The target control system at 290m

Today when we tried to align the beam in the arm, we found the system to control the target at 290m.

So from the first picture you can see the blue pipe, it is connected to a pump, then it can move the platform in picture two to move the target up and down. Then in the second picture, there is a motor used to turn the target. So both of these two controller are connected to the blue box in picture three. From what written on this box, we found out we can control this system locally and also remotely. So we followed the cable from this box to the end room, found another controller there(Pic 4&5). Now we keep the target there with moving the platform and motor locally, but if we want to make future work easier, it is better to find out how to do the remote control with the controller in the end room.

Check and align the beam

Today we checked the beam at several different place and tried to find where the astigmatism came from.

First in the situation as last Friday, we checked the reflected beam from the window, it was almost like before, very obvious elongated in horizontal direction, and also checked after the window, it seems even worse than before, it used to be about circular.

Then we tried to turn the dichroic mirror in the PR chamber to reflect the infrared beam enough far(into the west arm,PI) to look at the shape, it is more or less round beam.

The third beam is the transmitted of BS1, we checked across the table(P1), it is elliptical.

Next one we checked the transmitted beam of M2, luckily this beam pass successfully through the about 5cm gap between two tubes.We had enough distance to check it(P2), this beam is already started to be longer in horizontal.

Then the last check we put another mirror between L1 and M2(MT) to reflect the beam,checked with almost the same distance with P1, it is not a perfect round beam from my sight. But then we put the beam profiler at the edge of the bench, try to get the shape with it. Actually from the profiler, it seems a pretty good beam.

Then since we already finished all the picomotors, and I finished to make the cover of the extended wire today, so then we tested the extended cable again in case that I broke some during making the cover. All of them works well. But when we tried to move the picomotors of PR chamber, there is one layer of dirvers did not work. So now we have one problem is that we do not have enough drivers for the end room.

After fixed all the problems of picomotor, then we tried to re-align the beam. We recovered the last mirror on the bench for green first(M4), since we set the position with the target, it was not very hard to do it. But then we found out that the green beam on both the turning mirror and the dichroic mirror are both not very centered, I am not sure about the situation after the middle part of the chamber put back, but since we did not change M4 in horizontal, so we keep working with that. The we realign all the beam until the BS suspension mirror.

We took the 2cm shift into consideration(Logbook entry 450), and found out the beam is a little bit right on the mirror, left on the 10m target. So the dash line shows the situation now. So then we will move the PR and BS suspension mirror together to send the beam straight, after centered it on the window and the 10m target, we will try to center it on the 290m target.

Comment to Check the reason of astigmatism (Click here to view original report: 454)

We forgot to check the beam under the red line situation after the window and after the turning mirror, also the reflection beam of the window. So maybe we can get rid some of the reasons after these three checking.

Check the reason of astigmatism

We finished the picomotor pins of the PR chamber in the morning and checked all of them work well. So this afternoon we tried to move the beam outside the dichroic mirror.

At first we tried to move the beam in the horizontal direction out of dichroic mirror. But while we were moving, we thought that if the beam is elongated in the horizontal direction because of the mirror's wedge, when we scan the mirror maybe the beam shape will change. We scanned it,but the beam is too small,it was hard to say if it has some change or not, then we thought maybe we can put a lens with very short focal length on the BS bench to make the beam bigger in the short distance, but it was also hard to say since we scanned the beam in very small step, then on the BS bench the beam moved a lot and out of the lens, then we cannot exactly sure every time we put the lens in a good position to let the beam cross its center, if we did not cross center, the beam will also effected by the lens.

Then we followed our original plan to move the beam out of the dichroic in the horizontal direction, but it stopped by the mount of the mirror, so we tried in the vertical way, when we reached the pitch limitation of turning mirror, the beam was on the top edge of the dichroic, we thought it will be better if we move the beam totally outside the dichroic, so we decided to change a little bit the degree of last mirror on the bench. Before we changed the last mirror, we use the target to set the position of the green beam after the window for easier recover the beam. Then we let the beam go outside and far away from the BS chamber, to check the situation of it.

There were some strange situation that in the near field of the BS chamber, the beam elongation is much serious than the far field. We guessed that maybe because there are some overlap in the near field to make us feel the beam is longer, then in the far field, the other small beams separated from the main one. Actually, we did see that in the far field there were more small beams. But at least, the beam got better in this test.

The other situation I want to mention is that, I am not sure that the beam got better is only because of moving out from dichroic, we also have other changes in this test. Like I showed the simple drawing in the first picture, the circle 1,2,3 is the changed point.(It maybe a little bit hard to understand since I change the 3D situation into a 2D drawing, the red line is after we made the beam path goes up, so the red beam reached the higher position of the turning mirror and pass the dichroic from top of it)

1. The beam position on the window
2. The beam position on the turning mirror
3. The beam did not cross the dichroic

Also I showed the beam shape in two situation and in the near field and far field.

The second picture is I showed yesterday on the meeting for better understanding of the situation.

Comment to Position of stack in NM2 ? (Click here to view original report: 450)

I repeat the same procedure but this time I injected the He-Ne laser beam from behind the mirror i.e.
the He-Ne laser beam goes through the input mirror. Also in this case I centered the He-Ne laser beam
on the the first target in the tube and on the window at the entrance of the tube.
In order to do so the injection point from the back of the suspension is 21.8 cm in height and 2.4 cm
to the west.

Comment to Position of stack in NM2 ? (Click here to view original report: 450)

I check again the axis and re-adjusted a little bit the He-Ne laser beam position
trying to have it better centered on the valve's window.
The height respect to the stack doesn't change. The lateral position is now 1.4 cm
west.

Mirror in NM2 chamber

I tried to investigate which mirror is suspended in the NM2 chamber.
According to the records it should be a LISM mirror with the two faces flat.
So I reflect a green pointer on the mirror and collect the two reflections
from the two sides of the mirror. I let the beams propagates over about
15 m. I can't see any difference between the beams along the propagation.
So the two sides of the mirror are both flat (or both curved with a large
curvature). The distance between the two reflections is about 2.7 cm and does
not change in a significant way along the 15 m, so the mirror does not
have a large wedge.

Position of stack in NM2 ?

Today I tried to evaluate how far is the center of the NM2 stack from the tube axis.
I define as the tube axis the axis defined by the window on the valve between the NM2 chamber and the
tube and first target in the tube. So I placed an He-Ne beam on that axis.
I doubt to be able to defined that axis to better than 0.5 cm in position and 1 cm over ~10 m in angle.
This axis intercepts the stack in the NM1 22.2 cm in height and 1.8 cm to the west.
I estimate that I have about 1 cm error on this numbers.

Update of picomotor working

Yesterday Marc and I finished all pins for all picomotors (5 for input mirror, 8 for BS chamber, 9 for PR chamber), including extending the cables for BS suspension mirror(all the green and yellow wires in 1st picture), since the BS chamber and the input mirror will use the same picomotor driver, and the cable we have now is not long enough. But we still need to make the cover for these extending cables, we already found some plastic tubes and will finish it today.

In the second picture, there are totally five layers of the picomotor driver, except the first layer(command layer) is for pad, external port, which cannot connect to picomotors, the other four layers each has 3 ports, so now we have 12 ports for BS chamber and input mirror, and actually we still need one more port.

Yesterday, we test all the picomotors connected to this driver, all of them worked well with the command send from the computer, we tried with pad for control the five picomotors for input mirror, they worked well, but there is one thing we cannot understand is that on the pad(3rd picture), on the top of it, there are two axis, x and y, some of the picmotors work with x axis and others work with y, we cannot figure out what these axis means.

The other problem is that on the pad, the maximum layers we can control is 3, so if we have more than three layers, we cannot control with the pad.

For the PR chamber, we are going to use the other driver with 1 command layer with other 3 layers totally 9 ports to control, we will try to set a new IP address for the new driver.

Also we got a set of driver from Kamioka yesterday, one command layer with other 2 layers. So now we have enough command layer(one for BS and IM, one for PR, and one for EM), the port layer(5 for BS and IM, 3 for PR,1 for EM), we still lack of one port layer if all the driver we have now work well.

Comment to Change the new picomotor driver (Click here to view original report: 447)

Add the pictures

Change the new picomotor driver

Today we changed the picomotor cable of the input mirror into the type matching the new driver(shows in the second picture). And according to the standard way of putting the pin, we put them into the right order, show in the first picture. The new picomotor driver's IP address has already set up by Eleonora(133.40.121.13). We connected this IP address with the computer, check all the picomotors, they all worked well.

From the second picture can also see that now, since we only need to control five picomotors, so we only put two layers(except the first layer).

I list this simple command to move the picomotor for easy checking later: now for us there are only a1,a2 two layers, and each layer have 0,1,2 motor

chl--> to see which motor is working in each layer

chl a1=1--> change the working motor of a1 to 1

vel--> check the velocity of each motor

vel a1 1=1000 -->change the velocity of a1 motor 1 to 1000

rel a1 1000 g --> move a1(the motor which move is defined by the second command)

Next step we are going to make and change the all the cables of the BS and PR chamber, the BS chamber can use the same driver with the input mirror, just add more layers. But for the PR chamber, we need to use a new driver, which means we need to set up another IP address for that driver. There is also one driver left then for the end mirror. Also we need to check if the picomotors also work well with the pad.

Check the green beam

I tried to put lens on the green path, for one side, to reduce the beam size for easier measurement, the other side to check if the distortion of the beam change or not.

I put the 500mm focal length lens after the lens we have now, shows in the first picture, under this circumstance, the beam is still circular after the bs mirror of the MZ, but after the mirror of the MZ, it becomes two separated circular beams because the second surface reflection of that mirror. These two beam goes along the path, at some point around the last mirror on the bench, they overlapped. So before the beam goes into the window, it is a really good beam, but after the window it’s separated into two again, so at first I thought maybe this is the reason of the distortion.

Then I blocked the reflection beam from the mirror on the bench, only left the main one, the second beam after the window is still there, so this second beam is produced by the reflection of the window.

Then inside the chamber, the beam after the window, only the main one arrives at the first dichoric mirror, the other one hit the frame of the suspension. So till here, we only have one circular beam, then I checked beam between the PR chamber and the BS chamber, it turns into ellipses. We talked with Matteo and we thought the problem is from the dichoric mirror which combine the green and the infrared. But since now we are not in a very good alignment, we will do the alignment again, and then check the shape of the beam. If it is still the same, we will change the dichoric mirror and to see if we can have some positive result.

For choosing the lens to reduce the beam, now I don't know what kind of focal length I should use. I think I will do one calculation with the measurement I did, got some result, and to see the roughly range of the focal length I can use, then put them there and do the measurement again to find better combination.

About re-align the beam, Matteo also gave us some steps to do that:
(All the things we need to move including, the turning mirror for green, the dichoric mirror for combining the green and infrared, the 2 inch mirror of the telescope, the PR suspension mirror, the BS suspension mirror. The mirrors are in the order of the beam pass through.)

1.Put the target in front of the 2 inch mirror, move the turning mirrors to center it.

2.Put the infrared card in front of the PR suspension mirror, center the green (and infrared?) with moving the 2 inch mirror.

3.Target in front of the BS suspension mirror, move the PR suspension mirror.

4.Check if the beam is centered at the 2 inch mirror(?)

5.Center the infrared beam on the BS suspension mirror with moving the dichoric mirror.

6.Check at the 2 inch mirror, the green and the infrared surpass or not.

Repeat these steps, until everywhere is centered.

Try to send the video signal from the end room to the central room

I tried to find a way to send the video signal from the camera at 290m to the central room.

Firstly, I tried the optical fiber used to send the PD signal,connected it to the camera at the end room, and connected it to the screen in the central room. There is only some flash when I turned on and off the receiver, but seems not capable to get the real signal from the camera.

Then we found out there is another system like a recorder that can be used. I plugged the recorder with the camera and the output to the screen at the end room. It works pretty well. And also there is a sticker with an IP address on it. We found the right internet cable for it, and tried to connected it with the computer in the center room. We successfully connected it, but cannot see the video signal.

Then we checked the old TAMA board which can convert the video into optical signal, send through the fiber and there is another this kind of board in the central room to convert it back, then connect to the screen, then we should see the video on the screen. At first, we tried with the cable 1-13 and 1-14, but we are not able to see anything from the screen. Then we tried to change the cable into 1-15 and 1-16, then we got the video in the central room.

The first picture is taken on the screen near the camera at 290m, the second picture is taken in the screen in the central room, both taken by my phone. It seems there are some loss during the signal transmission. Then we adjust the camera's position and also the focal lengths, and inject the red light into the arm, the third and the forth pictures are taken at 290m and central room.

The fifth picture is the board we are using now.

Picomotor control issue

I upload some slides I have prepared to summarize the picomotor control issue we are facing.

Finish the design of telescope on infrared path

With Matteo's correction, I found out I made some mistakes in the dimension of the final beam size we need on the 2 inch mirror and the FI.

The right dimension should be about 1mm when it arrives at the 2 inch mirror and a little bit larger like around 1.4mm at the FI, so the beam waist should almost at the mirror.

With these new conditions, I found some combination, chose the best one in the size and position, and check the position of the lens not overlap the mirror position we already mounted on the bench. The result shows as below.

The origin is set at the front surface of the BS mirror as I mentioned in my last entry.

L1: z=48.5cm f=500mm(already mounted)
L2: z=173.5cm f=300mm
L3: z=236cm f=350mm

With these lens, the final beam size at the FI is 1.368mm and the size of the beam waist is 0.97mm at the position of 648.57cm with the mirror's position at 648.15cm.

Also check again with JamMT, it shows the same result with the calculation.

The telescope of infrared design

We measured the infrared beam size last Friday and calculated the beam waist size and position:(set the front surface of the BS mirror as origin) the position of the beam waist is z=-12.0623 cm, size is 98.0277 um.

Then we measured the distance between the origin and FI in the PR chamber, and between the origin and 2inch mirror in the BS chamber.

The calculation process is as below:

The distance between the O and FI(z1)=277.5(The path length on the bench)+63.65(From the last hole of the bench to the window)+13.5(the depth of the viewport)+26.5(the distance between the chamber wall and the first mirror)+5.5(the length between and the FI)=386.65cm

The distance between the O and mirror(z2)=z1+16(the FI length plus the distance between FI output and the second mirror)+16(the second mirror to the dichoric mirror)+37(dichoric mirror to the chamber wall)+162(the distance between two chambers)+15(the BS chamber wall to the chamber bench)+57.5(the edge of the bench to the mirror)=648.15cm

The first lens is already put with focal length of 500mm at 48.5cm. Then there are other conditions need to be satisfied.

1.The beam waist should be around the 2inch mirror in BS chamber, and the size should be less than 103 um

2. The size of the beam at FI should also less than 103um.

3. All the lens should on the bench which means should located in the position z<=270 cm, because the last mirror is at 270cm.

I am trying to find a good combination with other two lens, but until now I did not get any result, I will try with more combination or I will add one more lens. Also today I measured the green beam path, but actually I did not know if I should trust the measure result or not, since the green beam is almost the same size or even larger than the size of the beam profiler, so I will try to put another lens first and try to measure it again.

Beam injection in the south arm

Participants: Eleonora, Manuel, Yuefan, Raffaele

Today we have worked on the injection of the beam, exiting the telescope, in the south arm cavity.

1) We have moved the 2" mirror telscope in the BS chamber 5 cm closer to the PR in order to have a distance of 272.5 cm between the two telescope mirrors. 

   distance  = f1 + f2  =  272.5 cm  where  f1 = 302.5 cm (see entry 419)  and f2 = -30 cm  (see entry 431)  

2) We have used a spare TAMA PR mirror (ROC of about 9 km, almost flat)  placed on a tripod, as steering mirror to send the beam in the corridor beside the pipe in order to check its features. We manage to send it into the end room and obseved its shape after 300 m. We remark that:

     a)  The beam is well collimated as it keeps roughly the same dimension after 300 m.

     b)  The beam moves a lot because of the air 

3)  We injected the green beam through the first viewport before NM2 chamber and tried to observe it on a target placed at 10 m,  without success. We changed the beam direction moving the yaw and the pitch of the last telescope mirror.

4) We injected a red beam in the viewport and we were easily able to make it impinge on the target at 10 m. We observed that, in order to be centered both on the target and on the viewport the beam has to start from a position about 4 mm higher than the green beam position (21.3 cm from the stack top plate)

Conclusion: It is not clear the reason why we cannot see the green beam on the target at 10 m. The only two possible reasons we could imagine are that we were not able to properly align the beam or that it is not enough transmitted by the viewports or by the temporary mirror installed in the NM2 chamber (a former LISM mirror ). Effects of a possibile antireflective coatings for the infrared light on the green light should be investigated.

Attached pictures:

1- Green beam at 150 m

2- Green beam at 300 m

3- Red beam impinging to the target at 10 m

PR spectra: possible evidence of intermediate mass touching the magnet holder plate

I have measured transfer functions and spectra for the PR mirror.

- Figure 1: TF when injecting noise in YAW

- Figure 2: TF when injecting noise in PITCH

- Figure 3: spectrum YAW (comparison open and closed loop)

- Figure 4: spectrum PITCH (comparison open and closed loop)

NB. It seems that there is some acoustic noise: I did the measurement with the light switched off but the chamber was open and I didn't put any boxex around the laser and the PSD

While looking at the error signals in the past days I have noticed that often some strong oscillations at 1 Hz and 3 Hz were present (see figure 5). We observed it also in the past and we were suspecting the stack vibratiion introduced by the steering mirrors used for the optical lever ( see entry 276:  the attached spectra taken last july are very similar to those of fig 5)

Since this oscillation is not present when the intermadiate mass is well centered on the magnet older plate (as it was just after the mirror installation or today after that I performed the check on the yaw motion) and it appeared after we tried to move as much as possible the yaw picomotor yesterday, I think it is caused by the intermediate mass touching the magnet holder plate.

Investigation on the PR yaw motion

In order to better quantify the yaw motion of the PR suspended mirror I made the optical lever reflected beam imping on a ruler put at a distance of about 88 cm from the mirror.(See attached picture 1)

I started from one side of the picomotor range (left column of the second attached picture) and I kept turing the screw as far as I was able to see a beam movements on the ruler. 

I had to stop well before that the end of the range of the picomotor (right column of the second attached picture) since the beam was not moving anymore (and the mirror was oscillating a lot)

Even if it difficult to clearly see it, I think that the intermiate mass was touching the magnet holder plate preventing a further motion.

The total motion of the beam on the ruler is about 1.5 cm which corresponds to 8.5e-3 rad.

Picomotor driver issue

After the problem reported yesterday here.  I have replaced the picomotors GPIB driver with a similar one that I have found in the south end room.

At the beginning it seems to work fine and I was able to move the 3 degree of freedom of the 2'' telescope mirror in both direction both with the pad that using the PC.

Then, I have noticed that while connecting more than one cable to the driver output ports,  it starts showing some problems. 

Its behaviour becomes very strange and it is no loger possibile to move properly the selected channel neither from remote nor with the pad.

For exemple: if I send a remote command to move a specific channel the driver display shows correctly the name of the selected channel but it cannot move it and will instead make other picomotor ( connected to a different channel) to produce some noise.

I could not find any repetable pattern in such kind of strange behaviour while trying to test different combination of slots and cables. 

I only noticed that everything is working fine when only one cable is connected.

Since Raffaele suggested that it can be a cabling problem, I spent some times to check the connections but I haven't find anything wrong so far.

In the attachement there is a picture of the connection we made between the 2" telescope picomotor and the invacuum cable.