BRSX continues to have large drifts of the DC position, due to chamber work, will have to wait until chamber is closed up to say much more about it. BRSY had drifted out of range a little while ago, the hook at the end is me re-centering it yesterday.
J. Kissel I've repeated the standard transfer functions on both SUS ETMX and TMSX to confirm that we're ready for doors this afternoon. There was a little bit of confusion on TMSX (see details in comments below), but I can now confirm that all suspensions are healthy, and we're ready for doors. Data templates: /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMX/SAGM0/Data/ 2018-06-01_1602_H1SUSETMX_M0_Mono_WhiteNoise_L_0p02to50Hz.xml 2018-06-01_1602_H1SUSETMX_M0_Mono_WhiteNoise_P_0p02to50Hz.xml 2018-06-01_1602_H1SUSETMX_M0_Mono_WhiteNoise_R_0p02to50Hz.xml 2018-06-01_1602_H1SUSETMX_M0_Mono_WhiteNoise_T_0p02to50Hz.xml 2018-06-01_1602_H1SUSETMX_M0_Mono_WhiteNoise_V_0p02to50Hz.xml 2018-06-01_1602_H1SUSETMX_M0_Mono_WhiteNoise_Y_0p02to50Hz.xml /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMX/SAGR0/Data/ 2018-06-01_1642_H1SUSETMX_R0_WhiteNoise_L_0p02to50Hz.xml 2018-06-01_1642_H1SUSETMX_R0_WhiteNoise_P_0p02to50Hz.xml 2018-06-01_1642_H1SUSETMX_R0_WhiteNoise_R_0p02to50Hz.xml 2018-06-01_1642_H1SUSETMX_R0_WhiteNoise_T_0p02to50Hz.xml 2018-06-01_1642_H1SUSETMX_R0_WhiteNoise_V_0p02to50Hz.xml 2018-06-01_1642_H1SUSETMX_R0_WhiteNoise_Y_0p02to50Hz.xml /ligo/svncommon/SusSVN/sus/trunk/TMTS/H1/TMSX/SAGM1/Data/ 2018-06-01_1552_H1SUSTMSX_M1_WhiteNoise_L_0p02to50Hz.xml 2018-06-01_1552_H1SUSTMSX_M1_WhiteNoise_P_0p02to50Hz.xml 2018-06-01_1552_H1SUSTMSX_M1_WhiteNoise_R_0p02to50Hz.xml 2018-06-01_1552_H1SUSTMSX_M1_WhiteNoise_T_0p02to50Hz.xml 2018-06-01_1552_H1SUSTMSX_M1_WhiteNoise_V_0p02to50Hz.xml 2018-06-01_1552_H1SUSTMSX_M1_WhiteNoise_Y_0p02to50Hz.xml
Regarding the TMTS confusion: Most of the measurement time was focused on the confusing transfer function that appeared in essentially only the T to T top mass (M1) transfer function. See attached screenshot showing (a) BLACK A reference from 2018-05-30 (see LHO aLOG 42231). Both stages of BSC-ISI are locked during this measurement. (HEPI is still locked.) (b) BLUEThis morning's 2018-06-01 confusing results, where the 1.4 Hz mode has split into several different modes at 1.23, 1.36, 1.43, 1.54, and 1.7 Hz. Both stages of the BSC-ISI are floating, but *not* damped during this measurement. (HEPI is still locked.) (c) REDThe same measurement, with the BSC-ISI damping loops ON. (HEPI is still locked.) In (a) and (c) the 1.37 Hz, T2, Transverse mode is exactly where expected. However with the ISI undamped in (b), the mode frequencies called above show up instead. The weird thing is that none of these frequencies corresponds to any SUS resonant mode in the chamber. Maybe they're the BSC-ISI modes, but I'm surprised that they're that high Q. The real point of confusion was that the BSC-ISI overview screens' border doesn't go red (normally indicating the inability to drive the DACs) upon an SEI IOP watchdog trip. The SUS IOP watchdogs had been cleared, but the only ISI-overview indication of the trip was a small red box above the DAC outputs, and that the DAC outputs were zero even with ISI damping loops ON. We should make the IOP watchdog actuation blockage a little more clear (and to be fair, it's only infrequently that I pull up the BSC-ISI screen at all when taking SUS transfer functions, but that's user conditioning and not anyone's fault). Along the way, assuming it was some sort of new, subtle rubbing that appeared between 2018-05-30 and today, I tried adding large offsets in all directions. First vertical, because I suspected a temperature drift by trending the vertical OSEMs in the chamber. When that revealed no change, I tried a Roll offset, and tried with & without the (rather large) P & Y alignment offsets. No dice. T'was then that I started thinking about the isolation level of the BSC-ISI and noticed the IOP watchdog, untripped it, and all became well. C'est la vie de mise en service!
Dan, Alexei, Thomas
This was about work done last night but I pushed backspace on my aLOG... you know the rest.
We took a beam profiler (nanoscan) to measure AS_AIR with the SRM CO2 and SR3 RoC heaters on/off to measure the beam size change at various powers. Also we measured the full beam profile of AS_AIR with the SRM CO2 Laser on/off and will fit the q-parameter to try and guess the relative gouy phase of the acutators.
We also scanned the OMC PZT and found that the mode matching increased from 90% to ~99%. Alexei will post the detailed analysis using his omc_scanalyzer scripts.
We're still in the process of analyzing the data but here's some of the preliminary results from when we are ramping the SRM heater power from 0 to ~800mW.
The profile of the AS_AIR beam with SRM heater on (800mW) and off
The SRM lens appears to be producing a beam that isn't very gaussian. We believe we are well aligned when we took this profile. The AS_C yaw and pitch doesn't change when the SRM heater is switched on and off.
Highlighted are the 0th, 1st and 2nd order peaks. Bottom plot shows the 1st/0th and 2nd/0th ratios. The 2nd order peak is being reduced as we ramp the SRM heater power from 0 to 800mW. However we get some increase in the 1st order peak. Likely the odd shaped beam we are generating as seen above.
Height of the TEM00 peak as we ramp the power. Overall the transmitted power through the OMC is improved as we increase the SRM lens
The LVEA has transitioned to LASER SAFE This is under work permit #7611. This completes work permit #7610.
[Mark, Tyler, Chandra]
This morning I burped dry N2 into blanked off volume above IP2's (new) gate valve to verify its o-ring doesn't leak prior to installing IP2 while corner is under vacuum. In the interest of time, we needed to reinstall this old pump in anticipation of opening to the beam tubes soon. Flange is leak tight (to background of 2.2e-9 Torr-L/s). It is being pumped with hung turbo overnight backed by leak checker. I tried turning HV on this evening, but voltage terminates at 800 V. We had vented this pump with room air thinking it would be shipped out for rebuild.
Today a newly rebuilt IP3 arrived, so I tested it by applying HV. The pumped shipped with good vacuum remaining (no need to pump out first). voltage = 7100 V; current = 11 micro-A (both channels combined); pressure = 5.4e-10 Torr. I then vented the pump body with dry N2 and burped/vented blanked off space of IP3's gate valve to verify it does not leak. Pump is ready for installation tomorrow morning.
When I was at the IP power supply rack, I noticed an error on IP5 PS: "high voltage not detected (error 11)." Will investigate tomorrow. May need to pump IP5 back down with aux cart.
Note that we plan to open up to beam tubes with IP1 and IP6 gate valves blanked off with rough vacuum on top side. We will install rebuilt pumps as they arrive from vendor, and hope to install chevron baffles at same time.
[Sheila, Keita, Jenne, with input and thoughts from several others]
We have looked at a few things today, trying to understand why the apparent signal level on AS_C changes with the state of the fast shutter. The size of the jump when the shutter is open vs. closed is similar to the expected signal size for true light on the PD. So, with the single-bounce beam, it looks like the amount of light on AS_C doubles when the shutter is opened. There shouldn't be any actual light change on AS_C as a result of the fast shutter state, since AS_C is before the shutter (and in fact used as the trigger for the shutter).
This jump in signal happens with the same amplitude whether or not the IMC is locked. So, opening the shutter makes AS_C look like there is an extra ~5mW on the QPD, even if there is no actual IR light in HAM6. This makes us suspicious of an electronics problem, rather than a mechanical interference with the fast shutter wires, or some optical thing like scattered light. Also, the signal is not affected if we move either SRM, OM1, OM2, or OM3 when there is light in HAM6, which is further evidence that it's not a real beam hitting AS_C.
The attached screenshot shows the jump in AS_C_NSUM as well as AS_C_SEG1 (there is a minus sign between them), when we close the shutter. These are the purple and green traces in the strip tool, and the shutter was activated around -7.5 minutes. At -5.2 minutes, we unplugged the input of the AS_C transimpedance amplifier, and plugged the output of the PD to the OMC QPD tranimpedance amp at -4 minutes. At -2.5 minutes I closed and re-opened the shutter. The scale of the NSUM signals are all the same as each other, and the scale of the SEG1 signals are all the same as each other. The whitening gain and filter settings of the OMC QPDs were set to be the same as the AS_C settings at the -7.5 minute time (no whitening filters, gain of 36 dB). So, if the problem were entirely on the PD, we would expect the same size jump when the PD was plugged in to the OMC QPD chassis. Since we don't see nearly the same size jump, it seems like at least some of the problem is in the transimpedance amplifier. Also, the inmons of OMC_A seemed much less noisy (when plugged in to the AS_C PD) than when the AS_C PD is actually plugged in to its regular chassis.
The fact that we do still see a jump, and in both OMC_QPD_A (which should actually have the AS_C signal) and OMC_QPD_B (which should be nothing) makes it seem like there is still potentially some funny business going on.
With no input to the whitening board, we didn't see the jump behavior. So, it's not by itself doing this jumping, but it isn't fully exonerated from being involved in some ground loop craziness. We did observe that the whitening board seems to be switching filters and gains as expected, although there was a weird time at 16:22:15 UTC where 2 of the 4 AS_C segments were totally weird. But, that was not reproduce-able. Sheila has a DTT template saved with that data, where you can see a big difference even below 5 Hz. But, interestingly, when I go back in time and check the INMONs (which should be the same, just slower data rate as the IN1 channels), I don't see any of that discrepancy. Confusing. And, also not reproduce-able thus far.
A good test will be to unplug the OMC DCPDs from the whitening board (which is on the same chassis as AS_C), since that shared connection ties the AS_C ground to chamber ground, and see if AS_C still jumps in a weird way.
There seems to be some extra noise on the analog AS_C sum channel that is used for the fast shutter trigger, when that signal is connected to the trigger controller. We had it T-ed to a 'scope, and then removed the connection to the trigger controller, and saw that the RMS got smaller.
tl;dr: We're still confused by AS_C. Maybe it's a problem with the transimpedance amplifier? We'll have to modify one of the spares, or see if one of the other Lab locations has a modified one, if we're going to switch it out, since it needs the sum channel to come out in analog for the fast shutter trigger.
About the weird time that Jenne mentioned:
Attached is a dtt template and screenshot, as well as dataviewer traces from the time. This was measured with the IMC unlocked, and no whitening filters on. We attempted to reproduce this several times by changing the whitening settings and setting them back, but weren't able to. When the IMC_LOCK guardian state is 80 it is offline, and when the whitening filter settings are 0 they are off.
About amount of light on AS_C compared to these spurious signals:
This diode is calibrated into W arriving in HAM6, (see 29078 and links in comments, the calibration was turned off in Jenne's screenshot above), between the beam arriving in HAM6 and the QPD there is OM1 with 800ppm transmission and a 48% beam splitter. So 5mW measured on the SUM channel in single bounce means about 2uW on the QPD.
Looking at the screenshot linked above, it looks like the change in the sum channel when the fast shutter closes is about 2.5mW into HAM6, or about 1 uW, the second attached screenshot shows that this is about the same as the change due to the shutter when the mode cleaner is unlocked.
The 1610 counts of dark current that we see with the shutter closed, 36dB of whitening gain and no whitening filters on is equivalent to 26mW into HAM6 or 10uW on the diode.
While fully locked in O2 we had about 0.4W into HAM6, meaning 150 uW on the QPD.
TL, DR: Our dark currents right now are about 7% of the total signal we will get in full lock, about 5 times larger than the signal size in single bounce (using this diode in single bounce is part of our initial alignment procedure), and about 10 times larger than the spurious signal from the fast shutter.
[Fil, Jenne]
After a long list of tests to isolate where the problem was, we have found and fixed the problem with AS_C! Hooray!
It turns out that we have an in-chamber short between pins 3 and 4 of the cabling that goes to the input of the transimpedance amplifier. Recall that this transimpedance amplifier chassis can serve 2 DC QPDs, although we are only using one. Pin 3 of the input from chamber is the "sense" input channel that is used to do some analog noise cancellation. Pin 4 is the anode from one of the segments of the 2nd QPD. So, we were taking any pickup noise from this unused QPD channel and feeding it into the input of the noise cancellation, thus actually making it a noise injector.
Fil has extracted pin 4 from the cable connector that goes into the transimpedance amplifier. After doing so, and plugging everything back in, the large rms noise was gone, the large dark current was gone, and there was no longer a jump when we actuate the shutter - it all looks good.
Fil noted that the whitening chassis that is currently installed is a spare, that does not have the new mods for the OMC DCPD half that prevent saturations when the violin modes are high. So, we should put the original whitening chassis back in place, now that we know it is not the problem. Sheila also noted that the dark offset of AS_C seems surprisingly large if she turns on the 3rd stage of whitening, so maybe there is a large DC offset on the 3rd whitening stage in this spare chassis - hopefully swapping back to the original will solve this also.
When we do in-chamber short checks, we typically only check pins against ground, not pins against other pins. We should add these noise sense pins on the DC QPDs to a list of pins that ought to be checked for shorts against any other pin (and similar, if there are similar noise cancellation circuits in other PD chassis).
Opened (and closed) FRS Ticket 10800 in order to capture this (and all previous aLOG's) history of the issue and relevant drawings. Opened (and marked as whenvent) IIET Ticket 10802 which indicates that the above solution is a temporary fix to the in-vacuum problem that pins are shorted in chamber. Note, we believe the short was created on Apr 26 2018 when searching for *other* "ground loops" (i.e. shorts to ground) (see LHO aLOG 41709).
This afternoon,
- I wiped the AERM and ETM barrel surfaces as best I could with swabs and methanol to remove particulate.
- Travis and I removed the FirstContact sheet from the optic - upon inspection, we still found some point features within the central ~6" of the optic HR surface. They did not blow away with 20psi N2 Top Gun, nor do they look like FC pieces. I will compare my pictures to the map we made during last year's lab inspection.
- Travis and I checked for charge via the "normal" procedure of looking with an electrometer at the back surface of the AERM with a special bracket. Details below to follow.
- Travis ocked all EQ stops nuts, taking into account sag once under vacuum.
- We set the top 4 QUAD BOSEMs to slightly more closed, also to take into account the sag of the suspensions once under vacuum.
- Removed all tooling, wiped floor and ACB surface.
- Travis swung the ACB back into it's nominal position.
- Jim unlocked the ISI and made a quick medm check.
- Laid new witness CC wafers and optics. - Pulled FC from 2x optics (1 vertical on QUAD, 1 horizontal under QUAD).
Tomorrow we will run TFs in the am and then launch the door crew.
Forgot to mention that just after the FirstContact pull, we installed the electrometer bracket to the back side of the AERM and measured in the Center, and 4 quadrants charge on the electrometer between +/-3V. Data to follow.
Finally getting around to putting in the actual numbers for these measurements taken on May 31, 2018 at 3:30pm. This Quad now has an AERM in the reaction chain.
Procedure: Pulled First Contact, blew all surface and the gap for 60 seconds. Took electrometer readings at 5 locations. UL = -3.1 V, UR = -3.3 V, Center = 3.4 V, LR = 0.1 V, LL = 3.8 V.
Tested electrometer fluctuations by putting the cap on the electrometer head and setting it on the floor of the chamber (no person touching it) and zeroed it. Reading fluctuated betwee 0 and 3 V.
Measured all 5 locations again 10 minutes after the first blow. UL = 2.5 V, UR = 2.0 V, Center = 3.0 V, LR = 2.0 V, LL = 2.0 V.
I am turning on the high voltage power supplies for the ITM ESDs, so I can run a by-hand charge measurement similar to that attempted in alog 41834, but this time with quiet optical levers.
Craig, Georgia We calibrated the EFM output channels H1:PEM-EX_EFM_BSC9_ETMX_X_OUT_DQ and H1:PEM-EX_EFM_BSC9_ETMX_Y_OUT_DQ from counts to volts/meter, starting on May 31, 2018 at around 21:00:00 UTC. Volts to electric field calibration was done according to alog 42250: X Cal Volts to Electric Field = 37.38 (V/m)/Vcal Y Cal Volts to Electric Field = 37.43 (V/m)/Vcal Counts to volts were calibrated using 40/2**16, since we have a 16 bit ADC with a +20 to -20 volt dynamic range. Both of these gains were added to the H1PEMEX_EX_EFM_BSC9_ETMX_X and H1PEMEX_EX_EFM_BSC9_ETMX_Y filter modules, which are located under /opt/rtcds/lho/h1/medm/h1pemex/.
The LVEA has transitioned to LASER HAZARD .
This transition is under work permit #7610.
This completes work permit #7608.
The alarm system was missing some cell phone alerts for Jeff Jones, these were added and the system was restarted. Due to intermittent drop-outs of the HAM1 cold-cathode, this channel has been silenced for the remainder of the afternoon.
Bypass will expire:
Thu May 31 15:56:31 PDT 2018
For channel(s):
H0:VAC-LY_X0_PT100B_PRESS_TORR
Sheila, Ronaldas
Residual gas noise consists of squeezed film damping noise and residual gas phase noise in arms. Live pressure noise channels are used for both noise sources. In addition, gas composition is taken into account, e.g. we use X contributions (H, H2, 17amu, H2O, N2) for squeezed film damping noise. Relative gas composition are taken from Chandra's RGA scan (thanks for that!). As for phase noise, we assume that gas composition in arms is dominated by H2.
Squeezed film damping noise should be reduced by factor 2.6 for O3 due to changed design for reaction mass, see the top plot of p. 6 in LIGO-T0900582. Thanks to Peter Frischel for the reference.
First plot ('res_gas.jpg') gives total gas noise contribution.
Osem noise now includes live channel data for all osem sensors (4 test masses * 6 sensors) rather than a model. Second plot ('model_vs_channels.jpg') shows a difference of using osem model and live channels, where red steady line represents model and all other lines are channel data.
Third plot ('osem_model_vs_channels.jpg') shows a total osem noise contribution.
Fourth and fifth plots ('RGA_*.pdf') are RGA scans made by Chandra for corner and end-Y stations.
As always, any suggestions for improving noise budget are welcome.
At Daniel's request I installed a neutral density filter (ND05A) on the photodiode located after the reference cavity in the ALS path. The power transmitted by the reference cavity was measured between the first turning mirror located after the step down periscope and a lens (see RC_Trans.jpg) to be 28.3 mW. At the time the FSS MEDM screen indicated a reference cavity transmission of 2.8 V. The 1 mW = 100 mV factor is consistent with a measurement taken a long time ago.
After Peter was done, I updated the calibration of H1:ALS-C_FIBR_EXTERNAL_DC_POWERMON.
When I was watching H1:PSL-FSS_TPD_DC_OUTPUT it was about 2.68V, so using Peter's measurement the power upstream of the BS for the PD should have been ~2.68/2.8*28.3=27.1mW.
I changed H1:ALS-C_FIBR_EXTERNAL_DC_SPLITTERR from 50% to 3% so the "power before pickoff" (H1:ALS-C_FIBR_EXTERNAL_DC_POWERMON) reads ~27mW.
(The BS should be 5% according to Peter's picture, ND05 means about a factor of 3 reduction, so it should be 5/3% ~ 1.7% instead of 3, something should be off by a factor of 2 or so but I wont investigate further because this is of no real consequence.)
ALS Y laser was turned on (EY is still laser safe, ISCTEY is locked). PLL was locked.
When I looked at the screen I thought the responsivity was off. This should be a Si diode.
I temporarily set responsivity to 0.36A/W assuming Thorlabs FDS1010 (but I don't know if it is), and "reflectivity of pick off beamsplitter" to 3%*0.64/.36=5.3% to keep the calibration correct. That's roughly a factor of 3 larger than expected from BS label and ND05.