Sheila, Keita, Jennie W, Jenne D, Georgia B.
We want to be able to power up to 20W in JAC to check the POP beam.
We were loosing lock with about 8W into JAC because the REFL shutter was closing. Jennie Wright measured 6mW on the REFL diode with 2W input to HAM1 and JAC unlocked yesterday. This corresponds to 0.58V on the shutter trigger diode. The threshold cannot be set above 2V, which means we would unlock when 21mW hit the diode. Jennie Wright added a ND05A into the path before the refl diode, and another ND05A in front of the shutter diode.
Now, with 2W input to HAM1 and JAC unlocked, we should have 2mW on the REFL diode, and the shutter diode votlage is 0.18V. The threshold of 2V now will shut the shutter with 22mW on it.
Gaurdian changes:
The JAC error signals are normalized by the PSL input power if we use the laser power guardian to change the input power, so we shouldn't need a power scaling like 89708. People have been using the rotation stage instead of the guardian to adjust the power because the laser power guardian would go into fault if the power was below 1W (people have been going below 1W while HAM1 is vented.) Jenne Driggers adjusted the fault in LASER_POWER and added a 200mW state to the laser power guardian, so now we should use this guardian whenever we want to change powers, even below 1W.
We also hard coded the gain used for locking JAC in the down state, although this could be reverted to allow the power normalization to work again, once that has been updated to take into account the new ND filters. Once this was done, we could lock JAC at a variety of powers and also change the requested power after it was locked.
Georgia B and I also had a look at the IMC guardian, which has not generally been able to lock the IMC except at 2W. There was some code in the down state of IMC LOCK that was supposed to adjsut settings for lcokign at different power levels, these were unused except for the IN1 gain setting used for acquisition. Georgia and I adjusted some of these numbers and watched if the IMC would lock, we didn't take much time to test it but we did once twice see the IMC lock with 10W + input power, so that is promising.
At Elennas' good suggestion, I added the IMC_power_adjust_func() to the IMC_LOCK's ACQUIRE state, so that it will adjust the IMC's FASTGAIN, so that the fast gain won't be wildly high when trying to acquire at higher powers.
I did modify the function, so that if we're in ACQUIRE, it uses a FASTGAIN 5dB lower than the operating nominal gain. This makes it match the 2W acquisition situation, where the fastgain was always acquiring at 0dB, and then for a 2W IMC lock would increase during the BOOST state to 5 dB.
The IMC will lock at 10W, but it takes a long time. It's a little happier at 8W. It's still perfectly happy at 2W (which makes sense, since none of the 2W settings have changed).
I'm pausing any further testing, since the Xarm is open for our green peek.