[kTanaka, Ushiba, Hirose]  PRXARM lock trial Day 2. Continued from klog30070

As the cause of the RF45 offset was mentioned as RFAM, we performed a fine tuning of the sideband frequency, but the offset did not disappear. it is possible that an AM component appeared in the EOM due to room temperature changes, but we still have no idea. 
And the RF45 offset cannot be erased yet, so we tried PRXARM locking once the CARM_CMS offset was added to make the error signal near zero. At this time we wrote up to PRXARM lock with VERTEX Guardian. However, because we did not adjust the gain or boost stage for XARM lock, we could not lock it properly. We will adjust that part in the next work.

Detail

• To clarify the identity of the offset, the PRX was locked by 1f. The offset was almost the same. We also locked the PRX at the carrier resonance with different gain and sign flip, and the offset was almost the same here too. When I turned the PRX down and did a PRM reflection, the offset was the same, so I assumed it was due to the AM component of the RF sideband. 
• We did the FINE TUNING work as shown in klog29385. This was done by adding an excitation signal from the DCCARM, going through the ALSsumming CMS and ALSCARMCMS and the IMCCMS to the respective IMCLSC control. In this case, the laser frequency was adjusted to eliminate the I signal of RF45. However, the offset did not go to zero. An offset drift also occurred during this time. From the appearance of this drift, it is possible that an AM component appeared in the EOM due to room temperature changes, but we do not yet know what it is. 
• As per Abst, we tried PRXARM lock with the error signal close to zero by adding the offset of the CARMCMS. At this time, code was written in VERTEX Guardian for the PRXARM lock. However, the XARMIR lock stage did not lock properly because the gain and boost stage were not adjusted. It is also thought that the alignment was bad from the initial alignment at this point. We will adjust that part next time. 
  Also, the RF45 signal was somehow stable while trying PRX to PRXarm on this Vertex Guardian. This is a mystery.

Note

• The HWP of IMC_REFL was changed from 146deg to 176deg to reduce the power going into the RFPD.
• The CARM offset value was also set back to its original value of -0.805.
• The offset did not resolve after tuning, so SeedFrequency was set back to 5.624365627 MHz.
• Also, error signals sinflip when Xarm is locked, so PRXARM LOCK step in the VERTEX Guardian has been set to sinflip IN1 of CARM_CMS.
• PRM and IMMT2 was recorded as "PRFPMI" in the OPLEV record after PRX ADS.