KAGRA Logbook

Dan, Takano, Fujimoto, Saito, Tanaka

## Abstract

We tried to find the SRC flash by moving alignment SRM. Yaw alignment seems to be larger than the range of IM actuator. We observed SRC flash after moving SRM and SR3.

## What we did

This morning, we tried find the resonancre in SRC by moving the alignment of SRM largely in both P and Y directions. Unfortunately, SRM DC control seems not work well. So we stopped the any DC controls of payload parts, and we decided to use OPTICALIGN to move alignments. This time, we aligned ITMY and misaligned other Type-As, that is, we made up SRY cavity. Moreover, we increased IMC power up to 10 W. We used awggui and set the excitation amplitude ~1000 cnts and the frequnecy 0.05 Hz in Yaw and 0.04 Hz in Pit, respectively. In this parameters, SRM alignments moved largely enough TM oplev gots out of ranges. However, any flash could not be observed in AS RF34 IQ signals and DC power in AS PDs. Therefore, we put the additional PD at the POS table to observe the flash.

This afternoon, we entered the mine and installed the additional PD just after the 2 inch lens in main IR beam path on POS table. Also, we used the POS PPOL PD channel (K1:LSC-POS_PPOL_DC) for this PD tempolarly. After that, we tried again. However, any flash could not be observed. We used TCam to find the beam spot reflected SRM on ITMY.

Then, we increased Yaw scan amlitude to ~5000 cnts, which is the almost maximum. Then, Saito-kun found that the scattering at the edge of the TCam image.So we adjusted the actuator output when we observed the scattered light. Then, we oscllated the SRM only in Yaw direction. During the oscillation, we adjusted PItch by applying the DC offset with monitoring TCam image. After adjusting, the scattered light could be observed in the edge of both ITMY and ITMX TCam images once per 20 seconds. This duration seems to be consistent with the Yaw excitaition frequency. Therefore, the beam reflected from SRM seems to be shifted largely in Yaw direction. The shift amounts seems to be larger than the IM actuator range. So, it is necessary to use IP to move SRM more largely.

This time, we tried to moved SR3 in Yaw direction with oscllating SRM in Yaw direction. When SR3 moved to -100 urad from initial good setpoint, we can see the beam spot refleted from SRM in POP-SPOL camera. Moreover, the flash signals were observed in the additional PD and REFL PD when the beam spot reflected from SRM was overlaped on the beam spot reflected from ITM. Then, we stopped the excitation and set the actuator output when flash signal is observed in PDs (fig.1).

However, the beam went away from AS PDs and camera when SRC flashes.

What we did

Initial alignment of IFO

First, we performed the initial alignment of the IFO. Since the transmissivity of SRM was changed, the usual initial alignment procedure cannot be used for the AS side alignment. Therefore, we adjusted the alignment by referring to klog36759.

For X-arm and Y-arm, we used the usual initial alignment procedure. After that, we continued the alignment according to the procedure described in klog36759. As written in the klog, we moved OMMT1 while monitoring OMMT1_TRAS_QPD1. When the beam position on OMMT1_TRAS_QPD1 became almost centered, we regarded the AS side alignment as good.

Search for SRC flash

Next, we tried to find the SRC flash by adjusting the alignment of SRM. We set only ITMY to LOCK_ACQUISITION and misaligned the other Type-A suspensions. We also restored the SRM IM OPTICALIGN pitch value to yesterday’s value of 3825. In this condition, we largely moved only the yaw alignment of SRM. We used the stepping motor and moved SRM IP F0_Y from about -12073 to -27073. Then the flash could be seen. After that, we continued the alignment while monitoring the flash signal. Finally, we found good SRC flashes with the following SRM IM OPTICALIGN values:

P: 3900

Y: 480

The flash signal was monitored with K1:LSC-POS_PPOL_DC_OUT_DQ. This is the signal from the temporary PD installed yesterday on the POS table, and the flash appeared clearly in this channel.

However, since the suspension was still oscillating, it was difficult to further optimize the alignment at this moment.

Next, we entered the mine, center the QPDs, and try to turn on the local controls.

Summary

What we did

Initial alignment of IFO

Search for SRC flash