I spent the morning playing the picomotor game, to improve as much as possible the beam centering on the ISS photodiodes. The procedure is the same explained in 14211: I moved picomotor #8 and then used a python script to recenter the beam on the QPD using picomotor #1. My figure of merit was the sum of the power read by all photodiodes. I improved the total power by something like 0.5%, which isn't impressive, but at least now I know that I'm very close to a maximum. For future reference, the total sum of all PD signals, in counts, as measured by the IOP-PSL0_MADC1_EPICS_CH24-31, is about 40050.

After this, I injected a 1 Hz line on IM3 pitch and then yaw, and looked at the variation of the PD powers. I moved a bit the beam with both picomotors, to reduce the oscillation that was clearly visible only in PD2 and PD4. Now I'm close to be dominated by the two omega oscillation in both diodes. The optimal position does not correspond to a exactly centered QPD: PIT = -0.06, YAW = 0.35. Note that PIT and YAW for the QPD are reversed with respect to PIT and YAW for IM3!

Then, I took some (medium) high resolution spectra of all PDs, to estimate the coupling of beam motion to RIN. I used a IM3 pitch excitation at 1 Hz, with an amplitude of 300 cts. This gives me a signal on the QPD of 0.67 1/rHz, corresponding to 105 um/rHz. I used the same frequency for yaw, but with an amplitude of 200 cts, corresponding to 0.80 1/rHz on the QPD or 125 um/rHz. Spectra of all signals are shown in the attached figures.

Here are the results:

In general, those numbers are not too much different from the best we could get in the past. The only exception is PD4, which looks quite bad.

From all of us at LHO, a hearty congratulations to Kiwamu and Rie Izumi, celebrating the 0th birthday of Hana Izumi (和泉はな)! 

* * *
Birth date: Nov.1st
Height: 19.5 inches
Weight: 6lbs 5oz
* * *

The TwinCAT/EPICS interface was updated to version 1.1 which includes an alias feature for symbols and structure items. This now makes it possible to export PCAL channels under the system CAL. See also here.

New PLC information has been added to describe the runtime and each configured online task. The update rate for the latency readbacks has been increased to 1Hz.

Previously, it was possible to circumvent the configuration control by making online changes and bypassing the installation scripts. The installation scripts will patch the svn revision number into an EPICS channel, if they were run from a fully updated source tree. A subsequent online change is now recorded and reported as a code error.

IP1 controller has indicated that pump B (1/2 of pump) has been inoperative for awhile now -> Swapping cables didn't change the indication at the controller that pump B still isn't working but has resulted in the "cold" 1/2 of the ion pump to be pumping now (i.e. problem is controller not HV cable or pump) -> CS pressure shows a "bump" reflecting this exercise -> IP1 controller is old style "MultiVac" type and cabling will need to be modified for, as yet to be acquired, new type replacement.  

Aaron S., Richard M., Patrick T.

I rescanned PLC1, PLC2 and PLC3 in the h1ecatx1 system manager. I then moved the link under 'End Link L0:End Link L3_4:ALS Laser Table Relay:Channel 2:Output' from 'PLC2:Standard:Outputs:AlsEndLaserHeadOut:NoiseEaterRelayOff' to 'PLC1:Standard:Outputs:IlluminatorOut:IlluminatorRelayOn'. I committed the change to svn. Richard and I switched it on and off in EPICS and Aaron verified that it turned on and off at end X.

model restarts logged for Mon 10/Nov/2014
2014_11_10 06:41 h1fw0

unexpected restart.

Okay, recall: WHAMs 2 & 3 HEPI had incorrect signs for the three rotational dofs on the Input matrices.  The output matrix, converting the cartesian drives from the control loops to the local actuator basis also had incorrect signs on the rot dofs but there were also screwy magnitudes with errors from 25% to 8x so all over the map.  While all the dofs run closed loop, having the output matrices correct will ease the burden on the loops and better enable open loop running.  It may also reduce unneeded strain cycling.  Remember, I have lots of opinions!

Anyway, unlike last week when the matlab script was using incorrect matrices for my controller development(obviously unbeknownst to me) and the switch I attempted was a spectacular failure, this time, turning the loops back on with correct matrices and new controllers was anticlimatic.  No problem turning things on, no trips, and the ISI remained isolated.  The most notable thing is that I learned

The HAM2 ISI OpLev Pitch and Yaw are Reversed.

I'll suspect HAM3 is similar.

See the attached for 50 minutes of trends with chans 1-8 being the HEPI Local Sensors, chans 9-14 being the HEPI Cartesian Locations, and the last two are the OpLev Pitch & Yaw.  Notice the right most vertical line I've drawn through the RZ steps as I'm trying to drive the OpLev 'Yaw' back to whense it came.  Of course you'll see that the Yaw doesn't move and the Oplev Pitch does.  Of course you say, "Hugh, why do you think your RZ channel is better than the OpLev channel?"  Well, notice too the other vertical lines positioned at the same time through the HEPI Local Sensors.  You should notice the at the RZ move is seen by the local horizontal channels and the vertical channels see nothing.  Okay, I know that is circular...just take my word huh.  We can do some physical sensor disconnects or something if you insist.

I did tweek the ultimate RZ Reference location to recover the OpLev actual Yaw of ~-8.2 units but the change was <200nrads.  I tweeked in the Pitch too but after taking the system down and back up with Guardian, the Pitch and Yaw numbers on the OpLev are changed, slightly.  We didn't have the mode Cleaner while I made this change but it relocked as soon as the LASER was back on.  The Beams on the AS AIR camera view are up in the upper right though, I don't know but that may be different.

The commissioners shoudl feel free to steer HEPI as they wish.

Finally, I may suggest a guardian change that isolates and steers the DOFs we want to restore and then get the steered free hanging position and isolate the remaining dofs.  Certainly you can see how that wold reduce the strains and possibly provide more repeatable position recovery.

A new safe .snap and the updated foton file has been commited for the HEPI.

WP 4939

The epics software for Mac OS X has been recompiled to eliminate the need for mounting /ligo via /Network/Servers/cdsfs0/ligo.  There are a couple of advantages to doing this, but it's for the benefit of your cheerful CDS administrators for the most part.

The epics version is the same one that has been running, just recompiled.  Hopefully OS X users won't notice any changes, but running epics programs like medm and StripTool may stop running at some point and need to be restarted.

Ubuntu workstations are not affected by this change.

The state of the PSL upon my arrival this morning was that it showed NO output power.

In preparation for tomorrow's maintenance on HAM2 and HAM3, I have set the following gains and whitening stages on HAM2 and HAM3 OPLEVs.

I added the dewhitening filters in the input flter banks of the oplevs and switched on two stages to mirror the analog state.   The analog switch states are shown in the attached pics. The label on the cable tells us the name of the oplev that is addressed by the dip-switch board. 

The oplevs are, as yet, not calibrated.  The HAM3 shows an uncompensated whitening though I have switched on the dewhitening filters stages.   Will investigate further.

There's a huge 364Hz line in ALS TRY.

I'm not sure if this was already there for a while. Though we probably changed the loop gain of the ALSY PDH loop when we realigned the green path on ISCTEX today.

J. Kissel

Continuing to compare L1 vs. H1 damping loop designs (see ), I've made a comparison of the QUAD's design, and also with the original low-noise design from which they're derived (see LHO aLOG 6760). Attached are the H1 and L1 designs compared against each other, 
dampingfilters_comparison_2014-11-07_LHOvs2014-11-10_LLO.pdf, as well as both against the original low-noise design dampingfilters_comparison_2014-11-07_LHOvs2013-06-14vs2014-11-10_LLO.pdf. 
As Sheila's quick comparison pointed out (see LHO aLOG 14923), the differences aren't that large (and detailed below).

In summary, both LHO and LLO have modified the low-noise design, but only slightly -- both apparently in order to get a reduction in test-mass impulse response. LLO took the "more sophisticated" in longitudinal by adding a boost instead of just increasing the overall gain, hence their modification preserves some phase margin. 

Because we're giving the LLO ALS DIFF control loops a try, however, we have copied over and installed the LLO design -- assuming that any little bit of difference will matter for these complicated global control transfer functions. Stay tuned...

- T, V, R loops are identical to the original design
The differences are the following modicifations:
- In L
     - LLO "resg1" boost ( resgain(f=1.07 [Hz], Q=4, height=13 [dB]) * gain(6, "dB") )
     - LHO overall gain increased by 2 (from -1 to -2).
- In P
     - LLO "notch60" 60 [Hz] notch ( notch(f=60 [Hz], Q=50, depth=40 [dB]) )
     - LHO overall gain increased by 3 (from -1 to -3).
- In Y
     - LLO "+12db" gain of 3.9811 ( gain(12, "dB") )

Comments:
In L, 
 - The extra "resg1" at LLO, significantly reduces the Q of the *second* (~1 [Hz]) L mode, and therefore significantly modifies the L to L and L to P global control transfer functions -- not only the resonant feature at 1 [Hz], but also the zero at 0.75 [Hz]. Other features are moved around a little, but no such significant change in shape. 
 - As such, the displacement from residual ground motion at 1 [Hz] has been reduced by a factor of 3, though (at least from the modeled input seismic motion) it doesn't contribute much to the over all RMS.  
 - The impulse responses of the two designs are comparable.

In V, and R,
 - As expected from the HSTS design studies, the impulse response of these DOFs reveals that without other local damping (say from optical levers), the highest V and R modes (at 9.7 and 13.8 [Hz]) get excited when the PUM and TST are kicked, and continue undamped at their original extremely large Q. 
 - If needed, both the fundamental V (at 0.55 [Hz]) and R (at 0.86 [Hz]) could use an increase in their resonant gains to decrease the 1/e time for those modes, which seem to dominate the amplitude of the time series for the initial 10-20 seconds. V would be much easier than R, as the LUGF phase margin for R is already pretty small.

In P, 
 - As with the HSTS, the global control transfer functions are barely affected by the differences in design, though -- to be fair -- the differences in design are much less dramatic than in the HSTS. 
 - Test mass impulse times are comparable.
 - The first "pitch" mode at 0.51 [Hz] is more damped (by about a factor of ~2) in the LHO model because of the increase in overall gain. However, since the second mode at ~1 [Hz], is more L motion at the test mass than P, increasing the gain at this frequency by a factor of 5 with the "resg1" in the L design seems to have reduced this "P" mode by the same factor at the test mass. Interesting!
 - The notch at 60 [Hz] has little affect on the loop design -- I suspect this was installed to kill a ground-loop feature in a particularly bad OSEM.

In Y,
 - This is pretty straight forward -- the yaw loop is not particularly limited in phase margin, only in noise re-injection. If we're willing to sacrifice a factor of 4 in noise, cranking up the gain reduces the impulse response by 4, and the Qs of the global transfer functions.

I could easily enage the ISS second loop, following the procedure described in 14291. It worked without problems.

However, the loop performances were very poor, as shown in the first plot. The dashed lines corresponds to the second loop open, the solid lines to the second loop closed. The inloop signal is squeezed down to a reasonable level. However, we're getting only a factor 10 of out-of-loop noise reduction. This is much worse than in the past.

I could improve a bit the situation re-centering the beam on the ISS QPD: it was quite far away. The second plot shows that the loop performance is improved, but still worse than what we got in the past. The thrid plot compares in-loop and out-of-loop signals when PD1-4  or PD5-8 are in loop. There is no significant difference, so it's not only one of the two PD sets to be misaligned.

Tomorrow I'll need to play again the picomotr game to recenter the photodiodes. The last centering was performed more than one month ago, on October 3rd, and then there has been no activity around the ISS, as far as I know. Therefore, it's maybe not surprising at all that the alignment is no more optimal. The IMC alignment might have changed.

Nic, Evan

We went down to EY to see what was up with the green WFS on ISCTEY (D1400241). To start with, we decided to resteer the beams so that they are not clipping on any optics.

• We steered M14 so that the beam passed through the clear aperture of BS5 (before it was exiting too close to the BS mount).
• We resteered onto PD8 by touching L9 and L15. We got a factor of 10 more dc power on the PD this way.
• We moved M16 (a piezo mirror) slightly so that the beam is centered on the mirror, and so that it travels to M18 (also a piezo mirorr) parallel to the hole pattern on the table.
• We moved BS6 and L12 so that the beam passes cleanly through these optics.
• Using M17, we resteered onto WFS A.
• We moved L13 so that the beam passes through cleanly.
• Using M19, we resteered onto WFS B.
• We moved the iris between M14 and BS5 so that the splotchy beam from the Faraday isolator can be stopped down to something vaguely circular.

We also tightened down PD4, which had some issues with loose mounting.

Upon taking a look at all large suspensions and small suspensions aux channels only ETMY stage L1 was found to have a noise aux channel which is showing some possible issue. ie ~ -4300 cts. This is showing on "noise" (4), volt (UL) and fast_I (LR). I have begun setting up DTT templates for all aux sus channels to further examine questionable readings.