[Kiwamu, Jenne, Vaishali]

Today we reset the green initial alignment setpoints (input laser pointing and ITM camera centroids) to match the SOFT offsets that we like at high power.  Hopefully this makes locking more smooth, since the SOFT loops won't have to work very hard anymore.

We also chose new input matrix elements for the SRM ASC at high power.  Kiwamu noted that AS36B was more responsive than AS36A (which is what we had been using), so we use mostly B with a little bit of A to get the total error point to be zero at the optimal SRM pointing. This is now in the guardian, although we haven't been able to relock to try running through the SRM_ASC_High_Power state.  It should be fine though.

We lost lock at basically NomLowNoise when we closed the beam diverters.  I'm not sure it was them - I think it was just time-coincident with a CSOFT pitch oscillation at 2.75Hz that came from my increase of the CSOFT Pit gain from 0.6 to 0.8 in an effort to squash the dP/dTheta instability.  I think we need to get locked and measure the CSOFT loop to see if we can increase the gain at all, although it looks like the more promising plan might be to re-engage the ISS 3rd loop.  We'll think on this more tomorrow.

Right now we're having trouble holding the IFO on ALS.  Both Ed and Patrick noticed that the FSS is oscillating pretty regularly, and they're concerned that it's what is causing our locklosses.  Peter and Jason, can you please take a look at the FSS in the morning?

We have reason to believe that CP3 is fixed and the ice blockage is gone. However, there was an auto overfill today at 11 am which may be skewing the reading, so we will let things settle overnight. Reservoir level reading is 100% on Beckhoff (software limit) and 120% on Magnehelic. Today we found the sensing line valves open to transducer, along with the valve that isolates them from each other, so we have been flowing much of the GN2 straight out the exhaust. Kyle checked these valves last night and thought the isolation valve was closed, but turns out it was just sticky and actually open.

We connected GN2 to CP4 sensing line, and will leave it connected for days vs. hours this time (readout on MEDM falsely shows 100% full). The flow is essentially zero right now, but set to 2 LPM in case it does open up. Isolation valve between two sensing lines is closed.

We are leaving CP3 LLCV in manual mode tonight.

TITLE: 05/31 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: Ed
CURRENT ENVIRONMENT:
    Wind: 11mph Gusts, 9mph 5min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.07 μm/s 
QUICK SUMMARY:

Jenne, Kiwamu, Vaishali, Jeff K, relocking.

TITLE: 05/31 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: Patrick
SHIFT SUMMARY:
LOG:

• The morning was wrought with IMC woes that were remedied by a late arrival of commissioners with tales of the night before.
• There was some re-aligning of arms but no full initial alignment
• There were some lock-losses trying to get locked
  • FSS oscillations inhibiting re-lock of IMC - have to constantly drop Fast Gain and then reset it to 9dB
• Kiwamu did some tunings on Soft Loops
• Jenne did some re-calibration of the rotation stage
• There was a tour group of Kindergartners in before noon
• Currently, locking is going well up to NLN without  SRM_ASC_HIGH_POWER

Performed a quick check of the ALS laser that was removed from EndX yesterday, InnoLight Prometheus S/N 2011B.
The datasheet for this laser is here.  The following settings
were as I found the laser:
  diode current                    1.832 A
  laser crystal temperature        29.02 degC
  doubling crystal temperature     33.41 degC
  diode 1 temperature              20.99 degC
  diode 2 temperature              20.30 degC

The output power at 532 nm was 47.4 mW as measured by a Thorlabs S140C power meter.  The output power at 1064 nm
was 1.53 W as measured by a Gentec TPM300 power meter.

    Initially the power at 532 nm seemed reasonably stable.  Then I observed it climb from 47.4 mW to ~60 mW and
back down a couple of times.  During these episodes the 1064 nm power remained stable.  The frequency doubling
crystal TEC error signal varied from 1 mV to 2.2 mV.  Which corresponds to a temperature change of
1.2 mV / (10 V/degC) = 0.12E-3 degC.  The change in wavelength with respect to temperature is ~0.03 nm/degC.
However just because the wavelength changes doesn't necessarily mean the output power changes, that depends on
the resonator finesse.

    I then set the laser settings to those listed in the datasheet, namely
  diode current                     1.750 A
  laser crystal temperature         24.00 degC
  doubling crystal temperature      33.20 degC
  diode 1 temperature               20.99 degC
  diode 2 temperature               20.31 degC

At these settings the output power at 1064 nm was 1.44 W.  Initially the output power at 532 nm was 41.4 mW
but was seen to vary as high as ~63 mW.  Again no temperature or diode power related signals appeared to vary
in sync with the observed power changes.

   Perhaps of note is the thermistor reference voltage(s) were measured to be 6.64 V and 6.58 V, instead of
6.85 V for both the frequency doubling crystal and diode 2 respectively.  Without knowing the circuitry for
the thermistor, I don't know if this is significant or not.

Everyone in the control room was sad that requesting 30W of injected power was only getting us 27W.  So, I ran the calibration scripts from alog 30479.  Now 2W is 2W, 10W is 9.9W, and 30W is 29.8W.  Much better.

Attached screenshots are the old calibration and the new calibration values in the calibration screen.  Jeff has made these values monitored in the SDF (were un-mon before).

J. Kissel, D. Sigg

Investigating the last corner station Beckhoff error, regarding the 9 MHz EOM driver offset. There are complaints that the read back (H1:LSC-MOD_RF9_AM_RFOUT and H1:LSC-MOD_RF9_AM_RFSETMON) is out of range at ~18.6 [dB], where the request (H1:LSC-MOD_RF9_AM_RFSET) is 16.8 [dB].  Unclear what the tolerance is; appears to be internally set and not broadcast over EPICs. Side note: leading up to and during O2, when IFO is down/acquiring, it's reduced to 10.8 in NLN.

The offset was set to 16.8 dB on Feb 23 2016 (see LHO aLOG 25687), to balance the RF power of the driver, and its readback has been slowly drifting *up* from there since.
Looking back further, we see similar upward drift during O1, even though the offset's request was different.
45 MHz Beckhoff readbacks are stable.

Fast ADC version of the control voltage (H1:LSC-MOD_RF9_AM_CTRL_OUT16) doesn't show the drift. Also the values don't agree. 

Tolerance increased LHO aLOG 30406 (perhaps unbenowst to the increaser) to accommodate the drift.

Chassis assembly E1400445
    Controller Circuit D0900761.

These channels are all readout by a single 4 channel ADC as the readback: ecatc6 Middle Rail 10 is the module (from D1300745). Maybe internal voltage reference drift?

Recommendations:
- either check the cabling at the ADC
- measure the input to the ADC to confirm the expected voltages
- replace the ADC.

Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 34 seconds. LLCV set back to 20.0% open.
Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 985 seconds. TC B did not register fill. LLCV set back to 39.0% open.

Last week we took advantage of the down time to do Z diagonalization measurements on the BSC ISI's, as Jeff outlined in his alog 36360. I used the data we got to calculate and install coefficients on all of the chambers that needed decoupling. The first five plots  are the closeout Z to X/Y transfer functions comparing the before and after results showing the reduced coupling via tilt from Z drive to X/Y motion seen by the St1 T240s. For these plots, blue is always before, red is the after measurement. I forgot to include Y units but they are in nm/s / nm*rthz because I didn't convert the T240 signal to displacement.

Yesterday I looked at repeating this on the output HAM's, I was just efficient enough to get HAM4 mostly done, but I need more time finish HAMs 2,3,5,6. The last attached plot is the Z to X/Y plots before and after for HAM4. The magnitude plots are in nm / nm*rthz. I also got data for HAM4 Y to RX, but it looks like the ISI is good enough in that DOF. HAM5 was similarly clean for Z to RX/RY, and I have a coefficient calculated for HAM6 Z to RX, but I would like to do a measurement after installing the cpsalign elements before I make a permanent change.

We've seen lately (since the IMC transmission has been different - see alog 36361 and others) that the IMC won't re-lock itself consistently.  Most of the time someone has to give a kick to the MC2 suspension to make the cavity flash so that it can lock.

Jim and I were looking at it, and it appears that with the different IMC transmission situation, the lowpass that effectively helps the IMC sweep while unlocked (IMC-MCL FM10) was not being triggered properly.  It is supposed to be on when the IMC is unlocked, and off once we get locked. It was properly off when the IMC was locked, but it was flickering on and off when the IMC was unlocked. The FM trigger thresholds just needed to be reset, which included changing the hard-coded values in the IMC_LOCK guardian. 

With one or two unlock tests, the IMC seems to be once again relocking itself reliably.  Please let me know if someone finds that it's not working again.

S. Dwyer, J. Kissel

We found that the Beckhoff error handling system was reporting an intermittent error on ALS Y WFS A Demod Local Oscillator (LO) Power (H1:ALS-Y_WFS_A_DEMOD_LOMON) having surpassed its threshold (H1:ALS-Y_WFS_A_DEMOD_LONOM). 

Trending reveals that
 (a) The error bit has been green since the Beckhoff ADC was replace on Sept 22nd 2016 (see LHO aLOG 29848) 
 (b) the LO's power has been slowly increasing over time, and was now on the hairy edge of the threshold.

After consulting Sheila, she suggests "it's probably fine," so I increased the threshold from 21 [dBm?] to 22.5 [dBm], and accepted the new threshold in both safe and OBSERVE.snaps in the SDF system. (I'm not confident that this monitor is actually calibrated into physical units, but 21 [dBm] doesn't sound crazy so I put confidence in the designer of the system to have done so.)

Hopefully this doesn't turn out to be a canary for the demodulator like the diode laser power was to the now replaced ALSX laser...

Temp A: 24.4 ºC
Temp B: 21.6 ºC
Diode: 1.80A
Laser Crystal Temp: 29.60 ºC
Doubler Temp: 33.62 ºC

Daniel, Kiwamu per WP6650,

We made two major changes to IOO today as follows.

• The IMC locking RFPD (36322) was replaced by the one with the correct resonant frequency.
• A new modulation path for 118 MHz was added to the existing 24 MHz modulation path via a power combiner.

After these tasks, we have confirmed that the IMC could still lock with an UGF of 50 kHz (which had been 54-ish kHz before we made changes today, approximately corresponding to a 1 dB loss in the sensing system). Tomorrow, we will try to measure the modulation index for 118 MHz using the Michelson fringes.

[IMC length RFPD]

The old unit (S1203263) was replaced by the one with the correct resonant circuit (S1203775). I have repeated the same measurement as yesterday with the AM laser (36322) to check out the response of the new RFPD. The first attached figure shows comparison of the new and old RFPD responses. The magnitude at 24 MHz was found to be lower than that with the old one by half a dB. So the response is virtually unchanged at 24 MHz. The raw data is attached as well.

I made sure about the alignment of the beam onto the RFPD by touching the 2" steering mirror in front of it. I also made sure that the reflection from the RFPD was dumped properly with a razor blade.

[Addition of 118 MHz modulation]

We newly installed two IFR function generators in an ISC rack in the CER. One of them provide us with the modulation rf source at 118 MHz while the other does for the demodulation at 72 MHz or whatever frequency we desire. The 118 MHz generator was then hooked up to an RF amplifier, ZHL-1-2W, and then to the patch panel which transfers it to the ISC field racks by the PSL. Then, the 118 MHz signals is combined with the existing 24 MHz modulation signal via a power combiner, MECA 2-way combiner. As it turned out that the power combiner gave us a relatively high insertion loss of ~3 dB, we decided to increase the rf power for 24 MHz as a compensation. We increased it by installing another MECA 2-way combiner and let it do the coherent sum. So in total we have installed two 2-way combiner in series as seen in the attached picture.

We also studied rf losses for 118 MHz and found extra frequency dependent losses in the cable that connects the field and remote racks. The cable loss for 118 MHz was found to be higher than that for 24 MHz by a couple of dB. In the end, we measured an rf power of 30 dBm for 118 MHz at the output of the last power combiner, which we think is reasonably high and not too high for causing serious problems with the EOM. Note that we tried inserting a balun which turned out to be as lossy as 3-4 dB. So we decided not to use a balun for 118 MHz. We are thinking of installing a DC block instead.

As this setup messed up the rf phase, we then re-adjusted the delay of the delay line unit for 24 MHz, by flipping 1 and 2 nsec switches. This gave us almost the same UGF of 50 kHz when the IMC was locked with a 2 W input and with the new RFPD in use. Good.