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ProbeAmy EckerleAndrew WhittingtonPhilip Witherspoon

Team 16

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Sponsors NHMFL Applied Superconductivity Center

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The Project Modify existing cryostat probe to

conserve the amount of liquid helium used during a critical current measurement test.

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Objectives Conserve Helium Test 6-8 straight samples 1 Spiral sample Capability to deliver 1000 Amps to

samples Durable

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Existing Probes

Current leads

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Concept 1 – Heat Exchanger Exposed

Copper leads source of major heat leak

Cooling these exposed leads will decrease temperature difference

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Concept 1 – Design Covers current

leads Cools leads using

excess gaseous helium

Vent valve at top

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Concept 1 - Pros & Cons

Pros Simple concept Reduces

temperature difference

Uses excess helium as cooling gas

Cons Self design and

manufacture May not decrease

temperature enough to implement

Concept 2- HTS Leads Replacing Copper with HTS leads Path of least resistance

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Concept 2

Pros Reduces amount

of helium used Provides current a

path with less resistance

Reduces heat leak from current leads

Cons Possible

quenching expensive

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Concept 3 – Structural Support Concept 2

HTS leads – tape Shell

Casing Currently a stainless steel casing, 16

W/m*K Replace

Spacers

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Concept 3 – Pros & Cons

Pros Lower thermal

conductivity If correct

materials, should reduce heat leak and provide structural support

Cons Material must

withstand cryogenic temperatures

Sacrifice structural support for thermal conductivity?

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Concept 4 – Reduce Leads Reduce the amount of leads

Leads are major heat leak Temperature gradient Possible double PCL Possible Parallel

Maintain 6-8 samples with least amount of leads possible

Optimization

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Concept 4 – Pros & Cons

Pros Optimizes system Less leads = less

heat generation = less helium consumption

Cons None because it is

an optimization

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Concept 5 - Fins Increase heat transfer

Reduce the temperature gradient Ideally use circular fins

Easy to manufacture

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Concept 5 – Pros & Cons

Pros Increases the

surface area Decreases the

heat transfer taking place in the liquid helium

Cons Effectiveness of

fins may be hard to determine due to space

Hard to implement

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Concept 6 – Gas Insulation Using the helium burn off gas to insulate

the material. Layer of gas between the leads and fluid

Non-boiling, Nucleate boiling, film boiling

Changing the orientation of leads Vertical Vs. inclined

Trapping of gas, wells

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Orientation Wells

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Concept 6 – Pros & Cons

Pros Create an

insulating layer Can theoretically

decrease heat transfer by an order of magnitude

Cons Space Design constraints

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Concept 7–Spoke Thermal Cap G-10, a fibrous material, is used as a

current lead spacer Modification to this part can interrupt

thermal conduction of the stainless steel tube.

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Concept 7- Design Thermal cap

protrudes through stainless steel

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Concept 7 – Pros & Cons

Pros Increases thermal

resistance through the stainless steel tube

Cons Difficult assembly Increase in

resistance may be small

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Next Step Evaluating each concept by modeling

and experimentation Assign value to ease of use,

effectiveness, cost and other criterion Decision matrix or other methods of

concept selection

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Questions

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References Ekin, J. W. Experimental Techniques for Low-

temperature Measurements: Cryostat Design, Material Properties, and Superconductor Critical-current Testing. Oxford: Oxford UP, 2006. Print.

Cengel, Yunus A., Robert H. Turner, and John M. Cimbala. Fundamentals of Thermal-fluid Sciences. Boston, MA: Mcgraw Hill Higher Education, 2008. Print.

"October 2010." Gaming News and Reviews. Web. 24 Oct. 2011. <http://gamingnewsreviews247.blogspot.com/2010_10_01_archive.html>.