Summary:

When we tested the in-vac picomotors on HAM3 again though these picomotors and also in-vac QPDs were tested OK before (here's the alog of these tests done by me, Cheryl and Daniel), nothing moved. Without these things, HIFO test never works.

The problem was traced back to an error in in-vac cabling. ISC IR QPDs were connected to the picomotor feedthrough and vice versa though I have no idea why this happened (see the comments attached to this entry for details). 

The cabling was fixed and the picomotors now work again, but ISC QPDs are likely broken because of multiple attempts to drive picomotors back and forth, which put more than 100V on diodes. We used laser pointer to test the QPDs with the handheld QPD interface but were never able to convince ourselves that they're working. We forgot to test if any of the quadrants are short-circuited.

IO QPD for MC transmission should be OK as it is on a separate cable.

Anyway, we have spare QPDs and we'll replace them on Monday, entering HAM3 from the north opening. It's probably less than 2 hours for replacing, plus an hour for testing. We've done the same thing in EY and we know how to do this.

Spare S/N 20 and 24 from our stock of IR QPDs were bagged and left in a clean room by HAM2 so we can continue on Monday morning.

Richard cleaned the fiber this morning at the Y end patch panel, and after that we had 18-19uW at the table feed-through and I measured 14uW with the power meter in air on the table.  After realigning for the swapped beamsplitter, (and re-aligning the power monitor PD) the beatnote was -38dBm, around -20 dBm after the amplifier.  

A plot of the OLG will follow,  but the main message is that the ALS PLL is working.  It has been locked for almost hours now, based on looking at the striptool of the beat frequency and the control signals.  

The settings are: cg -15, fg 22, common compensation on, slow ugf set to -0.015Hz and slow pole set to 0.0001 Hz. 

The beatnote frequency has glitches that are not present in the channel for the VCO frequency, where the signal level is much higher.  It might be easier to write an autolocker if we could get rid of those glitches, perhaps by amplifying the signal.  

Today we fine tuned the rotation of the HWP that rotates the polarization of the beam after the IMC. We followed these steps:

- we used an HWP at the bottom of the PSL periscope to set the polarization approximately "wrong", so to have considerable power transmitted through the unlocked IMC

- we used the HWP after IM1 to make sure that a good amount of power would go in the first forward rejected beam

- we rotated IM2 in yaw so that the first forward rejected beam would clear the FI and be transmitted all the way to (almost) IM4

- we position a power meter there

- we removed the HWP on HAM2, and rotated the HWP in the PSL so to minimize the power in the forward rejected beam. Because of the absence of the HWP in HAM2, this beam contained the "good" polarization: this way we made sure that the polarization off the PSL was as bad as possible.

- we steered IM2 back in its original position, and we placed the power meter in the main beam

- we re-inserted the HWP in HAM2 and optimized it to minimize the power in the main beam, thus rotating the polarization coming out from the IMC by 90 deg, that is what we want.

Unfortunately, during this process we had the opportunity to compare the beam out of the IMC with the re-routed IMC_REFL beam that had been setup couple of weeks ago and used since then as a more powerful reference for alignment. What we discovered is that the beams are not well aligned (more than a beam diameter at the FI). Note that:

• the beam from the PSL, reflecting off of MC2 is still well centered in two irises that we have in HAM2, in front and behind MC3. Thus, is seems that the beam out of the IMC has not drifted.
• To center the beam into the FI, IM2 now needs to be steered in yaw by about 10000 cts, while it's aligned position is supposed to be -520 cts (and still work with the rerouted REFL beam). This suggests that the misalignment between the two has not happened this week, but probably much earlier in the process of IO alignment.

The good news is that the situation can probably be easily recovered, without moving other components, using IM1 and IM2 to make sure that the current IMC beam is aligned, at the FI and further downstream, to the reference we have been using up to now. If the offsets turn out to be big, we may need to relieve them.

This morning I started floating the BS ISI, after asking SUSsers to lock their optic up. No real problems, beyond a missing wrench that had to be retrieved from staging and a CDS laptop that had too aggressive power saving settings (it would sleep the monitor after 1 minute, enough time to change out gloves...sigh). The ISI is currently floating within spec, cps were regapped where necessary, lockers were adjusted, the actuators were visually inspected for spacing, and cables were surveyed for rubbing. This should mean BSC2 is in a good position for in-chamber testing, but the BS is still locked.

- Mark L, and group changed pre-filters for AHU 1 and 2, per WP 3783.
- LVEA transition to laser safe at 9:00 am.
- Corey G. work in the squeezer area, East Bay of LVEA.
- Rick S, Michael R, and others to visit MID-Y, inventory of 3rd IFO PSL items.
- Jim W work at BSC2, top area.
- Betsy W and Filiberto C, work at HAM2, mission aborted.
- Betsy W and Travis S, BS is locked now.
- LVEA transition to laser hazard for IO work.
- IO group work, PSL enclosure --> HAM02.
- LVEA transition to laser safe, 3:32 pm.

 

After two rounds of transfer functions two nights ago and yesterday night (aLog 5907 and 5920) the beamsplitter look(ed) fully supsended (it had to be locked again this morning)

The attached pdfs show

1. Transfer functions comparing :
   
   • BSFM model
   • Measurement on March 27th with one of the top EQ stop touching
   • Measurement on March 28th after Travis found the source of rubbing and fixed it
      
2. Power spectra comparing :
   
   • LLO measurement on October 2012 Phase 3a
   • LHO measurement on March 27th with one of the top EQ stop touching
   • LHO measurement on March 28th after Travis fixed it

Yesterday we continued to struggle to get light from the fiber to the end station. Richard is helping us trace down the problem.  Even with the fiber working well, we only get 10uW onto the ALS table, then there are two 50/50 beam splitters, so there were only about 2.5 uW on the PD, giving us a signal level around -40dBm, which is marginal and might be why I thought the ohase frequency discriminator was not working (it works as expected with larger signal levels).  I changed out the 50/50 beam splitter that sends a pick off to the PDs that monitor the power out of the fiber and the polarization to a 10% beamsplitter.

Chris and Max also rerouted the fiber from the patch panel to the table feedthrough. This fiber was on the floor, and probably stepped on, but it seems to work fine, the probelms we are having are upstream of that.  

Also, I spent some time yesterday afternoon labeling cables inside the ALS table, were there is a suprising number of cables with no labels at all.  Most of these cables are also not included in the cable plan, for the cables that go to feedthroughs I've been naming the cable after the cable on the other side of the feedthrough and adding an A to the end of the name. Otherwise I just make a name up.    

[Keita, Corey, Kiwamu]

The alignment of the POP paths in HAM3 are done. We removed the green fiber laser.
The next step is a picomotor test at HAM3 with the Beckoff system.

Forward propagating POP
 The POP path behind PR2 for the forward propagating beam (going from PRM to PR2) were successfully adjusted within a precision of ~ 1 mm or less at the QPDs. Comparing the alignment precision with the QPD diameter of 3 mm, we conclude that our alignment is good enough. This time the issue of the transparent BS [1] was mitigated by fully opening the aperture of the irises to make the HR beam as bright as possible. Luckily the HR beam became visible enough to work with. We tweaked the two steering mirrors to get the beam aligned on the QPD sled.   
 Actually we repeated this alignment twice. After the first round it turned out that the first steering mirror (a 3" mirror) which we established its alignment yesterday [2] gave a beam too low for the other POP path (i.e. backward POP path). The first steering mirror is relatively tall by design because it needs to be at the same height as the PRs and therefore the beam reflected by this mirror has to be angled downward such that the beam height gets lowered to the standard height of 4". Yesterday we adjusted the angle such that only the forward beam hits the center of its second mirror but apparently this wasn't a great idea. It resulted in such a low beam in the backward path due to the fact the backward beam propagates a longer distance than that of the forward beam by 6-ish inches. This too-low-beam was found after we removed the green laser setup at HAM2. Therefore we had to setup the green laser again and repeated the same alignment process. We adjusted the first mirror such that the beam is a bit too high for the forward path by 5-ish mm and a bit too low for the backward path by the same amount.


Backward propagating POP
 The backward propagating POP beam behind PR2 was aligned using the green fiber laser and we confirmed that the beam got through to HAM1. The same fiber laser was used to simulate the backward path. The laser was set up at HAM3 and injected at the front of PR2. We let the reflection go through the two irises. The position of the second steering mirror (2" reflector) was intentionally displaced toward east by ~ 7 mm in order to keep a large clearance for the downstream beam which passes by the west side of the mirror. Hence the beam spot on this mirror is also off by the same amount which shouldn't be a problem because the mirror is large enough and also the incident angle is small (about 10 deg ?). Although the green beam diverges a lot when it arrives at HAM2 we aligned the beam such that it passes by any of the towers in HAM2 with the same amount of the clearance. This resulted in a beam off-centered at the viewport in between HAM2 and HAM1 but this is OK. Some alignment of the optics at HAM1 will be performed later.


BS wedge on POP QPD sled
 This is a minor issue and we write this simply as a record here. We found that the BS on the POP QPD sled had its wedge at a wrong side. Ideally we want the fat side to be at the QPD side to let the ghost beam diverge away, but it seems we placed the BS in the opposite way --- skinny side at the QPD side. We checked the engrave mark on the barrel of the BS and found a "W" mark at the far side from the QPD, indicating that the fat side is at the far side and this is wrong. We are not going to fix this as the ghost beam will not hit the QPD anyway since the QPD is close to the BS.

[1] LHO alog 5774 "50-50 IR beam splitter is a good AR for green"
[2] LHO alog 5911 "Alignment of POP QPD path : ongoing"
 

- Joe, Giacomo, Cheryl

- Filiberto started the process to attach pins/connector to FI HWP pico motor.  Lack of information about the connector convinced us to push this out to at least tomorrow.

- the half wave plate was re-installed in the IMC trans beam path after IM1.  The beam through the FI was misaligned with IM2 to give an unclipped Forward Rejected Beam to minimize, which was minimized to around 40 uW of power.

- IOT2R was moved into place today, on the East side of HAM2, beams were aligned onto the single periscope and onto the table.  The table position needs to be marked before moving the table.

- beams transmitted through IM4 were measured - some measurements will be used to compare expected and actual transmittance of 2" fixed optics.  Actual power readings to be attached.

- AOE1 was aligned downstream of HWP per Rodica's instructions to move it along the beam path by 20mm.  With HA1 at 0, the front of the HWP is at 25mm , and the front plate of AOE1 is at 95mm along the beam path.

- PR2 scrapper baffle was installed.  Joe did the install, and centered the baffle w.r.t  the PR2 optic, since the beam at HAM3 iris was about a beam radius off in yaw, and off in pitch.  Earlier work of adding the HWP back into the beam path is the likely source of the change seen at PR2.  Using IM2, we deturmined that the correction was 100 slider counts or less, i.e. small.

Friday:
Plan is to flash the IMC, though there have been rumors of locking it in air...

Attached are plots of dust counts > .3 microns and > .5 microns in particles per cubic foot requested from 5 PM March 27 to 5 PM March 28. Also attached are plots of the modes to show when they were running/acquiring data.

Data was taken from h1nds1.
T0=13-03-28-00-00-00; Length=86400 (s)
1440.0 minutes of trend displayed

Occupy Mon AM506 (-2133.6x,-182.8y) at HI -82.9 Lz, BackSite LV-22 (-2133.6x,-22692y)
Nominal Turn: HAR 270-01'45" ZA 90-00'02".  Sited Baffle Target at BS at HAR 270-03'10" ZA 89-59'28" for 85" & 34" error.
Over 1931mm these angles give position errors 0.8mm -Y & 0.3mm +Z from nominal
BS position (-202.7x,-183.8y) yields distance from AM506 1930.9mm nominal.  EDM w/ -30mm prism offset shot 1.8617m to retro-reflector.  Retro-reflector measured to be 2.709"=68.8mm from optic face (FC).  1930.9-1.8617-68.8 = 0.4mm -X of nominal.  I am told this is within spec (percomm DCook.)
Of course to get it here we did a number of HEPI moves monitoring the Dial Indicators on the ends of the Support Tubes.  Based on the DIs and 'adding' to the Optical Table leveling results from 25 March, the 'level' of the Optical Table is still +-0.1mm so should be fine.  Would like to confirm with AutoLevel shots directly on the Optical Table, maybe tomorrow.

Starting a round of transfer functions overnight on the beamsplitter.

The numerous 80K pump alarms today (and tomorrow, this weekend?) are the result of my cracking open the LN2 "bypass" valves on the site dewar plumbing.  The motivation for doing this is to prepare for the upcoming extended power outage.  As such, there are now two flow paths for the LN2 to fill each 80K pump, one is via the nominal CDS PID-controlled valve and a second which "goes around" this valve and which has no external control.  A few days of tweaking should allow us to maintain the pump levels with only a minor contribution from the PID-controlled flow path.  This will guarantee that some LN2 is always flowing through the "transfer" line even when the PID-controlled valve is closed (as will be the case with the loss of instrument air during the outage).  Having a minimum flow will prevent the transfer line from warming up and will greatly facilitate manual adjustments to the pump levels during the outage.  

Starting a round of matlab transfer functions overnight for the beamsplitter.

Before the power outage of next week, new h1sus${mc1/mc2/mc3/prm/pr2/pr3}safe.snap files have been saved in /opt/rtcds/userapps/release/sus/h1/burtfiles.
It includes alignment offsets with the right values from aLog 5851 for PR3/PR2 and 5825 for MC1/MC2/MC3. It also includes the ODC recent update aLog 5809

The safe state has been defined as the following :

**alignment offsets off
**damping filters on
**master switch off

The snap files have been commited in the svn repository.