See LHO aLog 28649. The voltage regulator has been replaced and this original unit returned to service.
WP 6063 FRS 5948
J. Kissel There are several front end models with out-standing SDF diffs prior to the timing system upgrade boot fest. I attach screenshots because there's no chance we can reconcile these before all front ends go down. Models with the biggest collection of DIFFs: h1pslfss h1psliss h1pslpmc h1asc h1lsc h1sysecatc1plc1 h1sysecatc1plc2 h1sysecatc1plc3 Hope this helps us in the recovery!
Travis S, Darkhan T,
Overview
On August 4th PcalX maintenance measurements were taken at EX. During maintenance we adjusted AOM bias. The offset value for the OFS drive was also adjusted, but incorrectly (see details). Today we re-ajusted OFS offset value to +5.14V.
Details
During Pcal maintenance measurements of the Pcal laser power in the Transmitter module were taken to assess Pcal drive range. Analysis of the measurement will give us an efficiency of an AOM driver (max diffracted power), assessment of pick-off power levels for the transmitter PD, OFS PD, maximum available output power modulation range. At the moment the measurements have not been fully analyzed.
The AOM bias voltage was adjusted for it to give ~50% out of max available AOM drive when the OFS loop is open. The OFS offset was adjusted accordingly in the front-end. Originally this was not done correctly, cause the OFS offset was adjusted when the loop was not closed.
Later when Evan tried to close the loop, the error signal, i.e. sum of the OFS PD signal and the OFS offset (when excitations and injections are turned off), saturated the AOM driver.
This is now fixed by adjusting the OFS offset to +5.14V.
We turned back on the excitations (currently one line with 39322 ct amplitude at 3501.3 Hz) and hardware injections.
[Betsy, TJ, Fil, RichM, Peter, Koji, Calum, RichA (remote)]
Progress
- The OMCT path (Y+) was aligned. Using 10W input instead of 2W helped us to find the leakage cavity flash through the PZT mirrors with 50ppm transmission. In the end we confirmed that the beam is well close to the center of the viewport (simulator) using a sensor card+an IR viewer and a CDD setup.
- The other OMCT beam (Y- side) was found to be blocked by one of the panels of the black glass shroud. We needed to shift the Y- panel more than the allowed range by the design. In order to allow this shift, we flipped a PEEK bushing and removed some of the washers and viton O-rings on the captive compliant fixing screws. Two screws to hold the glass holder were also removed to widen the sliding range. (See attachment 1, 2)
- The light powers in HAM6 were measured at various positions. This will be analyzed in a different entry.
- The funtionarity of the picomotors were confirmed (cf. channel assignment ALOG LHO 16422). Also we confirmed that the two beam diverters are working.
- We found that failure of the fast mechanical. We could not close the shutter because the coil wire has an open connection. Close inspection revealed that the coil wire has a kink (attachment 3). By jiggling this kink we actually could fluctuate the coil resistance from 20Ohm to infinity. The replacement shutter was immediately sent from CIT. It is coming here tomorrow morning.
To Do (Tue afternoon)
- Install the replacement fast shutter.
- Ground loop check
- Other SUS/SEI exit procedure
9:50AM MON AUG 8th, 2016 - Chamber entrance Particle counts with hand held CC counter:
| Particle size | Outside of chamber cover, in CR | In chamber above table |
| 0.3um | 0 | 0 |
| 0.5um | 0 | 0 |
| 1.0um | 0 | 0 |
Evan G., Jeff K.
We investigated the time delay of an injection made at H1:CAL-PCALY_SWEPT_SINE_EXC to H1:CAL-PCALY_TX_PD_VOLTS. The measured phase delay is 100.2 deg at 960 Hz (or equivalent delay of 290 usec).
Attempting to account for the phase from timing diagrams (see attached diagram, figure 1, DCC: G1501170), we find:
15.05 deg ("43.5 usec") 16-64k IOP upsampling
21 deg (61 usec) DAC "processing" delay
13.11 deg ("37.9 usec") AI (analog)
--- PCAL --- (negligible)
13.11 deg ("37.9 usec") AI (analog)
21 deg (61 usec) ADC "averaging" delay
15.05 deg ("43.5 usec") 64-16k IOP downsampling
Total = 98.3 deg ("284.8 usec")
We wanted to repeat the measurements made by Shivaraj at LLO (aLOG 27207) and verify the measurements yield consistent timing results.
We injected a 960 Hz signal in H1:CAL-PCALY_SWEPT_SINE_EXC and recorded the following time series (see figure attached): H1:CAL-PCALY_TX_PD_VOLTS_OUT H1:CAL-PCALY_RX_PD_VOLTS_OUT (measured to be equivalent to the TX_PD channel) H1:IOP-ISC_EY_ADC_DT_OUT H1:CAL-PCALY_FPGA_DTONE_IN1 H1:CAL-PCALY_DAC_NONFILT_DTONE_IN1 H1:CAL-PCALY_DAC_FILT_DTONE_IN1 H1:CAL-PCALY_SWEPT_SINE_EXC
The phase of the H1:IOP-ISC_EY_ADC_DT_OUT signal (measured at 65k) is determined from the amplitude of the signal at time T=0 with respect to the overall peak amplitude. We measured -2551 cts amplitude at T=0, where the sine wave has a peak amplitude of 4090 cts. The arcsine of the ratio gives the phase of -38.6 degrees in the range of -90 deg. to +90 deg. Since the true phase is outside of this range (more negative) we wrap instead to 180+38.6 = 218.6 degrees. This is the reference phase of the DuoTone signal.
We repeated the measurements to find the phases of all of the channels: H1:IOP-ISC_EY_ADC_DT_OUT = 218.6 deg <---- marked as time T=0 H1:CAL-PCALY_FPGA_DTONE_IN1 = 203.8 deg <---- also T=0 but filtered by the digital AA H1:CAL-PCALY_SWEPT_SINE_EXC = 219.4 deg H1:CAL-PCALY_DAC_NONFILT_DTONE_IN1 = 182.7 deg H1:CAL-PCALY_DAC_FILT_DTONE_IN1 = 100.2 deg H1:CAL-PCALY_TX_PD_VOLTS_OUT = 96.5 deg H1:CAL-PCALY_RX_PD_VOLTS_OUT = 96.4 deg
The difference in phase of H1:CAL-PCALY_SWEPT_SINE_EXC to H1:CAL-PCALY_TX_PD_VOLTS_OUT is 122.9 degrees at 960 Hz (= 355.6 usec)
So now there is a weird discrepancy in our measurements. The H1:CAL-PCALY_SWEPT_SINE_EXC to H1:CAL-PCALY_TX_PD_VOLTS measurement says 290 usec. The timing diagram predicts 285 usec. The phase of the waves measured in a time series is 355.6 usec. The difference is about 61 usec.
Still open questions:
Returned laser power to 2.4W, see alog 28931. Jenne set the guardian LASER_PWR node to 2.0 W. Note, the PSL rotation stage is operational and not locked out.
Krishna
The low-frequency (<0.1 Hz) noise in c-BRS looked much higher (~10X) than normal and we also noticed that the frequency and Q of the system were lower than that measured at UW. We suspected that the flexures suspending the beam-balance might have been damaged. Therefore, today I replaced them with spares that are fairly close to the original ones in size.
As a consequence of the flexure replacement, the mass distribution of the beam-balance has changed, hence the 'd' value is likely to be much larger than the previous value (~ 3 micrometers). The balance has currently been tuned to ~50 mHz frequency, which is close to the original resonance frequency. As is normal after a new flexure replacement, the mean angular position is drifting in one direction and will likely settle in 1-2 days.
If the low-frequency noise improves, I will likley measure a tilt transfer function tomorrow and try to improve the 'd' value, if needed.
ECR E1600230-v1
WP 6053
We analyzed the transfer function through the ETM ESD Driver before and after the capacitor and TVS were applied (see ECR). Using the Dynamic Signal Analyzer (SR785) set to sweep from 1kHz to 100kHz at 1000mV, the driver performs as expected when the waveform is applied to the PI input. I have attached a plot of the transfer function displaying modified HV, modified LV, and pre-mod HV values.
For future reference, this transfer function was taken from the differential PI input (pins 1/9 or 2/10 of the DB15 connector on the bottom of pg 1 in D1500016) on the front of the chassis to the BNC output inside the chassis itself (P5, P6, P9, or P10 in the middle of pg 1 in D1500016). The AC gain of this path is nominally 2.0, or +6 dB (G = 1 + R28/R30 on pg 6 of D1500016), but what mark shows here is that the gain changes by ~2 dB when the high voltage path is engaged. Also, the capacitor is 1 [nF] as quoted from the ECR. However, given the components surrounding this cap, I can't really figure out why the pole frequency is at 10 kHz. The input impedance to the relay (pg 8 of D1500016) is 200 [Ohm] from the summing node (pg 9 of D1500016). Thus, I would guess that the pole frequency would be at 1/(2 * pi * 200 [Ohm] * 1e-9 [F]) = 0.79 [MHz], not 10 [kHz]. One would need a resistance of ~15 [kOhm] to bring the pole frequency down to 1/(2 * pi * 1.5e4 [Ohm] * 1e-9 [F]) = 10.6 [kHz]. Because the pole frequency doesn't change, regardless of the relay state, it implies some other resistance to ground some where... Eh well. Measurements don't lie -- 10 [kHz] it is!
Checking/adjusting RGA temps
SInce the ETMs were available, I carefully tuned the PUM to TOP mas offloading gain for PIT and YAW. To do this, I drove the PUM at 0.1Hz with 20000cts on the L2_LOCK_[P/Y]_EXC, and set the gain on the TOP mass to exactly cancel the signal in the optical lever.
For YAW this can easily be done with sub-percent precision. The PIT TOP/PUM ratio features a lag filter with a complex pole zero douple-pair at 0.52Hz and 0.56Hz, which can be seen in the QUAD model. I designed a lead filter with those frequencies, but Qs low enough to match the phase at 0.1Hz exactly. The corresponding lead filter is in the M0_LOCK_P FM7 module:
zpk([0.325+i*0.405925;0.325-i*0.405925],[0.349999+i*0.437149;0.349999-i*0.437149],0.999999,"n")
The regquired gains in the M0_LOCK filter modules were:
ETMX PIT 898 *1e-6
ETMX YAW 1428.7 *1e-6
ETMY PIT 1294 *1e-6
ETMY YAW 1650 *1e-6
I put gain of 898, 1428.7, 1294 and 1650 into the M0_LOCK FM6 modules. By selecting FM4, FM5, FM6 (and FM7 for PIT) this implements a xross-over at exactly 0.1Hz. (pictues).
The same has to be done for the ITMs, and the guardian has to be updated to use those filters.
Also set the PUM to TOP cross-over to 0.1Hz for the ITMs, following the same procedure as for the ETMs. The gains were tweaked in the OFFLOADED configuration. The required gains were:
ITMX PIT 1147 *1e-6
ITMX YAW 1547 *1e-6
ITMY PIT 1155 *1e-6
ITMY YAW 1573 *1e-6
I also moved the gain filters to FM3 (removing the old +10dB filter), so it can be switched before the integrator. This was done for all 4 test masses, pit and yaw. With these filters, the settings shown in the attached screen shot result in a 0.1Hz x-over.
The guardian was updated to set this x-over just before engaging the soft loops. I havent switched the guardian to use the offloaded design for the ITMs though.
Title: 08/08/2016, Day Shift 15:00 – 23:00 (08:00 –16:00) All times in UTC (PT) State of H1: IFO is unlocked. HAM6 Vent Commissioning: Commissioners are commissioning as HAM6/IFO condition allow. Outgoing Operator: N/A Activity Log: All Times in UTC (PT) 13:55 (06:55) Chris S – Going to End-X to check wind fence 14:30 (07:30) Chris S – Back from End-X 15:00 (08:00) Start of shift 16:08 (09:08) Filiberto & Ed – In LVEA to prep for power and cabling work at HAM4 16:15 (09:15) Enable the Rotational Stage for Koji – Needed 10W of laser power for alignment 16:32 (09:32) Koji & TJ – Going to HAM6 16:36 (09:36) Betsy & Calum – Going to HAM6 16:38 (09:38) Hugh – Going to End-Y 16:40 (09:40) Filiberto & Ed – Out of LVEA 16:41 (09:41) Kyle – Going to End-Y 16:55 (09:55) Richard – Going to HAM6 17:01 (10:01) Hugh – Back from End-Y 17:08 (10:08) Richard – Out of LVEA 17:11 (10:11) Gerardo – Staging for Ion Pump work at GV3 17:16 (10:16) Jonathan – Going to H2 Enclosure to reboot computer on test stand 17:22 (10:22) Chandra & Gerardo – Going to GV3 to change Ion Pump (WP #6064) 17:28 (10:28) Kyle – Back from back from End-Y 17:20 (10:20) Jonathan – Out of H2 Enclosure 17:45 (10:45) Chandra & Gerardo – Out of LVEA 18:14 (11:14) Jim W & Ian – Going into LVEA to look at HAM6 18:16 (11:16) Kyle – Going into LVEA to look for controllers 18:50 (11:50) Richard – Going to HAM6 19:00 (12:00) Filiberto – Shutter controller work at HAM6 (WP #6065) 19:02 (12:02) Richard – Out of LVEA 19:07 (12:07) Koji, TJ, & Betsy – Out of the LVEA 19:31 (12:31) Krishna – Going into the LVEA (Biergarten) to work on BRS 20:07 (13:07) Chris – Going to Mid-X Fan room to change filters 20:08 (13:08) Richard – Going to HAM6 20:15 (13:15) Richard – Out of the LVEA 20:15 (13:15) Koji, TJ, Betsy – Going to HAM6 20:18 (13:18) Gerardo – Going into LVEA to move AUX cart 20:20 (13:20) Chandra – Going into LVEA to the measure piping for annulus pump 20:38 (13:38) Richard & Filiberto – Out of the LVEA 20:53 (13:53) Chris – Leaving Mid-X – Going to Mid-Y 21:02 (14:04) Kyle – Going to the Vertex RGA 21:07 (14:07) Filiberto – Going into LVEA for shutter controller work (WP #6065) 21:14 (14:14) Richard – Going into LVEA 21: 25 (14:25) Richard – Out of LVEA 21:26 (14:26) Gerardo – Out of LVEA 21:33 (14:33) Richard – Going into the CER 21:37 (14:37) Richard – Out of the CER 21:45 (14:45) Chris – Back from Mid-Y 22:04 (15:04) Chandra – Going to Mid-Y to fill CP3 22:14 (15:14) Ed – Going to Mid-X to look for a power supply 22:36 (15:36) Ed – Finished at Mid-X – Coming back to CS 22:56 (15:56) Chandra – Going into the LVEA to make measurements 22:57 (15:57) Krishna – Out of the LVEA Title: 08/08/2016, Day Shift 15:00 – 23:00 (08:00 – 16:00) All times in UTC (PT) Support: Cheryl Incoming Operator: N/A Shift Detail Summary: IFO is unlocked due to HAM6 vent for OMC repairs. Koji requested 10W of PSL power. Unlocked and re-enabled the Rotational Stage. Cheryl checked and aligned IMs. OMC alignment and HAM6 closeout work continues.
3:10 pm local Took 39 seconds to manually overfill CP3 with 1/2 turn open on LLCV bypass valve and bypass exhaust valve open.
Peter pointed out to me that the L2_LOCK filter bank for ETMX had FM8 (EvanR) engaged for both pitch and yaw, while for the other 3 test masses it was FM3 (EvanBR). All 4 test masses should be the same, so I've fixed ETMX and accepted it in SDF so that it'll come back correctly upon reboots. It looks like we've had the wrong filters engaged for ETMX since July 5th. I didn't check the ITMs, but ETMY has been correct since before July 5th.
Recall that we have the option between roll-only or both bounce and roll notches so that we could try running with the roll-only filters, which would give us more phase in the ASC loops so that we could make harder cutoffs. However, we've pretty consistently found that we ring up the bounce modes if we don't have the notches on, so we (should) have been using the combo EvanBR filters for all test masses.
Also, for some reason the decimation filters for the OUT16s on all of the ETMX L2 LOCK filter banks were off, and have been off for more than 100 days (that's how long I looked back for the bounce / roll filters). Evan, Peter and I agree that there's no reason for them to be off, so we've turned them back on.
PSL: SysStat: All Green, except VB program offline Frontend Output power: 34.1W Frontend Watch: Green HPO Watch: Green PMC: Locked: 0 days, 1 hours, 56 minutes Reflected power: 25.0W Transmitted power: 128.7W Total Power: 154.3W ISS: Diffracted power: 2.8% Last saturation event: 0 days, 1 hours, 57 minutes FSS: Locked: 0 days, 1 hours, 57 minutes Trans PD: 4.802V
Koji requested 10W of laser power for HAM6 alignment work. Set Guardian LASER_PWR node to 10W and re-enabled the rotational stage.
Recall the rotation stage has been disabled since Monday Aug 1 at the start of the HAM6 vent -- see LHO aLOG 28786.
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
This shouldn't be right. The PSoC board is supposedly clocked by half of the provided 71 MHz signal. However, looking at the photos on E1400155 I see that the 2 crystal oscillators of the development are still soldered in. Please tell me this is not true for the units installed in the field.
Tagging SEI and CDS.
Our understanding of the electronics is based on the same DCC document/photos that Daniel linked to.
Some background info on what led us here: the comb was first reported in May by Brynley Pearlstone (alog), and again by Keith Riles in his ER9 narrow lines report (alog). Per Keith's report, the spacing is 1.999951-Hz, visible on approximate odd-integer-Hz frequencies. Robert and I looked back in older data for its appearance, and isolated the date range between February 26 and April 2, but there was not enough good DARM data in that window to track it further. Turning to magnetometer data, we found the comb in a channel at EX (H1:PEM-EX_MAG_VEA_FLOOR_X_DQ), and tracked its appearance down to March 14th using data from that channel (with help from one of Keith's students, Eilam Morag, who has written code for tracking the strength of known combs). We initially suspected the computer system restart on that date, but have not found evidence to support this hypothesis by examining data around subsequent restarts. As a second guess, we looked into the changes to the CPS timing system made on that date (alog) (both end stations). Coincidentally, Robert had placed a magnetometer in the CPS rack at EY to search for blip glitches, and this magnetometer showed the comb strongly, which motivated us to look into the CPS timing fan out.
In the PSoC software, you can select where its clock comes from. They are clocked from 1/2 the site 71MHz. The oscillators are not removed from the board, just de-selected from the clock menu in software.
[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
J. Kissel Now that the re-assembly of the OMC is complete including EQ stop spacing, EQ stop lock-nut securing, and OMC shroud replacement, I've reconfirmed that the dynamics of the OMC SUS are still free-and-clear as they were this afternoon. Nice work Koji and co.! There is no further planned installation work in and around the OMC SUS, so we suspect these will be the last full in-air transfer functions before chamber close-out next week. Templates live here: /ligo/svncommon/SusSVN/sus/trunk/OMCS/H1/OMC/SAGM1/Data/ 2016-08-06_0007_H1SUSOMC_M1_WhiteNoise_L_0p02to50Hz.xml 2016-08-06_0007_H1SUSOMC_M1_WhiteNoise_P_0p02to50Hz.xml 2016-08-06_0007_H1SUSOMC_M1_WhiteNoise_R_0p02to50Hz.xml 2016-08-06_0007_H1SUSOMC_M1_WhiteNoise_T_0p02to50Hz.xml 2016-08-06_0007_H1SUSOMC_M1_WhiteNoise_V_0p02to50Hz.xml 2016-08-06_0007_H1SUSOMC_M1_WhiteNoise_Y_0p02to50Hz.xml Note, I've finally listened to my own advise and made sure that these in-air transfer function templates all have the same frequency resolution and excitation amplitude and coloring.
While HAM6 is open, it would be good to do a close inspection of the fast shutter. Specifically the wires attaching the bobbin (toast) to the integral terminal block. These wires are tiny and are the most likely item to fail. Also good to check for any delamination of the mirror to the bobbin.
Photos from Friday's work is on Resource Space here:
https://ligoimages.mit.edu/?c=1703
9:30AM FRI AUG 5th, 2016 - Chamber entrance Particle counts with hand held CC counter:
| Particle size | Outside of chamber cover, in CR | In chamber above table |
| 0.3um | 60 | 25 |
| 0.5um | 20 | 10 |
| 1.0um | 0 | 0 |
1:30PM FRI AUG 5th, 2016 - Chamber entrance Particle counts with hand held CC counter:
| Particle size | Outside of chamber cover, in CR | In chamber above table |
| 0.3um | 60 | 0 |
| 0.5um | 0 | 10 |
| 1.0um | 0 | 0 |
[Betsy, Corey, TJ, Koji]
- Now the OMC cavity is flashing!
- The OM1~3 and OMC suspensions have been debiased, and the OSEMs were tweaked to have the flags at the center of them.
- The optical paths such as the OMC incident path, OM1 transmission path, OMC refl path ahve been aligned.
We still need to align the WFS and OMCT paths and confirm viewport paths if the beams are hitting the viewport.
- Currently the OMC PZT HV is ON.
Shutter mirror inspection
The surface of the shutter mirror was checked with the green lantern. We didn't observe any sign of degradation.
Mass balance
- We adjusted the weight of the new OMC to match with the old one as much as possible. Then the mass was moved to have reasonable flag positions in the OMC suspension.
|
OLD OMC OMC ASSY-D1201439-002 Balance mass arrangement (Topview)
OMC (6960g) + Mass (201g) = 7161g |
New OMC OMC ASSY-D1201439-3_2 Balance mass arrangement - final (Topview)
OMC (6978g) + Mass (189g) = 7167g |
- The lateral position of OMCS RT OSEM was adjusted to have the flag at the center in the OSEM.
- The centering of the OMCS OSEMs were checked to be within the tolerance range.
- Along with the mass balancing, the positions of the EQ stops for the OMC breadboard were checked. We found several EQ stops were too close or too far. The EQ stop holders were adjusted to have them reasonable gaps to the glass breadboard.
Electrical functionality check
- The DCPDs were illuminated by a white flash light to check which DCPD responds to which channel. DCPDA and DCPDB are related to the DCPD on the transmission anfd reflection sides of the BS prism, respectively. (DCPD(T) = DCPDA, DCPD(R) = DCPDB). This seemed opposite to the case with the previous OMC. It was found that the difference in the internal cabling on the OMC caused this difference. This will be noted in the OMC testing procedure document (T1500060) athough this does not affect the calibration.
- The OMC QPDs were illuminated by the flash light. QPD1 (short arm) and QPD2 (long arm) correspond to QPDA and QPDB, as nominal.
Incident beam alignment & suspension debiasing
- Prep: IMC was locked at 2W. The beam was aligned on to the center of AS_C QPD.
- At this point, we already could observe the beams were on the OMC QPDs. Very good reproducibility.
The signal ratios between OMC_QPD_A/B_SUM and AS_C_QPD_SUM (0.56 and 0.59 today) were confirmed with the ones with the numbers on Jul 28 (0.48 and 0.45).
These ratios were enough similar to convince ourselves that they are the real spots.
From this point, we could follow the procedure in T1400588 (sec 2.3.3 and later).
- OMCS and OM3 were debiased to have (0,0), and used OM1 and 2 to align the spots on the OMC QPDs.
- This made OM1 Yaw ~-2000, and the OMC2 Pitch ~1500.
- The OM1 suspension cage was twisted to remove the OM1 Yaw bias.
- The OM2 suspension pitch adjustment screw was adjusted to remove the OM2 Pitch bias.
- The resulting offsets were: OM1 (116.9, -229.0), OM2 (94.5, 113.0), OM3 (0,0), OMCS (0,0) => Requirement <250 = 1/10th of the full scale => OK!
- We quickly checked some suspension transfer functions for OM1/OM2 and OMCS. OM1 and OM2 showed consistent TFs as the previous measurements. OMCS had the same resonant structures as before except for the resonant frequency of the lowest frequency mode. JeffK is checking the TFs more carefully.
- We turned on the PZT HV and scanned the PZT2 voltage. We confirmed that the OMC DCPDA and DCPDB were observing the OMC flahses.
Optical path check
- Main path: The spot positions on OM1/2/3 were checked. They looked fine.
- Shutter path: The mechanical shutter path was checked. It is still nicely aligned.
- OM1 trans path: The beam alignment in the OM1 transmission was checked. They looked fine. We still need to check the AS AIR viewport path with the viewport emulator.
- OMCR path: The beam spots on the OMCR steering mirrors were checked. The beam was not on the center of the steering mirrors. The first steering mirror (so-called M8) in the OMCR path was moved. The reflection path for 90:10 BS and the beam diverter path was checked. They looked just fine. M10 and M11 were used to align the spots on the OMCR QPDs. We didn't use M9 this time. We'll check this path again once the viewport emulator is attached on the chamber tomorrow.
- WFS path / OMCT path: We will work on these paths tomorrow.
Next steps
- Restore OMC blackglass shroud if the OMCS TFs look OK.
- Restore OMCT steering mirror
- Place the viewport emulator
- Confirm spot locations on the viewport
- We want to check the calibration between AS_C QPD SUM, the incident power on OM1, and the incident power on the OMC breadboard.
- Ground loop check
- Other SUS/SEI exit check
More detailed assessment of the OMC and OM SUS can be found here: LHO aLOG 28883. The OMC is locked up in Transverse / Roll, otherwise all SUS look healthy.
Assuming this is the case, we need to check the upper mass EQ stops to make sure the upper mass gets completely free.
Also this action will change the position of the OMC glass breadboard. Therefore the beam alignment should be revisited again.
(Photos From Yesterday's Work)
Not many taken with alignment/optic work mainly on the plate. Photos can be found here:
https://ligoimages.mit.edu/?c=1702
9:30 AM THUR AUG 4th, 2016 - Chamber entrance Particle counts with hand held CC counter:
| Particle size | Outside of chamber cover, in CR | In chamber above table |
| 0.3um | 10 | 10 |
| 0.5um | 0 | 10 |
| 1.0um | 10 | 10 |
