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Reports until 14:27, Saturday 06 September 2014
H1 ISC (ISC)
lisa.barsotti@LIGO.ORG - posted 14:27, Saturday 06 September 2014 - last comment - 14:42, Monday 08 September 2014(13797)
OMC scan - single bounce ITMY 
Nic, Jamie, Lisa

With the QPD alignment engaged, we did a scan of the OMC in ITMY single bounce configuration. Data are being sent to Koji right now for a careful analysis, but our rough estimate is that indeed the matching to the OMC is around 90%, so slightly better than for ITMX, as expected. 

Scan data: Sep 9, 2014 21:10:08 - 21:12:00 UTC
Comments related to this report
nicolas.smith@LIGO.ORG - 14:34, Saturday 06 September 2014 (13798)
Link

Screenshot of the scan data. Koji will post a more complete analysis (a la 13767)

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koji.arai@LIGO.ORG - 00:01, Sunday 07 September 2014 (13801)
Link

I don't know if Lisa, Nic, and Jamie believe this or not, the mode matching was 0.82 for this scan, which was indeed worse than the result with ITMY.
Note that this mismatch still includes the effect of the misalignment. This scan involved more 1st order mode.

Should we just incorporate the 1st order into the 0th order, qualitatively to saying? In this assumption, both arms are not so different.

Carrier Mode X arm (mA) Yarm (mA)
0th 13.13 9.15
1st 0.088 0.28
2nd 1.65 1.25
1 - 2nd/(0th+1st) 0.88 0.87

Here are the result of the mode decomposition for the Y arm

Carrier  
Order mA
0 9.153
1 0.28
2 1.251
3 0.102
4 0.264
5 0.0192
6 0.04144
7 0.02544
8 0.0108
   
Upper sidebands (45MHz)
Order mA
0 0.319
1 0.005
2 0.0294
3 0.004
4 0.0065
   
Lower sidebands (45MHz)
Order mA
0 0.318
1 0.005
2 0.0297
3 0.004
4 0.0065
   
2nd order Upper sidebands (90MHz)
Order mA
0 0.0021
1 0.00002
2 0.00075
   
2nd order Lower sidebands (90MHz)
Order mA
0 0.0021
1 0.00002
2 0.00075
   
Upper sidebands (9MHz)
Order mA
0 0.13
1 0.0026
2 0.012
3 0.0012
4 0.0035
   
Lower sidebands (9MHz)
Order mA
0 0.13
1 0.0026
2 0.012
3 0.0012
4 0.0035
   
Sidebands of sidebands
(+/-9MHz+/-45MHz) mA
-54 0.002
-36 0.002
36 0.002
54 0.002
Carrier TEM00 9.15 mA
Carrier TEMnm 1.99 mA
Sideband   1.04 mA
       
Mode matching  0.821  

Here "mode matching" is defined by 1-(CR_TEMnm / CR_TEM00)

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lisa.barsotti@LIGO.ORG - 14:42, Monday 08 September 2014 (13814)ISC
Link 

Yes, that makes sense to me. Once the dither is working we can make more precise measurements. But I guess the point is that the mismatch is around 10%, and we don't see a significant asymmetry between X and Y as in L1.
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