Sapphire Q measurement meeting

2023 September 21st (Thu) 14:30-16:00

Yamada, TSuzuki, Miyoki, RTakahashi, Baipai, Aso, Komori, Tomaru, KYamamoto

(1)Onsite mirror Q measurement
Q (24kHz) of all mirrors around 250K are on the order of 10^4.
https://klog.icrr.u-tokyo.ac.jp/osl/?r=27117
Q (24kHz) of both ITM's (ETM's) around 80 K are on the order of 10^6 (10^5). 
https://klog.icrr.u-tokyo.ac.jp/osl/?r=26904


(2)Offsite Mirror Q measurement (Yamada and Suzuki)

Yamada-kun introduced quotation (including commecial products by Misumi and Thorlans for suspension frame and wire breaker gluing) 
and Miyoki-san shows his idea for budget.
Yamada-kun will consider which parts are made by companies or KEK machine shop.

Cost for KEK shop is lower but its lead time is longer. 
If we asks all parts to a company, the lead time is 1.5 month. This is also trade off which must be taken care of.
 
After Yamada-kun writes design drawings, TSuzuki-san checks. Then they are uploaded to JGW doc.

Aso-kun's requests the measurement of Q of polished bulks for new ITM on January 2024 since its chamfers have damage. 
If measured Q is not so excellent, we ask Okamoto to polish chamfer (it takes a few months).
So parts must be delivered as soon as possible.

HCB box can be used as jig for wire breaker gluing (Ushiba-kun agrees). 


(3)Onsite violin Q measurement (K. Komori)

Q-values of first violin mode are derived from measured peak width of power spectrum.
https://klog.icrr.u-tokyo.ac.jp/osl/?r=26113 
Violin peaks are idetified (which peak belongs to which sapphire suspension) by white noise excitation to each sapphire suspension.
Q of many modes around 250K are consistent with thermoelastic damping. On the other hand, Q around 80K is smaller than thermoelastic
damping Q and comparable with Shishido-kun's memasurement as below.

When we assume Q of mirror (fiber) is 10^6 (10^5), binary range is 55 Mpc (comparable with Virgo O3). 

After DC readout is realized, violin Q measured (ring down method, at first around 80K, later 20K).


(4)offsite fiber Q measurement

Shishido-kun measured Q of fiber with sumiceram (as KAGRA sapphire fibers) without anyload. Q at 5K was about 10^5. He confirmed 
this Q is limited by fiber itself.

Rishabh-kun proceeds with preparation. His strategy is as follows. At first he measure Q of short monolithic fiber. If measured Q
is high, he measures Q of KAGRA size fiber. Otherwise, he improve support system.
He will prepare by middle of January. 

He try to use Onosokki displacement sensor. If it does not work, he uses shadow sensor.


(5)Misc

After we measure Q of mirror and fiber, we measure Q of sapphire suspension (offsite).

Next meeting will be on the week of 30th of Oct. Kazuhiro circulate doodle later.


Remained A/I
(0)Yamada-kun will consider which parts are made by companies or KEK machine shop (trade off of budget and lead time).
(1)Yamada asks Hirata-san details of breakres later.
(2)Glue
Discussion is in progress. EP-30 in Type B and Bp.
What we discussed in the previous meeting. 
Glue must be removed. What kinds of glue ? Are In or Ga feasible (this glue need 
not to support heavy load) (Dan's suggestions) ? -> We continue discussion.