Whilst observing the IMC trying to lock this morning and its moving the laser frequency around,
it appeared that in the lock acquisition phase as soon as light was resonating in the IMC cavity
the boost gain was engaged.
I asked TJ to insert a 2 second delay prior to engaging the IMC servo boost gain so that things
had a chance to settle down. Behaviourally things seemed better with the delay in.
TJ/Jason/Peter
TITLE: 07/22 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
INCOMING OPERATOR: Jeff
SHIFT SUMMARY: After performing initial alignment this morning, the IFO has been locking well all day. We had a brief wrestling match with the FSS again, but since then, no issues.
LOG:
16:30 FSS oscillations, Peter and Jason looking at it
16:52 Richard to both ends electronics room
17:45 Richard back
22:07 Gerardo to CP3
I am working on the Noisebudget Model these days and made a summary of the WFS in use with calibrations:
| WFS |
Serial No. |
RF Trans. [Ω = V/A] |
Responsivity [A/W] |
Demod. Gain [dB] |
Whit. Gain [dB] (40W) |
ADC [cts/V] |
Digital Gain |
Cal [cts/W] |
|||||
|
Freq. |
Q1 |
Q2 |
Q3 |
Q4 |
AVE |
||||||||
|
REFL_A |
S1301242 |
9 MHz |
894 |
894 |
1069 |
974 |
958 |
0.85 |
21 |
21 |
1638 |
1 |
1.7E8 |
|
45 MHz |
642 |
662 |
657 |
634 |
649 |
21 |
1 |
1.14E8 |
|||||
|
REFL_B |
S1301243 |
9 MHz |
822 |
873 |
742 |
861 |
824.5 |
0.85 |
21 |
21 |
1638 |
1 |
1.44E8 |
|
45 MHz |
678 |
644 |
635 |
648 |
651 |
21 |
1 |
1.14E8 |
|||||
|
AS_A |
S1300635 |
36 MHz |
810 |
828 |
872 |
891 |
850 |
0.85 |
21 |
12 |
1638 |
1 |
5.3E7 |
|
45 MHz |
707 |
718 |
732 |
766 |
731 |
3 |
1 |
1.6E7 |
|||||
|
AS_B |
S1300634 |
36 MHz |
846 |
904 |
826 |
832 |
852 |
0.85 |
21 |
15 |
1638 |
1 |
7.5E7 |
|
45 MHz |
644 |
711 |
719 |
691 |
691 |
3 |
1 |
1.5E7 |
|||||
Calibration (from W to cts) = RF Trans. * ADC * Responsivity * Digital Gain * 10^(Demod. Gain + Whit. Gain)/20
Attached is a plot of the pre-modecleaner heater signals similar to that posted at LLO: PMC glitches. No glitches observed here. Jason/Peter
The OMC was behaving funny, as seen on the trans camera, so I glanced at its control screen. I noticed that the PZT was super railed, and the "OFF_RESONANCE" guardian state was just making it larger and larger.
The logic for dealing with this failed, since it checks if the offset is identically equal to 50, it moves the PZT to -50. I have changed it so that if the offset is larger than 50 it'll reset to -50.
Attached is a 3 day trend - this railing started sometime yesterday.
I made a map which plots my measured locations of the NN array L4C sensors to scale against a LVEA layout drawing from D970308. Each location has a number indicating the channel number of that sensor. The channels are H1:NGN-CS_L4C_Z_#_OUT, where # is the number of the sensor on the map. It's hard to quantify the uncertainties in my position measurements, but the positions look correct by eye. I'll update this map when I place more sensors next week.
The data dropouts observed in second trend data (see alog 28579) are a result of missing data caused by restarts of frame writer 1. If the raw data is used instead of second trend data, you can see that dropouts are not present, see attached example. Both nds0 and nds1 are reading the same second trend data, and only frame writer 1 is currently writing second trend data as we explore frame writer instability.
fw0 continues to be 100% stable, fw1 is now restarting about 12 times a day.
Currently fw0 is writing the two 64 second frames (commissioning and science) and fw1 is writing all four frame types (commissioning and science 64S-frames, second and minute trends). Hence the second trend drop-outs when fw1 restarts. Next week we will work on making the second trends contiguous.
Attached are screenshots for the past 7 days optical ever trends for PIT, YAW, and SUM.
This completes FAMIS request 4685.
The laser tripped around 3:20 this morning. Suspect it is the "usual" problem. The crystal
chiller was found off but with its dummy still in place.
The data drops out looks like an artifact of data acquisition.
Another observation is that the head temperatures all increase when the flow rates drop.
That is not surprising but the humidity also rises. It might be that we have a tiny water leak
whose effect on humidity is noticeable when the temperature rises. We have seen evidence of
tiny leaks before because of some corrosion stains in the laser base plate, however when the
laser is observed over time scales of ~30 minutes, no leak is visible. The (possible) leak is
small enough that it does not make a noticeable difference in the water level of the chiller.
Jeff B, Kiwamu,
We powered up the input power to 50 W tonight with SRM controlled by the dither alignment. We held the interferometer at 50 W for 30-ish minutes but this was ended because of a PI at 18056 Hz (28259).
During this short period, we moved the PRM pointing (or PRC1) in pitch and confirmed that moving PRM further in the negative direction (by introducing an offset in the error point of PRC1) improved the recycling gain. See the attached. The recycling gain slowly went back to 28 or so at 50 W. We did not get a chance to explore the optimum point yet. POPX started railing when we steered PRM at 40 W on the way to reach 50 W.
Title: 07/21/2016, Day Shift 23:00 – 07:00 (16:00 – 00:00) All times in UTC (PT) State of H1: IFO locked at DC_READOUT. Wind is Calm to Moderate Breeze (0 to 18mph). Seismic is a bit elevated at the End Stations; but should pose no operational difficulties. Microseism is low. Commissioning: Commissioners are commissioning. Outgoing Operator: Travis Activity Log: All Times in UTC (PT) 23:00 (16:00) Take over from Travis 23:08 (16:08) Nutsinee – Going to TCS-X Table 23:11 (16:11) Sheila & Jenne – Going to ISCT1 to add a new lens 23:45 (16:45) Sheila & Jenne – Out of LVEA 00:16 (17:16) Jenne – Going to ISCT1 00:25 (17:25) Jenne – Out of LVEA 00:39 (17:39) Jenne – Going back to ISCT1 01:26 (18:26) Jenne – Out of the LVEA Title: 07/21/2016, Day Shift 23:00 – 07:00 (16:00 – 00:00) All times in UTC (PT) Support: Sheila, Jenne, Kiwamu Incoming Operator: N/A Shift Detail Summary: IFO has been mostly up while the commissioners were working. The lock losses were relativity easily recovered. Had to do some minor touch up of PRMI a couple of times, but nothing too serious. The wind has come up over the last 3 hours. Base winds are in the mid to upper teens with gusts into the mid-30s. Microseism remains low and seismic activity has rung up with the increase in the winds.
Added 150ml water to the Crystal chiller. Diode chiller was OK. Noted no new contamination or debris in either chiller filter. Trended the pressures and flows for the Diode and Crystal chillers. The pressures are still slowly trending upward and the flows are trending downward. Both are changing by very small amounts. I have the new (higher flow and less restrictive)filters for the chiller room in-line filters. Plan to swap these at the next maintenance window.
Just a theory here...But I believe the H2 coil driver needs attention.
H2 Drives off as RZ and X Loops, H2 only directly affects RZ and X. If it were the loops, of Actuator Drives would respond. Page 11 of attached show the CD I & V INMONs going wacky impacting the RZ and X(page 4) loops 1 or more seconds before the model responds.
I know this is long winded, you should see the stuff in the text file not preinted here as I went down other rabbit holes.
ITMX ISI Tripped Wednesday July 13 AM from M6.3 EQ in New Zealand. No other platforms tripped. The extra sensitivity of the ITMX to EQs is not new. Based on the ground Seismometer STS2-B, it looks like the trip occurred with the arrival of the S-Wave (Shear, not surface.) See page 1 of attachment. Based on the EPICS records, ST2 tripped first; based on the FIRSTTRIG_LATCH value, the Actuators hit their rail first.
Page 2: 80 seconds with the Actuator drives. The upper right graphs have the horizontals and verticals on the same plot. Given that there is no RX or RY loop closed, it makes sense that the three vertical drives are exactly the same. Leading up to the trip, the H1 and H3 drives appear to be getting a greater request from the loops compared to the corner2 horizontal. The H2 GS13 is parallel to the X arm and so contributes nothing to the Y DOF. The verticals are well behaved. However, a couple of seconds before the EPICS INMON registers the state change (1 to 2,) the H2 drive shoots almost straight to the rail. This delay makes sense with the 8192 saturations required before tripping on this 4k model. The upper left plot zooms out on the H2 drive as it ramps its way up to e7 before the watchdog trip takes it to zero. The H1 and H3 drives continue along until the trip when they start to ring. After the trip the three horizontals behave similarly. You might believe there is a kink in these other drives a few seconds earlier,...ehhh.
So the behavior of Drive2 may be of interest. Is this a coil driver problem or does it originate from up stream?
Upstream is the damping, isolation, and feedforward paths. There is no indication that the vertical loop is a problem and feedforward only goes to Z; and, there are no DQ channels for the damping loops—they will have to wait for further upstream examination. This leaves the isolation loops.
Page 3 shows 80 seconds of the Isolation loop inputs. The ITMX and ITMY IN1s are overlain on the same plots. Also shown are the horizontal ground motions; the vertical is uninteresting. The ground motion signals overlain on the isolation plots are scaled and shifted so as to be seen. This shows that both ITMX and ITMY X & Y DOFs are doing about the same and are fairly well correlated with the input ground motion hence the control loops are pretty much the same. I've also verified this looking at the Matlab Controller figures. Around xx8505 gps, the Y ground motion quickly increases, this may be the arrival of the s-wave. The Y loop responds but within several seconds, the response doesn't seem as reasonable and looks to be ringing up and getting behind the curve. The X gets hit with this some 30 seconds later. I don't know if the mostly flatish nature of the RZ loops is or is not remarkable. As well, is the scale of noise/buzz difference between ITMX and Y worth noting? Conversely, the Z DOFs seem to be responding to the same input but certainly drive harder on the ITMX.
So the H2 Drive goes wacky before the others. The X and RZ loops feed the H2 Drive and both those ISOs head off to the outer reaches. The Y loop sees a blip and then gets buzzy/noisy; the Z sees nothing. The H2 Drive is pushing the platform and the X and RZ motion is seen back at the ISO_IN1. It makes sense that the Y DOF would also see something if the H2 actuator is the only one pushing. The push on H2 Drive could produce canceling affects on the H1 and H3 sensors and not push that DOF iso off the page. If the RZ loop was driving it, the response would be the same on all Horz GS13s but they are not responding the same.
On page 4 the Drives and ISO Ins are plotted together for 4 seconds. Clearly the H2 Drive leads the other drives as already established. On the top plot of the ISOs, the X and RZ loops respond dramatically compared to the blip on Y. Further, the ISOs are scaled by 5 to emphasize their behavior before the Drive goes off. The Y loop looks to be trundling along but X and RZ and maybe more clearly RZ changes what it had been doing.
This might suggest the loops are causing this but the fact that only the H2 Drive reacts implies that circuit is more sensitive.
On page 5, only ISOs X and RZ are shown with the H2 Drive. On the top plot, the drive is scaled down to be visible with the zoomed in ISO loops. The RZ loop really seems to be headed somewhere bad before the drive freaks out. Again however, if the loop was the source, the other drives would be reacting similarly and they are not.
On Page 6, one sees the ITMY loops don't respond like the ITMX X and RZ loops--not caused by the common ground motion.
On pages 7 & 8, an interesting beat is seen on the HEPI L4C RZ loops. Otherwise nothing else on the HEPI IPS or L4Cs of either ITM.
Page 9, the GS13s of ITMY are overlain on the ITMX GS13s for 20 seconds showing the motion on the platform is nearly identical on the two ITMs.
On page 10, the horizontal GS13s of ITMX are plotted together (left middle graph) showing the relative magnitudes. This implies only corner 2 is being driven and the others are just seeing the rotation caused by the one corner.
Page 11 plots the H2 CD INMONs, 80 seconds to show the normal before some badness at the trip time.
Page 12 zooms into 10 seconds showing the Coil Driver current and voltage making some really ugly step and excursion one or more seconds before the RZ loop starts to head off. The model did not tell the coils to do this or it would be seen on the DRIVE. The RZ loop and the X loop (page 4) are responding to what the coil driver is doing to the platform. I'm pretty sure this tells us the coil driver is the source of this problem.
Maybe the coil driver is marginal in some way and when the extra demand of dealing with the work of the earthquake motion occurs, something lets go.
NDS2 Data Storage Timing Issue???
Attached is a ddt plot of the H2 INMONs, the ground motion, and the H2 MASTER DRIVE (the output of the model.) I had to go to NDS2 extraction as the full data is now gone from h1nds1.
On this ddt plot, the hump up to ~500cts on the I mon (RED) starts about 10 seconds whereas the rapid increase of MASTER_H2_DRIVE (violet?) is starting around 9ish seconds.
On page 11 of the pdf above, the ramp up of the Drive channel (center graph) clearly happens after the step in the I_INMON channel (upper middle channel.)
The INMON channels are slow whereas the DQ channels are fast...
I suspect my dataviewer looks are correct but...
Okay--false alarm on the timing, but a warning to DDT via NDS2 users looking for time series with mixed data rate (16 & 4k) channels---these are the conditions I was working under.
See the attached plot where the red trace is a 16hz FE channel and the reference in green is a 4kHz channel and the measurement setup has the stop frequency at 1 hz and BW of 0.01 hz. Lower in the attached is the fourier tools settings for the Blue data where the only thing changed from the green is to set the stop frequency to 7 hz. The reason for the change in the shape of the data may be obvious to many of you much sharper in your signal and fourier analysis than I but should serve as a warning to all those using DDT to display time series. I had to slow things way down due to the 16 hz channel and just went to and it greatly impact the accompanying fast channel. 2, 3 & 4 HZ stop frequency all produce the brown trace; 5, 6 & 7 all produce the Blue trace. 7 Hz was as high as it would go.
We closed some alignement loops for SRM using a dither and demodulating POP90 this morning. These loops seem to have a ugf below 100 mHz, so we may want to increase their gain, but they seem to be working well for now. They come on in the guardian durring the DRMI ASC and leave them on. They maintain POP 90 (and the ratio of AS90/POP90) at a reasonable level as we go through the CARM offset reduction, engaging the soft loops, and increasing the power.
We saw a instability that seemed to be a cross coupling between SRM and SOFT yaw loops, Jenne increased the gain in the soft yaw loops by a factor of 10 which seems to have taken care of the problem and is now in the guardian.
As long as this keeps working, operators should no longer have to adjust SRM.
Somehow, running this loop durring acquisition was causing an HLTS bounce mode (28 Hz ish, probably PR3) to ring up, which also saturated the quad L2 drives and therefore cause violins to ring up. We are now using the normal 36 WFS during DRMI, turning them off, and turning on the dither loop in the ENGAGE_SRC_ASC state once we reach full lock. This donesn't ring anything up.
Hugh, JeffK, JimW
Short version:
I noticed this afternoon that all of the BSC-ISIs were pushing large DC-ish drives on their St1 vertical actuators (generally about 2000 counts, normal drives are ~100). When I trended the BS and ITMX drives against their Sus oplevs, there seems to be a very clear correlation between large ISI drives and oplev yaw. I think this may be the cause of the drifts that Sheila complained about yesterday. The first attached plot shows the BS 3 vertical drives and BS oplev yaw, second is for the same for ITMX.
One possible cause of this is the actuators heating up the ISI. During the timing kerfluffle yesterday, all of the ISIs sat for ~6 hours with no acuator drive. The control room then recovered all of the platforms and proceeded to start aligning the interferometer, so the ISIs went from a "cold", immediately to an aligned state. Arnaud found a similar effect at LLO, where large ISI tidal drives caused angular drift during locks, when LLO tried offloading tidal to the ISI ( https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=20222 ).
In the future we should try to at least get the ISIs damped as soon as possible after similar maintenance, or go through a cycle of de-isolating/re-isolating after the ISIs have been running for a while, before trying to relock the IFO. The morning of Jul 11th, ITMX was down for almost 14hrs, but the damping loops were still on, and the actuators were still getting a drive signal. When the ISI was re-isolated, the oplev didn't see any appreciable drift over the next several hours (see third plot). Similarly, sometime before the commissioners start locking tomorrow, all the BSCs should be taken down to damped and then re-isolated.
We also considered that something in the timing system could have been responsible, but were unable to find anything to support that. None of the timing signals we looked at showed anything like the drift we saw in the ISIs. We also saw a similar alignment drift after the June power outage, that would seem to support a thermal drift over a some timing shenanigans.
I can think of two fixes for this,
1) we could have a new "off" state where the actuators have a DC value that represents the offset that they were at in the running state
2) we measure the temperature of the the stages (Quad top mass vertical position for stage two, possibly stage one vertical force for stage one) and feed forward to the yaw control
Arnaud's comment in case we come across this problem again: turn off the RZ loops. The drift is caused (we think) by thermal expansion of the stage, this changes the free hanging position of the ISI and the drift that the interferometer sees is likely dominated by RZ. If we turn the loop off, the stage will stay in a neutral position, rather than following a spurious thermally driven alignment.
Stefan, Matt, Evan
We thought a bit about how thermally driven fluctuations in the polarization density of the test mass substrate could couple into DARM. We made a preliminary calculation of this noise for a single test mass biased at 380 V. This is not currently limiting the DARM sensitivity (since bias voltage reduction tests showed no effect), but could be important once aLIGO is closer to design sensitivity.
The test mass substrate and the reaction mass electrodes can be considered as a capacitor with position-dependent capacitance , where d is the gap distance. The dielectric loss of the substrate will contribute a small imaginary part
to this capacitance. If a significant fraction of the electrostatic field density from the electrodes is located inside the test mass substrate, then the loss angle of the capacitance will be similar to the dielectric loss of the substrate.
If a sinusoidal voltage is applied to the bias electrode (and the quadrant electrodes are held at ground), then the charge accumulated on the electrodes is
. The time-averaged power dissipated per cycle is then
.
Since , we therefore have
.
This voltage noise can then be propagated to test mass motion in the usual way. Using an ESD coefficient 2×10−10 N/V2 and a gap distance of 5 mm, this fixes the capacitance at C0 = 2 pF.
The loss tangent of Suprasil is quoted as 5×10−4 at 1 kHz. If this is assumed to be structural, then for a 380 V bias, the expected displacement ASD is 8×10−22 m/Hz1/2 at 100 Hz, falling like f5/2. This is shown in the attachment, along with the aLIGO design curve.
We have not considered the capacitance of the ESD cables, or of nearby conductors (e.g., ring heaters). (The effect of the series resistors in the ESD cables was considered by Hartmut some time ago.)
The Dynasil web site quotes dielectric properties of fused silica from MIT's Laboratory for Insulation Research, circa 1970.
These vales for the loss tangent are much lower, e.g.: < 4e-6 at 100 Hz.
Upgrade of Timing Firmware
Daniel, Ansel, Jim, Dave
Most of today was spent upgrading the entire timing system to the new V3 firmware. This did not go as smootly as planned, and took from 9am to 6pm to complete. By the end of the day we had reverted the timing master and the two CER fanouts to the orginal code (the end station fanouts were not upgraded). We did upgrade all the IRIG-B fanouts, all the IOChassis timing slaves, all the comparators and all the RF Amplifiers.
The general order was: stop all front end models and power down all front end computers, upgrade the MSR units, upgrade the CER fanouts, upgrade PSL IO Chassis (h1psl0 was restarted, followed by a DAQ restart), upgrade all CER slaves (at this point the master was reverted to V2), at EY we upgraded IRIG-B and slaves (skipping fanout), at MY we upgraded the PEM IO Chassis, at EX we did the same as EY and at MX the same as MY.
All remaining front ends were now powered up. The DAQ was running correctly but the NDS were slow to complete their startup. Addiional master work in the MSR required a second round to restarts, at this point comparators which had been skipped were upgraded and the CER fanouts were downgraded. Finally after h1iopsush56 cleared a long negative irig-b error all systems were operational.
During these rounds of upgrades FEC and DAQ were restarted several times.
Addition of Beam Splitter Digital Camera
Richard, Carlos, Jim
An analog camera was replaced with a digital video GIGE-POE camera at the Beam Splitter.
New ASC code
Sheila:
new h1asc code was installed and the DAQ was restarted.
Reconfigured RAID for ldas-h1-frames file system
Dan:
The ldas-h1-frames QFS file system was reconfigured for faster disk access. This is the file system exported by h1ldasgw0 for h1fw0's use. After the system was upgraded, we reconfigured h1fw0 to write all four frame types (science, commissioning, second and minute). As expected, h1fw0 was still unstable at the 10 minute mark, similar to the test when h1fw0 wrote to its own file system. h1fw0 was returned to its science-frames-only configuration.
Just curious -- it's my impression that the point of "upgrading the timing system to the new V3 firmware" was to reprogram all timing system hardware's LED lights so as to not blink every second or two, because we suspect that those LEDs are somehow coupling into the IFO and causing 1 to 2 Hz combs in the interferometer response. The I/O chassis, IRIG-B, comparators, and RF amplifiers are a huge chunk of the timing system. Do we think that this majority will be enough to reduce the problem to negligible, or do we think that because the timing master and fanouts -- which are the primary and secondary distributors of the timing signal -- are still at the previous version that we'll still have problems?
With the I/O chassis timing upgrade we removed the separate power supply form the timing slaves on the LSC in the corner and both EX and EY ISC chassis. Hopefully the timing work will eliminate the need for the separate supplies.
Could you clarify that last comment? Was yesterday's test of changing the LED blinking pattern done in parallel with removal of separate power supplies for timing and other nearby electronics?
Ansel has been working with Richard and Robert of the past few months testing out separate power supplies for the LEDs in several I/O chassis (regrettably, there are no findable aLOGs showing results about this). Those investigations were apparently enough to push us over the edge of going forward with this upgrade of the timing system. Indeed, as Richard says, those separate power supplies were removed yesterday, in addition to upgrading the firmware (to keep the LEDs constantly ON instead of blinking) on the majority of the timing system.
To clarify Jeff's comment: testing on separate power supplies was done by Brynley Pearlstone, and information on that can be found in his alog entries. Per his work, there was significant evidence that the blinking LEDs were related to the DARM comb, but changing power supplies on individual timing cards did not remove the comb. This motivated changing the LED logic overall to remove blinking. I'm not sure whether the upgrades done so far will be sufficient to fix the problem. Maybe Robert or others have a better sense of this? Notable alog entries from Bryn: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=25772 https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=25861 https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=27202
I have gone through and manually compared FScan spectrograms and normalized spectra for the 27 magnetocometer channels that are processed daily: https://ldas-jobs.ligo-wa.caltech.edu/~pulsar/fscan/H1_DUAL_ARM/H1_PEM/fscanNavigation.html, to look for changes following Tuesday's timing system intervention, focusing on the lowest 100 Hz, where DARM 1-Hz (etc.) combs are worst. Because of substantial non-stationarity that seems to be typical, it's not as straightforward as I hoped it would be to spot a change in the character of the spectra. I compared today's generated FScans (July 20-21) to an arbitrary choice two weeks ago (July 6-7). But these six channels seemed to improve w.r.t. narrow line proliferation: H1_PEM-CS_MAG_EBAY_LSCRACK_X_DQ H1_PEM-EX_MAG_EBAY_SUSRACK_X_DQ H1_PEM-EX_MAG_EBAY_SUSRACK_Y_DQ H1_PEM-EX_MAG_EBAY_SUSRACK_Z_DQ H1_PEM-EY_MAG_EBAY_SUSRACK_X_DQ H1_PEM-EY_MAG_VEA_FLOOR_X_DQ (before & after figures attached) while these four channels seemed to get worse w.r.t. narrow lines: H1_PEM-EX_MAG_VEA_FLOOR_Z_DQ H1_PEM-EY_MAG_EBAY_SEIRACK_X_DQ H1_PEM-EY_MAG_EBAY_SEIRACK_Y_DQ H1_PEM-EY_MAG_EBAY_SEIRACK_Z_DQ In addition, many of today's spectrograms show evidence of broad wandering lines and a broad disturbance in the 40-70 Hz band (including in the 2nd attached figure).
Weigang Liu has results in for folded magnetometer channels for UTC days July 18 (before changes), July 19-20 (overlapping with changes) and July 21 (after changes): Compare 1st and 4th columns of plots for each link below. CS_MAG_EBAY_SUSRACK_X - looks slightly worse than before the changes CS_MAG_EBAY_SUSRACK_Y - periodic glitches higher than before CS_MAG_EBAY_SUSRACK_Z - periodicity more pronounced as than before CS_MAG_LVEA_VERTEX_X - periodic glitches higher than before CS_MAG_LVEA_VERTEX_Y - periodic glitches higher than before CS_MAG_LVEA_VERTEX_Z - periodic glitches higher than before EX_MAG_EBAY_SUSRACK_X - looks better than before EX_MAG_EBAY_SUSRACK_Y - looks better than before EX_MAG_EBAY_SUSRACK_Z - looks slightly worse than before EY_MAG_EBAY_SUSRACK_Y - looks slightly better after changes EY_MAG_EBAY_SUSRACK_Z - looks the same after changes (Weigang ran into a technical problem reading July 21 data for EY_MAG_EBAY_SUSRACK_X) A summary of links for these channels from ER9 and from this July 18-21 period can be found here.
The shot noise level from last night seems higher (worse) than the O1 level by 6%. Here is the spectrum:
You can see that the red trace (which is the one from the last night) is slightly higher than the (post-) O1 spectrum. The 6% increment was estimated by dividing the two spectra for frequencies above 1200 Hz and taking a median of it.
Evan H. suggested looking at the null and sum channels to see if the excess in shot noise is from an addition technical noise or not. The attached shows the spectrum of the null and sum channels at the same duration as the spectrum in the above entry.
From this plot, it is evident that the excess is not due to technical white noise.
I have checked the calibration of the DARM signal by comparing it against the Pcal excitation signals. I used the same lock stretch as the above entry. The height of the Pcal line at 331.9 Hz in the DARM spectrum was found be too high by 13% relative to the Pcal TR and RX PDs. See the attached. This means that we have overestimated the DARM signal at 331.9 Hz due to a calibration error. If we assume this is all due to an inaccurate optical gain, actual shot noise level should be smaller by the same factor of 13% that what we thought, corresponding to a ~7% smaller shot noise level than that in O1. We need to nail down whether this is an error in the optical gain or cavity pole in order to further evaluate the calibration error.
Note that the Pcal Y uses a fresh set of the calibration factors that was updated a month ago (27983). The ratio of RX PD over TX PD was found to be 1.002 at 331.9 Hz and this makes me think that the Pcal Y calibration is reliable.
Here I have attached plots of the optical gain during this lock as well a few locks randomly picked during the month of July. I used O1 model as reference (wasn't not quite sure whether there was new time zero reference after O1 with all kappas set to 1). The first plot showing kappa_C over a few locks during July show that kappa_C values were close to 1. However here we note that the gain in the inverse sensing function during July was set to 1.102e-6 compared to 8.834e-7 during O1 (the referene model has changed). At high frequencies, the relation between corrected h(t) and h(t) recorded in front-end is,
corrected h(t) ~ h(t) / kappa_C ~ inv_gain * DARM_ERR / kappa_C
So for same DARM_ERR, kappa_C of 1 during July 2016 corresponds to 0.8 * h(t) (= 8.834e-7 / 1.102e-6) as that of during O1. This assumes that there wasn't any change in the gain of the electronic chain on the OMC side. The second plot show trend of kappa_C during the lock Kiwamu was looking at. An interesting thing to note here that there was ~10% change in the optical gain during this lock. Kiwamu's plot correspond to time of the second peak we see in the plot (a coincidence!). The kappa_C value of 1.15 suggests that the measured h(t) in the above a-log would correspod to 0.70 ( = 8.834e-7/1.102e-6/1.15) times that of h(t) we would be measured during O1. Since the trend plot show that there were times in the same lock during which the kappa_C values were different, I tried to compare the power spectrum between those times. The third plot show that comparison. The mystery is that eventhough the ratio between the 331.9 Hz photon calibrator line and DELTAL_EXTERNAL line is ~10 % different between the times compared (and hence corresponding to ~10% different optical gain), the shot noise level looks same! We couldn't get the exact cavity pole frequencies because at this point I don't have the new LHO DARM model function, but the trend indicated that it didn't change during the lock. For completeness we also added the acutation strength variation during this time. The values are close to what we expect. Since 35.9 Hz ESD line we used during O1 wasn't available, for actuation strength comparison we used 35.3 Hz ESD line.
EDIT: We corrected the earlier estimate of high frequency h(t) level change.
Just a note for ASC WFS REFL_A: S1301242 was swapped out in 2022 for S1301248. See alog #63544.