I locked both cavities and trying to search for the beat signal, I have not succeeded yet.
I used lenses that could get the two transmitted beam to be close and small enough for the beat PD (new focus 1811) (we ordered what we need but they are not here yet).
I locked ACAV at a fixed SLOW DC level (1.207 V), and varied RCAV's SLOW DC level from 1.199V, 0.33V, -0.554V, -1.477V (1FSR ~ 4GHz is about 1 V). The slider for RCAV slow is set to +/- 2V so I have not tried other values yet. It can be changed to -2V to 9 V, but I have to restart the crate which will disturb the temperature servo, so I'll try to adjust RCAV slow value using a voltage calibrator instead.
I talked to Evan about the beat measurement in GYRO lab, the SLOW DC for both lasers can be different up to 6 V (for ~100MHz beat). see gyro1832
I varied RCAV's SLOW DC first because this path does not have a PMC, so I don't have to worry about locking the PMC.
From PSl:1124 ,the beat frequency should be ~60-100 MHz, without the heater on any cavity. I'll try the same method to check the beat frequency between the two cavities one more time. If it is still ~ 100 MHz, I'll increase the range of SLOWDC, and see if the beat will show up of not. The setpoint was not changed that much (31.2 to 31.25), So I expect the beat frequency should still be close.
If the beat still not show up, I'll try to realign the beam.
Vac chamber Setpoint = 31.25
Vheat for RCAV = 0
Vheat for ACAV = 0