kyle.ryan@LIGO.ORG - posted 10:44, Wednesday 13 April 2016 (26565)
0930 hrs. local -> Moved pumping from HAM5 to HAM6
Path is clear to reconnect table to North door of HAM6
Path is clear to reconnect table to North door of HAM6
Fil, Richard, Craig, Evan
We measured the voltage noise on the EY ESD in the nominal low-noise configuration, close to the flange. The measured noise is too small to impact DARM.
Above 50 Hz, the noise of each quadrant electrode relative to the bias electrode is about 25 nV/Hz1/2. At the nominal bias (380 V), this implies a white force noise at the test mass of 1.4 fN/Hz1/2, which amounts to 6×10−23 m/Hz1/2 at 100 Hz.
Based on a design by Rai (T1600088), Richard built a passive box which picks off the voltages going to the ESD and ac couples them with 5 µF capacitors (see attached image). This enables us to pick off the bias voltage and a particular quadrant voltage, ac couple them, and then differentially amplify them with a dc-coupled SR560. The 5 µF works against the 100 MΩ impedance of the SR560 to give a high-pass corner of about 0.3 mHz. The SR560 gain was 100, with an input-referred voltage noise of 4–6 nV/Hz1/2 above 10 Hz.
We installed the passive box after the current-limiting resistor box, which sits in the cable tray close to the cable feedthrough on the BSC.
We took two kinds of measurements.
First, we had the ESD signal pass through the passive box and into the chamber to the reaction mass electrodes. The bias electrode was held at 380 V. We measured the ac-coupled signal differentially between the bias signal and a particular quadrant signal. This measures the voltage noise being applied to the electrodes. On each quadrant, we had a calibration line running at 35 Hz, with an amplitude of a few hundred DAC counts.
Second, we disconnected all five driver signals before they entered the passive box, but left the connections to the chamber alone. We again measured the ac-coupled differential signal between the bias and the quadrant (LR only). This measures the voltage noise between the electrodes.
The attached plot shows the results of the two measurements for LR. For the configuration with the driver connected, we also checked the other three quadrants and the spectra looked almost identical. We also briefly tried injecting band-limited white noise from 0.8 to 8 Hz, just to see if exercising the DAC had an effect on the noise floor above 50 Hz (it didn't).
We would like to take measurements on EX in its low-noise configuration, as well as with the driver disconnected.
IP-5 power supply was giving a polarity error since Friday. Suspect this was due to receptacle activities at rack last Friday. Reprogrammed PS for "spare" pump with LIGO specific parameters. One channel fired up. The other gave an "over temperature" error. Waited many minutes, raised voltage from default stepping 3000V to 5000V on fixed V setting. Second channel started to work again (external fan is blowing on it). We are ordering more Gamma PSs as these old Varians are failing at a fast rate.
The beam tube cleaning was completed last week. I am at LLO now and will post the final test results when I return next week.
As a test I changed the FSS autolocker settings. MIN [K] from -0.2000 to -0.0150 MAX [K] from 0.0000 to 0.0100 A fringe occurred when the NPRO crystal temperature was somewhere between -0.0130 and -0.0140. I reduced the autolocker temperature search ramp range so that hopefully the autolocker won't spend so much time hunting for the fringe. Engaging the autolocker did not knock the FSS out of lock. It might be that over time the NPRO crystal temperature will exceed -0.0150, in which case the autolocker settings may need to be changed.
Attached is a plot of the NPRO crystal temperature for when the FSS was locked. So it might be that the minimum temperature can be set to -0.035 in case the autolocker cannot find the fringe with the current (ie modified) settings. /* standard disclaimer */ Past performance is not an indicator of future results.
Continuing PSL work ... The pre-modecleaner transmission photodiode (D1002929 #69 S1107860) was swapped out for another monitoring photodiode (D1002164 #62 S1107854). The latter having its transimpedance gain reduced from 20k to 3.3k. This fixed the problem with the pre-modecleaner transmission signal that is observed on the MEDM screen. The calibration is correct to within one or two watts. In getting the power stabilisation up and running again it was noted that the amount of diffracted light from the acousto-optic modulator was at most 1%. Far less than what is required. Either the alignment for the AOM is off, which is quite likely, or the modulation signal to drive the AOM driver is insufficient. A plot of the measured AOM driver output versus modulation input is attached. With the 0.457V from the power stabilisation servo, 24.6 dBm (320mW) was measured. This may be insufficient for the AOM which has an operational RF power of 2.8W (34.5 dBm). Jason, Peter
C. Cahillane I made a "calibration movie", or a gif of the entire O1 calibration for C01 and C02. The darkest line is the current systematic error, and the dashed lines are the current uncertainty. Kiwamu made the helpful suggestion that I leave a trace of previous calibrations. Previous calibrations are the light lines left behind from the dark trace. You can imagine these movies as a trace over the spectrograms from LHO aLOG 26535. I like this visualization of the high-frequency dither we see in our calibration. Also this gives a good impression of how much our cavity pole affects us in the C02 calibration movie, since the cavity pole is the only time-dependent parameter not corrected for in C02. For the LLO Calibration Movies, please see LLO aLOG 25647
Krishna, Michael The winds have yet to pick up so we spent the past two days working on software upgrades. At ETMY, we integrated our previous PLC code into Daniel's template which will bring our code closer to standards. There was an error in the PlcInfoFB structure which we didn't know how to fix so we commented out the call in the main program. Also, the previous state initialization was re-initializing our variables on every loop so we disabled that function as well. Besides those two errors, the program runs as expected. At ETMX, we upgraded the C# code to closely match the version we use at ETMY. The most substantial change is in the pattern to angle algorithm. The angle used to be calculated from the average difference of the collection of peak pairs which involved fitting each peak to a Gaussian. The new algorithm involves calculating the cross correlation of the patterns with respect to pixel shifts of the main pattern which is then fitted to a Gaussian. These changes reduce the computation required for each frame while also decreasing outside dependencies. We hope this new version will remove the bug which caused the previous code to crash periodically.
gathering free-swinging data overnight per WP5824
damping will be re-engaged tomorrow morning
Richard, Patrick, Filiberto Beckhoff based vacuum control chassis and computer were installed at EY. Sorted out some issues with internal wiring for the 4-20ma inputs (LN2 gauges) inside the beckhoff chassis. Installed shorting plugs for the LN2 control valve watchdog. PT425, PT426, and PT427 guages were connected to the end Y vacuum chassis. We are still trying to sort out some issues with the readback signal for ion pump II411.
I have updated the control room alarm handler. I have also put the CP7 LLCV on PID control. It appears to be recovering well.
Fairly busy full day of Maintenace today. The HPO work continues. The hope is for beam to be back tomorrow.
Day's Activities
WP 5823
I have edited the h1lsc and common lsc models in order for us to be able to route the TR signals to the intensity stabilization system. As a result, the LSC model is now able to output a linear combination of TRX_NSUM and TRY_NSUM through a DAC. This signal can be then routed via an analog cable to the ISS, enabling us for a 3rd ISS loop.
To really engage this loop, one still needs to pull a few meter cable from the DAC output on the ISC field rack to the ISS module (either TRANSFER_1 or _2 analog input) in the same rack area. Additionally, to shave off undesired DAC noise above 10 Hz, we need an SR560 or equivalent in this analog path.
[Modification on the common lsc model]
I have added two new outputs. Because the TRX and TRY were already acquired in LSC and properly normalized, only things I added are two "From" tags and two outputs. The modified version is uploaded to SVN. For LLO, they can just terminate these two outputs at the top level until they need these signals.
[Modification on the h1lsc model]
I have added a new subblock called "PSL_ISS" in which I placed a matrix to combine the TRX and TRY signals and placed a filter. The output of this subblock is then routed to channel 11 of DAC0. Because DAC0 was occupied by an unused channel ALS_STATE_A, I have disconnected and terminated ALS_STATE_A. This should not impact on anything. The model is checked into SVN. After the installation of the new model, I checked the output signal with a voltmeter at the floor and it was doing what it should do.
[Medm screen]
I made a medm screen for this new ISS loop. It is accessible from the PSL tab on SITEMAP. This screen is also checked into SVN.
Created system environment variable XKEYSYMDB and set it to 'C:/Program Files/Xming/XKeysymDB' (with backslashes instead of forward slashes). http://www.aps.anl.gov/epics/tech-talk/2007/msg00075.php
Drove to end X and re-enabled it.
I noticed during my site inspection that the X-mid in-house vacuum cleaner was running for some unknown reason -> I unplugged it.
Chandra, Kyle Chandra noticed that IP8 had shut-down. The LPC controller was displaying an error "High Voltage not detected" -> This error isn't listed in the "list of error codes" but was the result of a loose HV connector in the back of the controller -> Deenergized controller, reseated connectors, pwrd on - OK now.
After a LN2 delivery the liquid level control valve setting was lowered to 18%, previous setting of 20%.
I have terminated the LO inputs to the AS 90 WFS chassis (as well as the cables that normally go to these ports), so that we can see if the dark offsets are more stable without the triplexer. Later today, I'll swap the terminators to be at the front of the triplexer box, to see if that changes things.
I have reverted this back to its nominal configuration. It looks like the signals got much cleaner on 9Apr, around 10UTC, so I want to see if they are still clean after going back to the nominal config. I can't find any cables that seemed bumped or out of place from the vacuum team's work, although they were working in the HAM6 area on both Thursday and Friday last week.
