KAGRA Logbook

M. Yamamoto (Toyama Univ.), Nakano, K. Tanaka with the help of T. Yamamoto-san, Ikeda-san, Shimode-san

## Abstract

We implemented a frequency search system for the axis-symmetric elastic mode of the IY mirror, which can be done completely remotely using DGS. After implementation, with the FPMI locked, we used the system to oscillate the IY at 250 Hz in the L direction and confirmed that a 250 Hz peak appeared in the DARM sensitivity curve spectrum. We then attempted to excite the elastic modes by injecting white noise in the 23.64 kHz to 24.05 kHz bandwidth into the IY; unfortunately, white noise could not excite the elastic modes. At any rate, we try to find them tonight by doing a frequency sweep overnight.

## What we did

Shimode-san modified the ch9 - ch16 ports of the AI charssis (s2011357) to bypass 10 kHz cutoff lowpass filter.
Yamamoto-san and Ikeda-san made and the 64 kHz models for the 24 kHz siganl transmitter to Type-A TMs except for ETMX (k1sendbeaconiy, k1sendbeaconix, k1sendbeaconey). And they added the channels to receive the 24 kHz resonant peak signal from each TM drumhead mode in the k1ascbeacon model and restart the model (For detail, see klog26552 )
We replaced the current AI charssis in the IY1 rack as DAC2 (the s number not found) to modified AI charssis (s2011357). We used a Dsub cable to connect the ch12-16 port of the modified AI chassis to the DRIVE INPUT port of the TM coil driver.
- We confirmed that the spectra of the FLDACC signals (K1:VIS-ITMY_IP_FLDACCSERVO_xx) originally connected to DAC2 was unchanged before and after the AI chassis replacement.
When we replaced the current AA filter as ADC3 in the OMC0 rack, we found there are no empty ports in ADC3. So we give up the AA filter replacement.
Instead, we unplugged the Dsub cable for I1, I2, Q1, and Q2 of the OMCREFL WFS, which are not used now, that were stuck in the ch1-ch4 port of ADC3, and replaced it to the Dsub cable for this Q value measurement. The signal flow shows below.
- I MON port on the IQ demodulator for AS RFPDA1 RF17 in the OMC1 rack -> SR560 -> ch 6 port on the BNC2Dsub converter in the OMC0 rack -> ch 2 port on ADC3 in the OMC0 rack
- Q MON port on the IQ demodulator for AS RFPDA1 RF17 in the OMC1 rack -> SR560 -> ch 8 port on the BNC2Dsub converter in the OMC0 rack -> ch 4 port on ADC3 in the OMC0 rack
- We use SR560 amps as the preamp for the drumhead mode signals. We set the bandpass filter from 1 kHz to 100 kHz and set the 100 times gain.
After the installation, with the FPMI locked, we used the system to oscillate the IY at 250 Hz in the L direction from the K1:SEN-ITMY_L_INF_EXC ch and confirmed that a 250 Hz peak appeared in the DARM sensitivity curve spectrum (K1:CAL-CS_PROC_DARM_DISPLACEMENT_DQ).
We then attempted to excite the elastic modes by injecting white noise in the 23.64 kHz to 24.05 kHz bandwidth into the IY; unfortunately, white noise could not excite the elastic modes.