Results of degassing PT170 & PT180 nude ion gauges in corner station are attached. Total pressure reading dropped slightly.

Note: the corner was/is currently isolated from two cryopumps with GV 5 & 7 closed.

1415 - 1425 hrs. local -> To and from Y-end checking RGA bake that was started Thursday morning (discovered that I don't have a WP for this!  Will initiate one today and ask for forgiveness later - its easier than getting permission!)

GV3 AIP died -> will address during the week.

Will make comment to this entry when leaving site.

Ansel and I put the end station CPS timing fan outs on separate +/-18V power this evening in hopes of eliminating the comb of odd harmonics of 1 Hz in DARM. A similar comb had been evident in the magnetometer that I set up at the EY ESD to look for blip glitches, and it went away when we powered the fan out with a separate supply. We think that this is because the magnetometer was detecting ripple in the field radiated from the +/-18V connector on the low V ESD drive and that we eliminated the ripple on ESD power by powering the CPS timing fan out on a separate supply. For this reason we varied from the work permit and didnt put them in a different rack. Ansel will fill in details of the studies he did that made us think that this is the source of the comb (especially if it really does go away in DARM), but we think that the comb isn’t GPS synched because it is driven by a clock on the PSoC board of the CPS timing fan out.  Isolation of BSCs 9 and 10 has been restored to nominal.

Ansel Neunzert, Robert Schofield

[Corey, TJ, Betsy, Koji]

RESOLVED ISSUES:
- The issue of the suspension TF was resolved by adjusting one of the OMC EQ stop holders [LHO ALOG 28900]
- The sign-flip issue of the DCPD signals has been explained by the accoustic noise of the OMC [LHO ALOG 28901]

PROGRESS:
- The lock nuts of the upper mass EQ stops were fastened (by fingers)
- The black glass panels of the OMC shroud were restored. We checked the input/reflection apertures to be well aligned against the beams.
- The OMCT steering mirror was restored to the optical mount.

- The alignment of the WFS path was reviewed. It was found that the path is still well aligned. Just the WFS QPDs were manually aligned by the mounts with picomotors.

- We attached the viewport simulator on the flange to check the alignment of the in-air paths. The AS AIR path was very well centered on the viewport without touching. The OMCR path is about 50% towards East (-Y) from the center of the viewport. We could not find the OMCT spot no matter how we flash the OMC. This could be just the beam was too dim, or was blocked by the shroud. We'll investigate this on Monday again.

TO DO:

- Continue to work on the OMCT path alignment. This requires ~10W IMC input. Try to find a dim flashes. Use a CCD camera on a tripod to find the spot around the viewport cover.
- We want to check the calibration between AS_C QPD SUM, the incident power on OM1, and the incident power on the OMC breadboard.
- Other ISC items function check (picos, beam diverters, fast shutter - see Rich's comment below, etc)
- Ground loop check
- Other SUS/SEI exit check

Purge air has been mysteriously throttled to a "trickle" going into HAM6 (no longer my battle)

Looking at the voltage of the AS port trigger PD as seen by the shutter controller, we have just under 2V at 50W input. The maximum threshold is 2V, so this won't work. The QPD chassis of AS_C has serial number S1301506 indicating an R23 of 26.7K in the sum output. This needs to be reduced to 12.4K, or we have to reduce the modulation depth of the 45MHz before we reach 50W.

The current configuration of the BSC-ISI's does not use any high gain ST2 RX/RY isolation loops because we dont have a blend filter design that rolls off fast enough at low frequency to avoid injecting GS-13 noise back into the X/Y dofs. However, above 1 hz the suspension point motion is dominated by ST2 RX/RY motion. One way we can improve this is by using relatively low gain AC coupled loops on ST2 RX/RY. With RichM's help I've tested this some on a couple ISI's and it seems to work, but there are trade-offs. First attached plot shows the improvement in ETMX longitudinal motion I've managed to get. Green and brown are the ground for both measurements, pink traces are RY loops on, light blues is off. In the 2-10 hz band I can get about a factor of about 2.5 reduction (I've seen up to ~5) , but at about 1 hz the motion is worse by about a factor of 2. Not spectacular, and I'm not sure that the improvement at a few hz is worth the loss at 1 hz. I've looked at the oplev (second plot, pink is on, light blues is off) and the oplev doesn't seem to see a substation difference at 1 hz.

One reason to do this would be to speed recovery after a lock loss. The ISI RX/RY loops get rung up by the impulse from the suspension, and it seems plausible that the ISI would settle down quicker is the RX/RY loops had more gain.

The designs for the ETMs RX/RY loops are included in the attached pdf. The lugfs are around 1 hz, uugfs are around 10-20 hz, phase margins are around 40-50 degrees. Higher gain loops didn't seem to provide much more isolation, but made the motion around 1hz worse.

J. Warner

Jim has put gathered some data on the wind fence. Check out SEI aLOG 1050.