J. Kissel

Remembering that we may need to re-balance the recycling-cavity HSTS drives after having replaced the lower stage drivers with increased-range, modified, coil drivers (PRM, PR2, SR2, SRM; see Integration Issue 936 for links log entries), I began to balance SRM M3 this morning. 

I used the same pringle-drive, demodulation-of-the-OSEM-sensors, balancing technique that we've used in the past (see e.g., LHO aLOGs 11392, or 9453). 

I was able to confirm that the balancing *is* now worse by a factor of ~6 (by not changing the previous COILOUTF gains and simply comparing the new results with the balanced old), but was unable to balance to many better than this newly bad value. My time was limited because of priority DRMI work, but I'll continue to investigate as time allows. For now, I've left the COILOUTF gains as they were balanced to the unmodified driver, 
 
H1:SUS-SRM_M3_COILOUTF_UL_GAIN  0.972
H1:SUS-SRM_M3_COILOUTF_LL_GAIN -1.014
H1:SUS-SRM_M3_COILOUTF_UR_GAIN -0.972
H1:SUS-SRM_M3_COILOUTF_LR_GAIN  0.964

See attached for plots.

Plots, Data, and Diary live in and have been committed to
/ligo/svncommon/SusSVN/sus/trunk/HSTS/H1/SRM/Common/Data/

I finished preparing the online calibration filters for the DRMI which I started in the last week (see alog 14030). The output spectra are now monitored on projector1 (see alog 14042) in the control room as shown in the above pitcture.

I checked the HSTS and BS suspension filters in the calibration paths in h1oaf. While the HSTS suspensions looked good to me, the BS suspension did not look similar to the suspension model. In particular, the location of resonances did not look correct in the first place. So I changed the BS model by running the BS design Matlab script in the SVN and, copying and pasting the result in foton. The DC gain was then re-adjusted by hand such that it is at 8.85 x 10^-5 um/cnts (= 46.40 um / (4 x 2¹⁷ counts)). Note that this 46.4 um came from DCC-T1100602-v2. And the factor of 4 in the denominator compensates to the Euler matrix in the suspension realtime controller.

Saw the HAM6 HEPI was tripped this morning.  It tripped on a large Actuator spike Saturday about 4pm, just a few hours after I go it fixed.  Attached are the IPS spectra for HAM6 like I've plotted before--obviously V2 is back to its old ways.  Also attached are all the local IPS sensors when it tripped.  Again, V2 is not like the others and it is a bit hard to be sure but it looks like the big glitch on the V2 channels preceeds the other sensors moving off their previous values.

What to do?

Wiggle the cable some more and/or look closer at thecable going into the Pier Pod?

Change the sensor?--Requires changing both V2 & H2 sensors as these are matched to the Kaman Box within the Pier Pod--And yes you guessed it, pull the Pier Pod box and mount the matching Kaman box within.

Last week with Seb here, I started playing with sensor correction on the ETM ISI's. ETMX turned on and did good things around a half hz, as it should. ETMY so far has not done as well, so I'm still investigating there. This morning I looked at the ITM's, just seeing if filters were installed. ITMX seems to have had it's filters modified, so I used foton and gedit to fix the IIR and FIR filters. That did not happen as transparently as I would have hoped, so, my apologies to the ISC crew. After talking to Kiwamu and Sheila, they let me try to turn sensor correction on on ITMX this morning. Looks like it's working so far, only on Z ,see attached plots. The upper right plot on each picture shows most of the action, but there does seem to be a reduction in the low frequency motion on RX and RY as well, that is probably just an artifact of only having 20 minutes of data. We can't use sensor correction on other DOF's, as the blends are too low.

PSL Check: 9/22/2014

Laser Status: 
SysStat: Warning “VP program online” is red
Output power is 29.6 W (should be around 30 W)
FRONTEND WATCH is active
HPO WATCH is red

PMC:
It has been locked 5 days,0 hr , and 59 minutes (should be days/weeks)
Reflected power is 2.2 Watts and PowerSum = 25.9 Watts.
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 3 d, 20 h, and 38 min (should be days/weeks)
Threshold on transmitted photo-detector PD = 2.03 V (should be at least 0.9V)

ISS:
The diffracted power is around 7.1 % (should be 5-15%) 

Last saturation event was 4 d, 22 h and 51 minutes ago (should be days/weeks)

Over the weekend I ran a transfer function on the BS with optical lever damping filters off, and FM2 of both L2P and L2Y filters on. These two filters were installed last week (alog 14046 and alog 14022). This transfer function was taken to determine the residual motion of the BS in yaw and pit given a drive in length on the M2 stage. We can compare this to the previous rediula motion with FM1 filters on for both L2Y and L2P as measured by Stefan alog 9394.  The attach screen shot shows a side by side comparion. The red traces are all YAW/L and the blue traces are all PIT/L. And the left most windows, or the traces with square symbols are the TF with FM2 (current version), while the right most windows, or the traces with the circle symbols are the TF with FM1 on (old version). The L1Y coupling improved by about 16dB at low frequency, and 24dB at high frequency. Meanwhile, in L2P the high frequency magnitude is about the same (it's actually slightly worse by about 2dB), but at low frequency we have imporoved by a factor of about 19dB. The new filter for L2P was intended to mostly correct the low frequency motion, so this result is about as expected. Also, in the process of creating the new filters, we did not concern ourselves with any of the resonances, which is why you don't see much of a change (and it may be a bit worse) compared to the older values. Jeff and I also checked that the BS coil balancing did not change between Stefan's measurement and mine, indicating that the improvement clearly came from the coupling filter change. I was unsure why the phase between the new and old version are no longer the same, given the that old and new filters have the same phase. Kiwamu explained to me that this came from whether we were pushing too much or too little to compensate for the L2Y/P coupling. The phase can change by 180 when we adjust for this.

Next, I plan on inspecting the power spectrum of the BS oplev with the PRMI locked on the sideband. One question we have though, is what constitutes good enough residual motion?

 Attendees: Fred, Jim, Vern, Greg, Peter, Ed, John, Kyle, Gerardo, Jeff B, Jodi, Jason, Bubba, Patrick, Alexa, Daniel, Richard, Corey, Aaron, Filiberto, Kiwamu, Betsy, Travis, Hugh, Sheila, etc …

Today's Tasks:


Hugh reported about the WHAM6 HEPI V2 IPS sensors Problem. New HEPI TFs will need to be run. 

Work on 3IFO QUAD will continue today in LVEA (Betsy/ Travis)

Getting ready to test 3IFO (Quad 9) in Staging Building – Jeff B

Circuit breaker failure (Replacement part needed) – Richard  

Moving TCS HWS table into position (HAM4) – Greg/Aidan

Illuminator control work in LVEA – Richard/Filiberto

Fans work on all Mid/End stations – Bubba

model restarts logged for Sun 21/Sep/2014
2014_09_21 03:27 h1fw1

unexpected restart of h1fw1

Kiwamu, Rana, Sheila

On Friday, we measured the spot position on PR2 using the A2L technique:  vertical / horizontal   ~   5mm / 3 mm.

We wonder if the spots are far off center and might explain the low recycling gain that we see. The camera images are not detailed enough to tell us about positions better than a couple cm.

The concept of the A2L measurement is that we drive the optic angle and measure the response in the cavity length sensor (REFL 45, in this case). We assume that the LSC photodiode has a very small angle sensitivity (which is true as long as the cavity is non-degenerate and has a high finesse and the beam on the photodiode is a few times smaller than the diode active area and that the photodiode has a small non-uniformity). We also assume that the mechanical coupling from torque to longitudinal motion is smaller than the centering precision we want. I don't know if all of these assumptions are true, but we proceed as if they are.

To make the measurement robust, we want to avoid the GDS testpoint dropouts, and so we use the front end digital lockins. Unfortunately, the LSC does not have capability to drive mirror angles and the SUS/ASC do not have capability to demodulate the LSC signals. So we make a temporary workaround in the SUS DRIVEALIGN matrix by routing the L drive to P or Y**. Then the LSC drive can drive apply torque on PR2-M3 and demodulate REFL45_I. We then null the demodulated signal by also sending some of the torque to the L2L path. By taking into account the size of the optic (R = 8 cm from T0900435-v9), we can use the ratio of L2L/L2A gains to determine the beam position on the optic (we also take into account the non-unity gains in the EULER2OSEM matrix: L=0.25, P/Y=5.3).

For PR2, we used a drive frequency of 9.57 Hz and amplitude 555 counts. Since we do not have WFS feedback yet, there were large beam spot motions. The 9.57 Hz digital lockin we use to demodulate the 45 MHz demod outputs have I and Q outputs. The I-phase corrresponds to the the steady beam spot position and the Q-phase gives us information of how much the beam is moving (?).

** This hacky technique won't work for the optics being used for LSC feedback, so we need to come up with a better hack or make some model rewiring. Now that we have larger range coil drivers, we can swap the control from PRM to PR2 to allow us to measure the spots all over the DRMI. And, of course, we can use the front end dither system to automatically center the spots as well.

model restarts logged for Sat 20/Sep/2014
2014_09_20 01:02 h1fw1
2014_09_20 12:32 h1fw1

unexpected restarts of h1fw1.

This is a report from yesterday

In the afternoon of yesterday, Sheila noticed that the POPAIR_B_RF18 did not reach a high value in the PRMI no matter how she steered IM4, PRM and PR2. So I tried looking for the cause. Then I found two clipping issues as follows:

• The in-air POP beam was clipped at the bottom periscope mirror of ISCT1.
  • I realigned the optics on the table. This increased the POP_RF18 from 60 uW to 80 uW.
• The in-air POP camera showed a clipped beam image, which I could not identify where this happened. But it smelled like a intra-cavity clipping.
  • This persisted even after I fixed the periscope bottom mirror on ISCT1.
  • Steering a combination of PR2 and PR3 allowed me to improve the clipped image.
  • Steering PR2 and PR3, I could increase the POP18 power to 160 uW which is higher than what we usually have (~ 120 uW).  The image on the POP camera improved.
  • Also this must have increased the actual cavity power build up because both LSC-MICH and PRCL servos started oscillating due to a too-high-UGF as I steered the PRs.

The work will continue in parallel to the main DRMI lock project.

(Some detailed notes)

* POPAIR_B_ calibration changed

In the process, I found the POPAIR_B_RF18 saturating at its ADC. So I decreased the whitening gain to 24 dB from 33 dB. Also I changed the FM9 of POPAIR_B_RF18 in order to maitaing the same calibrated numbers. Now POP18 does not saturate. Also, I noticed that the demodulation phase was not quite good. So I rotated it from -100 to -113 deg. This increased the RF18_I power by a few percent.

* Clipping on ISCT1

The clipping on the ISCT1 bottom periscope was due to the beam at too low height. Also the horizontal position was off toward north by roughly a beam spot size. I could not precisely assess the spot position on the upper periscope mirror because of a narrow available space in the ISCT1 enclosure. But, with a sensor card, it did not seem clipped at the upper periscope. The image below is a POP camera before I improved the two clipping issues:

Since the camera does not have a TV lens, the image is up-side-down and right side left. It is clear that the beam is clipped in its lower part (or upper part on the camera view). However, fixing the bottom periscope mirror situation did not change the beam image. This is how I found another clipping issue.

* Steering PR2 and PR3

I wanted to move the (back propagating) POP beam in pitch to see how the clipping situation changes. Since touching IM4, PRM and PR2 did not seem to give a significant effect on the clipped image, I started using PR3. Note that before I touched PR3, it was right on the center of the oplev QPD. I have moved PR3 toward the positive side in the suspension bias slider. At the same time, in order to maintain a high build up, I moved PR2 toward the negative side in the bias slider. So this operation is equivalent to an introduction of translation in the beam line between ITMX and PR3 downward while mantaining the same spot on PRM and PR2. Also, this alignment operation introduced a tilit in the beam line between PR3 and PR2 such that the forward propagating beam goes downward as it approaches to PR3 from PR2. Note that looking at the PR3 GigE camera, I noticed that the beam spot was a bit too-low on the mirror from the beginning. Unfortunately I could not see a spot on the BS because of the too low power in the PRC.

As I improved the clipped image and the POP18 power, both MICH and PRCL servo started oscillating due to a too high UGF. I derecased both of them by 40% rom the nominal guardian-commanded gains in order avoid the servo instabilities. i did not get a chance to check the open loop transfer functions.

We should carefully study what this means. Does it mean the spot position on PR3 and ITMX matters ? Or, the angle of the beam line between PR2 and PR3 matters ?

With a little bit of jiggling of the IPS sensor wires I got the sensor to completely fail, that is output to go to -10v (-32000 counts.)  By power cycling the Kaman satelite box (not the HEPI Pier Pod) the sensor recovered.  I repeated the process, jiggled the cable at the sensor end--no fault; jiggle at the Kaman box end--fault.

The Kaman satellite box is an off the shelf housing that is mounted inside the HEPI Pier Pod, the sensor cables go through a cutout in the Pier Pod to plug in.  Maybe the shield of the lemo-like cable end is shorting on the Pier Pod box wall, or, hopefully not, it is a worse problem.

It is a little head scratching but I think the DC level of the IPS is problematic,  This is regards to the alignment position.  As the IPS was running yesterday after I unlocked, it was in a partially failed state during which the IPS readout was -7500cts; now with a coarse observed spectra looking pretty good (waiting to record a better one) it is now running about -5000.  That 2500count difference is about 97000nm.  Do I need to figure out how this will affect the Z, RX & RY Target Positioins...?  It now should think it is higher than it was and will attempt to pull it down too low.  Problem is most of the trends are on stops, before calibration, with a bad V2, etc.

Okay, assuming the current unlocked IPS values are what they would be if the V2 channel had not gone bad and my -7500 counts is correct for the unlocked bad state on V2.  I calculated simple Z RX  & RY values from the vertical IPS for the two states of the V2 sensor.  I then applied the same percentage change to the Cart Bias Target positons for those dofs--close enough I think.

The loops are closed now, with no boost still, that problem remains.

The first plot  attached here is the IPS & L4C caibrated spectra with the V2 IPS fixed and the HEPI Loops open.  Compare this to the ones I put in last night, alhough most of those I'm pretty sure were with the HEPI Loops closed.  V2 is certainly better and now V3 looks a bit worrisome but not as bad.  However, if you look at the first plot from last night, where I show HAM4 from April, many of the IPS look similar to this HAM6 V3 channel.  I'm pretty sure this HAM4 data from April are with the HEPI released from stops but with the control loops open.

Finally, attached is the HEPI Sensors with the loops closed.  I'm not sure about the details but overall it looks like this fixed the IPS.  I would suggest we look closer here to see if simple connector shell shorting to the Pier Pod case could be a systemic problem for all these sensors.  If anyone wants to put their finger on this issue and decide on bug report, integration issue, or what, please do.  I'll take assignments to further trouble shoot.  To begin, I'll suggest using our HAM1 (still on stops) for a test unit.

Meanwhile--I still don't understand the Isolation controller magnitudes.  I think this is why the boosts won't work.  I'd like to collect new TFs with the ISI Damped and our final payload in place, although maybe HEPI isn't that sensitive to that change.  Still new TFs and then go through all the commissioning steps to see if that changes the controllers and gets the boosts on.

Also remember, many of the IPS have limited range with the Bellows Shields position and I haven't run full static test diagnostics.

Yesterday, the PRMI alignment was kind of bad, so I walked the PR2 and PRM alignments to move the SPOP18 level back up to ~70 cts. 
After this I set the offsets in the POP VAC QPD filter banks (after normalization by the sum) so that 
0,0 would be the good reference for initial alignment:

controls@opsws4:~ 0$ cdsutils read H1:ASC-POP_A_PIT_OFFSET H1:ASC-POP_A_YAW_OFFSET H1:ASC-POP_B_PIT_OFFSET H1:ASC-POP_B_YAW_OFFSET
-0.03
 0.23
-0.32
-0.27

Rana, Alexa

We repeated a similar procedure as to alog 14022 but this time for L2P. At low frequency, i.e. 0.01Hz we found the optimal gain to be 0.0106.  As Stefan mentioned in his alog, the L2P coupling seems to fall off faster than 1/f^4 at high frequnecies (ie about 3Hz). Therefore at high frequencies we want our filter to be essentially zero. The attached screen shot shows the original filter (FM1 red trace) and two new filters (FM2 blue trace, FM3 green trace). FM2 has a gain at low frequency to match our measurement. The phase is flipped so that the gain in the filter module can remain -1. Then the filter falls off as 1/f^2. FM3 is intended to provide the user an option to include a notch at the resonance at 0.7Hz as seen in Stefan's L2P TF. The other two resonances at 1.1Hz and 0.5Hz seem to cancel with the P2P TF, so we did not include these.

As a reference, the FM2 filter: zpk([],[0.766044+i*0.642788;0.766044-i*0.642788],-0.0106,"n") and FM3 filter: notch(0.749,10,30)

Dan, Koji (from a distance), Rana

We used an OMC mode scan to measure the modulation depth of the 9 and 45MHz sidebands, to close the loop on the recent changes to the amplification path before the EOM.  Koji had done this previously, and measured Gamma1 (9MHz) = 0.198, Gamma2 (45MHz) = 0.305.

Today, we measured Gamma1 = 0.208, Gamma2 = 0.240 +/- 0.01.  The error in Gamma2 is due to an asymmetry between the upper and lower sidebands; using the ratio of the 45MHz USB to the carrier returns Gamma2 = 0.251, while the LSB returns 0.233.  This 10% discrepancy between the 45MHz LSB and USB is consistent across several sweeps of the cavity.  The analysis code used today was thrown together a little quickly and doesn't do a sophisticated job of integrating the curve around the peaks (in fact, doesn't do any integration, just compares the peak heights to the carrier), but when applied to the same data that Koji used earlier this month it finds values similar to his to within a few percent. 

The attached plot has an overlap of five cavity sweeps, with the peaks of the 9 and 45MHz sidebands used in the calculation marked with a cross.  The data are here.  The mode scan was performed off a single bounce from ITMX.  This weekend we'll do a more careful scan for both ITMX and ITMY to calculate (more?) accurate numbers of the mode-matching for each path.