About the control and alignment

Tip from Matteo
Note to switch on alert light after turning on the laser.

Some tips from Yuefan
1.Remember to switch off the piezo driver of SHG, otherwise it will drift away from the right position. It's located in the right side of the third shelf counting from the bottom.
2.The Laser power we use is around 1.2W, the value can be adjusted by the left knob on the panel.

The procedure of using the control system(the computer is always on, the system is based on Labview)
1.The document is under Project Explorer, the name is Eleonora-e-Manuel.
2.Control and demonstration panel:
BS and PR: under SAS_NM2b, the name is: tele12_control.vi
IM: under SAS_NM1b, the name is: IM1_contol.vi
Em: under SAS_EM2a, the name is: EM_contol.vi
3.Measurement of transfer function:
PR and BS: under SAS_NM2b, the name is: advtransfer_functions_tele.vi
IM: under SAS_NM1b, the name is: transfer_functions.vi
EM: under SAS_EM2a, the name is: transfer_functions2.vi
4.The local control and mode-matching of each mirror:
After opening each document, we can see clearly the mirror we want to control. Just by clicking on the dark green button, we can close the control loop. There is a very important parameter, offset. By setting different value, we can get a different orientation of this mirror. By this way, we can adjust the mirror to the right place. The right place can be checked by confirming the reflecting reference laser is on the right remark. The remark is made by Yuefan. For example, there is a remark on the viewport of BS tank. If the reference laser is reflected to this point, it means that the PR is in the right position.
For BS, we need to adjust its position slowly. We can do it with the help of diaphragm. Because we have several diaphragms in TAMA's arm pipe(between IM and EM).
After adjusting BS, we should see some high order modes in the CCD. Then we need to align the optical layout. There are two kinds of higher order modes. By adjusting BS and PR, we can eliminate the Hermite-Gaussian mode. However, the Laguerre-Gaussian mode is caused by the waist mismatch. We can solve this by moving two lenses behind AOM.
5.Try to find the reason of BS high motion of microrad
(1)The power supply. We usually stabilized voltage supply for the laser. Because PR's control is good enough. We changed their power supply, and then we find nothing changed.
(2)The data acquisition system. By changing the connection port of BS, we find nothing changed. Because we use the same data acquisition for all the data taking. PR doesn't have problems means other ports is fine. So no problem in data acquisition system.
(3)Output connection. We check the difference between using 50 Om and not using. This connection noise comes from the resistance thermal noise, we also call it Johnson noise. Johnson noise is proportional to the resistance. But, there is no obvious difference. Or just 0.6 in motion of microrad. (It's hard to read because the motion of microrad keeps changing.)
So we think the problem comes from the Laser.
6.We check the saturation level of each actuator
By changing the offset, we check the output. Beyond a certain value, the output will keep increasing. This is the saturation level because the actuator cannot offer enough force. Details are shown in the attached photos.
So we need to read the sum value first and type it into our Labview program. This will make sure the right normalization.
7.Taking transfer function
We should note that the transfer function is measured in mechanical part(actuator part). So we insert the noise in port NOISE2, which is white noise. And then we should make sure the loop is closed. And we have a good PSD angle. Finally, we can start measuring.
Besides, there is another influencing factor. It is the driving matrix. We should take care.
8.Checking the PSD angle to reduce the coherence.
By changing PSD angle, we find a good angle to have the least coherence. The result is plotted and attached. But Yuefan said the optimal PSD angle will change overtime.