1. Amy Eckerle Andrew Whittington Philip Witherspoon 1 Team 16

2. Sponsors  NHMFL  Applied Superconductivity Center 2

3. The Project  Modify existing cryostat probe to conserve the amount of liquid helium used during a critical current measurement test. 3

4. Objectives  Conserve Helium  Test 6-8 straight samples  1 Spiral sample  Capability to deliver 1000 Amps to samples  Durable 4

5. Existing Probes 5 Current leads

6. Concept 1 – Heat Exchanger  Exposed Copper leads source of major heat leak  Cooling these exposed leads will decrease temperature difference 6

7. Concept 1 – Design  Covers current leads  Cools leads using excess gaseous helium  Vent valve at top 7

8. 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 8

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

10. 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 10

11. Concept 3 – Structural Support  Concept 2  HTS leads – tape  Shell  Casing  Currently a stainless steel casing, 16 W/m*K  Replace  Spacers 11

12. 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? 12

13. 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 13

14. Concept 4 – Pros & Cons Pros  Optimizes system  Less leads = less heat generation = less helium consumption Cons  None because it is an optimization 14

15. Concept 5 - Fins  Increase heat transfer  Reduce the temperature gradient  Ideally use circular fins  Easy to manufacture 15

16. 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 16

17. 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 17

18. 18 OrientationWells

19. Concept 6 – Pros & Cons Pros  Create an insulating layer  Can theoretically decrease heat transfer by an order of magnitude Cons  Space  Design constraints 19

20. 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. 20

21. Concept 7- Design  Thermal cap protrudes through stainless steel 21

22. Concept 7 – Pros & Cons Pros  Increases thermal resistance through the stainless steel tube Cons  Difficult assembly  Increase in resistance may be small 22

23. 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 23

24. Questions 24

25. 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.. 25