picomotors connection issues

In the past days we made some tests in order to check the communication between the computer and the picomotor controller.

Details on the picomotors drivers can be found in the user's manual at this link:

http://164.54.212.3/control_systems_manuals/87XX_Manual_RevC.pdf

We followed the instructions to configure the ethernet connection at page 48/50 of the manual but we didn't succeed in setting the communication.

We did the following steps:

1) Connect a PC to the serial port and send a IPADDR MCL command to get the IP address of the controller. For the controller named NM2 we got the IP 10.68.10.241.

2) Connect the controller and the computer to the same ethernet network in TAMA and try to ping the drivers from the pc without success.

3) Since we are convinced that the IP we got is not the good one to connect to TAMA newtwork ( all the other adresses are of the form 133.40.XXX.XX) we tried to ask the IP adress (again by using serial port) after having connected the drivers to the ethernet but we got the same answer.

We probably need the advice of a TAMA network expert in order to fix the problem.

Crystalline coating roughness

We have 2 crystalline coating samples from CMS company, one attached on a silica substrate and one on a sapphire substrate.

I plot the surface roughness of the crystalline coating samples we measured at LMA.

I calculated the PSD of the surface profile.

Progress of Feb 28th

I removed the EOM and checked the polarization, if not there is not enough space for PBS. The total power inject onto the PBS is 768mW, and the reflect part is 764mW, so I think this is enough to prove the polarization is S.

Then I put the EOM back and adjust it to a good position, also change the move the BS mirror a little bit for not let the beam goes too closed to the edge. After these, I do the alignment again and get pretty good mode matching.

I changed the laser power, to see with different amount of infrared what is the efficiency of the green production. And at one infrared power I measured the green beam with different SHG temperature, and found the best phase matching temperature. I tried to make a plot, but found at there are two points are not very reasonable, I will measure it again tomorrow to see if the problem comes from the measurement.

Some problems found today

The first problem is that I found out the upper part of the cavity(pointed by the arrow in the picture) can be moved, and if I twist a little bit in counterclockwise to maximum, I will get TEM00.

Then the EOM is very sensitive, even touch it can change the transmit power. There are some possibility, one is while touching, the alignment changed, the other one is there are some electric effect, but not quiet sure about this guess. Or it maybe caused by the polarization before the EOM.

So I will check the following things: the alignment of the EOM, the polarization between the laser and the EOM.

Checking the alignment of EOM is also because we lose too much power there, and also between the waveplate, I have already check the waveplate all have AR coating. At the very beginning of the experiment, I checked the transmission rate of the Faraday Isolator and EOM are both less than 90%.

There are also a small problem with the BS mirror, the beam is near the edge of the mirror which will lead to more scattering. So I will also adjust the position of it.

Status of vacuum system in South arm of TAMA

I checked the vacuum system for South arm in TAMA on 20th.
The 300m arm tube is in vacuum, 71mTorr at the South End and 92mTorr at the Mid point.
Three TMPs (Near, Mid, and End) along the arm can work with the rotary pumps (RPs).
We can start to evacuate the tube without initial pumping by a large RP.

The next step;
1) Start evacuation.
2) Check the penning gauges in HV (<10^-4 Torr).
3) Check the ionization pumps (IPs) in UHV (<10^-7 Torr).

Infrared power

I add a figure for better understanding the infrared power at each position.

Uncoated half ball glueing test

before gluing the coated spherical mirrors to the 1"-support, I made a test with an uncoated one. It is cured with UV light, so I put it under a neon light wich have a small part of UV. The higher the UV intensity, the faster the cure, so now I have to wait some days for curing and bonding.

Polarization and power

I checked the polarization with PBS, found out that we are using the p in infrared and s in green.So the dichoric mirror should be changed.

Then I checked the infrared power at different position with less output power of laser.The result:

Laser-(808.3mW)-waveplate-(795.5)-waveplate-(794)-Faraday Isolator-(728.4)-waveplate-(650)-EOM-(517)-BS mirror-\(429.4)-(399,6)-lens1-(331.9)

-mirror/-(323.2)-lens2-(307.9)-waveplate-(303.0)-lens3-(299.2)-mirror\-(293.7)-dichoric mirror-/-(292.8)-SHG

Between the BS mirror and the lens1, the power seems reduce with the distance.

And after checked the power, I found out I lost the alignment seriously. No matter how I change, the TEM00 cannot get larger. I think I did not move the cavity, but I cannot find other reason for this situation.

Check the power (part of)

After the ATC people return the table leg back, I found out I need to the alignment again. But after I finished it, tried to get some data of the infrared power. I found out the table was not put back in a good position, when I pushed on one corner, the other side will lift. So Manueal helped me to fixed the table more, and of course I need to adjust the alignment once again after it. I forgot to check the table is horizontal or not, I will do it tomorrow.

So until now I only checked power of half beam path. But it does not seems very reasonable, so I will reduce the power and do it again to check.

I checked the polarization, we are using the S polarization in infrared and get P polarization in green. The dichoric mirror we are using now is HBSY21 from Thorlab, which has a better performance in S polarization in reflection and better in P in transmission. Below is the website for more information:

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=7035&pn=HBSY21

The green power now is about 46mW which measured after the dichoric mirror, and since I cannot put a power meter in the beam path, so I tried to measure the green beam which is reflected by the back surface of the dichoric mirror, and it is separated from the input beam,so I could measure it without block the infrared. And the power of this beam is aobut 4mW. But I need to check about other information of the back surface of the mirror.

Comment to Check the phase matching temperature (Click here to view original report: 385)

- Indeed the Pound-Drever signal looked strange.
Out of the resonance is very close to zero as it should. So there is no large electronic offset.
On one side of the resonance the signal is positive and looks relatively normal.
But on the other side of the resonance it's only slightly negative and when the cavity is at
resonance the signal is positive. A picture would have helped this explanation.

- When the cavity is at resonance we measured about 65 mW on the green beam coming
from the SHG and transmitted through the dichroich mirror. It would be nice to see how much
IR power we are injecting into the SHG cavity. It would also be interesting to see how much
green light is not transmitted by the dichroic mirror to have a full picture.

Change the PD

Today we changed the 15MHz tuned PD, which is also more sensitive to infrared than the one we used before(Thorlabs PDA36A).

After the readjustment of the beam, we got a better error signal than before, about 100mV peak to peak and also the positive and the negative part are almost the same.

With this error signal, we try to lock the cavity but it seems the signal is wrong. After changing the modulation phase, we locked the cavity and it last longer time.

But even with the new PD,there is still the 'jump' when goes near the resonance, so we get rid of another possible reason.

The next step is try to get the transfer function of the loop to see more details.

Check the phase matching temperature

I found the green beam power as a function of the cavity temperature while scanning the cavity with 28Hz triangle wave. And the result shows in the first figure. Compared to the figure we got without the miniscope, it looks different.

Since directly we cannot see the temperature, the peak of the figure has the resistance of 3.265 kiloohm.

And in the following three pictures, the beam shape changes while the temperature change.

The second and the third pictures show that the beam start to get strange, inside this range, the beam basically is a spot, but as the temperature goes away from the maximum, there are more things around the spot.

We did some test today find out the reason why there is asymmetric of the resonance peak.

1.Set the temperature back to near room temperature, when there is no green light produced. In this way, we get rid of the effect of the green beam. But the asymmetric does not change much.

2. Change the laser crystal temperature, still nothing change.

We did not find the reason for the asymmetric, and also from the error signal, it seems there is some offset, but did not very clear where it comes from. I will change the PD to the one more sensitive to the infrared and with the 15MHz tuned.

Filter cavity servo preparation

I attach some slides where I have summarized the work done to prepare the filter cavity servo.

In the second attachement there is a computation of the optical gain of the cavity.

Better green beam

I tried to change the cavity temperature to see if the beam gets better. And then at some point I got the green beam shows in the picture, it looks good and much more bright then before. And I also tried to put some filters to see if there is any detail I can not find with this brightness, but even when it's very week it still looks good.

Before when we tried to get the relationship between the temperature(resistance) and the green beam power we did not install the miniscope ,so that's maybe the reason why now we need to change the temperature a little bit to get better phase matching.

I will take some data points to get the exact new best temperature.

Translation stage: final assembly test

I got the parts I draw (elog entry 359) from ATC machining shop. Hirata-san washed them and  I assembled the translation stage putting the parts to make the mirror height as low as possible.

Check the infrared beam with CCD

I checked the infrared beam with the CCD camera.

The first picture is set to check the beam in front of the dichoric mirror, and the second picture is what I got. It seems a really normal beam.

The third picture is set to check before the cavity, since I tried many different ways but cannot put another mirror in the middle of the dichoric mirror and the cavity without moving them, so I used the filter to reflect the beam. The fourth is what I got, it does not look like a round one.

So I change the mirror in first picture to filter to see if it is the reason of beam shape change, and I got the fifth picture.After checking the infrared beam many many times, I think the strange green beam probably not caused by the infrared beam.

GigE Camera

I bought a GigE camera.

http://www.baslerweb.com/en/products/cameras/area-scan-cameras/ace/aca2040-25gmnir

 

You can find information on KAGRA camera system.

http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=4237

 

To use this camera, we need

* Giga-bit Ethernet cable

* Power supply : http://www.baslerweb.com/en/products/accessories/ios-power/power-supply-12v-hrs-6pin

* PoE (Power over Ethernet) Injector:  http://www2.elecom.co.jp/network/injector/lan-gsw01es1/

and

* Pylon software: http://www.baslerweb.com/en/support/downloads/software-downloads

Mirror Glueing JIGs

Together with Yuefan and Manuel,

I confirmed that two mirror glueing jigs are storaged in small clean booth.

One is for 100mm diameter mirrror, and the other is for 150mm diameter mirror.

 

Related parts are packed into one large container box.

This large box is placed at large shelf. It is around the desiccator.

Inside this large box, magnets (phi 2mm x 10 mm) and stand-off (wire breaker)

are storaged in each small containers.

Check the infrared beam

I checked the infrared beam at different position: before the telescope, before the dichoric mirror and before the cavity.

The former two positions, I just put a mirror to reflect the beam and look at it at far field, since the space before the cavity is narrow, so I used the filter to reflect the beam.

For now, the infrared beam looks normal even in far field, but I cannot manage to look at with the CCD.

And I changed the BS mirror after the cavity to another dichoric mirror(CVI 1 inch one) as the picture shows, which reflect infrared and transmit green.

According to Raffaele's advice, I used the signal generator to send a sin wave at modulation frequency but with 100mV amplitude to the oscilloscope, and with a T shape lemo connector plug in and out the RF in port of the demodulation board to see the change of the amplitude. When the RF in port did not connect, the amplitude showed on the oscilloscope is A, when the RF in port plug in, it changes to nearly a quarter of A.

And Manuel found these two PD while clean-up, it can be used in infrared.

Optical Signal Transfer from End-room to Center room

There is two systems.

When we replaced the system to new one, I wrote the attached report.

New signal transfer system has low latency for monitoring the transmitted light of 300 meter FP cavity.

 

Today I found two receiver modules in the center-room.

Both of old and new system modules are placed behind a LCD monitor for digital control system of optical lever.

Maybe signal sender modules can be found at both end rooms.

Because optical cables are unplugged for new system, please check the cable assignments

by sending some signal from the end-room.