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R&D (Cryogenic)
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SatoshiTanioka - 18:44, Monday 17 August 2020 (2170)Get code to link to this report
Cooling test

I turned on the refrigerator on Friday to see the temperature the cavity can reach.
Actually, the mirror temperature was below 10 K.
Therefore, we can measure the mirror properties from room temp. to around 10 K where the ET's test mass target temperature.
Fig. 1 shows the measured temperature, A represents the temperature of the mirror and B represents that of the table.

In addition, I could lock the laser to the cavity.
The red line in Fig. 2 shows the transmitted beam power though this picture is taken when the cavity was not locked.

I will make the servo to add the offset to feedback signal.
After that I will implement it to stabilize the lock.

Images attached to this report
2170_20200817114214_20200817temp.jpg 2170_20200817114220_20200817trans.jpg
R&D (FilterCavity)
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YuhangZhao - 00:48, Friday 14 August 2020 (2169)Get code to link to this report
CC1 investigation (3)

Aritomi, Yuhang

We are having issue of offset and bad SNR.

We checked the 14MHz peak from TAMA PD (as shown in figure 1 and 2). Usually it is amplified to -42dBm after an amplification of 21dB from -63dBm. The SNR before amplification is about 14dB, which is increased to about 20dB after the amplification.

The local oscillator used for demodulation is -7dBm, as shown in figure 3 .

The demodulated signal before and after amplification are shown in figure 4 and 5. Compared with the linewidth shown in figure 6, the SNR for demodulated signal is only about 1.5.

We could see that there is a almost constant offset around 8mV. Therefore, a larger LO may solve the offset problem.

(TAMA1991 demodulator was used and shown in this entry. We also tried other two demodulators, which give much larger offset)

Images attached to this report
2169_20200813175113_wechatimg17.jpeg 2169_20200813175120_wechatimg18.jpeg 2169_20200813175130_wechatimg20.jpeg 2169_20200813175139_wechatimg16.jpeg 2169_20200813175236_wechatimg19.jpeg 2169_20200813175243_wechatimg21.jpeg
R&D (FilterCavity)
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NaokiAritomi - 23:06, Thursday 13 August 2020 (2168)Get code to link to this report
CCFC preparation
 
First I removed a faraday on the bench in the reflection path and put a flipping mirror for CCFC locking. 
 
I measured 14MHz CCFC signal reflected from filter cavity. Pic.1,2 show 14MHz CCFC peak with 25 mW, 56 mW pump green. Measured CCSB power difference is 9.4dB.
 
MZ offset pump power (mW) p pol PLL (MHz) CCFC 14MHz peak (dBm)
4.2 25 190 -61.9
4.8 56 120 -52.5
 
From the pump power, we can calculate the theoretical CCSB power.
 
pump power (mW)  x = sqrt(P_pump/P_th)  Normalized CCSB power x/(1-x^2)^2
25 0.56 1.2
56 0.84 9.7
 
Theoretical CCSB power difference is 10*log10(9.7/1.2) = 9.1dB which is consistent with the measurement.
 
I also measured CCFC demodulated signal with 25, 56 mW green when CCSB are off resonance of FC and CC1 is scanned. I used CC1 LO for CCFC LO and used TAMA mixer for demodulation (Pic.3,4). There is an offset in CCFC signal. We'll try to put DC block in CCFC RF signal if we can remove the offset.
 
CCFC signal with 56mW green is only 4 mVpp, so we need to amplify the CCFC RF signal.
 

 
Images attached to this report
2168_20200813160540_img8602.jpg 2168_20200813160550_img8605.jpg 2168_20200813160600_img8603.jpg 2168_20200813160608_img8604.jpg
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NaokiAritomi - 22:40, Thursday 13 August 2020 (2167)Get code to link to this report
Check of QPD1,2 optimal demodulation phase and WFS1 rotation phase

[Aritomi, Yuhang]

Yesterday we optimized QPD1,2 demodulation phase and WFS1 rotation phase. Today we checked them if they change from yesterday or not. WFS1,2 signals for INPUT PIT measured today is shown in the attached picture. For WFS1, I and Q decoupling is fine, but it is not good for WFS2. Also there are pitch and yaw coupling for both WFS1 and WFS2. We need also WFS2 pitch and yaw rotation.

We optimized WFS2 demodulation phase by DGS. WFS2 DGS demodulation seems working. Optimal WFS2 demodulation phase is 10 deg while it was 0 deg yesterday.

WFS2 DGS demod (deg) WFS2_I_PIT WFS2_Q_PIT
0 0.2 0.07
10 0.31 0.02
20 0.3 0.05

We optimized pitch and yaw WFS1 rotation. WFS1 pit and yaw rotation phase is now 20 deg while it was 10 deg yesterday.

WFS1 rotation (deg) WFS1_I_PIT WFS1_I_YAW
0 0.46 0.17
10 0.51 0.08
20 0.45 0.02
Images attached to this report
2167_20200813154056_20200813inputpitnooptimization.png
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YuhangZhao - 14:07, Thursday 13 August 2020 (2166)Get code to link to this report
The implementation of AA telescope with another design (QPD 1/2 are located at Gouy phase -45 and 45 deg)

Aritomi, Yuhang

We had issue of pitch and yaw sensing coupling, as reported in elog2141, especially from end mirror motion. We see from that entry that the driving of end mirror pitch/yaw goes into yaw/pitch sensing mainly in WFS1.

Therefore we tried a new design of AA telescope as shown in attached figures. The first figure is contain the phase information. The second figure shows how components are organized on top of bench.

Images attached to this report
2166_20200813074206_24.png 2166_20200813074212_45.png
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NaokiAritomi - 23:14, Wednesday 12 August 2020 (2165)Get code to link to this report
Movement of QPD positions

[Aritomi, Yuhang]

As we reported before, demodulation phase for QPD1 changes day by day, and pitch and yaw coupling in WFS1 is not good. We guess that this may be because QPD1 is at the waist position. QPD1 is sensitive to gouy phase change and astigmatism.
As we reported before, optimal demodulation phase for QPD1 changes day by day and pitch and yaw coupling in WFS1 is not good. We guess that this may be because QPD1 is at the waist position. QPD1 is sensitive to gouy phase change and astigmatism.
 
We moved QPD positions to have +- 45 deg gouy phase. Yuhang will report the new optical design for WFS.
 
First we optimized DDS demodulation phase for WFS2 by looking at 12Hz line in INPUT PIT. The optimal DDS demodulation phase for WFS2 is 135 deg.
 
Then we optimized DGS demodulation phase for WFS1. The optimal DGS demodulation phase for WFS1 is 157.5 deg.
 
We measured sensing matrix. For WFS1, pitch and yaw coupling for END YAW is much better while others are more or less similar with previous configuration. For WFS2, only INPUT PIT is good and others are worse than previous configuration.
 
  INPUT PIT INPUT YAW END PIT END YAW
WFS1_I_PIT 0.41 0.06 0.2 0.02
WFS1_I_YAW 0.1 0.48 0.13 0.19
WFS2_I_PIT 0.21 0.05 0.23 0.09
WFS2_I_YAW 0.01 0.18 0.1 0.25
 
Since there is still pitch and yaw coupling in WFS1, we rotated WFS1 pitch and yaw by 10 deg to minimize 11 Hz BS pitch peak in WFS1. Then we measured sensing matrix again.
 
  INPUT PIT INPUT YAW END PIT END YAW
WFS1_I_PIT 0.37 0.14 0.23 0.03
WFS1_I_YAW 0.03 0.45 0.07 0.17
WFS2_I_PIT 0.21 0.05 0.23 0.09
WFS2_I_YAW 0.01 0.18 0.1 0.25
 
Rotation of WFS1 pitch and yaw makes INPUT/END PIT better and makes INPUT/END YAW a bit worse.
Images attached to this report
2165_20200812161534_20200812inputpit.png 2165_20200812161540_20200812inputyaw.png 2165_20200812161548_20200812endpit.png 2165_20200812161553_20200812endyaw.png 2165_20200812161609_20200812inputpitrot.png 2165_20200812161614_20200812inputyawrot.png 2165_20200812161618_20200812endpitrot.png 2165_20200812161623_20200812endyawrot.png
R&D (FilterCavity)
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NaokiAritomi - 18:21, Wednesday 12 August 2020 (2164)Get code to link to this report
CC1 investigation (2)

[Aritomi, Yuhang]

Today we found CC1 error signal is only 35.2 mVpp with old mixer while TAMA mixer gives similar value (~150mVpp) as yesterday. We need good mixers for CC1 and CCFC.

We swapped LO and RF of CC1 with TAMA mixer, but there is still offset and the CC1 error signal got smaller (first attached picture: before swap, second attached picture: after swap).

We checked RF power in LO and RF for CC1.

LO: -7.3 dBm

RF: -42 dBm

Note that this 14 MHz CC1 LO should be divided for CCFC LO.

Images attached to this report
2164_20200812112122_img8596.jpg 2164_20200812112129_img8594.jpg
R&D (Cryogenic)
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SatoshiTanioka - 11:25, Wednesday 12 August 2020 (2163)Get code to link to this report
Alignment improvement

This entry is a log on Aug. 11.

I opened the chamber in order to improve the alignment of the cavity.
The transmitted power was improved by a factor of 2.

Then I closed the chamber and started evacuating.

[note]

One temperature sensor shows fluctuation.
It may come from the connection of the cable inside the chamber.
I think it does not have serious impact on the experimet because the fluctuation is within 0.2 K though our requirement is about 1 K.

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NaokiAritomi - 02:26, Wednesday 12 August 2020 (2162)Get code to link to this report
WFS1 pitch and yaw rotation matrix

[Aritomi, Yuhang]

Today we found WFS1 optimal demodulation phase changed again. The optimal demodulation phase for WFS1 is changed from 107.5deg to 127.5deg.

We tried to decouple pitch and yaw in WFS1 I by changing the rotation matrix of pitch and yaw in WFS1 (elog2149). When the rotation angle is 20deg, 11Hz BS pitch peak in WFS1_I_YAW minimized.

Then we injected a 12Hz line to INPUT/END PIT/YAW and measured sensing matrix again (previous measurement). Although 11Hz BS pitch peak and 12Hz INPUT PIT peak are decoupled in WFS1, coupling in WFS1 for INPUT YAW and END PIT got worse and coupling in WFS1 for END YAW is still bad.

  INPUT PIT INPUT YAW END PIT END YAW
WFS1_I_PIT 0.32 0.16 0.03 0.08
WFS1_I_YAW 0.02 0.24 0.07 0.08
WFS2_I_PIT 0.14 0.03 0.42 0.06
WFS2_I_YAW 0.01 0.14 0.02 0.29
Images attached to this report
2162_20200811192622_20200811inputpit.png 2162_20200811192631_20200811inputyaw.png 2162_20200811192636_20200811endpit.png 2162_20200811192641_20200811endyaw.png
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NaokiAritomi - 23:10, Tuesday 11 August 2020 (2160)Get code to link to this report
CC1 investigation

[Aritomi, Yuhang]

First we checked nonlinear gain with 25mW green.
 
BAB with green: 210mV
BAB without green: 46mV
Nonlinear gain: 4.6
 
This is more or less consistent with theoretical value (elog1131).
 
Then we found that the TAMA mixer for CC1 has offset. We changed the TAMA mixer to an another mixer (attached picture) and the offset in CC1 error signal disappeared. TAMA mixer for CCFC also has offset, so we need an additional mixer for CCFC.
 
However, when we try to lock CC1 with the new mixer, GRMC and MZ always unlock.
 
 
Images attached to this report
2160_20200811161033_img8591.jpg
R&D (FilterCavity)
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NaokiAritomi - 22:40, Tuesday 11 August 2020 (2159)Get code to link to this report
RF peaks in QPD2 input1

[Aritomi, Yuhang, Matteo, Eleonora]

We measured RF peaks in QPD2 input1. This is the same measurement as elog2111, but this time the green is reflected from FC and galvo is engaged and there is no 32dB amplification. Setting of spectrum analyzer is the same as elog2111. Green power at QPD2 was 2.3 mW. 

Measured RF peak values are as follows. Note that 62.8 MHz and 93.2 MHz peaks are beatnotes of 15.2MHz and 78MHz.

Frequency (MHz)

FC locked+galvo locked (dBm)

FC unlocked+galvo locked (dBm) FC unlocked+galvo unlocked (dBm)
15.2 -47 -42 -35
30.4 -58 -58 -58
62.8 -61 -61 -61
78 -58 -49 -49
93.2 -67 -67 -67
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NaokiAritomi - 20:29, Tuesday 11 August 2020 (2158)Get code to link to this report
Comment to Replacement of flipping mirror for BAB and CC with 95:5 BS (Click here to view original report: 1352)
 
We measured reflection and transmission of 95:5 BS.
 
CC injection: 84 mW
CC reflection: 81.8 mW
CC transmission: 2.2 mW
 
This means this BS is not exactly 95:5, but 97.5:2.5.
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NaokiAritomi - 20:20, Tuesday 11 August 2020 (2157)Get code to link to this report
FC gain

Green injection to FC: 20 mW

Gain of FC servo: 9

UGF: 13 kHz (attached picture)

Images attached to this report
2157_20200811132200_fcoltf.jpg
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YuhangZhao - 16:57, Tuesday 11 August 2020 (2156)Get code to link to this report
Measurement of optical losses for HWP (being used and new ones)

To investigate more about the optical losses in our set-up and have idea how to reduce more about optical losses, the measurement about half-wave plate (HWP) losses was done.

The test used the infrared beam before IRMC, which is directly from main laser. By measuring infrared beam power with power meter before and after HWP, the optical losses was evaluated. The power meter was fixed in this measurement while the HWP was taken away or put back several times. Therefore, for each HWP, there were several measured data. The difference between each measurement is that beam is hitting on HWP with different angle and different position.

Three HWP were tested: Two used CVI HWP (being used for SQZ reflected from FC, being used before injection to filter cavity), a new CVI HWP, a new thorlab HWP.

The result of optical losses measurement is listed in the following table:

  average best
used CVI inj 0.69% 0.37%
used CVI ref 1.18% 0.73%
new CVI 0.17% 0.02%
new thorlabs 0.33% 0.19%
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EleonoraCapocasa - 14:58, Tuesday 11 August 2020 (2155)Get code to link to this report
Comment to Computer next to standalone cannot connect to network (Click here to view original report: 2153)

[Matteo, Yuhang , Eleonora]

The problem was solved just by replacing the LAN cable that connects the desktop PC to the router. Note that the light at the LAN cable connection is still yellow/red and blinking. Probably it doesn't need to be green.

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NaokiAritomi - 02:43, Tuesday 11 August 2020 (2154)Get code to link to this report
Strange CC1 error signal

We checked CC1 error signal with 25 mW green power (attached picture) and found that peak to peak value of CC1 error signal is smaller than before.

The CC1 error signal also has offset. Currently we don't know the reason.

Images attached to this report
2154_20200810194319_img8590.jpg
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NaokiAritomi - 02:39, Tuesday 11 August 2020 (2153)Get code to link to this report
Computer next to standalone cannot connect to network

Today we found we cannot access to remote desktop (first attached picture).

Then we found the computer next to standalone cannot connect to network. Even after we restart the PC, it cannot connect to network. Second attached picture shows LAN cable connection to the PC. 

Images attached to this report
2153_20200810193854_img8582.jpg 2153_20200810193900_img8589.jpg
Comments related to this report
EleonoraCapocasa - 14:58, Tuesday 11 August 2020 (2155)

[Matteo, Yuhang , Eleonora]

The problem was solved just by replacing the LAN cable that connects the desktop PC to the router. Note that the light at the LAN cable connection is still yellow/red and blinking. Probably it doesn't need to be green.

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YuhangZhao - 15:52, Monday 10 August 2020 (2152)Get code to link to this report
commands to kill firefox

 

ps -ef | grep firefox

 

then kill the grepped number

R&D (Cryogenic)
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SatoshiTanioka - 14:25, Saturday 08 August 2020 (2151)Get code to link to this report
Comment to Trial of measurements at cryogenic temperature (Click here to view original report: 2145)

Though I did ringdown measurement, the sampling rate was not enough to estimate the decay time...
I will modify it next time.

Anyway, I can lock the cavtiy at least 120 K.

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EleonoraCapocasa - 18:29, Friday 07 August 2020 (2149)Get code to link to this report
WFS RF rotation matrix implemented in DGS

I have added a rotation matrix to combine pitch and yaw WFS RF signals in order to compensate a possible physical rotation of the sensor (see entry #2144).

See attached the screenshot for model (pic1) and medm (pic2) modification. For the moment I didn't modify the DC part.

Images attached to this report
2149_20200807112947_model.png 2149_20200807112957_medm.png