The user environment for controls on video0 - video6 and projector0, projector1 has been modified to eliminate redundant and outdated command aliases.  The aliases are now supposed to be set by a common file of aliases at login.  If there are any problems running programs that used to work, let me know.  This was driven by an outdated "sitemap" alias found on these computers.

Laser Status: 
SysStat is good
Output power is 29.3 W (should be around 30 W)
FRONTEND WATCH is GREEN
HPO WATCH is RED

PMC:
It has been locked 6 day, 1hr 15minutes (should be days/weeks)
Reflected power is 2.0 Watts  and PowerSum = 25.6 Watts.
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 1 h and 37min (should be days/weeks)
Threshold on transmitted photo-detector PD = 1.59V (should be 0.9V)

ISS:
The diffracted power is around 4.7% (should be 5-15%)

People have asked for my alignment/lock acquisition DTT and StripTool templates. They can be found here:

/ligo/home/alexan.staley/Public/DTTTemplate

/ligo/home/alexan.staley/Public/StripToolTemplates/AlignmentStripTemp

Following Jeff's log last week, we wanted to try a different blend filter on HAM3 to see if we could get any improvement. Arnaud suggest a 500 mhz blend that is installed on the Livingston HAMs, shown as the the green traces in the first attached image (01_28 blend is shown in blue, 250mhz blend is in red) . I copied the filters over this morning, and turned the new filter on in the RY dof. It didn't do anything good, shown second and third images. Current confguration is shown in solid lines ( normal 01_28 blends everywhere), dashed lines are with 500 mhz blend on RY only. The .6hz peak disappeared, but a new one at 1.14hz appeared, there's some more junk just below 2 hz, and it looks like a bunch of CPS noise is being reinjected above 1hz. I've returned the ISI to the nominal config.

model restarts logged for Sun 25/Jan/2015
2015_01_25 03:28 h1fw1
2015_01_25 06:40 h1fw0
2015_01_25 09:43 h1fw0
2015_01_25 17:49 h1fw0
2015_01_25 23:05 h1fw0

all unexpected restarts. Conlog frequently changing channels report attached.

Both x and y arm were locked for most of the past 18 hours. The attached plot shows the tidal motion together with the alignment controls. The only clear correlation seems to be ETMY/TMSY yaw.

Currently, iscex reports maximum CPU times of 29µs in an average 1 second period with an absolute maximum of 36µs. iscey reports average maxima of 28µs and an absolute maximum of 33µs. The fiber delay is 21.5µs for the x-arm and 21.7µs for the y-arm. The absolute worst case delay to the corner is then 58µs and 55µs for iscex and iscey, respectively. This is still well below the cycle time of 61µs. However, the corner lsc model still reports IPC errors. Something doesn't add up. The attached plot shows the IPC error counts in the corner lsc, their timestamps and the iscex/y CPU times.The IPC errors are latched when when they occur. This has the unfortunate side effect of making the first twelve plots in the attachment essentially useless, except indicating that "errors are happening".

In contrast, the lsc uses an average maxima of 35µs with an absolute maximum of 40µs. Both susetmx and susetmy report around 10 IPC errors per second in each and every second.

I followed the Dan Hoak prescription from the December OM / RM damping work and applied it to the IMs today.

The filters are now all the same for all the IM DoFs. Also, each of the IMs now have the same set of L, P, and Y gains (-20, -0.02, & -0.04 respectively). The low pass I installed is almost the same as what's at LLO, but slightly less agressive so as to allow for more damping later if we want.

I have also turned on limits of 555 counts on all of the damping loops. This gives them a huge margin, but better than what they had, which was no limits.

I reduced the pitch gains from -0.04 to -0.02 since they were overdamped before. From the attached in-loop spectra (with the new settings), you can see that there is still some anomalies, but all in all, I think the IMs can now be considered OK and can be left alone until we want to make a jitter noise budget to get past 100 Mpc or so.

Introduction Initial LIGO accelerometers were sampled at 2048 Hz.  This rate gives accelerometer coverage over about 1/8 of the DARM band. This coverage is better than it may seem because displacement, and the effect on DARM, tend to drop rapidly with frequency. Nevertheless, complete coverage over the detection band may help build the confidence of a detection paper reviewer, allowing us to say that there was no increase over ambient motion during the event.  For this reason I have been pushing to increase the bandwidth. Peter F. has tentatively approved an increase in bandwidth to 4096, and I mentioned to him that I might want to redistribute that, having some accelerometers sampled at lower rates so that some could be sampled at higher rates. Hence this investigation.

How high in frequency do the accelerometers sense the vibrational background?The accelerometer specs claim +/- 3dB out to 1300 Hz with a resonance at 2.4 kHz. But, for us, the data is useful beyond the flat region if the accelerometer senses the ambient background (and is thus able to detect any changes). Figure 1 shows that accelerometers on a test mass chamber see background up to at least 7200 Hz.

How well are high frequency vibrations sensed by the 16k microphones?   To test whether 16k microphones offered comparable coverage to accelerometers for high frequency vibration of the vacuum enclosure, I used a piezo shaker to inject 3000 Hz vibrations onto the GV-1 gate valve seat (which is visible to the test mass, has been identified as a potential glint site, and could conceivably be excited by a failing annulus ion pump or actuator), and compare the responses of nearby accelerometers and microphones. Figure 2 shows that accelerometers in the vicinity tended to have at least an order of magnitude greater SNR than microphones. This suggests that microphones are not a very good substitute for accelerometers for high frequency vacuum enclosure vibrations. The Y-manifold and other more distant accelerometers also show the signal with fairly high SNR, suggesting that the signals travel pretty far through the vacuum enclosure and so a smaller number of accelerometers could provide fairly good high-frequency coverage.

So I propose we increase the rate of a subset of accelerometers to 16384 Hz, and maintain the total data rate by getting rid of all quad sum channels and reducing all other accelerometers to 2048 Hz.

Robert

Increase the following channel rates to 16k, reduce all others to 2048 and eliminate accelerometer quad sums:

H1:PEM-CS_ACC_PSL_PERISCOPE_X

H1:PEM-CS_ACC_BEAMTUBE_MCTUBE_Y

H1:PEM-CS_ACC_BSC1_ITMY_Y

H1:PEM-CS_ACC_BSC3_ITMX_X

H1:PEM-EY_ACC_BSC10_ETMY_X

H1:PEM-EX_ACC_BSC9_ETMX_Y

H1:PEM-CS_ACC_HAM6_OMC_Z

L1:PEM-CS_ACC_PSL_PERISCOPE_X

L1:PEM-CS_ACC_HAM6_OMC_Z

L1:PEM-EY_ACC_BSC5_ETMY_X

L1:PEM-EX_ACC_BSC4_ETMX_Y

L1:PEM-CS_ACC_BSC3_ITMX_X

L1:PEM-CS_ACC_BSC1_ITMY_Y

L1:PEM-CS_ACC_HAM2_PRM_Z

Summary: tap tests from summer, along with GS13 coherence, suggest that the 878 peak in OMC spectra is from a tip tilt. Coherence between HAM6 geophones and DARM at LLO suggests that this acoustic noise is likely to be below the aLIGO floor, though not by a factor of ten.

I have been concerned that acoustic coupling at HAM6 will be a borderline noise source for aLIGO in the 400-500 and 700-1000 Hz bands (here). The ISI transfer function in these bands can approach 1. This was the source of acoustic coupling that remained at the end of eLIGO even after we suspended all of the optics that touched the beam. For this reason I have been watching for the appearance of these features.

I checked the peaks Koji and Dan noted in their recent OMC studies (here, here, and here) by looking at coherence between the HAM6 GS-13s and the DC PD. Figure 1 shows that a good fraction of the peaks are attributable to vibrations on the table in the 450 and 900 Hz bands, although a couple are not.

During the summer, Christina Daniel and I “tap” tested a number of parts of the HAM6 ISI and the ISI payload so that we could later identify peaks in this band. Of all the structures we tested, only TT2 had a resonance at 878 Hz, the frequency of the largest peak in the OMC spectrum (Figure 2). While this is not conclusive, we should probably look first at the TT structures if we need to damp this resonance.  If the 878 Hz resonance indeed comes from a structure that interacts with the light, I would expect 878 to be overrepresented on the light, relative to other motions detected by the GS13s. This would explain why the 878 peak in the OMC spectrum is, relative to surrounding peaks, much larger than in the geophone spectra. For the tap test the situation was similar, the accelerometer was on the tip tilt so tip tilt resonances would be enhanced relative to other table motions detected by the GS13s.

I checked LLO’s DARM to see if there might be coherence between DARM and the geophones in these bands in order to get an idea of whether these peaks will be a problem. Figure 3 shows that I was able to see some coherence, at the 0.002 level, between the HAM6 geophones and DARM (notice that all six geophones show increased coherence at some peaks). So I would guess that the amplitude is roughly 1/20^th of our current noise floor. At 1000 Hz we are currently about a factor of 6 away from our 195 Mpc sensitivity curve. Thus these features may not be a factor of ten below the sensitivity, as we would like, but they are unlikely to be prominent. 

The tidal state code was updated to engage the common feedback path in the Transition state. This needs to be booted into the front-end next Tuesday.

I also cleaned up the gain allocation in the ARM path. Previously, the calibration factor was part of the integrator which made the output values display in units of ~50pm. This calibration factor has been pushed into the ARM_DRIVE filter bank. Meaning, the displayed displacement values are now roughly in µm.

On another topic: The WFS trigger "LEDs" were somewhat misleading upon engaging, because of the long delay. We have 30 sec before the WFSs engage and 60 sec before the boost is engaged. However, the TRIG_MON channel only reports the state before the delay. However, we also have a channel TRIG_DELAYED which reports the state after the delay. The WFS trigger "LEDs" have been updated to show a red state when the trigger is off, a yellow state when the trigger criteria is met and waiting, and a green state when the trigger is actually engaged. This is an medm only change.

model restarts logged for Sat 24/Jan/2015
2015_01_24 01:26 h1fw1
2015_01_24 05:42 h1fw0

both unexpected restarts. Conlog frequently changing channels report attached.

Sheila, Alexa, Elli, Rana, Evan

Summary

Building on this afternoon's work of transitioning control of the X arm from ALS COMM to sqrt(TRX) [LHO#16250], we have been able to recover the handoff of CARM from ALS COMM to sqrt(TRX+TRY).

Next steps are to try to reduce the CARM offset further, transition to RF DARM, transition to the in-vacuum transmon QPDs for CARM, transition to digital REFL9I for CARM, and then reduce the CARM offset all the way to 0 pm.

Details

The transition sequence is largely the same as for the X arm case. I repeat the sequence here, with modifications as appropriate:

• Adjust the ALS COMM VCO so that the TRX and TRY signals are around 1 ct in magnitude.
• Engage the sqrt(TRX) path with a 1 Hz pole and a 40 Hz zero, an offset of −1.0 ct in TR_CARM, and an overall TR_CARM/REFLBIAS/REFLDCBIAS gain of 50 ct/ct. The common-mode board has an input gain of 0 dB (ALS COMM has an input gain of −4 dB). Addtionally, we have the usual filters engaged in TR_CARM/REFLBIAS/REFLDCBIAS:
  • a 1 kHz pole and a pair of complex zeros at 35 Hz (with a Q of 1) which are meant to make sqrt(TRX+TRY) fall off as 1/f out to high frequency
  • a 1.6 Hz pole and a 40 Hz zero which imitates the response of the ALS COMM VCO.
• Turn off the COMM VCO frequency servo. Tune the VCO voltage so that the sqrt(TRX+TRY) output (as monitored via REFLDCBIAS_OUT) is close to zero.
• Engage a 0 Hz pole and 1 Hz zero in the sqrt(TRX+TRY) path, so that sqrt(TRX+TRY) has a true integrator.
• Turn off the ALS COMM PLL boost (pole at 1.6 Hz, zero at 40 Hz).
• Ramp down the analog gain of ALS_COMM on the summing node board to −32 dB. Attempting to switch off the input will blow the lock, so we ramp down the analog gain on the common-mode board by about 20 dB. But both inputs are left on.
• Remove the 1.6 Hz pole and 40 Hz zero engaged earlier, by engaging FM4 in REFLBIAS (it is an anti-boost which undoes the effect of FM3). It is an unnecessary boost which prematurely cuts off the lower edge of the phase bubble of the TR-controlled CARM loop.
• Turn the gain of TR_CARM/REFLBIAS/REFLDCBIAS to 35 ct/ct, so as to place the UGF in the best portion of the phase bubble.

Sheila has put these steps into the Guardian, but they haven't been extensively tested yet.

The attached plots and data give the OLTF of CARM controlled by sqrt(TRX+TRY).

During this afternoon's arm locking to tune the ALS / TRX handover, we measured the out of loop performance using the AS beam PDH detector.

The CARM feedback loop used for this arm locking has a UGF of ~100-200 Hz, so the noise measured in ASAIR_45_I is the sensing noise of the other detector impressed upon the arm length (assuming the sensing noise of the AS 45 detector is negligible at this level).

In the attached plot, you can see that the out of loop noise shows a bunch of acoustic noise when the ALS (BLACK) is used as the sensor. In the RED trace, the low frequency noise is ~10x lower and the high frequency noise is higher, but smooth. Around 20 Hz-rms of the noise comes from the 60 Hz power line in the Thorlabs detector used for TRX and ~15 Hz-rms comes from the sub-Hz sensing noise which is most likely due to angular motion of the suspensions producing RIN in the cavity transmission. Presumably, the 60 Hz peak will go down as we start recycling and increase the power (and switch to the in-vac QPDs), but the low frequency stuff will not get better. To get the TR error signals to be better than 15 Hz-rms, we should figure out which suspension is moving at 0.67 Hz by so much.

Calibration: to turn the ASAIR45 signal into Hz, we looked at the peak-peak signal when scanning through the resonance using ALS. That was 400 counts. With a cavity pole of 42 Hz, this means that the peak-peak discriminant corresponds to 84 Hz. Since we are making this measurement not at the zero crossing, but ~20 Hz detuned from resonance, I assume that the calibration is close to (2*84 Hz)/(400 counts), with a low Q zero pair at ~60 Hz.

At around 3:30 this morning, the ETMX T240s started to drift to some large values.  This morning we were having trouble locking the X arm with green light, and noticed that the REFL CNTRL output was huge, indicating that the cavity length was changing by ~20 um in about 10 seconds.  We looked at the ISI screens, saw that the T240 mons were red.  After interupting Jeff's Saturday morning errands, we decided to try zeroing the T240s by turning on FM6 (labeled AutoZ) in the T240 X filter banks, when we did this the ISI tripped.  It started to Isolate, the outputs of the T240s were still large but not as large as they had been, stage 2 watchdog tripped, then it isolated and the cavity motion is much much less.  

The firt attached screen shot shows the green laser control signal roughly calibrated in um, you can see the abrubt change when we tripped the ISI and the much smaller fluctuations after.  The second screen shot shows a trend of the outputs over the last two days.