The laser in EY looks unstable. It may be multimode.
The first attached plot shows the ALSY locking attampts over the past day. The laser was adjjusted to the new PSL frequency about 10 hours ago. Afterwards there is a distinct variation in the green output accompanied by a smaller inverse change of the red power. In the past 6 hours good ALS locks (red trace near +1.0) are correlated with the lower green power states. At higher green p[owers we seem to be locking a intermediate transmitted powers indicating the possibility of a multimode laser.
The second attached plot shows how changing the frequency of the laser changes the green and red powers. The green power varies much between -600 and +400MHz and seems to be stable outside this region.
We need to try adjusting the pump diode current and crystal temperature and see if we can resolve it this way.
Went to EY and adjusted the laser diode current and temperature. Hopefully, we are now in a more stable region of operation.
current as found: 1.600
doubler as found: 33.64
new current 1.511
new temp 30.00
new doubler 34.20
This resulted in a lower green power output. Correspondingly, the normalization of H1:ALS-Y_LASER_GR_DC, H1:ALS-C_TRY_A_LF, and H1:ALS-C_TRY_A_DC_POWER were lowered by a factor of 1.4.
The nominal laser diode power was also updated for H1:ALS-Y_LASER_HEAD.
The EY controller and/or laser is still somewhat flaky when trying to adjust the temperature. If this doesn't work, we may have to consider swapping in a spare.
