Sapphire Q measurement meeting

2023 July 19 17:30-18:30

Bajpai, Ushiba, Yamada, Tamaki, Chiba, Suzuki, Miyoki, Aso, Dan, Komori, KYamamoto


Yamada : If CLIK will be used, sapphire mirror can be included.
Heat swith mechanism. Heat link between mirror and frame is pushed by bar. The top of the bar is above CLIK upper flange.
Heat exchange gas is useless because exchange gas can touch the vacuum chamber at room tempearature.
Wire brittleness must be checked before cooling (CuBe wire is used in KAGRA cryo payload. Rahul measured 
strength of some wires and results are summarized at KEK wiki).

-> Conclustion : Our first priority is measurement at room temperature as soon as possible
because Q of mirror at site at 250K is lower than our expectation.


Radiation cooling by cooled shield : It takes time and maybe achieving tempearture is 100K ?

-> Conclusion : If we have time, it is worth to try because Q around 100K could be larger than that near 300K.  


Bulk Q and Q with ears (HCB) must be checked (@300K) at first .


Stock check is necessary.
(1)Kashiwa : Ushiba-kun will check in this week.
(2)Mitaka : Aso-kun will check.


For Suspension, frame, 2 loop wires, and jig to suspend are necessary. 


Sensor, QPD, electrostatic actuator, Michlson interferometer, Ono sokki ?
-> Michelson interferometer is the best.
 

Komori-kun and Rishabh-kun can assist Yamada-kun.

Schedule : 6 months for room temperature measurement as first plan (if necessary we will change)
(1)Design by end of August 
(2)Procurement : 3 months
(3)Measurement 
 
In next 2 weeks, Yamada-kun and Suzuki-san prepare disign and we discuss. 


A/I
Yamada and Suzuki : Design of experimental apparatus
Ushiba and Aso : Sapphire mirror stock checks at Kashiwa and Mitaka
KYamamoto : Evaluation of Q by residual gas damping


Next meeting will be on 3rd(Thu) or 4th(Fri) of August. KYamomamot circulates doodle later.


Memo about details

Thickness 
HCB lambda/4 = 150 nm 
Galium several tens micro m
Sumicearm 0.1 mm 
  
Schedule for new ITM's : Polish until March 2025. -> 6 month for coating