1. Magnetic Refrigeration down to 1.6K for FCC_ee Jakub Tkaczuk Supported by: DRF Energy Program – DESA41K CERN FCC Collaboration

2. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

3. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

4. Magnetic refrigeration Magnetic refrigeration is based on the Magneto-Caloric Effect (MCE) (reversible variation of internal energy when applied magnetic field in a suitable material) Remove magnetic field spins randomize temperature decreases Apply magnetic field spins align temperature increases

5. Magnetic refrigeration Ideal Carnot cycle 2 adiabatic transformations 2 isothermal transformations

6. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

7. State of the Art CEA design Hitachi rotating design Hitachi static design CERN design MIT design

8. State of the Art Cold source Temperature 1.8K Warm source temperature 4.2K 4.5K4.2K Useful power1.35 W1.8 W0.5 W10 W12 mW Q / m_GGG10.6 W/kg1.7 W/kg0.7 W/kg1 W/kg0.1 W/kg η0.530.340.13?0.12 See presentation: FCC Week 2015

9. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

10. Active Magnetic Regenerative Refrigerator Large DT possible But : More material More exchanged power ADR Adiabatic Demagnetization Refrigerator AMRR Active Magnetic Regenerative Refrigerator Every part of magneto-caloric material goes through its own cycle

11. Active Magnetic Regenerative Refrigerator

12. Inputs for one GGG core: Outputs for AMRR: Limited efficiency in comparison to other designs

13. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

14. Static Magnetic Refrigerator

15. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

16. Static Magnetic Refrigerator – Heat exchange conditions Warm source Kutateladze correlation: Nucleate boiling – far from film boiling transition

17. Cold source Condensation is limited by Kapitza resistance For small temperature differences: For larger temperature differences: Static Magnetic Refrigerator – Heat exchange conditions

18. L5 cm D No heat losses taken into account yet

19. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

20. Energy balance with Kapitza resistance Static Magnetic Refrigerator – Heat losses Largest heat losses: GGG – warm source So large heat loss is not possible Conclusion: GGG temperature is not homogeneous, it is significantly influenced by the heat exchange with the warm source.

21. Diffusion inside GGG: Static Magnetic Refrigerator – Heat losses Largest heat losses: GGG – warm source

22. Other heat losses Static Magnetic Refrigerator – Heat losses negligible Scaling the SMR: 670 kg of GGG is needed to obtain 1kW. GGG dimensions: D = 50 cm, L = 50 cm

23. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

24. 50 µm Static Magnetic Refrigerator – Possible improvements Gas heat switch “off ” conduction is satisfying “on” conduction is not satisfying – 2-5 µm heat switch required – technically impossible

25. Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives

26. Short term Study of heat switch solution on the warm source interface Experimental, cryogenic validation of selected heat switch Mid-term design of a 0.3 W magnetic refrigerator for laboratory demonstration Long term design of kW range refrigerator for FCC

27. Thank you