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Reports until 11:18, Thursday 31 July 2025
H1 SQZ
camilla.compton@LIGO.ORG - posted 11:18, Thursday 31 July 2025 - last comment - 13:49, Tuesday 05 August 2025(86117)
2W Mid SQZ Data for 5kHz and 10kHz HOM Spacing
Sheila, Camilla
Took data mid sqz only data once Ryan had the IFO locked at 2W on DC READOUT, he paused at CHECK_VOILINS_BEFORE_POWERUP. Aim is to see the HOM spacing at 5kHz and 10kHz to compare to the thermalized 60W data took in 85957. They have definitely shifted: at 2W at 5kHz and 10kHz and at 60W were at around 5.35kHz and 10.5kHz.
 
We saved  H1:OMC-DCPD_524K_A2_IN1 data with the PD sum after I changed the matrix as in 85937. DTTs saved as /ligo/home/camilla.compton/Documents/sqz/templates/dtt/20250731_SQZdata.xml screenshot attached and /ligo/home/sheila.dwyer/Noise_Budget_repos/quantumnoisebudgeting/data_files/higher_order_modes_sqzdataset2W.xml screenshot attached.
 
Starting angle is (-)130, requested SQZ_MANGER to FREQ_DEP_SQZ and once we got there, took SQZ_ANG SERVO to DOWN.
 
Type Time (UTC) Angle DTT Ref in SQZ DTT ref in HOM Notes
No SQZ 15:20:00 -15:25:00 N/A ref 0 ref 0,1  
FDS Mid - SQZ 15:31:00 - 15:34:00 (-)120 ref 1 ref 2,3 Was close to ASQZ so retook below
FDS Mid + SQZ 15:36:00 - 15:39:00 (-) 30 ref 2 ref 4,5  
FDS Mid - SQZ 15:40:00 - 15:43:00 (-)150 ref 3 ref 6,7  
 
Checked the NLG the normal way, checked OPO crystal temp but it was already optimized, unsure why is is so low already, we left it at 15.8 on Tuesday 86067.
OPO Setpoint Amplified Max Amplified Min UnAmp Dark NLG Note
80 0.0533596 0.00250 0.007039 -1.93e-5 7.6 Temp already optimized
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Comments related to this report
sheila.dwyer@LIGO.ORG - 16:15, Monday 04 August 2025 (86182)

In this data I only see evidence of one mode at 5kHz, and one mode at 10kHz.  If the astigmatism that caused the X arm second order modes to separate into two in 86107 is due to the point absorbers or some other laser heating, it could make sense that we don't see astigmatism at 2W.  However, the ring heater settings for the two arms are different, so I would have expected the X and Y arm HOMs to be separated even at 2W.  This data was taken with 0.44W on ITMX RH (per segment), 1W per segment on ETMX RH, 0W on ITMY RH, and 1.5W per segment on ETMY RH.

Using a cursor to find the edges of the rotation from the three mid sqz traces that Camilla tok, the 5kHz mode frequency is 4956.5+/- 20 Hz, and the 10kHz mode is at 9981.5 +/- 19.5 Hz.  This suggests that the second order mode is at 99% of 2* first order mode frequency, similar to the ratio that we saw at full power.  86107. In the attached screenshot, the top panel shows where I put the cursor to measure the location of the 5kHz mode, the lime veritcal line in the bottom plots shows twice that frequency, 9913 Hz, which is clearly below the sqz rotation caused by the HOMs.

 

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camilla.compton@LIGO.ORG - 13:49, Tuesday 05 August 2025 (86208)

The hour times in my data table are all incorrect, should be starting at 17:20UTC.

When we started the data taking with NO_SQZ at 15:20UTC, the IFO had been down and the CO2 lasers off for 2hours 5mins.

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