = χH

• Diamagnets, paramagnets, 

ferromagnets, 

superconductors, etc

No Field

With Field

Material: Response:

Para- or Dia- Magnet ~0

Superconductor -1

Ferromagnet Very large
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How It Works

• Drive coil makes field

• Pickup coils measure response

• Sample sits in the center
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Constraints

• Size

• Low Temperature

• Vacuum Sealed

• Time

• Sensitivity
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Solutions to Constraints

• Designed thin profile coil
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Solutions to Constraints

• Designed thin profile coil

• Which must be supported
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Solutions to Constraints

• Designed thin profile coil

• Which must be supported

• And the sample stick must 

be modified
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Solutions to Constraints

• Designed thin profile coil

• Which must be supported

• And the sample stick must 

be modified

• And given motion
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Winding the Coils

• Lathe controls turning
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Winding the Coils

• Lathe controls turning

• Raspberry pi counts turns
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Winding the Coils

• Lathe controls turning

• Raspberry pi counts turns

• A lot of turns...
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Wiring and Programming

• Function generator 

controls drive coil
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Wiring and Programming

• Function generator 

controls drive coil

• Multimeter measures 

drive current
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Wiring and Programming

• Function generator 

controls drive coil

• Multimeter measures 

drive current

• Oscilliscope measures 

pickup coil response
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Wiring and Programming

• Function generator 

controls drive coil

• Multimeter measures 

drive current

• Oscilliscope measures 

pickup coil response

• LabView controls all 

three instruments and 

records data
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Wiring and Programming
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Testing the Coils

• Baseline

• Empty pressure cell

• ~0.5g steel

• ~6g steel
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Test Samples

• Empty pressure cell

• MgB2, a low temperature superconductor (TC=39K)

https://www.ncnr.nist.gov/

equipment/Pressure.html

wikipedia
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Results
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Results
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Results, Continued
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Results, Continued
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Results, Continued
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Results, Continued

Pressure: Tc (K):

Ambient ~38.4

0.65 GPa ~38.6
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Results, Continued

Buzea, Cristina, and Tsutomu Yamashita. "Review of the 

superconducting properties of MgB2." Superconductor 

Science and Technology 14.11 (2001): R115.

Pressure: Tc (K):

Ambient ~38.4

0.65 GPa ~38.6
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Summary

• Many constraints

• Useful capability

• It works!
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Acknowledgements

• Nick Butch and Juscelino Leão

• NIST and the SURF program

• The NCNR and CHRNS

• Julie Borchers and Joe Dura

• Dan Neumann

• Doug Johnson, Patrick Connelly, Scott Slifer, Colin 

Wrenn, Andrew Malone

• Markus Bleuel, Alan Ye, Shannon Watson
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References

• Feynman, Richard P., Robert B. Leighton, and 

Matthew Sands. The Feynman Lectures on Physics, 

Desktop Edition Volume I. Vol. 1. Basic books, 2013.

• Nikolo, Martin. "Superconductivity: A guide to 

alternating current susceptibility measurements 

and alternating current susceptometer

design."American Journal of Physics 63.1 (1995): 

57-65.