Everyone


- ITMX motion has been largely reduced by the seismic teem, now the motion at 0.5 Hz is around 0.03 urad, A LOT less than before;

- The tuning of the ETMX is still in progress, but in the meantime Stefan implemented a 'dirty' optical lever feedback which reduced the ETMX PIT motion by about a factor of 5 at 0.5 Hz. With the OL feedback on, ETMX PIT @ 0.5 Hz is around 0.1 urad. There is some gain peaking around 1 Hz.

- In this state, the one arm is stably locked on green with 32 uW (calibration to be confirmed) in transmission (~840 counts in ALS-C-TRX_A_LF_OUT) power fluctuations are small, around 5%. We are not seeing the 01 coming into resonance, so we can make a measurement of the frequency noise red/green. (P.S.: Sheila says that ~800 counts is a good number, corresponding to a good cavity alignment.)

(Sheila, Alexa)

1. We wanted to re-visit the EX PLL shot noise measurement we had previously done.

• From the direct output of the pre-ampifier we measured the beatnote signal to be -33dB at 39.8MHz with 100 Hz BW
• The RF spectrum analyzer had a noise floor of -126dbm with 100 Hz BW (no attenuation)
• From the direct output of the pre-amp with the BBPD blocked, we measured an electronic noise of -118dbm at 100 Hz BW from the PD
• With the fiber blocked we measured noise of -114dBm at 100 Hz BW
• We meaured the power at the BBPD to be 5.8mW with a DC reading of 1.04V --> .52mA at the PD. We calibrated the PD responsivity to be .09 A/W
• To confirm we were measuring shot noise, we increased the optical power by a factor of 2, and saw that the noise with the fiber blocked increased to -111dBm at 100 Hz BW. We expected this increase, so are confident we were measuring shot noise.

2. WIth the EX PLL locked, the arm cavity well aligned, and the green beam flashing, we looked at the PDH error signal out of the demod IMON and measured the peak-to-peak of the signal to be 230mVpp

3. We went on to investigate the fringe wrapping we saw in the PDH amplitude spectrum at the error point. With the arm locked, we only saw a slight difference in the spectrum with the HEPA fans on or off (Sheila will attach pictures). There did not seem to be fringe wrapping, and the acoustic noise seemed minimal. I will look at the PDH shot noise again when I can misalign ITMX and see if the fringe wrapping is still there.. 

Results of last set of ETMY transfer function after finishing the alignment (see this alog for alignment numbers) are attached below, and look similar to what was taken monday night. TMS team can start (and probably already did) work on the installation. SUS will go in the next days check for lower masses flag/osem centering as well as top mass verticals. 

Attached files :

H1 ETMY fiber after finishing alignment (in black) compared to first alignment (in orange) compared to LLO ETMX fiber in chamber. Main chain (1st pdf) and reaction chain (2nd pdf)

To notice :

- First pitch mode of the main chain fiber quads are shifted down (0.52Hz) compared to the model (0.562Hz). Cf p5 of first attachment.

Jim Rich and Hugh have been working on the ITMX ISI, and found a sign flip. Here are plots of the sus witness sensors (L2WIT) and OpLevs:

• early this morning (brown traces) when we had 750mHz blends on all stage 1 DOFs and could not include any trilliums in the blends without tripping.
• the last half hour or so, (blue traces) with stage 1 blends Tcrappy on all DOFs, stage 2 100mHz on X and Y, 250 Hz on all other DOFs. 

Modified instructions for turning on ITMX ISI after a trip:

• set all blends to 75omHz. 
• make sure T240 WD is disabled by setting the treshold to be large (later you will need to reset this)
• isolate stage 1 level 3
• isolate stage 2 level 3
• change all stage 1 blends to Tcrapy
• change all stage 2 blends to Tcrapy

Of course this mght change, especially the stage 2 blends might work with a different set of blends.

Looked at photo diode forward voltage for ETMY ACB per LIGO-T1100637.
PD forward voltage(≈ 0.5V)

Pin 13 & 12 
PD forward voltage: 0.428V

Pin 10 & 9 
PD forward voltage: 0.421V

Pin 7 & 6
PD forward voltage: 0.428V

Pin 4 & 3
PD forward voltage: 0.421V


Filiberto Clara & Mitchell

Andres and Jeff working on SR2

Working on ACB with Apollo.

• Longitudinal: -0.4 mm
  • Tolerance: ±3.0 mm
• Lateral: +0.1 mm
  • Tolerance: ±1.0 mm
• Vertical: -0.3 mm
  • Tolerance: ±1.0 mm
• Pitch: 645 µrad down
  • Target: 639 µrad down
  • Error: 6 µrad down
  • Tolerance: ±100 µrad
• Yaw: 80 µrad CCW
  • Target: 0 µrad
  • Tolerance: ±100 µrad

Also measured & aligned the ERMy (Note: the ERMy is aligned parallel to the AR surface of the ETMy) and measured the gap between the ETMy and ERMy.

• ETMy/ERMy Gap: 5.05 mm
  • Tolerance: ±0.25 mm
• ERMy Pitch: 1.671 mrad down
  • Target: 1.971 mrad down (to match the ETMy AR surface)
  • Error: 300 µrad up
  • Tolerance: ±1.47 mrad
• ERMy Yaw: 245 µrad CW
  • Target: 80 µrad CCW (to match ETMy AR surface)
  • Error: 325 µrad CW
  • Tolerance: ±1.47 mrad

Mitchell, Scott (Apollo)

The assembly of the Arm Cavity Baffle was completed yesterday. Final weights need to be taken then, it will be suspended from the solid stack to begin balancing.

It had the usual problem of asking me to choose a run time system in the active and run step, and not being able to log in.  
I also did an svn update, and got a message about the redoubt certificate. 

Lisa, Stefan

To get the PRMI locking we had to turn off all 2-stage ISIs.

With the 1-day old heating of ITMY at 1.5W, and an alignment tweak, we got 6000cts of POP18. Unfortunately I am not 100% sure how much of that is alignment, and how much is heating.

At UTC 08:4:33 we turned the ring heater to 4Watt total (2Watt each).

I believe the ITMX optical lever signals are calibrated in urad. If that's the case, the ITMX PIT motion right now is 0.3 urad RMS  (this is with the ISI in the configuration Rich left it in).

All the RMS comes from 0.1 - 0.7 Hz and I see 1 urad / sqrt(Hz) @ 0.5 Hz. 

This is significantly worse than ETMY/ITMY motion during the one arm test (0.2 urad/ sqrt(Hz) and 0.3 urad / sqrt(Hz) @ 0.5 Hz T1200450), and normal operations at LLO (0.4 urad RMS, and 0.05 urad/ sqrt(Hz) at 0.5 Hz - LLO log 8637).

Need to double check that I am comparing apples to apples.

Rick, Sheila,

at 00:16 the PSL turned off. Rick and Sheila think the power watchdog may have tripped. Sheila has started the recovery procedure.

I have been silently checking the signal chain of the REFLAIR and POPAIR RFPDs using the AM laser (a.k.a. PD calibrator) to make sure that they are functional expectedly.

Summary

• REFLAIR_A and POPAIR_A looked good as they showed reasonable signal gains
• On the other hand, REFLAIR_B and POPAIR_B RFPDs showed relatively large discrepancy from the expected values. I might have missed some gain factors somewhere. I will revisit these RFPDs later when I get a chance.

The RF frequency of the AM modulation was adjusted in each measurement such that the demodulated IF signal was below 50 Hz.

Calibration of the amplitude modulation depth

We recalibrated the AM laser.

The current setting of the laser was changed recently because we opened up the current driver when we thought the laser diode had been dead in the early December. Then the laser head and its current driver were sent to Rich at Caltech for his extensive testing although the laser magically fixed itself and he didn't find anything wrong. So this was the first time for us to use the AM laser which had been fixed. Because of that mysterious event, I wanted to recalibrate the laser. First of all, Yuta and I measured the power to be 2 mW with an Ophir Vega without the attenuation filter. Then we measured the modulation depth for the amplitude modulation by using a Newfocus 1611 as a reference.

The new calibration for the amplitude modulation is:

P_am =  5.13 mW x (P_dc / 1 mW) * (1 V / V_drive)

where P_dc is the laser power at DC and V_drive is the drive voltage when it is driven by a 50 Ohm source. For example, if one puts this laser to a PD which then shows a DC laser power of say 2 mW, the AM coefficient is now 5.13 mW x ( 2 mW / 1 mW) /V_drive = 10.26 mW/V_drive.

• Some details for derivation:
  • DC transimpedance of NF1611= 10k Ohm
  • AC transimpedance of NF1611 = 700 Ohm
  • Responsivity of NF1611 at 980 nm = 0.5 A/W
  • Measured DC voltage = 7.36 mV
    • => DC laser power of 7.36 mV / 10kOhm / 0.5 A/W = 1.47 uW
  • Measured AC voltage when driven by 0.5 Vpp at 10 MHz = 1.32 mVpp (measured by a 50 Ohm oscilloscope)
    • => P_am = 1.32 mV / 700 Ohm / 0.5 A/W = 3.771 uW
    • => AM coefficient is 7.54 uW / V_drive
  • Therefore the AM calibration is:
    • 7.54 uW / 1.47 uW x 1 mW = 5.13 mW x (P_dc / 1 mW) * (1 V / V_drive)

REFLAIR_A_RF9 (S1203919)

Remarks:

The signal chain is OK. The PD response is smaller by 15% for some reason.

It seems as if the transimpedance is smaller by 15% than what had been measured at Caltech (LIGO-S1203919). The cable loss from the RFPD to the rack was measured to be 0.47 dB. Be aware that the demod gain is half of the quad I/Q demodulator because this is a dual channel demod (see E1100044). The demod conversion gain is assumed to be 10.9 according to LIGO-F1100004-v4.

• Measured DC at BNC jack = 108 mV
  • DC laser power = 108 mV / 100 Ohm / 0.67 A/W = 1.61 mW
• Expected AM signal when driven by 0.1 Vpp = 5.13 mW x (1.61 mW / 1 mW) x 0.1 Vpp x 0.67 A/W x 245 Ohm = 135.6 mVpp
• Measured AM signal at the SMA jack of the RFPD enclosure = 115 mVpp
  • This is already smaller by 15%.
  • If we blame the transimpedance, it must be 208 Ohm rather than 245 Ohm.
• Measured AM signal at the rack = 109 mVpp
  • cable loss = 0.47 dB
• Expected IF signal = 135.6 mVpp x 10.9 / 2. = 622 mVpp
• Measured IF signal = 570 mVpp
  • If we take the 15% and 0.47 dB losses into account, we would expect this to be 527 mVpp.
• Expected ADC counts = 135.6 mVpp x 10.9 x 2^16 counts /40 V x 1/2 = 1209 counts pp
• Measured ADC counts = 900 counts pp
  • If we take the 15% and 0.47 dB losses into account, we would expect this to be 973 counts pp.
  • This is within 10% divation. Good enough.

REFLAIR_A_RF45 (S1203919)

Remarks:

The signal chain is healthy.

Found cable loss of about 1.5 dB. The measurements excellently agree with the loss-included expectation.

• DC laser power = 1.61 mW (the same as REFLAIR_A_RF9)
• Expected AM signal when driven by 0.1 Vpp = 5.13 mW x (1.61 mW / 1 mW) x 0.1 Vpp x 0.67 A/W x 341 Ohm = 188.7 mVpp
• Measured AM signal at the SMA jack of the RFPD enclosure = 190 mVpp
  • Very good agreement !
• Measured AM signal at the rack = 160 mVpp
  • Corresponds to loss of 1.5 dB
• Expected IF signal = 188.7 mVpp x 10.9 = 1028 mVpp
  • If the loss is taken into account, it is going to be 1028 mVpp x -1.5 dB = 865 mVpp
• Measured IF signal = 880 mVpp
  • Consistent with the loss-included expectation
• Expected ADC counts =1028 mVpp x 2^16/40 x 2 = 3369 counts pp
  • If the loss is taken into account, it should be 3368. x -1.5 dB = 2837 counts pp
• Measured ADC counts = 2784 counts pp
  • Good agreement with the loss-included model

POPAIR_A_RF9 (S1300521)

Remarks:

The signal chain is healthy.

The measurement suggests that there is loss of 1 dB somewhere. I didn't measure the cable loss this time.

• Measured DC at the BNC jack = 95.6 mV
• Estimated DC laser power = 95.6 mV / 100 Ohm / 0.67 A/W = 1.42 mW
• Expected AM signal = 5.13 mW x (1.42 mW / 1 mW) x  0.1 Vpp x 0.67 A/W x 741 Ohm = 361.7 mVpp
• Expected ADC counts = 361.7 mVpp x 10.9 x 2^16/40 counts/V = 6454 counts pp
• Measured ADC counts = 5705 counts pp
  • If we assume this discrepancy is from a loss, it corresponds to loss of 1.07 dB.

POPAIR_A_RF45 (S1300521)

Remarks:

The signal chain is OK. Though loss sounds a bit too high.

The measurement suggests a possible loss of 2.6 dB somewhere. I didn't measure the cable loss.

• Estimated DC laser power = 1.42 mW
• Expected AM signal = 5.13 mW x (1.42 mW / 1 mW) x 0.1 Vpp x 0.67 A/W x 837 Ohm = 408.5 mVpp
• Expected ADC counts = 408.5 mW x 10.9 x 2^16/40 counts/V = 7295 counts pp
• Measured ADC counts = 5391 counts pp
  • If the discrepancy is assumed to be from loss somewhere, the loss should be 2.6 dB.

REFLAIR_B_RF27 (S1200234)

Remarks:

The signal gain is bigger than the expectation by a factor of 2.3.

• Measured DC at the BNC jack = 836 mV
  • This corresponds to a laser power of 836 mV / 2000 Ohm / 0.4 A/W = 1.045 mW
• Expected AM signal = 5.13 mW x (1.045 mW / 1 mW) x 0.05 V_drivepp x 0.4 x 1000 Ohm = 107.2 mVpp
• Expected ADC counts = 18 dB x 107.2 mVpp x 10.9 x 2^16/40 counts/V = 15206 counts pp
  • I assumed that the gain factor of the diplexer (LIGO-D1300989) to be 18 dB at 27 MHz.
• Measured ADC counts = 35431 counts pp
  • This is bigger than the expected by a factor of 2.3

REFLAIR_B_RF135 (S1200234)

Remarks:

The signal gain is bigger than the expectation by a factor of 1.5

• Measured DC laser power = 1.045 mW
• Expected AM signal = 5.13 mW x (1.045 mW / 1 mW) x 0.0014 Vdrivepp x 0.4 A/W x 1000 Ohm = 3 mVpp
• Expected ADC counts = 43 dB x 3 mVpp x 10.9 x 2^16/40 counts/V = 7573 counts pp
• Measured ADC counts = 11689 counts pp
  • This is bigger than the expected by a factor of 1.54

POPAIR_B_RF18 (S1200236)

Remarks:

The signal gain is bigger than the expectation by a factor of 2.3

• Measured DC at the BNC jack = 744 mV
• DC laser power = 744 mW / 2000 Ohm / 0.4 A/W = 0.93 mW
• Estimated AM signal = 5.13 mW x (0.93 mW / 1 mW) x 0.1 Vdrivepp x 0.4 A/W x 1000 Ohm = 191 mVpp
• Estimated ADC counts = 191 mVpp x 10.9 x 2^16/40 counts/V = 3404 counts pp
• Measured ADC counts = 7803 counts pp
  • This is bigger than the expected by a factor of 2.3

POPAIR_B_RF90 (S1200236)

Remarks:

The signal gain matches with the expected value, but I don't believe this.

• DC laser power = 0.93 mW
• Estimated AM signal = 5.13 mW x (0.93 mW / 1 mW) x 0.1 Vppdrive x 0.4 A/W x 1000 Ohm = 191 mVpp
• Estimated ADC counts = 191 mVpp x 10.9 x 2^16/40 counts/V = 3408 counts pp
• Measured ADC counts = 3549 counts pp
  • This suspiciousely shows an excellent agreement with the expected one.