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ID Date Author Type Categoryup Subject
  2375   Thu Dec 10 00:46:15 2009 KojiUpdateSUSRe: free swinging spectra of ETMY and ITMX

Well, I get the point now. It could be either seismic or change in the suspension Q.

The pendulum memorizes its own state for a period of ~ Q T_pend. (T_pend is the period of the pendulum)
If the pendulum Q is very high (>104), once the pendulum is excited, the effect of the excitation can last many hours.

On the other hand, in our current case, we turned on the damping once, and then turned off the damping.
Again it takes ~Q T_pend to be excited. 

In those cases, the peak height is not yet before in equilibrium, and can be higher or lower than expected. 

So, my suggestion is:
Track the peak height along the long time scale (~10hrs) and compare between the previous one and the current one.
This may indicate whether it is equilibrium or not, and where the equilibrium is.

Quote:

If such variation of the peak heights is cased by the seismic activity, it means the seismic level change by several 10 times. It sounds large to me.

 

  2391   Thu Dec 10 17:13:36 2009 kiwamuUpdateSUSFree swiging spectra under the atmospheric pressure

The free swinging spectra of ITMs, ETMs, BS, PRM and SRM were measured last night in order to make sure that nothing wrong have happened by the wiping.

I think there are nothing wrong with ITMs, ETMs, BS, PRM and SRM successfully.

For the comparison, Yoichi's figure in his elog entry of Aug.7 2008 is good, but in his figure somehow PRM spectrum doesn't look correct.

Anyway, compared with his past data, there are no significant changes in the spectra. For PRM which has no counterpart to compare with, its shape of spectra looks similar to any other spectra. So I think PRM is also OK. The measured spectra are attached below.

Indeed the current data are still showing smaller peak height for their pitch and yaw modes (roughly factor of 10 ).
 
Attachment 1: summary_freeswing.pdf
summary_freeswing.pdf summary_freeswing.pdf summary_freeswing.pdf summary_freeswing.pdf summary_freeswing.pdf summary_freeswing.pdf summary_freeswing.pdf
  2405   Sun Dec 13 17:43:10 2009 kiwamuUpdateSUSfree swinging spectra (vacuum)

The free swinging spectra of ITMs, ETMs, BS, PRM and SRM were measured under the vacuum-condition. The attachment are measured spectra.

It looks there are nothing wrong because no significant difference appear from the past data and the current data (under atmosperic pressure).

So everything is going well.

Attachment 1: summary_FreeSwinging_vacuum.pdf
summary_FreeSwinging_vacuum.pdf summary_FreeSwinging_vacuum.pdf summary_FreeSwinging_vacuum.pdf summary_FreeSwinging_vacuum.pdf summary_FreeSwinging_vacuum.pdf summary_FreeSwinging_vacuum.pdf summary_FreeSwinging_vacuum.pdf
  2433   Sun Dec 20 14:34:24 2009 KojiUpdateSUSETMY watchdog tripped Sunday 5:00AM local

It seemed that the ETMY watchdog tripped early Sunday morning.
The reason is not known. I just looked at ETMX, but it seemed fine.

I called the control room just in case someone is working on the IFO.
Also I did not see any elog entry to indicate on going work there.

So, I decided to reset the watchdog for ETMY. And it is working fine again.

Attachment 1: Y.png
Y.png
  2457   Mon Dec 28 12:35:57 2009 JenneUpdateSUSMC2 is having a bad day

MC2 is having a bad day, and I'm not yet sure why.  It's to do with the damping though.  When the damping is off, after a little while it will settle to ~30mV or so on the Watchdog screen.  When I enable all of the outputs and then turn on the damping, the optic gets kicked up.  It's like there's a minus sign error somewhere, maybe in a bad burtrestore?  This has been going on since I did my morning bootfest.

It's started to sit down and play nicely now.  Is someone doing magic remotely that is fixing things that I hadn't figured out yet?

  2458   Mon Dec 28 12:45:55 2009 KojiUpdateSUSMC2 is having a bad day

The MCL path of MC2 was in a strange state as the filters were activated as if it is in lock even though we had no lock. So I manually ran "mcdown". This reset the filters of the MCL path.

Quote:

MC2 is having a bad day, and I'm not yet sure why.  It's to do with the damping though.  When the damping is off, after a little while it will settle to ~30mV or so on the Watchdog screen.  When I enable all of the outputs and then turn on the damping, the optic gets kicked up.  It's like there's a minus sign error somewhere, maybe in a bad burtrestore?  This has been going on since I did my morning bootfest.

It's started to sit down and play nicely now.  Is someone doing magic remotely that is fixing things that I hadn't figured out yet?

 

  2494   Sun Jan 10 13:32:09 2010 HaixingUpdateSUStransfer function measurement of the quadrant maglev circuit

I have assembled the circuit and the control box for the quadrant magnetic levitation yesterday. The final setup is shown

in the figure below:

Quad_maglev_ctrl_box_in.JPGQuad_maglev_ctrl_box_front.JPG

 

Due to my carelessness, I I connected the wrong ends of the power supply. I damaged 4 op-amp and one voltage 

regulator during this assembly. This stupid mistake spent me several hours to fix, and I got a bitter lesson;-(

 

Afterwards, I replaced those op-amps and reconnected the power supply . Kiwamu helped me and we measured

the transfer function of this circuit.  The transfer function agrees with  the specification in the schematics which

has a integrator below 1 Hz and a differentiator from 5 to 20 Hz. The bode plot for the measured transfer function

is the following:

quad_mag_tf_amp.png

 quad_mag_tf_phs.png

Today I tested the photodetector parts and found that there is a mysterious oscillation. Whenever I connect the

photodector input A of the circuit (as indicated in the figure below),

PD.PNG

the output of the op-amp has a 500k Hz oscillation shown up in the oscilloscope.This happens even A is disconnected from

the photodetector and connected to an open end wire. I don't know how to eliminate it, and its amplitude is so large (peak to

peak is around 2.5 V) which completely dominates the photodetector output. Does anybody has some ideas? Thanks.

 

Quad_mag_lev_osc.JPG

  2495   Sun Jan 10 15:47:26 2010 KojiUpdateSUStransfer function measurement of the quadrant maglev circuit

1. Why do all of the BNCs have no GND connection? Each should have the individual cables to the ground. Each signal line and the corresponding ground line should be twisted together.

2. This looks the (usual) oscillation of the V-I conversion stage but I can't tell anything as I don't have the circuit diagram of the whole circuit.

3. In a certain case, putting some capacitance at the feedback may help. Read P.11 of the data sheet of LT1125. Try to put some capacitors from 20pF to some larger one whether it changes the situation or not. I suppose the bandwidth of your sensor can be ~1kHz. So putting a capacitance less than 10nF still has no effect to the servo.

  2497   Sun Jan 10 16:50:34 2010 HaixingUpdateSUStransfer function measurement of the quadrant maglev circuit

Quote:

1. Why do all of the BNCs have no GND connection? Each should have the individual cables to the ground. Each signal line and the corresponding ground line should be twisted together.

2. This looks the (usual) oscillation of the V-I conversion stage but I can't tell anything as I don't have the circuit diagram of the whole circuit.

3. In a certain case, putting some capacitance at the feedback may help. Read P.11 of the data sheet of LT1125. Try to put some capacitors from 20pF to some larger one whether it changes the situation or not. I suppose the bandwidth of your sensor can be ~1kHz. So putting a capacitance less than 10nF still has no effect to the servo.

 1. They are all connected to the box which has a single connection to the board ground. If I connect each of them to the ground, there would be many small loops

of ground. Of course, I should have replaced all the connectors such that the they are disconnected to the box as point out by Robert.

2. The oscillation disappears after I add 5 nF capacitor in parallel to the existing resistor. Thank you very much for pointing this out.

  2498   Sun Jan 10 17:15:25 2010 KojiUpdateSUStransfer function measurement of the quadrant maglev circuit

1. Yes. That is the bad. You should eventually replace the BNCs to the isolated ones.

2. OK. I like to emphasize again that everyone works on electronics should read data sheets more carefully and seriously because they have many important practical instructions to exploit full performance of the components. 

Quote:

Quote:

1. Why do all of the BNCs have no GND connection? Each should have the individual cables to the ground. Each signal line and the corresponding ground line should be twisted together.

2. This looks the (usual) oscillation of the V-I conversion stage but I can't tell anything as I don't have the circuit diagram of the whole circuit.

3. In a certain case, putting some capacitance at the feedback may help. Read P.11 of the data sheet of LT1125. Try to put some capacitors from 20pF to some larger one whether it changes the situation or not. I suppose the bandwidth of your sensor can be ~1kHz. So putting a capacitance less than 10nF still has no effect to the servo.

 1. They are all connected to the box which has a single connection to the board ground. If I connect each of them to the ground, there would be many small loops

of ground. Of course, I should have replaced all the connectors such that the they are disconnected to the box as point out by Robert.

2. The oscillation disappears after I add 5 nF capacitor in parallel to the existing resistor. Thank you very much for pointing this out.

 

  2510   Tue Jan 12 13:24:50 2010 HaixingUpdateSUSQuadrant Magnetic Levitation

I have tried to make the quadrant magnetic levitation work but unfortunately I did not succeed. During the experiment, I have made

the following changes to the circuit and setup:

 

(1) I added small resistors (6K) in parallel to R11, R23, R35 and R47 (indicated in the following schematics)  to increase

the control bandwidth from 20 Hz  to 80 Hz.

 

 

schmematic.png

 

(2) I changed RLED1, RLED2, RLED3, RLED4 from 2.2K to 1.5K  in the LED driver such that the current of the

LED increases and in turn the displacement sensitivity increases.

 

(3) I changed R51 and R51 (in the differencing block for PD1 and PD2) from 5K to 1 K. Correspondingly,

I increased R52 and R54 from 5K to 50K. This changes increase the gain in the differential control by a

factor of 50, which compensates the gain loss after increasing the control bandwidth.

 

 (4) The trim pots in the coil drive block have the following values: 100K for pot1 and pot4, 1K fro pot 2 and pot3.

To increase the gain, I replaced R17, R30, R31, R41 by 102 Om resistors (we run out of 100 Om chip resistors.)

 

(5) I wrapped the OSEM flags by plastic tubes to block the light from the LED more efficiently. This also removed

the changes of the photocurrent in the photodetector when the levitated plate moves horizontally.

 

Possible issues that cause the setup not working at the moment:

 

(1) The feedback gain could be probably still not enough. During the experiment, I can't feel any force changes when the

flags crossing the zero point. The error signals and control signal has the right sign.

 

(2) The levitated weight may be not enough and the working point is below the extremum of the DC attracting force.

This could give rise to a large negative spring which requires unreasonable feedback gain to compensate.

 

(3) The DC attracting force between the magnets are differing each other too much (mismatch) and can't

be compensated by the coil driving force.

 

(4) The control bandwidth may be still not  large enough. Initially my design was 100 Hz, but I forgot to divide

the angular frequency by 2pi and the resulting circuit has a bandwidth of 20 Hz. Later I increase it up to 80 Hz

by changing the resistors as mentioned before.

 

(5) The polarization of the coil could have a wrong sign. I have checked with Gauss meter, but still the absence

of zero-point crossing force change makes me worry about this.

 

For continuation of this work, I will finish writing my document and summarize all the results and outline what

needs to be done in the future. If everything goes well, I will be back in June and can spend more time on this

experiment. I can also work with the summer students together on this project.

  2574   Fri Feb 5 14:31:46 2010 JenneUpdateSUS2 SOS towers assembled

[Jenne, Kiwamu]

The 2 SOS towers for the ITMs have been assembled, and are on the flow bench in the cleanroom.  Next up is to glue magnets, dumbells, guiderods and wire standoffs to the optics, then actually hang the mirrors.

DSC_1156.JPG

  2641   Thu Feb 25 19:59:50 2010 KojiConfigurationSUSITMX OSEMs

Koji, Steve

ITMX OSEM CONFIGURATION

 

Attachment 1: osem_config_ITMX.png
osem_config_ITMX.png
  2651   Tue Mar 2 23:11:43 2010 KojiUpdateSUSITMX hung

Jenne and Koji

We successfully hung ITMX on the SOS. Side magnet is ~2mm off from the center of the OSEM. ITMX aligned using the QPD. The OSEMs changes the alignment. It looks that something magnetic is inside the OSEM PD or LED.

Reguled ITMY side magnet.

Cleaned up the lab for the safety inspection.

  2652   Wed Mar 3 02:57:29 2010 JenneUpdateSUSITMX hung

Quote:

Jenne and Koji

We successfully hung ITMX on the SOS. Side magnet is ~2mm off from the center of the OSEM.

Reguled ITMY side magnet.

Cleaned up the lab for the safety inspection.

 Some details on the side magnet situation from today: 

To glue the magnets+dumbbells to the optics, we use the magnet-dumbbell gluing fixture.  This fixture is supposed to have teflon 'pads' for the optic to sit on while you align it in the fixture, however the fixture which we received from MIT (it's Betsy's....but it came via MIT) only had one of the 4 teflon pads. 

Kiwamu and I decided (last week, when we first glued ITMX's magnets) that it would be bad news to let the AR face of the optic sit on bare metal, so we fashioned up some teflon pads using stock in a cabinet down the Yarm.  We were focused on thinking about the face magnets, and didn't think about how the thickness of the teflon affected the placement of the side magnet.  We chose some teflon that was too thin by ~1mm, so the optic sat too low in the fixture, resulting in the side magnet being glued too close to the HR side of the optic (this is all along the Z - axis, where Z is the direction of beam propagation). 

Why it ended up being 2mm off instead of only 1mm I don't really have an explanation for, other than perhaps tightening the set screws to hold the optic (by the barrel) in the fixture pushes the optic up.  I observed this happening when I didn't put any effort into keeping the optic flat on the teflon pads, but I thought that I made sure the optic was seated nicely in the fixture before starting to glue.  When I glued the new ITMY side magnet tonight I tried to make sure that the optic was seated nicely in the fixture.  We'll see what happens.

Before gluing the new ITMY side magnet (and now it's set for all future magnet gluings....), I found 4 teflon pads of all the correct thickness.  It turns out that we have a magnet gluing fixture of our own, which I found in the cabinets in the clean room.  This fixture had all 4 teflon pads, so I stole them and put them into the one that we're using for this round of upgrade / suspension hangings.  The height of all future side magnets should be correct. The thickness of the pads in the 'spare' fixture matched the one which came with the fixture from MIT as closely as I could feel by putting them on the same flat surface next to each other and feeling if there was a step. 

A side note about this magnet gluing fixture that I found:  It has the word "TOP" etched into it, to prevent exactly my problem with the ITMY side magnets in the first place.  Unfortunately the threads for the set screws which hold the optic are shot (or something is funny with them), so we can't just use this fixture. 

Gluing notes regarding the standoffs and guiderods:

There's more glue than I'd like on the guiderods / standoff for ITMX.  The glue was starting to get a little tacky when I glued the standoff in place after we balanced the optic, so it was hard to get it in the right place.  I'm confident we have a good epoxy contact, and we don't have much glue that I think it'll be a big problem.  Certainly I'll be a lot better at manuvering my glue-stick a.k.a skinny piece of wire around the suspension tower to get to the standoff for the rest of the optics that we're hanging, and I won't have glued something like ITMY side magnet immediately beforehand, which took enough time that the glue started to get tacky (not very tacky, just barely noticeably tacky).

I'd say that most gluing activities should be completed within ~10-15min of mixing the glue, after spending ~2min stirring to make sure it's nice and uniform.  It doesn't dry fast enough to be a huge rush, but you should get right on the gluing once the epoxy has been mixed. 

  2658   Fri Mar 5 11:21:18 2010 steveUpdateSUSused OSEMs are magnetic

Quote:

Jenne and Koji

We successfully hung ITMX on the SOS. Side magnet is ~2mm off from the center of the OSEM. ITMX aligned using the QPD. The OSEMs changes the alignment. It looks that something magnetic is inside the OSEM PD or LED.

Reguled ITMY side magnet.

Cleaned up the lab for the safety inspection.

 The brand new OSEM LED and PD can be picked up with a weak magnet. These ferrous metals of LEDs and PDs will be magnetized by sitting in the sus next to the

magnets for years. I hanged optics with new OSEMs and never saw this effect before.

 

 

We have to demagnetize them.

  2659   Fri Mar 5 18:04:56 2010 ranaUpdateSUSused OSEMs are magnetic

The OSEM LEDs and PDs from Honeywell have always had some ferromagnetic material in them. These are the same OSEMs we had since 2000.

You must be thinking of the really old 20th century plastic OSEMs.

  2668   Thu Mar 11 17:51:04 2010 KojiUpdateSUSRecent status of SOSs

Jenne, Koji

Recent status of SOSs:

We completed one of the suspension (ITMY).

ITMX: 6 Magnets, standoffs, and guide rod glued / balance to be confirmed / needs to be baked
ITMY: 6 Magnets, standoffs, and guide rod glued / balance confirmed / needs to be baked
SRM: 6 Magnets, one standoff, and guide rod glued,  / waiting for the release from the gluing fixture.
PRM: one standoff, and guide rod glued / waiting for the magnet gluing. 

We think we solved all the problems for hanging the suspensions.

--- Magnet gluing fixture ---

  • There is the two kinds of fixtures. Neither does work propery in the original form!
  • The height of the side magnets should be finely adjusted by changing the teflon sheets beneath the optics in the fixture.
  • Be aware of the polarity of the fixture in terms of the side magnets
  • Wrongly glued magnets (and others) can be removed by a razor blade with some amount of acetone.
  • The pickle picker frequently knocks the magnets down during the release. Don't s be down in the dumps too much.

--- Suspending the mirror ---

  • The wire winches must be carefully attached to the suspension tower such that the wires are not streached during fastening the clamps.
  • There are a couple variations of the drawings for SOS. The one we have has #4-40 for the earthquake stops at the bottom.
    Zach and Mott made the EQ stops with the right size.
  2677   Tue Mar 16 09:37:30 2010 steveUpdateSUSeq 4.4 seen by oplevs and osems

The oplev plots clearly show the alignment effect of this eq.

Attachment 1: opleveq4.4.jpg
opleveq4.4.jpg
Attachment 2: eq4.4.jpg
eq4.4.jpg
Attachment 3: opleveq4.4d3.jpg
opleveq4.4d3.jpg
  2717   Sat Mar 27 16:23:10 2010 KojiUpdateSUSanother SRM sidemagnet glued

Kiwamu and Koji

Last night we have released PRM from the gluing fixture. All of the six magnets are successfully released from the fixture.

We put SRM on the fixuture and glued a side magnet which we had failed at the last gluing.

We let it cure in the Al house. This should be the last magnet gluing until ETMs are delivered.

[Current status]

ITMX (ITMU03): all of magnets/guiderod/standoffs glued, mirror baked; balance to be confirmed
ITMY (ITMU04): all of magnets/guiderod/standoffs glued, balance confirmed, mirror baked
SRM  (SRMU03): magnets/guiderod/standoff glued; a side magnet gluing in process, balance to be confirmed, last stand off to be glued, mirror to be baked
PRM  (SRMU04): magnets/guiderod/standoff glued; balance to be confirmed, last stand off to be glued, mirror to be baked

TT:            magnets/guiderod/standoff glued; balance to be confirmed, last stand off to be glued, mirror to be baked

  2730   Mon Mar 29 18:41:34 2010 KojiConfigurationSUSStarted to build TTs

Steve and Koji

WE started to build 5 TTs. 4 of them are used in the recycling cavities. One is the spare.

We built the structure and are building the cantilever springs.

Attachment 1: IMG_2348.jpg
IMG_2348.jpg
  2731   Mon Mar 29 18:50:14 2010 KojiUpdateSUSPRM sidemagnet glued

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.

Attachment 1: StatusTable.png
StatusTable.png
  2753   Thu Apr 1 17:35:24 2010 KojiUpdateSUSWorking on ITMX/Y

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.

 

Attachment 1: IMG_2353.jpg
IMG_2353.jpg
  2766   Mon Apr 5 09:48:57 2010 KojiUpdateSUSITMs placed on the tables in 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.

 

  2769   Mon Apr 5 11:39:41 2010 steveUpdateSUSITM-south installation

Quote:

Steve and Koji (Friday, Apr 02)

Summary

Installation 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

 

  2773   Mon Apr 5 14:10:06 2010 steveUpdateSUSsus damping restored

Quote:

This morning, at about 12 Koji found all the front-ends down.

At 1:45pm rebooted ISCEX, ISCEY, SOSVME, SUSVME1, SUSVME2, LSC, ASC, ISCAUX

Then I burtestored ISCEX, ISCEY, ISCAUX to April 2nd, 23:07.

The front-ends are now up and running again.

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

  2777   Tue Apr 6 22:54:34 2010 KojiUpdateSUSITMY (south) aligned

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

The OSEMs were adjusted with the aligned optics, but still a bit off from the center. They need to be adjusted again.
One round-shaped counter-weight removed from the table. Some counter weights are moved.

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.

IMG_2362.jpg

 


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.

  2796   Mon Apr 12 22:51:31 2010 KojiUpdateSUSITMX installed and aligned

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.

 IMG_2381.jpg

 


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.

  2800   Tue Apr 13 20:02:02 2010 KojiUpdateSUSBS chamber opened, PRM/SRM SOS removed from the table

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.

Attachment 1: IMG_2384.jpg
IMG_2384.jpg
  2813   Tue Apr 20 08:00:52 2010 steveUpdateSUSETMY damping restored

ETMY sus damping was restored

  2848   Mon Apr 26 21:12:53 2010 KojiUpdateSUSPRM/SRM standoffs glued

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.

  2862   Fri Apr 30 23:16:51 2010 KojiUpdateSUSSRM/PRM ready for baking

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.

  2863   Sun May 2 13:04:51 2010 KojiSummarySUSCoil Actuator Balancing and Spot Position

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]

Attachment 1: coil_balance.png
coil_balance.png
  2865   Sun May 2 15:38:12 2010 ranaSummarySUSCoil Actuator Balancing and Spot Position

 

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...

  2866   Sun May 2 16:52:44 2010 KojiSummarySUSCoil Actuator Balancing and Spot Position

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.

 

Quote:

 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...

 

  2867   Sun May 2 17:16:43 2010 KojiUpdateSUSHow to steer the incident beam to the MC?

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.

Attachment 1: steering.png
steering.png
  2868   Mon May 3 00:36:49 2010 KojiUpdateSUSHow to steer the incident beam to the MC?

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

 

Quote:

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

 

  2870   Mon May 3 01:35:41 2010 KojiUpdateSUSLessons learned from MC spot centering

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.

  2901   Sun May 9 20:02:23 2010 ranaConfigurationSUSSUS filters deleted again to reduce CPU load on c1susvme2 again

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.

40.png400.png

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.

  2939   Mon May 17 10:57:16 2010 steveConfigurationSUSdamping restored to ETMYs

ETMY-south sus damping was restored

  3104   Wed Jun 23 12:47:43 2010 JenneUpdateSUSPRM, SRM ready for vacuum

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.

Attachment 1: SRM_pitch_offset_small.jpg
SRM_pitch_offset_small.jpg
  3162   Tue Jul 6 17:38:27 2010 JenneUpdateSUSTip Tilt Progress!

[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...

  3171   Wed Jul 7 19:41:27 2010 JenneUpdateSUS1.5 more ECD sets suspended for tip tilts

[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.

Attachment 1: ECDbackplane_blackdump_small.jpg
ECDbackplane_blackdump_small.jpg
Attachment 2: ECDbackplane_foil_small.jpg
ECDbackplane_foil_small.jpg
  3197   Mon Jul 12 15:49:56 2010 nancyUpdateSUSCharacterisation of the QPD

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

:fullyaw.jpg

The slope of teh linear region is -8356 /inch

yaw_linear.jpg

 For pitch

fullpitch.jpg

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

 

pitch_linear.jpg

 

  3198   Mon Jul 12 17:05:30 2010 nancyUpdateSUSCharacterisation of the QPD

Quote:

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 :

 

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

plot.png

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

Attachment 1: plot.png
plot.png
  3201   Mon Jul 12 22:01:13 2010 KojiUpdateSUSOne TT suspended. Still need fine alignment

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.

Attachment 1: IMG_2634.jpg
IMG_2634.jpg
  3233   Thu Jul 15 23:51:47 2010 Mr. MaricHowToSUSLevitate me if you can

You guys must work harder.

mag_lev.jpg


  3235   Fri Jul 16 13:05:48 2010 Kyung-haUpdateSUSLate update for 7/13 Tue (Tip Tilts)

[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?)

  3249   Tue Jul 20 11:49:31 2010 JenneUpdateSUSSome Suspensions not damping

[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.

  3278   Fri Jul 23 15:54:38 2010 kiwamuUpdateSUSPRM and TT installed

[ 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

 

Attachment 1: DSC_2275.JPG
DSC_2275.JPG
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