After last night's challenge (or inspiration), we levitated our magnet this morning.  Since the nice Olympus camera is not currently in the 40m, we had to use my less stellar camera, but despite the poor video quality you can still see the magnet returning to its stable equilibrium position.  Once we recover the better camera, we will post new videos.  Also, we haven't yet figured out how to put videos in line in the elog entry, so here are the youtube links:

levitation 1

levitation 2

We adjusted the gain on coil 1 so that the resistance from the pots was 57.1k (maximum gain of 101.2,).

currents from power supply, pre-levitation: 0.08 A and 0.34 A

post levitation: 0.08 A and 0.11 A

note: we're not sure why changing the gain on coil 3 changes the current through the power supply, so we'd like to investigate that next.

Suresh, Kiwamu and Steve

Heavy chamber doors replaced by light ones at  ITMX-west and ITMY-north locations.

I made a test installation of ligo_viewer in /users/volodya/ligo_viewer-0.5.0c . It runs on pianosa (the Ubuntu machine) and needs Tcl/Tk 8.5.

To try it out run the following command on pianosa:

cd /users/volodya/ligo_viewer-0.5.0c/

./ligo_viewer.no_install

Press "CONNECT" to connect to the NDS server and explore. There are slides describing ligo_viewer at http://volodya-project.sourceforge.net/Ligo_viewer.pdf

Installation notes:

Use /users/volodya/ligo_viewer-0.5.0c.tgz or later version - it has been updated to work with 64 bit machines.

Make sure Tcl and Tk development packages are installed. You can find required packages by running

apt-file search tclConfig.sh

apt-file search tkConfig.sh

If apt-file returns empty output run apt-file update

Unpack ligo_viewer-0.5.0c.tgz, change into the created directory.

Run the following command to configure:

export CFLAGS=-I/usr/include/tcl8.5
./configure --with-tcl=/usr/lib/tcl8.5/ --with-tk=/usr/lib/tk8.5/

This works on Ubuntu machines. --with-tcl and --with-tk should point to the directories containing tclConfig.sh and tkConfig.sh correspondingly.

Run "make".

You can test the compilation with ./ligo_viewer.no_install

If everything works install with make install

If Tcl/Tk 8.5 is unavailable it should work with Tcl/Tk 8.3 or 8.4

(Suresh, Yuta)

Summary:
  We need MC to be locked and aligned well to align other in-vac optics.
  We continued to align the incident beam so that the beam passes the actuation nodes of MC1 and MC3.
  From the previous measurement, we found that beam height at IM1 has to be increased by ~3cm.
  Today, we increased it by ~1cm and achieved about 1/3 of the required correction.
  But we cannot proceed doing this because the beam is hitting IM1 at the edge already.

What is the goal of this alignment?:
  If the beam doesn't hit MC optics in the center, we see angle to length coupling, which is not good for the whole interferometer.
 
  Also, if the beam is tilted so much, transmitted beam though MC3 cannot go into FI at right after MC3.
  Say, FI has an aparture of 3mm and MC3-FT distance is 300mm. The beam tilt should be smaller than 3/300 rad. MC1-MC3 distance is 200mm, so the displacement at each mirror should be smaller than ~1mm.
  1mm is about 7% (see Koji's elog #2863) TO_COIL gain imbalance in A2L measurement.
 
  We are currently assuming that each coils are identical. If they have 5% variance, it is meaningless to try to reduce the beam displacement less than ~5%.

  So, we set the goal to 7%.

What we did:
  1. Leveled the MC table.

  2. Measured the table height using DISTO D3 laser gauge.
    PSL table 0.83m (+-0.01m)
    OMC table 0.82m
    MC table  0.81m

  3. Using the last steering mirror(SM@PSL) and IM1, tilted the beam vertically

Result:


  At t=0 (this morning), the beam tilt was ~40%/(MC1-MC3 distance). Now, it is ~30%/(MC1-MC3 distance).
  30%/(MC1-MC3 distance) is ~5/200 rad.

Plan:
 We have to somehow come up with the next story. Too much vertical tilt. What is wrong? Table leveling seems OK.
 - measure in-vac beam height
 - maybe OSEMs are badly aligned. we have to check that.

It didn't make sense in several points.

1. Is the Faraday aperture really 3mm? The beam has the gaussian radius of ~1.5mm. How can it be possible to go through the 3mm aperture?

2. Why the MC3-FT distance is the matter? We have the steering mirror after MC3. So we can hit the center of the Faraday.
But if we have VERTICAL TILT of the beam, we can not hit the center of the Faraday entrance and exit at the same time.
That would yield the requirement.

3. If each coil has 5% variance in the response, variance of the nodal point (measured in % of the coil imbalance) by those four coils will be somewhat better than 5%, isn't it?

1. We didn't measure the aperture size last night. We have to check that.

2. We have to measure the length of FI. Or find a document on this FI.

3. Yes, 5%/sqrt(4). But I didn't think the factor of 2 is important for this kind of estimation.

1. Look at the Faraday.

2. Look at the wiki. There is the optical layout in PNG and PDF.

3. 5% (0.8mm) and 2.5%(0.4mm) sounds a big difference for the difficulty, but if you say so, it is not so different.

Actualy, if you can get to the 5% level, it is easy to get to the 1-2% level as I did last time.
The problem is we are at the 15-20% level and can not improve it.

Connecting to NDS Server fb (TCP port 8088)
Connecting.... done
No data found

read(); errno=9
read(); errno=9
T0=12-04-04-02-14-29; Length=3600 (s)
No data output.

It looks like this is actually just a limit of how long we're saving the second trends, which is just not that long.  I'll look into extending the second trend look-back.

Dec 22 between 6AM and 7AM, physical or logical failure has occure on the 4th disk in the RAID array on linux1.
This caused the RAID disk fell into the readonly mode. All of the hosts dependent on linux1 via NFS were affected by the incident.

Today the system has been recovered. The failed filesystem was restored by copying all of the files (1.3TB total) on the RAID to a 2TB SATA disk.
The depending hosts were restarted and we recovered elog/wiki access as well as the interferometer control system.

Recovery process

o Recover the access to linux1

- Connect an LCD display on the host. The keyboard is already connected and on the machine.
- One can login to linux1 from one of the virtual consoles, which can be switched by Alt+1/2/3 ...etc
- The device file of the RAID is /dev/sda1
- The boot didn't go straightforward as mounting of the disks accoding to /dev/fstab doesn't go well.
- The 40m root password was used to login with the filesystem recovery mode.
- Use the following command to make the editing of /etc/fstab available

# mount -o rw, remount /

- In order to make the normal reboot successfull, the line for the RAID in /etc/fstab needed to be commented out.

o Connect the external disk on linux1

- Brought a spare 2TB SATA disk from rossa.
- Connect the disk via an USB-SATA enclosure (dev/sdd1)
- Mount the 2TB disk on /tmpdisk
- Run the following command for the duplication

# rsync -aHuv --progress /home/ /tmpdisk/ >/rsync_KA_20131229_0230.log

- Because of the slow SCSI I/F, the copy rate was limited to ~6MB/s. The copy started on 27th and finished 31st.

o Restart linux1

- It was found that linux1 couldn't boot if the USB drive is connected.
- The machine has two SATA ports. These two are used for another RAID array that is not actually used. (/oldhome)
- linux1 was pulled out from the shelf in order to remove the two SATA disks.
- The 2TB disk was installed on the SATA port0.
- Restart linux1 but didn't start as the new disk is recognized as the boot disk.
- The BIOS setting was changed so that the 80GB PATA disk is recognized as the boot disk.
- The boot process fell into the filesystem recovery mode again. /etc/fstab was modified as follows.

- Another reboot make the operating system launched as usual.

o What's happen to the RAID?

- Hot removal of the disk #4.
- Hot plug of the disk #4.
- Disk #4 started to get rebuilt -> ~3hours rebuilding done
- This made the system marked as "clean". Now the raid (/dev/sdb1) can be mounted as usual.

o Nodus

- Root password of nodus is not known.
- Connect an LCD monitor and a Sun keyboard on nodus.
- Type Stop-A. This leads the nodus transition to the monitor mode.
- Type sync.
- This leads the system rebooted.

Well done Koji!  I'm very impressed with the sysadmin skillz.

Since this configuration change, the daily backup was speeded up by factor of more than two.
It was really limited by the bandwidth of the RAID array.

/cvs/cds/rtcds/caltech/c1/scripts/backup/rsync.backup.cumlog:

...
rsync.backup start: 2013-12-20-05:00:00, end: 2013-12-20-07:04:28, errcode 0
...
rsync.backup start: 2014-01-05-05:00:00, end: 2014-01-05-05:55:04, errcode 0

(The daily backup starts from 5:00)

At around 2:30pm today something brought down most of the martian network.  All control room workstations, nodus, etc. were unresponsive.  After poking around for a bit I finally figured it had to be linux1, which serves the NFS filesystem for all the important CDS stuff.  linux1 was indeed completely unresponsive.

Looking closer I noticed that the Fibrenetix FX-606-U4 SCSI hardware RAID device connected to linux1 (see #1901), which holds cds network filesystem, was showing "IDE Channel #4 Error Reading" on it's little LCD display.  I assumed this was the cause of the linux1 crash.

I hard shutdown linux1, and powered off the Fibrenetix device.  I pulled the disk from slot 4 and replaced it with one of the spares we had in the control room cabinets.  I powered the device back up and it beeped for a while.  Unfortunately the device was requiring a password to access it from the front panel, and I could find no manual for the device in the lab, nor does the manufacturer offer the manual on it's web site.

Eventually I was able to get linux1 fully rebooted (after some fscks) and it seemed to mount the hardware RAID (as /dev/sdc1) fine.  The brought the NFS back.  I had to reboot nodus to get it recovered, but all the control room and front-end linux machines seemed to recover on their own (although the front-ends did need an mxstream restart).

The remaining problem is that the linux1 hardware RAID device is still currently unaccessible, and it's not clear to me that it's actually synced the new disk that I put in it.  In other words I have very little confidence that we actually have an operational RAID for /opt/rtcds.  I've contacted the LDAS guys (ie. Dan Kozak) who are managing the 40m backup to confirm that the backup is legit.  In the mean time I'm going to spec out some replacement disks onto which to copy /opt/rtcds, and also so that we can get rid of this old SCSI RAID thing.

The liquid nitrogen container has a pressure releif valve set to 35 PSI  This valve will open periodically when contains LN2

The exiting  very cold gas can cause burning so it should not hit directly your eyes or skin.  Set the pointing of this valve into the corner.

Leave entry door open so nitrogen concentration can not build up.

We could use similar load cells   to make the actual weight measurement on the Stacis legs. This seems practical in our case.

I have had bad experience with pneumatic Barry isolators.

Our approximate max compression loads are 1500 lbs on 2 feet and 2500 lbs on the 3rd one.

1500 and 2000 lbs load cells arrived from MIT to measure the vertical loads on each leg.

 Atm2, Chilean 8.2M eq arrived to the 40m 16:57 in 10 minutes. Our OSEMs did not see them.  Hanford got it 2 minutes later.

M3.4 Colton shake did not trip sus.

All suspension tripped. Their damping restored. The MC is locked.

ITMX-UL & side magnets are stuck.

I freed ITMX and coarsely realigned the IFO using the OPLEVs. All the alignments were a bit off from overnight.

The IFO is still only able to lock in MICH mode currently, which was the situation before the earthquake. This morning I additionally tried restoring the burt state of the four machines that had been rebooted in the last week (c1iscaux, c1aux, c1psl, c1lsc) but that did not solve it.

Local EQ 3.1 mag at Jun 2, 2016 11:06:16 PM UTC, Muscoy CA........no damage

Our STS should seen this shake.

Local earth quake 3.1 magnitude in Valencia, Ca did not trip our suspensions.

Local EQ 3.5 mag  at 2:28 UTC May 24, 2016 Rancho Cucamonga, Ca.....no damage

I tried to figure out what can add noise below 0.5 Hz to the MC_F. I compared MC1, MC2, MC3 suspos, suspit, susyaw and susside positions with damping (black curves) and without (red curves). Local damping is fine.

Then I compared MC1, MC2, MC3 suspos, suspit, susyaw and susside positions with WFS on (black curve) and off (red curve). WFS add noise to MC1 and MC3 measured by osems (MC2 is fine though). WFS should change osem readings but is it a correct way to do this below 0.5 Hz (?) It looks like just a flat noise. Need to think about the conclusion.

    WFS servo is moving the MC mirror angles to minimise TEM01 and TEM10 modes within the MC cavity.    This means it will compensate not only for angular noise in the mirrors but also for the PSL beam pointing fluctuations.  So the extra "noise" we see when WFS loops are on is because they are active below the WFS UGF of about 2 Hz.  Also if the HEPA airflow is above 20% (of its max), the PSL beam jitter (caused by the airflow) will add broadband noise into the WFS servo loops and this will show up in the OSEM signals.  See elog 5943 for details.

So I tracked down where the currently-used filter function code is defined (the following is all relative to /opt/rtcds/caltech/c1/core/release):

Looking at one of the generated front-end C source codes (src/fe/c1lsc/c1lsc.c) it looks like the relevant filter function is:

filterModuleD()

which is defined in:

src/include/drv/fm10Gen.c

and an associated header file is:

src/include/fm10Gen.h

We are interested in the following question : Can the structures defined in fm10Gen.h (or some other *.c *.h files with defined as FLOAT variables) create single precision instead of double in the filter calculations?

typedef struct FM_OP_IN{

  UINT32 opSwitchE;     /* Epics Switch Control Register; 28/32 bits used*/

  UINT32 opSwitchP;     /* PIII Switch Control Register; 28/32 bits used*/

  UINT32 rset;          /* reset switches */

  float offset;         /* signal offset */

  float outgain;        /* module gain */

  float limiter;        /* used to limit the filter output to +/- limit val */

  int rmpcmp[FILTERS];  /* ramp counts: ramps on a filter for type 2 output*/

                        /* comparison limit: compare limit for type 3 output*/

                        /* not used for type 1 output filter */

  int timeout[FILTERS]; /* used to timeout wait in type 3 output filter */

  int cnt[FILTERS];     /* used to keep track of up and down cnt of rmpcmp */

                        /* should be initialized to zero */

  float gain_ramp_time; /* gain change ramping time in seconds */

} FM_OP_IN;  

up/down scripts are to be made

(Offset Edit on Dec 20 10:38PM)

Configuration:
POY11QMon -> CM Servo In1 -> CM Servo -->Out1 -> ADC -> CM Slow FM -> LSC MC Servo FM -> ETMY(x1.0) -> DAC -> ETMY
                                       |
                                       -->Servo Out -> SR560 (DC, 1st order 30kHz LPF) -> MC In2

Lock acquisition path 1


Initial condition:

CM Slow FM:

• Gain 2.6

CM Servo setting:

• In1 Gain 31dB, SW:OFF, Offset -1.880, Boost Off, Super Boost Off, AO +8dB

MC Servo setting:

• In2 10dB, SW:OFF

Acquisition:

• Engage LSC
• LSC MC servo gain +0.1, FM7/FM10 (Trigger FM2 with 3sec delay)
• Turn on MC

Transition:

• Enable AO path (CM servo In1 SW:ON, MC servo In2 SW:ON)
• LSC MC gain +0.1 -> +0.2
• AO path gain 8dB->14dB
• LSC MC gain +0.2 -> +0.35
• AO path gain 14dB->18dB
• CM servo offset -1.88 -2.7 -> 0.8 0.0 (gradually)
• Enable CM servo Boost

Lock acquisition path 2

Initial condition:

CM Slow FM:

• Gain 2.6

CM Servo setting:

• In1 Gain 31dB, SW:OFF, Offset -1.880, Boost Off, Super Boost Off, AO +20dB

MC Servo setting:

• In2 10dB, SW:OFF

Acquisition:

• Engage LSC
• LSC Yarm G=+0.25 FM4/5 (Trigger FM3/6/7/8)

Transition:

• Enable MC servo In2 (SW:ON)
• Set LSC MC gain +0.2 FM7/10
• Enable LSC MC (On)
• Enable CM servo In1 (SW:ON)
• Disable LSC Yarm (OFF)
• Change CM servo offset -1.88 -> +0.700 -2.70 -> 0.0
• Enable CM servo Boost
• Turn on LSC CM FM2 (optional)

Transition to ETMY LSC to MCL

• After all of the transition: LSC output matrix ETMY (+1.00)
• LSC output matrix MC2 (-1.00)
• LSC output matrix ETMY (0.00)

In an effort to familiarize myself with the analog CM servo, I've begun to replicate Koji and Den's work from the ELOG post that this is a reply to.

I hooked POX11Q into the IN1 of the CM board. (POX is rotated by ~86 degrees in the CDS, meaning analog Q is almost perfect.)

While there, I took out the too-long delay cables Jenne introduced for REFLs 11 and 55. (Also note: when we do cable-based analog phasing in the future, we should do it on the LO side, instead of the PD input side.) I also heard a dangerously crinkly sound from the short SMA cable for REFL11, so I replaced it with a beefy looking new one I found on the SP table.

I messed with the gain and offset in the CM_SLOW input filter to get it to look just like POX11_I_ERR, and was able to lock the arm on it without an issue. I then put the SR560 between the CM and MC (30k pole, but also AC coupled, because I figure the digital loop should be doing the work down there, and don't want to kick the AO with an offset), and was able to turn on the AO path with a gain of 8dB on the CM board and 10dB on the MC board, as detailed in Koji's procedures.

I wasn't able to increase the AO gain to 9dB without breaking lock, but maybe this is ok, because by judging by the LSC filter gains, POX11 might be about 3 times bigger than POY, so maybe 8dB AO gain on POX ~ =18dB AO gain on POY? I was able to put the CM servo offset at 0, but turning on boosts promptly kicked the MC out of lock.

I'm stopping for the night; but tomorrow I'll bust out a spectrum analyzer to see if I actually have won some bandwidth with the CM servo, and check out the situation with the offsets and boosts.

locks last for about an hour.  this was true last night as well (see "arm power curve" entries).   the second lock shown here evolves differently for unknown reasons.  the jumps in the arm powers of the first lock are due to turning on DC readout.  length-to-angle needs tuning.

A progress on the end PDH locking :

by using a modified PDH box the green laser on the X-end station is locked to the arm cavity.

So far the end PDH locking had been achieved by using SR560s, but it was not sophisticated filter.

To have a sophisticated filter and make the control loop more stable, the PDH box labeled "#G1" was installed instead of the SR560s.

After the installation the loop looks more stable than the before.

Some details about the modification of the PDH box will be posted later.

Although, sometimes the loop was unlocked because the sum-amp (still SR560) which mixes the modulation and the feedback signal going to the NPRO PZT was saturated sometimes.

Thus as we expected a temperature control for the laser crystal is definitely needed in order to reduce such big low frequency drive signal to the PZT.

The IFO is locked, at the operating point (zero CARM offset).  The problem with reducing the residual CARM offset in the last stage appears to have been because the common mode gain was getting too high, and so the loop was going unstable at high frequencies. 

The cm_step script is currently a confusing mess, with all the debugging statements.  I'll clean it up this afternoon and check that it still works.

I guess I succeeded in locking of the cavity with the green beam 

 Strictly speaking, the laser frequency of the end NPRO is locked to the 40 meter arm cavity.

Pictures, some more quantitative numbers and some plots are going to be posted later.

After the alignment of the cavity I could see DC fringes in its reflection. Also I could see the cavity flashing on the monitor of  ETMY_CCD.

I drove the pzt of the NPRO with f=200kHz, and then the spectrum analyzer showed 200kHz beat note in the reflection signal. This means it's ready to PDH technique.

And then I made a servo loop with two SR560s, one for a filter and the other for a sum amp.

After playing with the value of the gain and the sign of the feedback signal, the laser successfully got lock. 

To make sure it is really locked, I measured the open loop transfer function of the PDH servo while it stayed locked. The result is shown in the attached figure.

The measured data almost agrees with the expected curve below 1kHz, so I conclude it is really locked.

However the plot looks very noisy because I could not inject a big excitation signal into the loop. If I put a big excitation, the servo was unlocked.

The current servo is obviously too naive and it only has f^-1 shape, so the filter should be replaced by a dedicated PDH box as we planed.

Congratulation! Probably you are right, but I could not get this is a real lock or something else.

1) How much was the fringe amplitude (DC) of the reflected beam? (Vref_max=XXX [V] and Vref_min=YYY [V])
    Does this agree with the expectation?

2) Do you have the time series? (V_ref and V_error)

What did you use to filter the 2f components from your error signal? A homemade low pass or what?

Kiwamu:

I am using a homemade low pass filter.

It's just a RC passive LPF with the input impedance of 50 Ohm.

I locked MI while both arm length are stabilized at IR resonance. This could be done using DC READOUT, in other words, use AS_DC as MICH error signal.
Lock using RF signals are still not successful.

[Suresh, Kiwamu]

 We eventually succeeded in locking X arm with the infrared beam.

The PDH signal is taken at MCL's ADC instead of c1lsc's, and fedback to MC2_POS through the MCL path.

Right now the lock is not so stable for some reasons, so we need to investigate it more.

(what we did)

 - strung a long BNC cable to connect the demodulated signal and the ADC of c1ioo.

          We didn't touch anything on the demodulation system, so the setup for the demodulation is exactly the same as that of yesterday (see here).

 - disconnected the actual MCL cable from the ADC breakout board at 1X2 rack. And put the demodulated signal onto it.

 - checked the analog dewhitening filter state for the MC2 coil driver, found the analog filter are always off.

  So we just made simDW and invDW always on.

- changed the gain of the MCL loop to have a stable lock for the X arm.

    right now a reasonable setup in the MCL filters are:

         FM1:ON, FM10:ON, G=0.1

 - In fact the lock of the MC is not so stable compared to before, frequently an attempt of locking the X arm leads to the unlock of the MC.

I succeeded in locking the end green laser to X arm with the new ETM.

Though the lock is still not so stable compared to the previous locking with the old ETM. Also the beam centering is quite bad now.

So I will keep working on the end green lock a little bit more.

Once the lock gets improved and becomes reasonably stiff, we will move onto the corner PLL experiment.

(to do)

 - beam centering on ITMX

 - check the mode matching

 - revise the control servo

- Routine alignment

Locked the arm cavties. Ran ASS. As this was not enough precise alignment for PRMI locking, Yarm alignment was re-adjusted by sliders.
Xarm was also aligned in the same way.

- OPLEV alignment

Once the arms were aligned, OPLEV spots were adjusted. For this adjustment, PRM had to be aligned and OPLEV servos needed to be turned off.

- LSC offset nulling

While Jenne was measuring the dark output of the POP PD, LSC offset nulling script was executed.

- Compensation of the POP spot size fix

As Jenne reported the POP path now has a lens and the denominator for the normalization got bigger.
To compensate this change, PRMI(sb) was locked by the same configuration as yesterday (i.e. AS55Q for MICH, REFL33I for PRCL). 
After some try and error, configuration for stable locking was found. 

PRCL
Signal source: REFL33I / Normalization POP110I x 1.00 / Trigger POP110I 80up 10down
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+8.00
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: AS55Q / Normalization POP110I x 0.01 / Trigger POP110I 80up 10down
Servo: input matrix 1.00 -> MICH Servo FM4/5 Always On G=-30
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

This suggests that POP110I signal is 5~6 times more than before the lens was installed. 

- SQRTing option for POP110I was implemented

The PRMI optical gain is derived from (Carrier)x(1st order Sideband) or (2nd order SB)x(1st order SB).
Here the carrier and the 2nd order sidebands are nonresonant.
Therefore the optical gain is proportional to the amplitude power recycling gain of the 1st order sidebands.
On the other hand, POP 2f signals are derived from the product of the 1st and -1st order sidebands.
This means that we should take a sqrt of the POP signals to compensate the recycling gain fluctuation.

- Locking with SQRT(POP110I)

PRCL
Signal source: REFL33I / Normalization SQRT(POP110I) x 10 / Trigger POP110I 10up 3down
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+8.00
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: AS55Q / Normalization SQRT(POP110I) x 0.1 / Trigger POP110I 10up 3down
Servo: input matrix 1.00 -> MICH Servo FM4/5 Always On G=-30
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

The lock seems not so different from the ones without SQRTing.

The spot was still moving in yaw direction. If I chose a correct alignment, I could minimize the modulation of the internal power
by misalignment. As you can see in the following plot.

When the alignment was deviated from the optimum, the misalignment induced RIN was much worse although this was the longest lock I ever had with the PRMIsb. (more than 8 min)

- Locking with other signal sources

REF55I/Q trial:

Demodulation phase was adjusted to make the difference of the peak heights for MICH maximized.
After the lock is acquired, I tried to swap the signal source at the input matrix. PRCL swapping was successful but
MICH swapping was not successfull.

It is much more hard to lock the interferometer with REFL55I compared with REFL33I.

REFL165I/Q trial:

As REFL165 PD never produced any useful signal, I tried to swap it with the BBPD used in the green setup.

- Borrowed the PD, power supply from the green setup.

- Put REFL165PD aside. Placed the BBPD in the path. The DC output was 0.8V. This corresponds to the input power of ~5mW.

- Checked the signal but it was very litte (several counts even at the maximum whitening gain).

- Decided to use the power reduction pick off to introduce much more light on the PD.
  This PO mirror is 90% reflector. Therefore I had to be careful no to fry the diode.
  Currently there are OD1.3 (x1/20) power attenuator to reduce the input power down to 6.5V (40mW).

- The resulting signal is very wiered suggesting the saturation of the PD at the RF stages.

- Probably I need to make a new PD circuit which has the high pass filter to reject other low frequency components.

The goal tonight was to go through the locking scripts to see if I could recover the state from November 2019, when I could have the arm lengths controlled by ALS, and sit at zero CARM offset with the PRMI remaining locked and the arm powers fluctuating between 0-300. The IR-->ALS transitions went smoothly tonight, and the PRMI locking was also fairly robust when the CARM offset was large, but was less good when reduced to 0. Nevertheless, it is good to know that the system can be restored to the state it was late last year. Next step is to figure out how to keep the PRMI locked and get the AO path engaged, this was what I was struggling with before the new year.

Jenne, Den

Today we worked on PRM angular servos and Y-arm ALS stabilization.

In the current PRMI angular control configuration two servos simultaneously drive PRM - oplev and POP ASC. We considered 2 ways to redesign this topology:

• once lock is acquired, turn on POP ASC servo that corrects oplev error signal
• turn off PRM oplev and turn on POP ASC  servo

The first option requires model rewiring so we started from the second one. We had to redesign POP ASC pitch and yaw servos for this because PRM TF has changed. Attached is servo OLTF.

This method worked out well and once PRMI is locked we turned off oplev servo with ramp of 0.5 sec and enable ASC POP servo with ramp of 1 sec.

Once PRMI was locked and ASC running we have turned off PRM angular local damping that presumably prevents us from bringing arms into resonance due to IR coupling to shadow sensors.

PRMI was stable using only ASC POP servo and we moved on to ALS. We found Y-arm beatnote and enabled control to ETMY.

Cavity was stabilized but not robust - we were loosing IR in a minute because green relocked to 01 mode with transmission equal to more than half of 00 mode. This is probably due to angle to length coupling of ETMY.

We were also loosing IMC during cavity stabilization. We made MCL servo and will tune it tomorrow looking at the arm spectrum as an OOL sensor.