NaokiAritomi - 23:10, Monday 28 February 2022 (2853)
Recovery of CCFC lock
As reported in elog2852, the CC detuning and CCFC demodulation phase should be adjusted. Since the CC detuning in elog2852 was 76Hz, first I changed CC PLL frequency by ~22Hz, but the shape of CCFC error signal was strange. Then I decided to change CC PLL frequency by 10Hz. The setting of CC PLL is as follows.
| channel | function | frequency (MHz) | binary number |
| CH0 | CC PLL | 20.99112421 | 1010 10111111 01011001 01000000 |
| CH2 | CC1/CCFC demod | 13.99408281 | 111 00101010 00111011 10000000 |
| CH3 | CC2 demod | 6.99704140 | 11 10010101 00011101 11000000 |
The setting of LEMO cables for demodulation is as follows.
| Connection | Color of LEMO cable |
| Between CCFC RF amplifier and mixer RF port | green+yellow |
| Between DDS and mixer LO port | green |
Fig. 1 shows CCFC error signal. The CCFC calibration amplitude is 138mVpp. The mode matching is fixed to 0.9.
Today FC was quite stable and I could lock CCFC for the first time since last August! The CCFC filter gain is 1000 with 30Hz LPF. The Z correction, AA, BS pointing were engaged.
Fig. 2 shows the locking accuracy with CCFC.
Images attached to this report
