2. Development of Low Vibration Cryocooler KEK Tomiyoshi Haruyama 1. Cooling requirements 2. GM/Pulse Cryocooler 3. Vibration measurement 4. R&D of low vibration cryocooler 2003.2.6-7 TAMA Symposium, ICRR, Kashiwa

3. 1. Cooling Requirements -CLIO

4. Cooling Requirements-Cryostat concept

5. Seismic displacement

6. Cooling requirement COOLING POWER -Mirror cooling 0.5W at 4.2K 20W at 40K -5m Shield cooling 50W at 80K VIBRATION at COLDENDS -<10 -7 m at 1Hz

7. CRYOCOOLER Advantages -Easy to operate -Maintenance free (for 1-2 years) -No danger in tunnel (no cryogen) Disadvantages -Sound + vibration →Origin?

8. Driving mechanism

9. Origin and level of vibration Solid piston Driving motor Pressure wave GM ~ ~ ~ ~ ~ Severe ~~ Intrinsic Pulse tube Quiet ~~ Intrinsic

10. Commercially available 4K cryocooler GM -Sumitomo Pulse -Cryomech Pulse -Sumitomo Driving motor Buffer tank only

11. Vibration measurement at low temperature

12. Sensor setup (single stage PT) Photo sensor Sustaining post Cold end with reflection box

13. Vibration -real time

14. Vibration (GM)

15. Vibration (PT) GM→Pulse

16. Cryomech and Sumitomo 4K PT cryocooler Pulse-Cryomech Pulse-Sumitomo Driving motor +buffer tank Buffer tank only (separated motor)

17. Final problem?-Pressure wave k: bulk modulus E/3(1-2 ） Example: SUSφ40X200,t=1 Δp ＝ 2MPa Δx ＝ ~8μm （ Experiment ： 6~30μm ）

18. Soft thermal link at cold stage 25μm→ ＜ 3μm ＠ RT 1Hz Single stage, 77 K 6μm→0.5μm CRYOMECH Giessen Univ.

19. R&D results of KEK- Sumitomo4K Pulse 1st stage Flexible link 2nd stage Flexible link

20. Concluding Remarks -Pulse tube cryocooler: Final solution for mirror cooling -Thermal link (vibration free stage): Key technology (R&D is going on) -Innovative idea for vibration-free cold end: Prepare for testing

21. Concluding Remarks-Schedule -April 2003R&D cryocoolers will be dispatched -July 2003Vibration/Cooling performance test -September 2003 Production will be started -March 2004All the coolers will be available

22. Vibration image