Komori, Tanaka

We tried to identify the drumhead mode with OMC TRANS PD signals in the IOP model of k1omc0 (OMC DCPD A:K1:IOP-OMC0_MADC0_TP_CH0, OMC DCPD A:K1:IOP-OMC0_MADC0_TP_CH1). Since I expected the drumhead mode generates TEM00 mode and the other modes generate the HOMs, OMC should reject the other modes and only TEM00 mode can be detected with OMC TRANS PDs. We excited the 3 modes (23.5851 kHz, 23.6369 kHz, and 23.9403 kHz), which are found in the previous work, one by one and measured the spectra of OMC TRANS PDs and the ratio between RFPD and OMC TRANS PD Fig.1 shows the spectra (upper left panel) and the ratio (upper right panel). As you can see, all of 3 modes can be detected with OMC TRANS PDs. Their ratios seem to be the same. Komori-san pointed out that the beam position on ETMX was not the node of the elastic modes and the TEM00 mode could be generated by any mode in this case. If so, we could not identify the mode with this method, unfortunately. What detects the spatial mode generated by the elastic oscillation, such as a phase camera is necessary to identify the mode.

Then, I gave up to identify the mode in this time. I decided to attempt the OMC ASC

I implemented the OMC ASC with beacon as the same procedure of previous work (klog, klog). This time, we adopted 23.585 kHz as the beacon frequency. Their loops could be closed but the 0 setpoint seems to be not optimal in terms of the fluctuation of OMC TRANS PD. So I put the offsets to keep current alignment (fig.2). This offset seems to be reproducibility at least in the short term from lock loss to the relock (fig.3).  

Anyway, we left them tonight. I have not implemented them in OMC ASC guardian so the controls are not engaged automatically if the IFO lost the lock