PRM was released from the fixuture without any trouble. This was the last magnet gluing until ETMs are delivered.

The below is the up-to-date Jenne stat table.

The clean room is getting too narrow. I am thinking that we should install ITMs to the chamber so that we can accommodate SRM/PRM suspensions.

Steve and Koji

- We removed old ITMX/Y from the chambers. Now they are temporarily placed on the flow table at the end. Steve is looking for nice storages for the 5inch optics.

- We wiped new ITMX/Y by isopropanol as they were dusty.

- We put them into the corresponding towers. Checked the balancing and magnet arrangements with the OSEMs. They were totally fine.

- We clamped the mirrors by the EQ stops. Wrapped the towers by Al foils.

Tomorrow we will put them into the chambers.

Steve and Koji (Friday, Apr 02)

Summary

Intsallation of ITMs are going on. Two new ITMs were placed on the optical table in the vacuum chambers. ITM for the south arm was put at the right place in accordance to the CAD drawing. ITM for the east arm is still at a temporaly place.

Tower placement (10:30-11:30)

- Put the tower on the table at a temporary place such that we can easily work on the OSEMs.

ITM (South arm) (14:00-16:30)

- Put the tower on the table at a temporary place such that we can easily work on the OSEMs.

- Leveled the table approximately.

- Released the EQ stops

- Removed anchors for the OSEM cables as it was too short. The wire distribution will be changed later.

- Put the OSEMs. Adjust the insertion to the middle of the OSEM ranges.

- Clamped the EQ stops again

- Placed the tower to the right place according to the CAD drawing.

- Released the EQ stops again.

- Check the OSEM values. The LL sensor showed small value (~0.5). Needs to be adjusted.

ITM (South) damping adjustment

- Found the signs for the facing magnets are reversed.

- Otherwise it damps very well.

 The cabling on the seismic stack was rerouted so it could reach the south edge of the table: the cables  were removed from the viton padded clamps and repositioned this morning.

ITM-south tower's earthquake screw viton tips could be a little bit larger. They do not stay in their screw hole after a hard clamping action.

4-40 earthquake screws under the test mass:viton tips can fall out without action, the treads are cross threaded so the screws are wobbling

 I restored damping to all SUSes except ITM-east. The ITMX OSEMs are being used in the clean assembly room.

Kiwamu and Koji

ITMY (south) was aligned with regard to the 40m-long oplev with the green laser pointer. Now the cavity is waiting for the green light injected from the end table

Some tools and the level gauge were removed from the table.

BAD news: I could clearly see scatter of the green beam path because of the dusts in the arm tube. Also many dusts are seen on the ITM surface.

Picture of the ETM - reflection from the ITM is hitting the mirror and the suspension structures.

1. Shoot the ITM center with the green beam.

- Two persons with walkie-talkies required for this work.

- Turn on the end green pointer. We could see the long trace of the beam sliced by the beam tube wall.

- Look at the tube peeping mirror for the CCD.

- Adjust yaw such that the beam trace on the tube wall is parallel to the arm.

- Adjust pitch such that the beam trace on the tube gets longer. This means that spot gets closer to the ITM.

- Continue pitch adjustment until some scatter appears on the ITM tower.

- Once the spot appears on the tower, you can easily adjust it on the mirror

2. Adjust pitch/yaw bias such that the reflection hits the ETM.

- Initially the ITM alignment is totally bad. ==> You clealy see the spot on the wall somewhere close to the ITM.

- Adjust pitch/yaw bias such that the spot goes farther as far as possible.

- Once you hit the suspension tower, the scatter is obviously seen from the peeping mirror.

- You can match the incident beam and the scattering of the reflection. You also can see the reflection from the ETM towards the ITM as the spot size gets huge (1/2 tube diameter).

- We found that the bias is ~-2 for pitch and ~-6 for yaw.

3. Go into the chamber. Check the table leveling.

- Open the light door.

- I found that the table is not leveled. Probably it drifted after the move of the weight (i.e. MOS removal).

- Removed one of the round-shaped weight. Moved the other weights such that the table was leveled.

4. Remove the bias for yaw and rotate suspension tower such that the reflection hit the center of the ETM.

- Removed the yaw bias. This makes the reflected spot totally off from the ETM.

- Rotate suspension tower so that the beam can approximately hit the ETM.

- Look at the peeping mirror, the beam is aligned to the ETM.

5. Adjust OSEMs

- Push/pull the OSEMs such that we have the OSEM outputs at the half of the full scale.

6. Adjust alignment by the bias again.

- Moving OSEMs changes the alignment. The pitch/yaw biases were adjusted to have the beam hitting on the ETM.

- Bias values at  the end of the work: Pitch -0.8159 / Yaw -1.2600

7. Close up the chamber

- Remove the tools and the level gauge.

- Close the light door.

Koji

ITMX was aligned with regard to the 40m green oplev.
Now both cavities are aligned.

Next thing we are going to do is to remove PRM and SRM towers.

As well as the oplev construction for ITMs.

We anticipate the drift of the stack. So we need to revisit the alignment again.

Some tools and the level gauge were removed from the table.

Picture of the ETMX - reflection from the ITMX is hitting the mirror and Jamie's windmill.

0. The suspension tower had been placed on the table close to the door.

1. Brought the OSEMs from the clean room. Connected the satellite box to the ITMX suspension.

2. Went into the chamber. Leveled the table.

3. Released the mirror from the clamp. Put and adjust the OSEMs.

- Note that the side OSEM is located to the south side of the tower
  so that we can still touch it after the placement of the TT suspension at the north side of the SOS tower.

4. Clamped the mirror. Moved the SOS tower according to the CAD layout.

5. Leveled the table again.

6. Released the mirror again and adjusted the OSEMs.

7. Turned on the end green laser pointer.

- The spot was slightly upside and left of the mirror. Adjusted it so that the spot is at the center.

8. Align ITMX in Pitch

- The spot was hitting the tube. Moved the pitch bias such that the beam get horizontal.

9. Align ITMX in Yaw

- Moved the SOS tower such that the approximate spot is on the ETMX. If I hit the right spot I could see the tube get grown green because of the huge scatter.

10. Adjusted the OSEMs again and check the alignment again. Repeated this process 2~3 times.

- Bias values at  the end of the work: Pitch 0.7800 / Yaw 0.270

11. Close up the chamber

- Remove the level gauge. Some of the screws are still in the Al ship in the chamber.

- Close the light door.

Bob, Steve, and Koji

We opened North heavy door of the BS chamber in the afternoon.

In the evening, Koji worked on the PRM/SRM removal.

- Cleaned up the OPLEV mirrors to create some spaces near the door.

- Clamped PRM/SRM.

- Removed OSEMs. Made a record of the OSEMs. The record is on the wiki (http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_09/Suspensions)

- Found the SOSs are quite easy to remove from the table as they are shorter than the MOSs.

- Put a new Al sheet on a wagon. Put the SOSs on it. Wrapped them by the Al foils.

- Carried it to the clean room. They are on the right flow bench. Confirmed the wires are still fine.

- Closed up the chamber putting a light door.

ETMY sus damping was restored

Kiwamu and Koji

The PRM/SRM were balanced with the standoffs. We glued them to the mirror.

This was the last gluing so far until we get new PRM/ETMs.

Kiwamu and Koji

- Checked the SRM/PRM balancing after the gluing.

- The mirrors were removed from the suspensions for baking.

- Bob is going to bake them next week.

I liked to know quantitatively where the spot is on a mirror.

With an interferometer and A2L scripts, one can make the balance of the coil actuators
so that the angle actuation does not couple to the longitudinal motion.
i.e. node of the rotation is on the spot

Suppose you have actuator balancing (1+α) f and (1-α) f.

=> d = 0.016 x α [m]

Full Imbalance   α = 1      -> d = 15 [mm]
10% Imbalance α = 0.1   -> d = 1.5 [mm]
1% Imbalance   α = 0.01 -> d = 0.15 [mm]

Eq of Motion:

I ω² θ =  2 R f 
(correction) - I ω² θ =  D f cos(arctan(L/2/D))
(re-correction on Sep 26, 2017) - I ω² θ =  D f

m ω² x = 2 α f ,
(correction) - m ω² x = 2 α f ,

where R is the radius of the mirror, and D is the distance of the magnets. (kinda D=sqrt(2) R)

d, position of the node distant from the center, is given by

d = x/θ = α I / (m R) = 2 α β / D,

where β is the ratio of I and m. Putting R=37.5 [mm], L=25 [mm], β = 4.04 10^-4 [m²], D~R Sqrt(2)

i.e. d = 0.015 α [m]

Oh, but it gets even better: in order to trust the A2L script in this regard you have to know that the coil driver - coil - magnet gain is the same for each channel. Which you can't.

But we have these handy f2pRatio scripts that Vuk and Dan Busby worked on. They use the optical levers to balance the actuators at high frequency so that the A2L gives you a true spot readout.

But wait! We have 4 coils and the optical lever only gives us 2 signal readouts...

Yes, of course. But so far I am trusting that the coils are inheretly balanced.
Probably you are talking about the dependence of the nodal position on the frequency...I need to check if 18Hz is sufficiently high or not for 0.1mm precision.

Also I am practicing myself to understand how I can adjust them by which screws as we probably have to do this adjustement many times.
(i.e. removal of the MZ, move of the table, PSL renewal and so on)

For the actuator calibration, we may be able to calibrate actuator responses by shaking them one by one while reading the OPLEV P/Y signals.

Deviations of the MC spot from the center of the mirrors were measured.

MC1H = +0.29 mm
MC1V = -0.43 mm
MC3H = +1.16 mm
MC3V = -0.68 mm

1) The vertical deviation looks easy being adjusted as they are mostly translation. They are ~0.5mm too high.
The distance from SM2 to MC is 1.8m. Thus what we have to do is
rotate SM2 Pitch in CW knob by 0.25mrad.
1 turn steers the beam in 10mrad. So 0.25mrad is 1/40 turn (9deg)

2) The horizontal deviation is more troublesome. The common component is easily being adjusted
but the differential component (i.e. axis rotation) involves large displacement of the beam
at the periscope sterring mirrors.

(MC3H - MC1H) / 0.2 m * 1.8 m = 8 mm

The beam must be moved in 8mm at the periscope. This is too big.

We need to move the in-vac steering mirror IM1. Move SM2Yaw in 7mrad. This moves the spot on IM1 by 5mm*Sqrt(2).
Then Move Im1 Yaw such that we see the resonance.

For the alignment adjustment, try to maximize the transmission by MC2 Yaw (cavity axis rotation) and SM2Y (beam axis translation)  

Actual move will be:

- Move IM1Y CCW (assuming 100TPI 1.5 turn in total...half turn at once)
- Compensate the misalignment by SM2Y CW as far as possible.
- Take alignment with MC2Y and SM2Y as far as possible

This operation will move the end spot something like 15mm. This should be compensated by the alignment of MC1Y at some point.

Actually, I tried some tweaks of the input steering to get the beam being more centered on the MC mirrors on Saturday evening.

I made a mistake in the direction of the IM1Y tuning, and it made the horizontal spot position worse.

But, this also means that the opposite direction will certainly improve the horizontal beam angle.

Rotate IM1Y CCW!!!

The current setting is listed below

Alignment
MC1P 3.2531
MC1Y -0.5327
MC2P 3.3778
MC2Y -1.366
MC3P -0.5534
MC3Y -2.607

Spot positions
MC1H = +1.15 mm
MC1V = -0.13 mm
MC3H = +0.80 mm
MC3V = -0.20 mm

MC1H = +0.29 mm
MC1V = -0.43 mm
MC3H = +1.16 mm
MC3V = -0.68 mm

Lessons learned on the beam spot centering (so far)

Well-known fact:

The spot position on MC2 can be adjusted by the alignment of the mirror while maintaining the best overlapping between the beam and the cavity axes.

In general, there are two methods:

1) Use the cavity as a reference:
Move the MC mirrors such that the cavity eigenmode hits the centers of the mirrors.
-> Then adjust the incident beam to obtain the best overlapping to the cavity.

2) Use the beam as a reference:
Move the incident beam such that the aligned cavity has the spots at the centers of the mirrors.
-> Then adjust the incident beam to obtain the best spot position while the cavity mirrors keep tracking
the incident beam.

Found the method 1) is not practical.

This is because we can move the eigenmode of the cavity only by very tiny amount if we try to keep the cavity locked.
How much we can move by mirror alignment is smaller than the waist radius or the divergence angle.
For the MC, the waist radius is ~2mm, the divergence angle is 0.2mrad. This means the axis
translation of ~1mm is OK, but the axis rotation of ~4mrad is impractical.

Also it turned out that adjustinig steering mirror to the 10-m class cavity is quite difficult.
A single (minimum) touch of the steering mirror knob is 0.1mrad. This already change the beam position ~0.1mm.
This is not an enough resolution.

Method 2) is also not so easy: Steering mirrors have singular matrix

Indeed! (Remember the discussion for the IMMT)

What we need is the pure angle change of 4mrad at the waist which is ~2m distant from the steering mirror.
This means that the spot at the steering mirror must be moved by 8mm (= 4mrad x 2m). This is the result of the
nearly-singular matrix of the steering mirrors.

We try to avoid this problem by moving the in-vac mirror (IM1), which has somewhat independent move.
The refl beam path also has the big beam shift.
But once the vacuum manifold is evacuated we can adjust very little angle.

This can also be a good news: once the angle is set, we hardly can change it at the PSL side.

On Friday, I deleted a bunch of filters from the c1susvme2 optics' screens (MC1,2,3 + SRM) so as to reduce the CPU load and keep it from going bonkers.

This first plot shows the CPU trend over the last 40 days and 40 nights. As you can see the CPU_LOAD has dropped by 1 us since I did the deleting.

In the second plot (on the right) you can see the same trend but over 400 days and nights. Of course, we hope that we throw this away soon, but until then it will be nice to have the suspensions be working more often.

ETMY-south sus damping was restored

I fitzed with the PRM and SRM briefly, and I now believe that they're both ready to go into the chambers. 

For each optic, I used the microscope on a micrometer to check that the scribe lines on each side of the optic were at the same height.  Basic procedure was to center the microscope on one scribe line, move the microscope to the other side, to see how far the line was from center, and try to (very gently!!) rotate the optic in the wire about the z-axis about half the distance that the one scribe line needed to be.  Rinse and repeat several times until satisfied. 

I then checked that our HeNe oplev was still at 5.5" beam height, and that the beam traveled straight across the table.  I put the SRM in the oplev, unclamped the EQ stops, and waited for it to settle.  The HEPA filters were turned off, to minimize the breeze.  While the SRM settled, I worked on the height/rotation for the PRM on the other table. 

After checking the SRM balance, I clamped it and moved it, and checked the PRM balance, then turned off the HeNe and rewrapped everything in foil, and turned on the HEPAs.

Both the SRM and the PRM seem a little off in Pitch.  The beam returning to the QPD (placed just next to the laser) was always ~1cm above the center of the QPD.  The beam travel distance was ~3m (vaguely) from laser to optic to QPD.  This effect may be because the optics were originally balanced with OSEMs in place, and I didn't have any OSEMs today.  Koji and I found several months ago that the OSEMs have some DC affect on the optics.

Anyhow, since our optics are so small, I think the OSEMs and coils can handle this small DC offset in pitch, so I think we're ready to rock-n-roll with putting them in the chambers.

Still on the to-do list......Tip Tilts!

The photo shows the oplev beam position on (kind of) the QPD, for the SRM.  The PRM was basically the same.

[Jenne, Kyung Ha]

We successfully suspended the 4 eddy current dampers for the first Tip Tilt.  We had some lessons learned, including how to carefully get an allen wrench in between the dampers to do up some of the screws, and how to be careful not to bend the wire while tightening the screws.  More tomorrow...

[Jenne, Kyung Ha]

We made some good progress on suspending the Tip Tilt ECDs today.  We finished one whole set, plus another half.  The half is because one of the screw holes on the lower right ECD somehow got cross threaded.  The ECD and screws in question were separately wrapped in foil to mark them as iffy.  We'll redo that second half tomorrow.  This makes a total of 2.5 (including yesterday's work) ECD backplanes suspended.  The only thing left for these ones is to trim up the excess wire.

We also (with Koji) took a look at the jig used for suspending the mirror holder.  It looks like it was designed for so many Tip Tilt generations ago as to be basically useless for the 40m TTs.  The only really useful thing we'll get out of it is the distance between the suspension block and the mirror holder clamps.  Other than that we'll have to make do by holding the mirror and block at the correct distance apart, utilizing a ruler, calipers, or similar.  Rana pointed out that we should slightly bend the blade springs up a bit, so that when they are holding the load of the mirror holder, they sit flat. 

Attached below are 2 different pictures of one of the ECD backplane sets that has been suspended.  One with black background to illustrate the general structure, and one with foil background to emphasize the wires.

I and koji setup the measurement of the QPD response to the pitch and yaw displacements of the beam spot.

We did this using a 100mW 1064nm laser. Its power was attenuated to ~ 1.9mW, and the spot size at the QPD position was 6000-7000 um .

The QPD was put on a translation stage, using which, the center of teh QPD wrt the beam spot could be moved in pitch and yaw.

Following are the measurements :

For yaw

:

The slope of teh linear region is -8356 /inch

 For pitch

The slope of the linear region in this is 9085/inch

 The old plots looked horrible, and so here is a new plot

The slopes and other stats are

Pitch

Linear model Poly1:
     f(x) = p1*x + p2
Coefficients (with 95% confidence bounds):
       p1 =        8550  (7684, 9417)
       p2 =       -2148  (-2390, -1906)

Goodness of fit:
  SSE: 9944
  R-square: 0.9923
  Adjusted R-square: 0.9907
  RMSE: 44.59

Yaw

Linear model Poly1:
     f(x) = p1*x + p2
Coefficients (with 95% confidence bounds):
       p1 =       -8310  (-8958, -7662)
       p2 =        2084  (1916, 2252)

Goodness of fit:
  SSE: 6923
  R-square: 0.9954
  Adjusted R-square: 0.9945
  RMSE: 37.21

Jenne and Koji

We tweaked the alignment of the TT mirror.

First we put a G&H mirror, but the mirror was misaligned and touching the ECD as the magnet was too heavy. We tried to move the wires towards the magnet by 1mm.
It was not enough but once we moved the clamps towards the magnet, we got the range to adjust the pitching back and forth.
We tried to align it by the feaher touch to the clamp, we could not get close to the precision of 10mrad as the final tightening of the clamp screws did change the alignment.

We will try to adjust the fine alignment tomorrow again.

The damping in pitch, yaw and longitudinal looks quite good. We will also try to characterize the damping of the suspension using a simple oplev setup.

You guys must work harder.

[Jenne & Kyung-ha]

We suspended the mirror to one of the main frame with the ECD backplane we finished before. The hard task was to find the right balance for the mirror so that 1) it won't be tilted and 2) it'll be in the right position for the ECD backplanes so that the magnets attached to the mirror holder would be in the very center of each ECD holes. We used optical lever laser (red He/Ne) to check the balance of the mirror. We tried to use the jig for the mirror holder clamps but because of the size difference, we couldn't use it at all. (Since the magnets are very heavy, we thought the wire being not perfectly centered might work better. However, the jig dimension was way too different that the wire ended up in the middle of one of the holes.) Since there was no other clever way to attach the wire in the right position, we just tried to be as center/accurate as possible. After attaching wire to that mirror holder clamps, we hanged it to the frame. Again, we couldn't find any other accurate way to find the center so we held the wire and tried to adjust the mirror height as accurate as possible so that it can be in the right position in respect to ECD backplane and not be tilted at the same time. However, when we hanged the mirror, it was still tilted.. So we adjusted the mirror tilt using the mirror holder clamps. Since the holes on the clamps were ellipse shapes, we could adjust the position of the clamps a little bit. When we adjust the clamps, we started to tighten the screws when the mirror is NOT in the perfect position since the tightening up part changes the mirror angle anyways. Luckily, when we tightened up the last screw, the mirror was in the perfect position! After that, we poked the mirror several times to make sure that it comes back to the same place.

Amazingly, we could finish this whole hanging/adjusting process in about 30 mins! :D (Jan said it's because of his amazing moral support. :P Maybe he'll be there to support us everytime we work on the mirrors?)

[Jenne, Koji]

I moseyed into the control room this morning, to find ITMX and ITMY both with their watchdogs tripped.  ITMY (new convention) wouldn't damp.  Koji discovered that there was a sign flip in 2 of the sensors.  A set of reboots of c1susvme1&2 fixed the problem. 

A side note:  For the ETMs, the OSEM sensor readouts are gigantic (~20,000), whereas for the similar channels on all other optics, the readouts are on the order of 1.  After some looking around, it seems that this is just the way things have been (for at least 100 days), and the filters in the SUSPOS and other SUS filter banks have a high pass filter to take care of this.  It's weird, but it seems to be the way it is, and the ETMs damp, so it's all good.

[ Jenne, Koji and Kiwamu]

 We have installed the PRM and the tip-tilt (TT) in the BS chamber.

We have started the in-vac work which takes about a week.

Today's mission was dedicated to installing the PRM and two TTs, one for the PRC and the other for the SRC, on the BS table in the chamber.

The work has been smoothly performed and we succeeded in installation of the PRM and a TT for the PRC.

But unfortunately the other TT got broken during its transportation from Bob's clean room.

 (what we did)

 (1) opened the light door of the BS chamber.

 (2) moved the BS tower to the right position according to Koji's layout drawing.

    - Prior to this work we screwed down the earthquake stops so that the mirror is fixed to the tower. Also we disabled the watchdog.

    - When moving it we used an allen key as a lever with an screw as a fulcrum. This idea was suggested by Jenne and it really worked well.

     The reason why we used this technique is that if we slide the tower by hands the tower can't go smoothly and it may sometimes skips.

     After that we checked the postion from some reference screw holes by using a caliper and we made sure that it was on the right position.

 (3) removed all of the square-shaped mirrors.

    - After this removal the mirrors were wrapped by aluminum foils and put in a usual clear box.

 (4) removed some optics because they had made the chamber space crowded.

    - These were also wrapped by aluminum foils and put in the box. Later we will put them back to the BS table.

 (5) brought the PRM tower from the Bob's clean room  and put it on the BS table.

   - The position of the PRM were coarsely aligned since we still don't have any 1064 beam going through the PRM.

 (6) brought two TTs also from Bob's clean room and put one of the TTs on the table.  

   - The position of the installed TT was coarsely adjusted. 

   - After we brought them we removed the aluminum foils covering the TTs and we found the wire of a TT got broken.

     It may have been damaged during its transportation from Bob's room because it was fine before the transportation.

 (7) closed the door

(the next things to do)

  * Installation of the OSEMs to the PRM

  * Installation of the pick off mirror and its associated optics

  * Arrangement of  the pzt mirror

I updated the last entry.

 [Alberto and Kiwamu]

We installed the OSEMs to the new PRM.

As I wrote down on the elog (see here)  today's mission was to install the OSEMs to the PRM.

After putting them on the tower we adjusted the readout offsets by sliding the OSEMs so that they can stay in the linear sensing ranges. 

Now all of the OSEMs have almost good separation distances from the PRM.

In the attached picture you can see the OSEMs installed on the PRM tower ( middle: PRM tower, left: BS tower)

(what we did)

 1. moved the PRM tower close to the door so that we could easily access the PRM.

 2. leveled the table by putting some weights and confirmed the level by a  bubble level tool.

     - We must level the table every time when we set / adjust any OSEMs,  otherwise the readout voltages of  the OSEMs vary every time due to the tilted table.

 3. released the PRM by loosing the earthquake stops

 4. put the OSEMs with approximately right separation distances from the PRM.

      -  At this phase we can see the readout of the OSEMs, which were oscillating freely because we still didn't enable the damping.

        -  The OSEM positions were checked by looking at useful notes on the wiki (see here).

 5. turned on the damping servo of the OSEMs

       - Without changing any gains, it worked well. 

      - Then we could see stable readouts of the OSEMs which didn't show any oscillations in turn because of the damping.

 6. checked the level of the table again

 7. set each of the OSEM readouts to the half of its maximum value by sliding their positions slightly.

      - The readout offsets were at almost the half value within +/- 100 mV accuracy (this was the best accuracy we could adjust by our hands)

 8. screwed down the earthquake stops to lock the PRM.

      - Now the damping is off.

 9. closed the door

(to be done)

 *  Putting the PRM tower back to the designed place

 *  Installation of the pick off mirror

 *  Arrangement of the PZT mirror

[Koji, Jenne]

We were on Team Cleanroom, while Kiwamu and Alberto were on Team Chamber.  Team Cleanroom suspended and balanced 2 Tip Tilts this afternoon.

One of the TTs that was suspended today is the one which was broken on Friday (see elog 3278).  We resuspended it using the regular 0.0036" diameter wire (91um).  We balanced it using the HeNe oplev, and then set it aside.  This TT has serial number 2.

We noticed that, like the previous 2 TT suspensions (this one before it was broken, and the one actually installed in the BS chamber on Friday, which is #3), there seems to be a little bit of hysteresis in the pointing.  The difference comes if we poke the top of the mirror holder and observe the place the reflected beam spot comes to rest at, and if we poke the bottom of the mirror holder.  The beam spot stays a little higher when we poke the top vs. when we poke the bottom. 

To combat this, we tried suspending our second TT of the day (the one that Kyung Ha and I had half finished) using thinner wire for the mirror holder.  We used the 0.0017" diameter wire (43um) that is used for the SOSes.  Unfortunately, it still seems like there is a similar hysteresis.  The thin-wire TT has serial number 4.

While working on TT4, we recalled that we have to include rubber dampers for the vertical blade springs.  Oooops!  We used some of the leftover #4-40 screws with viton tips that Zach and Mott had made for Earthquake stops to damp the vertical resonance of the blades.  We measured the Q factor by flicking the blades up or down.  We changed the oplev setup to be a shadow sensor setup, and watched the ringdown of the vertical mode on the 'scope.  We counted #cycles/time = frequency, and the t(1/2) time for the exponential ringdown to calculate the Q.  For the shadow sensor, we positioned the QPD in line with the initial HeNe beam, and placed the edge of the mirror holder clamp partially in the beam, so the beam was partly occluded.  When the mirror shook up and down, more or less of the beam was blocked, and we could see this power fluctuation on the 'scope.

Using the formula Q = pi  f0 T_1/2 / ln(2) = 4.53 f0 T_1/2, where T_1/2 is the the time it takes for the amplitude to decay by half, we measured a Q of 31 for the vertical mode with no damping, and a Q of 14 with damping.  Koji confirmed the calculation and put it into wiki.

We need to go through the other TTs that have been assembled and give them their rubber dampers.

[Alberto and Kiwamu] 

We put the PRM back approximately on the right place.

Also we installed the pick off mirrors and the PZT mirror.

Since the main beam after the MMT still has not been well aligned , we put those optics approximately on the right place. A fine alignment of those will be performed later

The offsets of the PRM OSEMs are still kind of okay.

The next things we have to do are

(1) installation of a tip-tilt for the SRC, (2) alignement of those optics by using the main laser and (3) installation of the green optics.

what we did

 1. put the PRM back to the designed place.

     - After this, we released the PRM from the earthquake stops and turned on the damping servo.

      - Now the earthquake stops are at a distance of approximately 1mm from the PRM. These separation distances were tuned by counting the turn number when we screwed them off.

 2. leveled the table

 3. adjusted the separation distances from the PRM to the OSEMs.

    - The table below summarize the current OSEM offsets. LL may still need to be adjusted.

 4. put the PZT mirror on the right place.

      -  This PZT mirror is going to be used for beam steering after the MMT.

 5. put the pick off mirror and its associated optics.

     -  This pick off mirror provides with the beam eventually going to IP_ANG and IP_POS.

current status

The table below shows the current status of the installed optics.

Red letters represent the incomplete states which still need further adjustment.

Blue letters represent the complete status which don't need any further adjustment.

[Koji, Jenne]

We took measurements of the Q of all the modes that we could think of for TT#4, and then repeated several of the same measurements for TT#2.  We noticed that when we took off the backplane and then replaced it on TT#4, the pitch pointing had changed, so we had to repeat the balancing procedure by slightly shifting the position of the wire clamps relative to the mirror holder. No fun. We decided to quit removing the backplanes. 

The main conclusion of this evening's measurements of TT#4 is that everything looks very close to the design ideas.  Good work team!

TT#4:

'Free Swinging' values (just for interest)

Vert, no damping:   Q = 31.4

Pitch, no damping (ECD backplane removed): Q = ~700

Yaw, no ECDs: Q = ~900

Pos, no ECDs (no measurement) - we had already put the backplane back on, and didn't want to take it off again.

Damped Values:

Vert, with damping: Q = 14.3

Pitch, with ECDs: overdamped, so Q < 1/2

Yaw, with ECDs: Q = 2.3

Pos, with ECDs: Q = 1.4

Side, with ECDs: Q = 1.9

We also measured the resonant frequency of each of the ECDs for this TT (since we had the backplane removed anyway...)

ECD UL: 10.05Hz

ECD UR: 10.15Hz

ECD LL: 10.21Hz

ECD LR: 10.21Hz

TT#2:

Yaw, with ECDs: Q = 7.0

Pitch, with ECDs: overdamped, so Q < 1/2

Vert: Problematic.  No damping, f = 25.9Hz, Q = 36.  With rubber dampers, f = 20.0Hz, Q = 42.   Yes, you read that right.  The frequency is lower, and the Q is higher *with* the damping.  Perhaps our brains are fried.  Perhaps we've discovered new, inconsistent physics (awfully unlikely....). We'll revisit this again tomorrow to figure out what mistake we're making.

[Jenne, Koji and Kiwamu]

We have installed two steering mirrors and the green periscope.

Also we took the tip-tilt out from the chamber for characterization.

1. installed two steering mirrors

     - We installed IPPOSSM2 and IPPOSSM3.

    - Because IPPOSSM2 is a new 0 deg mirror so we newly engraved "Y1-LW1-2037-1064-0-AR" on the mount and deleted  the previous enegravement.

      For the 0 deg mirror itself, it had already been engraved by Koji. The wedge was horizontally aligned.

      Now IPPOSSM2 is off from the right place by 5 inch for convenience because it may touch our stomachs when we try to lean further into the chamber.

    - IPPOSSM3 is a 45 deg mirror which used to be in the chamber and had been already correctly engraved, so we didn't have to newly engrave on it. Now it's on the right place approximately.

 2. put three oplev mirrors

      - Two of them are approximately on the place, but one which is going to be on the center of the table is not on the place because there is a cable distributer sitting exactly there.

 3. installed the green periscope

      - Both the mirrors and the periscope were correctly engraved.

     - Now it's sitting on the right place approximately.

 4. removed the tip-tilt 

      -  This tip-tilt is now in the clean room and the mechanical mode will be characterized. 

 The next things to be done

* Cross-coupling evaluation of the PRM OSEMs

* Rearrangement of the cable distributer panel.

   - In order to do this we have to pull its cables which are attached to the stack.

* Installation of three green steering mirrors

   - All of them need to be engraved.

* Installation of two tip-tilt

  - One for the SRC and the other for the PRC

I updated the last entry about the in-vac work (see here)

[Koji, Steve, Kiwamu, Alberto]

- This afternoon we installed a few new optics on the BS table: GR_PBS, GRY_SM2, GRY_SM1.

- We pulled up the cables so that we had more freedom to move one of the cable towers farther South.

- Then we re-leveled the table. PRM OSEMs were adjusted to be nominal insertions.

- Koji released the earthquake stops on BS but the readout of the OSEMs was apparently frozen on the MEDM screens.
Initially we thought it was a software problem. a nuclear reboot didn't solve it. We spent the following three hours investigating the cause.
Eventually it turned out that the earthquake stops on BS weren't actually fully released.

We opened the tank and accessed to BS. Releasing the earthquake stops in full solved the issue. The OSEMs readout went back to normal.

[Jenne, Yoichi]

We characterized Tip Tilts numbers 2 & 3 today.  Recall #4 is the one which Koji and I measured some time ago, and #s 1 & 5 have yet to be suspended (that's on the to-do list for tomorrow).

When we began looking at #3 (the one which had been in the BS chamber for a few days, but was removed for characterization) we found that the pitch pointing was way off.  The beam was way too low after reflection.  So we adjusted that (and got it right on the first try....a miracle!).  This does however make me pretty concerned about our in-chamber pointing.  Are we destroying our pointing during travel between the cleanroom and the chambers?  Is there anything we can do about it? Pointing doesn't seem to be lost when we move them around on the tables in the cleanroom, ie we can pick up a TT, move it, leave it for a while, move it back to the oplev, and the pointing still seems okay.  But the TT which was sent to the chambers came back with bad pointing. I'm sure this is related to the hysteresis we see in the pointing if we poke the top of the mirror holder versus the bottom when exciting pitch motion.

For both #2 and #3, we measured the frequency and Q of Pitch, Yaw, Pos, Side, Vert motion.  For the Vert motion, we measured both without and with EQ stops as dampers.  For the other modes, all were measured with the ECD backplane in place.  Pitch and Yaw were measured with reflection off of the mirror surface onto the PD, while Pos, Side and Vert were measured using the wire clamp on the mirror holder to obscure the beam as a shadow sensor.

TT #2

Pitch: Overdamped, no freq measured, Q < 1/2

Yaw: freq ~1.8Hz, Q between 2-7

Pos: freq ~1.75Hz, Q too low to measure, but above critically damped

Side: freq ~ 1.8Hz, Q~5

Vert no dampers: freq ~20Hz, Q~36

Vert with dampers on outer screws: freq~24Hz, Q~8,

TT #3

Pitch: no freq measured.  Q~1/2?  Upon being excited in Pitch, the beam started down way below the photodiode, came up a little past its DC place, and went back down a tiny bit.  So not quite overdamped.

Yaw: freq ~1.96Hz, Q very low

Pos: freq ~1.72Hz, Q~3

Side: freq ~1.85Hz, Q~6

Vert no dampers: freq ~20Hz, Q~75

Vert with dampers on outer screws: freq ~20Hz, Q~34  (Frequency stayed constant....we did several measurements both with and without the dampers...but the half life time changed significantly)

Things we noticed:  Koji and I had been concerned the last time we were looking at TT#2 because the frequency got lower and the Q seemed to get higher when we added the damping to the vertical blades.  Yoichi and I did not find that to be true today.  We did notice, however, that the EQ stop screws with the viton had been placed in the holes closer to the clamping point, whereas with TT #4 the screws had been placed in the holes farther from the clamping point.  We moved the screws on TT #2 to the outer holes, and noticed that the frequency increased slightly, and the Q significantly decreased.  We then followed this outer-hole philosophy when installing screws in TT #3.

To Do List: We need to suspend the ECDs and the Optics for the remaining two Tip Tilts, and to characterize them.  We also (probably farther-future) need to take transfer functions using a shaker / shake table with our spare Tip Tilt.  After all the TTs are suspended and have their modes measured, we will be ready for installation into the chamber during the next vent.

The inner and outer screw holes of the EQ stop Jenne is talking about are shown in the photo below.

[Jenne, Yoichi]

The final 2 Tip Tilts (#1 and #5) have been suspended.  We have designated #5 the spare.  It looks like there might be a teensy bit of dust on the AR surface of the optic in #5, right near the edge of the coating.  Not a critical issue if this one is the spare, although we should see if we can blow it off with the Nitrogen.  Both #1 and #5's optics were suspended using the thicker wire, 0.0036" diameter.  This leaves 4/5 TTs with this thick wire, and 1 of the 5 has the thin wire.

To do still: Balance both #1 and #5, and then measure the modes of each.  Then we'll be ready to install them into the chambers, and we'll reserve #5 for shake table TFs for some later date.

[Yoichi, Jenne]

Hooray!!! The Tip Tilts are completely done!  The only things remaining are (1) Install 4 TTs in chambers sometime in September and (2) do shake tests / take TFs of the spare.

Today we balanced and characterized #'s 1 and 5.  All 5 TTs are waiting happily on the flow bench in the cleanroom for installation.

For the new CDS test, I turned off the watchdogs for PRM, SRM, BS, ITMs and MCs.

I will restore these watchdogs after several hours from now.

Now watchdogs are back.

The suspensions are well damped.

 [Joe, Kiwamu]

We found that the vertex watchdogs were not correctly running.

After I powercycled c1susaux, the problem was fixed successfully.

The symptom: the watchdogs didn't disable the coil signal even when PD_VAR signals went larger than the threshold values PD_MAX_VAR.

Also we replaced the label by the correct name "C1SUSAUX" on a tag which was tied to the front end machine mounted on the new 1X5 rack.

Two SOS suspensions for the ETMs were disassembled and packed for cleaning and baking by Bob.

These suspensions have been stored on the X end flow bench long years, and looked quite old.

They have some differences to the modern SOSs.

- The top suspension block is made of aluminum and had dog clamps to fix the wires.
- The side bars are not symmetric: the side OSEM can only be fixed at the right bar (left side in the picture).
- EQ stops were made of Viton.
- One of the tower bases seems to have finger prints (of Mike Zucker?).

I found that the OSEM plates had no play. We know that the arrangement of the OSEMs gets quite difficult
in this situation. Therefore the holes of the screws were drilled with the larger drill.

We decided to replace all of the screws to the new ones as all of the screws are Ag plated and got corroded
by silver sulfide (Ag₂S). I checked our stock in the clean room. We have enough screws.

Important note: Use stainless screws in aluminum / Silver-plated screws in stainless
There exists some study about galling: LIGO-G020394-00-D

The day before yesterday, I was cleaning a flow bench in the clean room.

I found that one SOS was standing there. It is the SRM suspension.

I thought of the nice idea:

- The installed PRM is actually the SRM (SRMU04). It is 2nd best SRM but not so diiferent form the best one.
==> Use this as the final SRM

- The SRM tower at the clean room
==> Use this as the final PRM tower.
==> The mirror (SRMU03) will be stored in a cabinet.

- The two SOS towers will be baked soon
==> Use them for the ETMs

This reduces the unnecessary maneuver of the suspension towers.

Because of the in-vac work on Oct. 4th (see this entry) , ITMX's OSEM offsets were changed.

The two upper OSEMs are still fine, but LL and LR seem to be out of the OSEM's range. 

The plot below shows the trends of LL's and LR's readouts for about two weeks. (The channel name are in the old convention, i.e. ITMY)

 Some data were missing due to the upgrade of the frame builder.

 It is apparent that the offsets are changed after the in-vac work on Oct. 4th, and now they just show almost zero numbers.

The damping of ITMX can still work, if LL and LR are disabled.

At some point before pumping down, we have to check the leveling of the ITMX table again.

Background:
 The output range of the OSEM is 0-2V.
 So, the OSEM output should fluctuate around 1V.
 If not, we have to modify the position of it.

What I did:
 Measured current outputs of the 5 OSEMs for each 8 suspensions by reading sensor outputs(C1:SUS-XXX_YYPDMON) on medm screens.

Result:

 White: OK (0.8~1.2)
 Yellow: needs to be fixed
 Red: BAD. definitely need fix