The first pumpdown of BSC9 with the iLIGO stack.

J. Kissel, P. Fritschel

Of interest to several on-going investigations, Peter and I took a look at the noise monitor channels for H2 SUS ETMY for the UIM (L1) and PUM (L2) stages. These signals pick off the output of each differential coil driver channel, and convert to a single ended, high-passed monitor signal, with a calibration of

Coil Output Noise [V_out/rtHz] = Noise Monitor Signal [ct/rtHz] * ADC Gain [V/ct] * Monitor Board Gain [diff. V_out/ sing. V_mon]  

where, since the high pass filter is flat by 10 Hz, we've assumed the Monitor Board is only a scale factor. Those gains are 

ADC Gain = 40 / 2^16 [V/ct]
Monitor Board Gain = 392 [Single-ended Volts Out / Differential Volts In]


According to the design studies [UIM = T0900233; PUM = T0900277], the output noise of the coil driver should be around,
 
     (Equivalent Current Noise) * (Out Resistors + Coil Impedance) = (Output Voltage Noise)
     (across the coil [A/rtHz])   (            [V/A]             )   ( [V/rtHz] (@ 10 Hz) )

UIM:         2e-12              *              7.84e3              =         1.5e-8 

PUM:       2.3e-12              *              4.42e3              =         1.0e-8


in the lowest noise modes. Note that this is what Ron Cutler calls the "component noise," which we traditionally call the "coil driver noise," or "output referred noise" the self-noise of the coil-driver due to the resistors, op-amps, etc. on the board. What he calls the "input noise specification" is the DAC noise, which is claimed to be 100 [nV/rtHz].

We see from the results attached, the results are more like 100 nV/rtHz. However, this was measured in the "acquire" modes of each driver, so we expect the noise to be basically the same as the noise input to the driver, i.e. the DAC noise, which we indeed expect to be about 100 nV/rtHz.

This appears to be the first pumpdown of BSC10 in 2000.

[Jeff B, Travis S, Andres R, Gerardo2 M]

Today we moved the HLTS PR3 from the test stand in the Staging Building to the LVEA. This is the first of the Hanford Triple suspensions to be moved to the LVEA. We need to make some minor adjustments to our lifting gear for future HxTS moves, but in general, things went smoothly and with no serious problems encountered.

Gross weight of PR3, without vibration absorbers, is 210lbs. 

PSL had a need to access a particular feedthru for their In-Vacuum Cable runs.  Although the LHAM2 layout managed to reflect this it did not get propagated to LHO documents.  So we had to swap the feedthrus on D2 & D5.  The layout is D1002873.  Version v6 shows how we initially installed them.  In v7 there is a text file to the effect of the change but the layout itself is not yet updated.
There are two open ports now on D5 as these take 5-way Coax.  These Feedthrus are in C&B now and I hope we can get these on before the next pump down.

• Cheryl:  Camera work at end stations
• In-Chamber cleaning continues
• Filiberto:  ISC cable/pin investigation
• Have seen ALS crew working around their optics table
• SEI crew have been working at HAM2 (swapping feedthrus, working with Table Extender, running in-vac cables, etc.)

Tomorrow Barker & Columbia will take H2 down for timing work

6 days of turbo pumping, pressure @ 2x10-6 torr, scan attached.

Work permits pulled for In-Chamber Cleaning.

First vacuum and wipe-down are complete. Second vacuum is likely to be completed by the end of the day. We expect to complete work in the dome by lunch tomorrow. We anticipate FTIR results for the permanent flooring either today or tomorrow. If all goes well, we may be out of BSC1 (including dome and door replacement) by tomorrow afternoon.

For the last several weeks we have been testing a rss feed of the alog.  It is now being moved to be a publicly exposed and advertised feature.

The feed is located at rss-feed.php.  If you are using a RSS aware browser you should be able to find the feed in whatever method your browser exports feeds.  For example in Firefox the 'Subscribe to this page...' entry of the bookmark menu becomes available.

This update is scheduled to be rolled out to the LLO logbook tonight.

END Y after 6 days of pumping. No change in trend - suggests this is not an air leak.

[Stuart A, Mark B, Jeff B, Vern S]

Whilst last visiting LHO I was able to quickly make some open-light and one dimensional responsivity measurements using three dirty AOSEMs and a test-jig kindly loaned from Mark. The test-jig has previously been used for characterising BOSEMs, and so had to be reconfigured to accommodate the smaller AOSEM coilformer. More importantly, rather than using the rectangular flag employed for the BOSEM, a ~1" long x ~2 mm diameter cylindrical flag was provided by Jeff B.

A UK production Satellite Box (D0901284) was connected up to the AOSEM under test using a dirty in-vacuum quadrapuss harness (D1000234). The Satellite Box was provided with it's required supply lines via a Satellite Box Testing Board (courtesy of Filiberto). For electronics set-up please see image 504 below. A DVM was used to read-out the amplified voltage signal via the diagnostics port (J4) on the Satellite Box (Pins 9 and 28). Note that, the production Satellite Boxes have a input gain of 242k V/A or 0.242 µA/V (double-ended).

Image 506 (below) shows the opto-mechanical set-up for the reconfigured test-jig, including the translation stages and flag assembly. For these tests, only the responsivity is sought, and therefore a one-dimensional characterisation along the sensitive axis is adequate.

When connected up to the Satellite Box, each of the AOSEMs had the following open-light differential voltage measurements:-

- Unit #1, open-light = 14.75 V (i.e. an open-light photo-current of ~61 µA). Corresponds to ~24k counts
- Unit #2, open-light = 10.14 V (i.e. an open-light photo-current of ~42 µA). Corresponds to ~17k counts
- Unit #3, open-light = 12.19 V (i.e. an open-light photo-current of ~50 µA). Corresponds to ~20k counts

Over a ~0.7 mm operating range, these AOSEMs were found to have the following responsivity (see plot below):-

- Unit #1, responsivity = 18784 V/m (i.e. 78 mA/m).
- Unit #2, responsivity = 13028 V/m (i.e. 54 mA/m).
- Unit #3, responsivity = 15721 V/m (i.e. 65 mA/m).

These responsivity results can be compared with the default value we have previously assumed of ~80 mA/m (see LLO aLog entry 2715).

To summarise, these measurements can be used to validate our assumption of using the AOSEM calibration factor of, 1/(80e-3 [A/m] * 240e3 [V/A] * (2^16)/40 [cts/V]) = 3.2e-8 [ct/m], is consistent for units with open-light counts above Jeff K's goal of 25k.

I have reorganized and added medm snapshot screens to the CDS web page (LIGO.ORG authenticated):

https://lhocds.ligo-wa.caltech.edu/screens/

Vacuum and FMCS detailed medm screens have been moved to their own web pages, the overview screens are shown on the main page

A H1 section has been added, it contains the H1 CDS OVERVIEW MEDM

The H2 IOP SUS/SEI watchdogs screen has been added to the H2 section

Yesterday Keita and I found that the output of the ALS PLL Phase-Frequency Discriminator unit was noisy and oscillating between its voltage rails.
We traced the problem back to a very noisy output signal from the frequency divider which provides the LO to the P-F Discriminator board.
Going up the chain, we found that the frequency divider unit was getting 0dBm instead of the nominal 13 dBm from the VCO unit. 

Apparently the VCO unit is not working properly. We removed it from the rack and took it to the corner station for inspection.
We are going to check it inside to find the cause of the mismatched power levels.

The problem of HAM front end startup corrupting the H1PSL data was tracked down to a switch configuration and was corrected.

The following front ends and models were created by porting the LLO running models to H1. 

All the models started with no problems except for h1susim (which has an undefined symbol).

All systems were added to H1 DAQ using the INI files generated from the models. The H1 frame size roughly tripled in size from 1MBps to 3MBps.

Laser current set to 1.5 amps.

IR output 1.125W (after the laser head), 50.0mW (after Faraday, we're using wave plate to intentionally dump some power), 10mW after PBS (another  attenuation, we can decrease this, or increase this up to 50mW)

With 10mW going to the PLL diode, we have about -3dBm beat note.

green output 22.9mW (right after the laser head), 17.5mW (after the first Faraday), 13.85 (after the second Faraday), 12mW (just before the bottom periscope mirror)

Retroreflection (measured after 10:90 splitter) 0.73mW, this means that the retroreflection is 7.3mW.

Apparent table efficiency is 7.3/12 = 61%.

Aluminum mirror reflectivity is probably not that good (95%-ish if they're good) (turns out that they're silver, not aluminum, coated, thanks Matt for pointing it out, and this means that the reflectivity of these is 98% or so rather than 95), and there are four such mirrors (TMS telescope mirrors), double path, meaning there are 8 reflections. This should amount to 0.98^8 = 85%-ish.

There is a splitter for QPD (5%? I don't remember), again double path, so if it's 5% splitter this removes 10%. 

0.85*0.9 = 77%-ish.

Helium spraying this afternoon has been inconclusive - intermittent response has been sufficient to keep us interested but we were not able to pinpoint any source. Maybe leakage through the annulus and orings.

We decided to try starting up the BSC10 RGA.

After finding and resurrecting the computer and controller we found that the controller would not power up. Retreived another unit from YMID, installed it, and found filament emission error on startup.

Documentation shows the last operation of this RGA was in 2008.

We will continue on Monday. I am starting to wonder if this can just be a very saturated system as we were vented for 3 months while the cartridge install was performed. For this period the iLIGO stack in BSC10 was exposed to the purge air.

Kyle,Gerardo,John