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ID Dateup Author Type Category Subject
  1415   Sun Mar 22 22:39:24 2009 ranaSummaryLSCCalibration of the ITM and ETM Actuation
I used the following procedure to calibrate the ITMX actuation signal.

Free Swinging Michelson:
------------------------
- Restore Michelson
- Align Michelson: Minimize AS_DC (PD3_DC_OUT) by tweaking BS alignment.
- Enable Whitening filters for PD1_Q and PD3_DC.
- Run offsets script to get rid of DC and RF offsets.
- Use DTT Triggered Time Series to get time series and measure peak-peak
amplitude of PD1_Q using DTT horizontal cursors. (Templates/Calibration/090322/FreeSwing.xml)

Michelson Sweeps:
-----------------
- Lock Michelson
- Drive ITMX_LSC_EXC using ITMX-MI-Sweep.xml template.
- (Next time remember to turn on a low pass in the MICH loop so that its an open loop measurement below 50 Hz).
- Fit and so some math.

Arm Sweeps for the ETMs:
------------------------
- Lock a single arm
- Sweep ITM & ETM.
- Then sweep MC2 and record drive signal from MC board to the VCO driver.
- Compare and contrast.
  1416   Sun Mar 22 22:47:58 2009 ranaUpdateDMFseisBLRMS compiled but still dying
Looks like seisBLRMS was restarted ~1 AM Friday morning but only lasted for 5 hours. I just restarted it on megatron;
let's see how it does. I'm not optimistic.
  1417   Sun Mar 22 23:16:41 2009 ranaDAQComputer Scripts / Programstpman restart
Could get testpoints but couldn't start excitations. Restarted tpman on daqawg. Works now.

Still no log file. Mad
  1418   Mon Mar 23 15:50:44 2009 ranaConfigurationLSCfilters deleted, lsc rebooted

The LSC time had gone too high. I deleted ~20 filters and rebooted. CPU time came down to 50 usec.

The filters all looked like old trash to me, but its possible they were used.

I didn't delete anything from the DARM, CARM, etc. banks but did from the PD and TM filter banks. You can always go back in time by using the

filter_archive/

  1419   Tue Mar 24 03:05:25 2009 YoichiUpdateLockingLocking tonight
MC1 issue:
The MC1 seems to be drifting still. I found it was off from the SUS drift-mon reference values and restored the alignment using the SUS drift-mon before I went home for dinner.
But when I came back being happy with the Japanese victory over S-Korea at the WBC final, the MC was unhappy again.
I restored the alignment of the MC1 using the SUS drift-mon once again and centered the WFS QPDs.
I will leave the MC unlocked again tonight to see the drift. You are welcome to lock the MC in the morning as I will have corrected enough data by the time people come in.

Computer overloads:
I removed some filters from suspensions to off load susvme computers.
Nonetheless, both susvme1 and susvme2 are still over loaded during the dither alignment. The alignment results are in general ok. So this is not a too serious problem.
But still it would be nice to resolve.

3.8kHz hunting:
I made several measurements of the AO path loop gains (using the SR785) and the transfer functions from the CARM excitation (actuation to the ETMs) to the PO_DC signal as the arm powers are increased.
There is a similar structure as in the AO loop found also in the CARM->PO_DC transfer functions. This implies that the problem is likely to be in the PO_DC sensor not in the MC->VCO actuator. But the MC and the VCO could still be the
cause of the problem because they were in the control loop when the CARM->PO_DC TF were measured.
The peak frequency does not seem to depend on the arm power, but the conclusion is not definite because I was only able to measure the TFs from arm power 5 to 10 (not much difference).
I will make plots and post them later.

To Do for tomorrow:
Tonight the CARM error signal was noisier than the reference spectra (broad band white noise appeared). I should check the beam centering of the SPOB PD.
Also someone should center the oplevs of the mirrors as some of them are off.
Continue to measure the TFs at various power levels.
Try to put another (Thorlabs?) PD at the POB port to get PO_DC from it.
  1420   Tue Mar 24 09:04:02 2009 steveUpdateSUS4.8 mag earthquake

SRM, ITMX, ETMX, ITMY and ETMY lost damping at 4:55am this morning from 4.8 magnitude earthquake.

Their damping were restored.

C1:SUS-ITMX_URSEN_OUTPUT swich was found in off position. It was turned on.

MZehnder  and MC were locked.

The WFS qpd spot needs recentering

  1421   Tue Mar 24 13:10:07 2009 AlbertoConfigurationPSLnew mirror installed on the AP table

New flipping mirror installed on the AP table on the beam path to the REFL199 PD.

If you're missing the double demod signal, please check that it is actually down.

  1422   Tue Mar 24 13:54:49 2009 JenneUpdateSUSOp Levs Centered

ITMX, ITMY, BS, SRM, PRM op levs were all recentered.  ETM's looked okay enough to leave as-is. 

  1423   Tue Mar 24 19:55:24 2009 JenneUpdateLSCNew PO DC

[Rana, Jamie, Jenne]

SPOB DC hasn't been so good lately, so we installed a new PO DC PD on the PO table.  We used a 30% reflecting beam splitter (BS1-1064-30-1025-someotherstuff).  We didn't check with a power meter that it's a 30% BS, but it seems like that's about right.  The beamsplitter is as close as we could get to the shutter immediately in front of the regular POB/SPOB PD's, since that's where the beam gets narrow.   The new picked-off-pickoff beam goes to a Thorlabs 100A PD.  We haven't yet checked for reflected beams off the PD,  but there is a spare razor blade beam dump on the table which can be used for this purpose.  The output of this PD goes to the LSC rack via a BNC cable.  (This BNC cable was appropriated from it's previous "use" connecting a photodiode from the AP table to a bit of air just next to the LSC rack.)  Our new cable is now connected where the old SPOB DC cable used to be, at the input of a crazy Pomona Box tee.

For reference, the new levels of POB DC and SPOB DC, as measured by their BNC DC out connections is ~4mV each.  Since the beamsplitter is 70% transmissive, we used to be getting about 5.7mV on each PD.

The new photodiode puts out about 40mV, but it has an ND1.0 filter on, so if more gain is needed, we can take it off to get more volts.

 

  1424   Tue Mar 24 23:23:05 2009 ranaUpdateLSCNew PO DC
We also found that the SPOB RF cable was going through a splitter before going into the SPOB demod board. The other
input of the splitter was open (not terminated). Using 50m Ohm devices without terminated inputs is illegal. It
makes there be standing waves in the cables and makes the RF phase very dependent on cable lengths. We took away
the splitter and ran the cable straight. So expect some change in the SPOB gain and phase plus some shame.
  1425   Wed Mar 25 01:37:35 2009 rana, yoichiSummaryIOONo Reference Cavity Required
We were wondering if we need to have a reference cavity. One possible reason to have one is to reduce the free running
frequency noise by some level so that the MC can handle it. According to my manifesto,
the free running noise of the laser is (10 kHz / f) Hz/rHz. The mode cleaner loop gain is sufficient to reduce this to
0.001 Hz/rHz everywhere below 1 kHz - radiation pressure noise and coating thermal noise limit the mode cleaner below
these levels.

So, since it seems like the reference cavity is superfluous (except for the 1 - 10 kHz band), we unlocked it and locked the
MC by feeding back directly to the laser.

In the old set up, the low frequency feedback is to MC2 and the high frequency to the VCO which actuates the FSS which
drives the NPRO PZT and the Pockel cell.

In this new way, we take the MC board's output to the VCO (the TNC monitor point) and send that to the TEST IN1 of the FSS
box. The FSS box then splits the drive to go to the PZT and the PC path. We also turned off the 40:4000 filter in the MC
board and inverted the sign of the MC FAST path.
Good settings for acquisition:
MC INPUT GAIN = 6 dB
40:4000        Disable
FAST polarity  MINUS
VCO Gain       -3 dB
MC LIMITER     Disable

FSS TEST1      TEST
FSS CG         -3 dB
FSS FG         13 dB

After our initial locking success, we realized that the new MC-FSS loop is conditionally stable: the old loop relied on
the 40 kHz refcav pole to make it stable. The new loop has a 4 kHz pole and so the phase lag in the MC-PZT path is too
much. We need to build a passive lead filter (40 kHz : 4 kHz) in a Pomona box to compensate.

There are several more issues:

- I think this will make the whole CM servo handoff easier: there is no more handoff.

- This will make the lock acquisition fringe velocity higher by a factor of the arm/mc length (40 m / 13 m) since
the frequency will be slewing around along with MC2 now. However, Jenne's FF system ought to take care of that.

- Having the laser frequency stabilized to the MC during lock acquisition will make all of the error signals quieter
immediately. This can only be good.

- If we can make this work here, it should translate to the sites directly since they have exactly the same electronics.
  1426   Wed Mar 25 04:18:28 2009 YoichiUpdateLockingTuesday Locking
After the new PO_DC PD was installed, I tweaked several gains to make the locking scripts work right.
First of all, I increased the gain of PD12 (PD12_I is SPOB) by a factor of 1.4 to compensate for the power decrease
by the insertion of the BS. SPOB is used by the PRM alignment script. I was too lazy to modify the scripts.

Then I optimized the SRC DD signal which is taken from the POB.

I also had to do some gain adjustments for the CARM loop.

The attachment (AO path open loop TF) shows a depressing fact that the 3.8kHz peak is still there with the new PO_DC PD. So it was not a problem of the SPOB PD.
Next, I will check the cross over frequencies of the PZT and PC paths in the FSS and the VCO/MCL cross over.
  1427   Wed Mar 25 09:55:45 2009 steveUpdateIOOglitching sensors of MC

SUS-MC1_SENSOR_SIDE and SUS-MC2_SENSOR_UL are glitching

Yesterday's 4.8mag earthquake at Salton Sea is shown on Channel 1

  1428   Wed Mar 25 17:22:58 2009 YoichiUpdateIOOMC lock without FSS
I made 40k:4k passive filter in a POMONA box and connected it to IN1 (not TEST IN1) of the FSS box.
With this modification and cut-and-tries with the gain sliders, I was able to lock the MC with 80kHz bandwidth by feeding back directory to the laser frequency.
The attached figure shows the open loop transfer function.
The phase margin is thin at 80kHz. Because of this, I could not turn on the MC super boost filters.
But I believe that we can increase the gain further by modifying the filter shape.

I used the following settings:
[MC Board]
C1:IOO-MC_REFL_GAIN 14
C1:IOO-MC_REFL_OFFSET -4.2381
C1:IOO-MC_BOOST1 0   (You can turn it on if you want, but turn it off for locking)
C1:IOO-MC_BOOST2 0
C1:IOO-MC_POL 1   (Minus)
C1:IOO-MC_VCO_GAIN 4
C1:IOO-MC_LIMITER 1 (Disable)

[FSS box]
C1:PSL-FSS_SW1 0 (Test1 ON)
C1:PSL-FSS_INOFFSET 0.1467
C1:PSL-FSS_MGAIN 30
C1:PSL-FSS_FASTGAIN 14 (Do not increase it, at least while locking. Otherwise the phase lag from the PZT loop gets significant and the MC loop will be conditionally stable).
I also turned down the FSS slow servo's RC transmission threshold to zero so that the slow servo works even without the RC locked.
  1429   Wed Mar 25 20:41:43 2009 JenneUpdateIOOMode Cleaner Servo Board Transfer Functions (to be updated)

When all things fail (netgpibdata.py is giving me weird data.  When I plot the data it has saved from the 4395A, it's some wierd other universe's version of my transfer function.  I don't really know what's up.  I'm pretty sure I'm getting the 'correct' data, since each TF looks vaguely like it should, but with some crazy humps.  I'll talk to Yoichi in the morning about it maybe.) (also, we're low on emergeny floppy discs), you can always take a picture of the Agilent 4395's screen, as shown below.

* Mode cleaner and PMC are both relocked after my shenanigans, and I'll try again in the morning (I assume locking is going on tonight) to get real TF's with real data, as opposed to the photo method.

Note to self:  post the data of the TFs in the elog along with the plots, for posterity.

 

These TFs are of the Mode Cleaner servo board, exciting IN1 (or the 3.7MHz notch pomona box which is connected to IN1), and measuring at the SERVO out of the board.

One with the box, one without the box, and one of just the box for good measure.

  1430   Thu Mar 26 00:45:24 2009 JenneUpdateIOOMode Cleaner Servo Board Transfer Functions (to be updated)

Quote:

netgpibdata.py is giving me weird data.  When I plot the data it has saved from the 4395A, it's some wierd other universe's version of my transfer function.  I don't really know what's up. 

 Yoichi, in all his infinite wisdom, reminded me that the netgpibdata script saves the data as the REAL and IMAGINARY parts, not the Mag and Phase.  Brilliant.   Using that nugget of information, here are the TFs that I measured earlier:

The last attachment is the .dat and .par files which contain the data and measurement parameters for the 3 TFs in the plots.

  1431   Thu Mar 26 04:01:24 2009 YoichiUpdatePSLFSS Open Loop Gain
Yoichi, Peter, Jenne

Attached is the open loop transfer function of the FSS as of today with the common gain = 12dB and the fast gain = 16dB.
The UGF is only 250kHz. If we increase the common gain, the PC goes crazy. Exactly the same symptom as before I fixed the oscillating op-amp.

I wanted to check the cross over frequency but there is no excitation point in the fast path nor PC path. Therefore, it is not easy.
  1432   Thu Mar 26 04:09:38 2009 YoichiUpdateIOOSingle X arm lock spectra with different MC lock schemes
The attached plots show MC_F, FSS_FAST_F and XARM IN/OUT spectra with different MC locking modes.
The conventional locking means the FSS is used. The direct frequency lock is the new way.
You can see that at low frequencies, the frequency actuator is working hard to suppress the MC pendulum motions.
The X-arm also sees a lot of frequency noise at low frequencies because of this.
The transmitted power of the X-arm fluctuates a lot making it difficult to align the mirrors.

The zoomed plots show that the structures in the kHz band are also present in the case of the direct frequency lock, although the frequencies are somewhat different.
  1433   Thu Mar 26 04:27:26 2009 YoichiUpdateLocking3.8kHz peak as a function of the arm power
During the power ramp-up, I actuated CARM using ETMs and measured the transfer functions to the PO_DC at several arm powers.
The peak grows rapidly with the power. It also seems like the frequency shifts slightly as the power goes up, but not much.

Some sort of an RSE peak ? An offset in the PRC lock point ?
  1434   Thu Mar 26 09:08:18 2009 KakeruUpdateoplevsarm cavity oplev calibration
I uploaded a document about my oplev calibration.
/cvs/cds/caltech/users/kakeru/oplev_calibration/oplev.pdf

At same place I put my matlab codes for calibration.
/cvs/cds/caltech/users/kakeru/oplev_calibration/oplev_calibration.m
  1435   Fri Mar 27 02:40:06 2009 peteSummaryIOOMC glitch investigation

Yoichi, Pete

The MC loses lock due to glitches in the MC1 coils. 
We do not know which coil for sure, and we do not know if it is a problem going into the board, or a problem on the board. 
We suspect either the UL or LR coil bias circuits (Pete would bet on UL).  If you look at the bottom 4 plots in the attached file, you can see a relatively large 3 minute dip in the UL OSEM output, with a corresponding bump in the LR (and smaller dips in the other diagonal).  
These bumps do not show up in the VMONS which is why we are suspicious of the bias.
To test we are monitoring 4 points in test channels, for UL and UR, both going into the bias driver circuit, and coming out of the current buffer before going into the coils. 
 

We ran cable from the suspension rack to the IOO rack to record the signals with DAQ channels.

The test channels:

UL coil      C1:IOO-MC_DRUM1  (Caryn was using, we will replace when we are done)

UL input   C1:IOO-MC_TMP1 (Caryn was using, we will replace when we are done)

LR coil      C1:PEM-OSA_SPTEMP

LR input   C1:PEM-OSA_APTEMP

We will leave these overnight; we intend to remove them tomorrow or Monday.

We closed the PSL shutter and killed the MC autolocker.

  1436   Fri Mar 27 02:50:54 2009 YoichiUpdateLockingDD demodulation phase suspicious
I noticed that the gain of PD6_Q (before the phase rotation) was 0 whereas PD6_I gain was 15.
This means the demodulation phase of the PD6 had no meaning other than changing the gain.
According to the conlog, it has been zero since March 2nd. I don't know how it happened.

While I was re-adjusting the DD phase, the MC started to unlock frequently (every 10 minutes or so).
MC1 is again drifting a lot (it is getting step-function like alignment changes intermittently).
This practically made it impossible to work on locking. So I decided to fix the MC first.
See Peter's elog entry for the MC work.
  1437   Fri Mar 27 15:05:42 2009 YoichiUpdateIOOMC glitch investigation
Attached plots are the result of the MC1 trend measurement.
See the attachment #1. The first two plots show the drift of the MC1 alignment as seen by the OSEMs. It is terrible. Other MC mirrors also drifted but the scale is smaller than the MC1.
From the VMon channels, you can see that the control voltages were quiet.
 
The monitor channels we added were:
 
MC_TMP1 = UL coil bias. Input to the coil driver board.
MC_DRUM1 = UL coil bias. Output of the current buffer.
OSA_APTEMP = LR coil bias. Input to the coil driver board.
OSA_SPTEMP = LR coil bias. Output of the current buffer.
 
The bias voltages show no drift except for a glitch around 7AM. This glitch did not show up in the SPTEMP channel (LR coil bias output). This was because the probe was connected to the coil side of the output resistor by mistake.
 
The second attachment shows a zoomed plot of MC1 OSEM signals along with the bias monitor channels (signals were appropriately scaled so that they all fit in +/-1).
There is no correlation between the OSEM signals and the bias voltages.
 
Since we were only monitoring UL and LR coils, I changed the monitor points as follows.
 
MC_TMP1 = LL coil bias. Output of the current buffer.
MC_DRUM1 = UL coil bias. Output of the current buffer.
OSA_APTEMP = UR coil bias. Output of the current buffer.
OSA_SPTEMP = LR coil bias. Output of the current buffer.
 
I will leave the MC unlocked for a while.

Quote:

Yoichi, Pete

The MC loses lock due to glitches in the MC1 coils. 
We do not know which coil for sure, and we do not know if it is a problem going into the board, or a problem on the board. 
We suspect either the UL or LR coil bias circuits (Pete would bet on UL).  If you look at the bottom 4 plots in the attached file, you can see a relatively large 3 minute dip in the UL OSEM output, with a corresponding bump in the LR (and smaller dips in the other diagonal).  
These bumps do not show up in the VMONS which is why we are suspicious of the bias.
To test we are monitoring 4 points in test channels, for UL and UR, both going into the bias driver circuit, and coming out of the current buffer before going into the coils. 
 

We ran cable from the suspension rack to the IOO rack to record the signals with DAQ channels.

The test channels:

UL coil      C1:IOO-MC_DRUM1  (Caryn was using, we will replace when we are done)

UL input   C1:IOO-MC_TMP1 (Caryn was using, we will replace when we are done)

LR coil      C1:PEM-OSA_SPTEMP

LR input   C1:PEM-OSA_APTEMP

We will leave these overnight; we intend to remove them tomorrow or Monday.

We closed the PSL shutter and killed the MC autolocker.

 

  1438   Fri Mar 27 17:52:16 2009 YoichiUpdateIOOMC glitch investigation
Per Rob's suggestion, I put the probes across the output resistors of the bias current buffers instead of measuring the output voltage with respect to the ground.
This way, we can measure the current flowing the resistor. The change was made around 17:30.

Quote:
Attached plots are the result of the MC1 trend measurement.
See the attachment #1. The first two plots show the drift of the MC1 alignment as seen by the OSEMs. It is terrible. Other MC mirrors also drifted but the scale is smaller than the MC1.
From the VMon channels, you can see that the control voltages were quiet.
 
The monitor channels we added were:
 
MC_TMP1 = UL coil bias. Input to the coil driver board.
MC_DRUM1 = UL coil bias. Output of the current buffer.
OSA_APTEMP = LR coil bias. Input to the coil driver board.
OSA_SPTEMP = LR coil bias. Output of the current buffer.
 
The bias voltages show no drift except for a glitch around 7AM. This glitch did not show up in the SPTEMP channel (LR coil bias output). This was because the probe was connected to the coil side of the output resistor by mistake.
 
The second attachment shows a zoomed plot of MC1 OSEM signals along with the bias monitor channels (signals were appropriately scaled so that they all fit in +/-1).
There is no correlation between the OSEM signals and the bias voltages.
 
Since we were only monitoring UL and LR coils, I changed the monitor points as follows.
 
MC_TMP1 = LL coil bias. Output of the current buffer.
MC_DRUM1 = UL coil bias. Output of the current buffer.
OSA_APTEMP = UR coil bias. Output of the current buffer.
OSA_SPTEMP = LR coil bias. Output of the current buffer.
 
I will leave the MC unlocked for a while.

 

 

 

  1439   Sun Mar 29 13:44:27 2009 steveUpdateSUSETMY sus damping restored

ETMY sus damping was found to be tripped.

It was retored.

All fluorecent light were turned off. Please try to conserve some energy.

  1440   Sun Mar 29 17:54:41 2009 YoichiUpdateSUSMC1 drift investigation continued
The attached plots show the trend of the MC OSEM signals along with the voltages across the output resistors of the bias current buffers.
The channel assignments are:
MC_TMP1 = LL coil
MC_DRUM1 = UL coil
OSA_APTEMP = UR coil
OSA_SPTEMP = LR coil

Although the amplitude of the drift of MC1 is much larger than that of MC2 and MC3, the shape of the drift looks like a daily cycle (temperature ?).
This time, I reduced the MC1 bias currents to avoid saturation of the ADCs for the channels measuring the voltages across the output resistors.
This may be the reason the MC1 has been non-glitchy for the last day.

OSA_APTEMP (UR Coil) shows a step function like behavior, although it did not show up in the OSEM signals.
This, of course, should not happen.

Today, I went to the MC1 satellite box and found that the 64-pin IDE like connector was broken.
The connector is supposed to sandwich the ribbon cable, but the top piece was loose.
The connector is on the cable connecting the satellite box and the SUS rack.
I replaced the broken connector with a new one. I also swapped the MC1 and MC3 satellite boxes to see if the glitches show up in the MC3.

I restored the bias currents of the MC1 to the original values.

The probes to monitor the voltages across the output resistors are still there. For OSA_SPTEMP, which was saturating the ADC, I put a voltage divider before the ADC. Other channels were very close to saturation but still within the ADC range.

Please leave the MC unlocked at least until the Monday morning.
Also please do not touch the Pomona box hanging in front of the IOO rack. It is the voltage divider. The case is connected to the coil side of the output resistor. If you touch it, the MC1 bias current will change.

  1441   Mon Mar 30 09:07:22 2009 ranaUpdateSUSMC1 drift investigation continued
Maybe we can temporarily just disconnect the bias and just use the SUS sliders for bias if there's enough range?
  1442   Mon Mar 30 12:29:17 2009 YoichiConfiguration MC1 glitches not seen during the weekend
The attached is the MC trend for the past 12 hours.
There is no MC1 glitches in the OSEM signals. Moreover, the total amplitude of the drift is smaller than it used to be (now the amplitude is less than 100 but it used to be a few hundreds).
There still is a small step in the OSEM signals at around 6AM this morning, but the amount of the jump is very insignificant.
The cause of the glitch in the TMP1, DRUM1 and APTEMP (LL, UL and UR coils respectively) at 7AM is not known.
Since the MC1 has been behaving OK during the weekend, I removed the probes from the MC1 coil driver board and locked the MC.
Hopefully the replacement of the broken connector fixed the problem, but I'm not sure.
  1443   Mon Mar 30 12:46:36 2009 YoichiConfigurationIOOIOO QPDs were missing the beam
When I re-locked the MC, I wanted to check the trend of the IOO QPDs to see if the input beam pointing has changed.
Then I found that the QPDs were not receiving light.
The attached trend plots show that the QPDs missed the beam on March 23rd.
The IOO-QPD_ANG was installed on Mar 11th by Kiwamu and Kakeru. Since then, they were serving as a reference of the PSL beam pointing.
But there is no record of the past week. This is very bad because then I cannot tell if I should relieve the MC WFS to make the mirrors follow the input beam or not.
I found that someone has moved the beam splitter which picks up the beam going to those QPDs. But there is no elog entry on this around March 23rd.
I re-centered the beam on the QPDs.

Since the X-arm locked to TEM00 with the MC WFS on (i.e. the MC beam axis is following the input beam axis), I guessed that the input beam has not drifted that much. So I relieved the WFS and centered the WFS QPDs.
  1444   Mon Mar 30 13:29:40 2009 YoichiUpdateSUSMC1 drift investigation continued

Quote:
Maybe we can temporarily just disconnect the bias and just use the SUS sliders for bias if there's enough range?


We could do this, but I'm suspicious of the cables between the coil driver and the coils (including the satellite box). In this case, disabling the bias won't help.
Since the MC1 has been quiet recently, I will just lock the MC and resume the locking.
  1445   Mon Mar 30 15:51:27 2009 steveUpdateElectronicsHP4291A left the lab to be repaired

Eric Gustafson is handling the old HP4291A rehabilitation. Tarac picked both units up today.

March of 2008 Tucker Electronics failed to fix it's intermittent ~25MHz 0.5V oscillation at the swept sine output

See 40m-elog id:398 on 3-24-2008 by Rob Ward

 

  1446   Mon Mar 30 17:02:46 2009 YoichiConfigurationGeneralAP OSA aligned
I aligned the AP OSA, which had been mis-aligned for a while.
  1447   Tue Mar 31 09:42:32 2009 steveUpdatePEMETMY sus damping restored again

The Caltech gasoline storage tank is being upgraded.

They are jack hammering and digging with bulldozer 50 yards south of  ETMY

  1448   Wed Apr 1 10:22:13 2009 steveUpdateVACRGA logging is working

Thanks to Joe B who made the SRS RGA working with linux

Last data file logged at 2008 Oct 24 with old Dycor unit

First data file logged at  2009 Feb 10 with SRS

 

  1449   Wed Apr 1 15:47:48 2009 YoichiUpdateLocking3.8kHz peak looks like a real optical response of the interferometer
Yoichi, Peter

To see where the 3.8kHz peak comes from, we locked the interferometer with the CARM fed back only to ETM and increased the arm power to 4.
The CARM error signal was taken from the transmission DC (not PO_DC).
The attached plots show the CARM transfer functions taken in this state (called ETM lock in the legends) compared with the ones taken when the CARM is locked by the feedback to the laser frequency (called "Frequency lock").
The first attachment is the TFs from the CARM excitation (i.e. the ETMs were actuated) to the TR_DC and PO_DC signals.

The second attachment is the AO path loop TFs. This is basically the TF from the frequency actuator to the PO_DC error signal.
I injected a signal into the B-excitation channel of the common mode board (with SR785) and measured the TF from TP2B to TP2A of the board.
For the ETM lock case, the AO loop was not closed because I disabled the switch between TP2A and TP1B.

The observation here is that even with no feedback to the laser frequency, the 3.8kHz peak is still present.
This strongly suggests that the peak is a real optical response of the interferometer.

To realize the ETM lock with arm_power=4, I had to tweak the CM loop shape.
I wrote a script to do this (/cvs/cds/caltech/scripts/CM/ETM_CARM_PowerUp).
You can run this script after drstep_bang has finished.
  1450   Wed Apr 1 16:14:36 2009 YoichiUpdateLocking3.8kHz peak does not change with SRC offset
Yoichi, Peter

We suspected that maybe the 3.8kHz peak is the DARM RSE somehow coupled to the CARM.
So we added an offset to the SRC error signal to see if the peak moves by changing the offset.
It didn't (at least by changing the SRC offset by +/-1000).
(I had a nice plot showing this, but dtt corrupted the data when I saved it. So no plot attached.)

I also played with the PRC, DARM offsets which did not have any effect on the peak.
The only thing, I could find so far, having some effect on the peak is the arm power. As the arm power is increased, the peak height goes up and the frequency shifts slightly towards lower frequencies.
  1451   Wed Apr 1 23:18:07 2009 rana, kojiSummaryIOONo Reference Cavity Required
Koji sent us a note about our "No Reference Cavity Required" entry. I thought that it nicely summarizes the
whole shebang and so I post it here for its pedagogical value.

Generally, frequency stabilization is a comparison of the two
frequency references.

1. In the conventional case you are comparing the NPRO stability with
the RC stability. The NPRO cavity is short and probably placed in a
less stable environment than that of the RC. Therefore, the PDH
signal only feels the frequency fluctuation of the NPRO, resulting
in the laser PZT fast feedback dominated by the NPRO stability. As
the MC length at low frequency is controlled by the mass feedback,
the resulting laser stability through the MC is virtually limited
by the RC stability.

2. On the other hand, you are comparing the stabilities of the NPRO
crystal and the MC cavity in the direct control configuration. The
stability of the MC at high frequency is better than that of the
NPRO. It is opposite at low frequency, of course, because of the
pendulum motion. The resulting laser stability through the MC is
limited by the MC stability.

3. In the CM servo, the length of the MC is stabilized such that the
arm stability is duplicated to the MC. As a result, your MC servo
compares the stability between the NPRO and the arm cavity. Again
at around 1Hz, the arm cavity is noisier than the NPRO. (This is
true at least TAMA case. I am quite unsure about it in the LIGO
long arm cases.)

One useful consequence is that in those configurations, the laser PZT
feedback at around 1Hz represents the stability of the NPRO, the MC,
and (possibly) the arm cavity, respectively. It was clearly seen
Yoichi's e-log entry 1432. At TAMA we call this signal as "MCPZTfb"
and use this for the diagnostic purposes of the suspended cavities. As
the laser fast PZT is rarely replaced and considered as a stable
actuator, this signal is considered as a good reference at low
frequency which is consistent across various configurations
(e.g. before/after replacement of the suspensions etc). Once the
response and the coefficient are calibrated you can easily convert
this signal to the length displacement.

Another remark: In the direct configuration, the frequency stability
of the beam goes through the MC is determined by the MC stablity. It
means that the beam to the arm has essentially worse stability than
the arm stability by factor of L_arm/L_MC. In the 40m case this factor
is just 3 or so. This is ok. However, for the LIGO 4km arm, the factor
becomes something like 300. This means that if you have 1um_rms of the
MC length fluctuation, the arm PDH feels 300um_rms. (Maybe some extent
less because of the common mode rejection of the MC suspensions.)

Yes, the actuator to the MC length is very strong this time, and
should be able to stop this amount of fluctuation easily... if the
things are all linear. I am not certain whether you can acquire the
lock even by this strong actuator when the arm is crazily swinging,
the PDH signals are ringing all the way, etc, etc...Particularly in
the recycling case!

One possible remedy is a technique developed by the German
necromancers, as always. They used the NPRO cavity as a reference
cavity. They actuate the MC length at low frequency. But I don't know
the exact configuration and how they accomplished the CM hand-off. We
have to ask Hartmut.

The other possibility is your adaptive stabilization of the MC by the
FIR technique. So far I don't know how much stability you can improve
in the LIGO 4km case.

There would be many possibilities like feedforward injection from the
green arm locking signal to the MC length, etc, etc.
  1452   Fri Apr 3 10:01:50 2009 steveUpdateVACrgascan with temp plot

Rga scan of day 231 since pumpdown pd66-m-d231

m stands for maglev pumping speed, vacuum normal condition of valves,

cc4 cold cathode gauge at the rga location,

cc1 is real ifo pressure from the 24" tube at the pumpspool,

PEM-count temp: vac envelope temp at the top of IOO chamber

 

 

  1453   Fri Apr 3 14:52:38 2009 JenneOmnistructurePEMGuralp is finally back!

After many, many "it'll be there in 2 weeks" from the Guralp people, our seismometer is finally back!

I have it plugged into the Guralp breakout box's Channel 1xyz (so I have unplugged the other Guralp).  Both of the Guralp's are currently sitting under the MC1/MC3 chamber.

Before we can have both Guralps up and running, I need to stuff the next 3 channels of the breakout box (back in the fall, I only had Caryn do 1x, 1y, 1z, and now I need 2x, 2y and 2z done with the fancy low-noise resistors), so all the gains match between the 2 sets of channels.

I'm leaving the new Guralp plugged in so we can see how it behaves for the next couple days, until I take out the breakout box for stuffing.

  1454   Fri Apr 3 17:20:05 2009 YoichiUpdateLockingThe 3.8kHz peak seems like the DARM RSE (not 100% sure though)
Yoichi, Kentaro,

Last night, we took several measurements of the AO path loop TFs with various offsets/demod. phases tweaked.
The first attachment shows the AO path loop TF as a function of the offset (in counts) added to the DARM error signal.
Though it is a bit crowded plot, you can see a general tendency that the peak becomes lower in height and higher in frequency as
the DARM offset goes from negative to positive. Since the peak height also depends on the arm power and it fluctuates during the measurements,
the change is not monotonic function of the offset though.

Being suspicious of the demodulation phase of the DARM error signal (AS166), we scanned it (see the second attachement).
But there is no significant change.
Note that the phase of the TF is 180 degrees different from the first attachment. This is because I changed the measurement point of the returning signal
on the CM board from TP2A to OUT2 to see POX_1I signal as well. These points should give the same signal for PO_DC except for the sign.

We also took the AO path TFs by changing the MICH offset (the third attachment). Again, there is no big change.

With the CARM locked with the PO_DC signal, we took the transfer function from the AO path actuation signal to the response of the POX_1I (4th attachment).
There is a huge 3.8kHz peak.

Finally, we measured the DARM response by exciting the ETMs differentially (the PDF attachment).
The shape of the 3.8kHz resonance looks like the DARM RSE peak.

It is speculated that somehow the DARM RSE resonance is coupled into the CARM loop. Don't know how though.
I'm now working on an Optickle simulation to get an insight into this issue.
  1455   Mon Apr 6 19:09:15 2009 JenneUpdatePEMOld Guralp is hooked back up to the ADC

Old Guralp is hooked back up, the new one is sitting next to it, disconnected for now.

  1456   Mon Apr 6 21:50:43 2009 ranaUpdateLSCArm Locking via pushing MC2
Inspired by our 'No Refcav' scheme here, I was inspired to re-explore the idea of locking the
CARM DOF using only feedback to the MC/laser. Last week I got this to work on the single arm and
full IFO at Livingston.
I also estimate the MC noise there.

Today I found the settings to allow X-arm locking here without any feedback to the ETM or ITM:

- Set the LSC Output Matrix to feed the XARM signal to MC2.
- Turn OFF the input of the LSC-ETMX filter bank (this does not disable tickling).
- Turn OFF FM7 (0.1:10) in MC2-MCL.
- Turn ON MC2-LSC with a gain of 0.2 and FM3 FM4 FM5.

That's enough to lock the arm - its pretty stable. This also assumes that the LSC-MC2 bank has its nominal gain of -0.178.

To determine the gain of +0.2 in the MC2-LSC filter bank, I measured the TF from MC2->PD3_I and from ETMX->PD3_I. I adjusted
the gain to be equal at 150 Hz for acquisition and the sign to be opposite to account for the (-) in LSC-MC2. The TF is
attached.

After locking, I type a zero into the MC2-MCL filter bank and that shuts off the feedback from the MC servo to MC2. This is
now topologically similar to the standard CM servo configuration.

The second attachment has the trends of this locking. You can see that the MC_F goes off into the weeds, but the MCL signal
does not so much. I think maybe the MC length is drifting a lot - not the arm.

The third attachment shows the spectra.
  1457   Tue Apr 7 21:39:57 2009 YoichiConfigurationComputersLSC code recompiled with a fix for denormalization problem
This is not my work but I will put it for the record.

A few days ago, Rob recompiled the LSC code with the fix of the denormalization problem provided by Alex.
Since then, the LSC code has been working fine. I recognize that c1lsc is now less loaded.

I believe Rob only recompiled the LSC code, so there could still be the problem in the suspension controllers.
  1458   Wed Apr 8 02:47:42 2009 YoichiUpdateLockingLocking status
This is a summary of activities in the last few nights, although there is not much progress.

The attachment 1 and 2 show the CARM and DARM responses around 3.8kHz at different arm power levels.
The CARM error signal was PO_DC and the DARM error signal was AS2Q.
The excitations were both applied to the ETMs (I temporarily modified the output matrix so that the unsed XARM filter bank can be used to excite CARM and DARM).
DARM and CARM show very similar behavior as the power goes up.

The third attachment shows transfer functions to various signals from CARM and DARM excitations (ETMs).
Though the plot contains many curves, look at PO_DC curves (green and black).
PO_DC is used as CARM error signal but it has a larger response to DARM than CARM (by 10dB or so).
This is not good.

Although the 3.8kHz problem still exists, tonight I was able to go up to arm power = 80 a couple of times, where we are ready to hand off from PO_DC to the RF CARM signal. The hand off failed. I'm now optimizing the hand off gain, but it is difficult because the interferometer is unstable at this power level.
  1459   Wed Apr 8 09:36:20 2009 steveConfigurationVAC valve condition changed to BG to calibrate the RGA

Vacuum normal valve condition was changed to accommodate SRS-RGA calibration.

 

The annulus valves were closed to free TP3 to pump on the RGA
VM1 was closed to isolate the RGA from the IFO.
 
 
VM3 opened to TP3.
 
This condition is called back ground (BG) mode. It is where we can calibrate and see the RGA background without the IFO.
  1460   Wed Apr 8 18:18:33 2009 ranaConfigurationComputersLSC code recompiled with a fix for denormalization problem
Below is the link to the anti-denormalization technique that Rolf and Alex implemented at the sites,
that was pointed out by Chris Wipf from MIT:

http://www.musicdsp.org/files/denormal.pdf
  1461   Wed Apr 8 18:46:50 2009 ranaConfigurationGeneralDMF, SVN, x2mc, and matlab

While waiting for the installation of the 32-bit Matlab 2009a to finish, I tried updating our seisBLRMS.m code.

Although DMF is in SVN, we forgot to check it out and so the directory where we have been doing our mods is not a working copy and our changes have not been captured: Shame.

We will probably have to wipe out the existing SVN trunk of DMF and re-import the directory after checking with Yoichi for SVN compliance.

Also wrote a script: LSC/x2mc, which will transition from regular ETM based X Arm locking to the MC2 based locking. It ran once OK, but I get a segfault on the 'trianglewave' which was trying to run the 'ezcastep' perl script which was calling 'ezcastep.bin'.

I also restarted the seisBLRMS.m on a terminal on Mafalda in the new Matlab 2009a to see if it loses its NDS connection like it did with 2007a. I also reduced the 'delay' parameter to 4 minutes and the 'interval' to 1 minute. This should be so that the total delay is now 5 minutes between seismic noise and seismic trend.

  1462   Thu Apr 9 11:27:19 2009 steveUpdateVACvac gauge reading problem

Cold cathode gauge CC4  is reading normal.

CC1 is glitching, it is probably dirty.

CC2 is fluctuating too much and it is cutting out for 6-7 minutes. It must be insulated by deposits and there is no emission current.

I think the same goes for P1

They will have to be replaced at the next vent

  1463   Thu Apr 9 12:23:49 2009 peteUpdateLockingtuning ETM common mode

Pete, Yoichi

Last night, we put the IFO in FP Michelson configuration.  We took transfer functions of CARM and DARM, first using CM excitations directly on the ETMs, and then using modulations of the laser frequency via MC excitation.  We found that there was basically no coupling into DARM using the MC excitation, but that there was coherence in DARM using the ETM excitation.  Therefore, I tuned the ETM common mode in the output matrix.  I did this by taking transfer functions of PD1_Q with PD2_I (see attached plot).  I changed the  drdown_bang script to set C1:LSC-BTMTRX_14 0.98 and C1:LSC-BTMTRX_24 1.02.

  1464   Thu Apr 9 20:56:12 2009 YoichiHowToGeneralRestore the alignment. Write elog entries.
I often find that the mirrors are left mis-aligned (like in X-arm mode) when I come in for the locking, including tonight.
As Rob stated repeatedly in the past elog, leaving the mirrors mis-aligned for a long time without a reason is an abomination.
It will cause a slow drift of the mirrors and the lock acquisition work is severely slowed down as I have to run the alignment script many times.

I also found that the GPIB-Ethernet box (named teofila) was taken away from the SR785 hooked up to the CM board.
I found it connected to Alberto's setup. Instead, another GPIB box was left on the SR785 but not connected.
I couldn't find any elog entry about this.
This is totally unacceptable.
The SR785 has been used as a very important tool for monitoring the AO path loop gain during the power up.
You can use it if you need, but you have to note it in elog.

The other GPIB box left on the SR785 had a wrong name labeled on it. It had a name "ERMINIA", but the IP address written next to the name was actually assigned to "crocetta" in the DNS server on linux1. I don't know who made the label. I put a new and correct label on it.
Now I'm using crocetta for the SR785 so Alberto can keep using teofila.

Anyway, I think recently people are lazy about elog.
Whatever work you did, please put it in the elog even if you think it is trivial.
I also would like to see more detailed elog entries from people. Many of the recent elog entries are too simple or superficial that it is hard for other people to figure out what was really done.
ELOG V3.1.3-