We report here a summary of the activities performed on the injection system during this morning shift:
- IMC locking point. We turned on the FmodErr line at 1111 Hz and we adjusted the offset on the locking point by looking at the transmission and by minimizing this line. We set the offset in ISYS Acl from -0.1 to +0.1.
- Rampeauto PSTAB. We tried to lock the PSTAB with the rampeauto (PSL-ELEC-1803-01), which we want to keep as a spare. We weren't able to lock in 1/f since it seems that the input signal has the wrong sign. We measured in fact the gain between the photodiode input and the correction by sending a sinusoid of 200 mV amplitude @ 400 Hz, finding a gain of +15 (while in the rampeauto which is currently working this gain is -10).
- PMC locking point. As already mentioned in the entry 43494, in order to minimize the frequency into power noise conversion, we tried to tune the offset of the locking point of the PMC. We already did it by looking at the error signal offset as a figure of merit and setting it to zero by adjusting the modulation frequency. Today we tried in another way: we sent in the perturb input a sinusoid at 1900 Hz of ampiltude 10 mV and we tried to minimize it in the PMC trasmission. We weren't able to do this since the PMC unlocked due to the fact that we were also changing the phase. We need to think to another way to adjust the locking point, knowing that for the moment the perturb input is used as a security in case the EIB starts to oscillate.
In order to check the PMC alignment we scanned it @ 4 Hz for a minute. You can find the scan starting from the GPS 1226142528. As you can see in the attached plot the misalignment mode is quite high and we need to quickly realign the cavity.
- weight added to the EIB and rebalancing. Since we are planning to replace EIB_M8 mirror with a larger one (3 inches) which weights 300 g more, we added an equivalent weight next to the mirror we want to change, we removed an unused mirror (the one was used for the optical lever), and moved a wehght on the EIB in order to rebalance it. We could enable the actuators and the PID, and finally B. Boom moved the stepper motors to bring back the actuation signals to less than 2V. We are ready to replace this mirror whenever it is possible.
