Thomas, Georgia, Dan Brown, Craig, Sheila, Jenne
We have been able to lock PRMI and DRMI without the arms, and PRMI with the arms, so weve made a comparison of some parameters between the configurations. Edit: In the first version of this table, I was not consistent in using the normalized and unnormalized values of POP18. The trigger is based on the un-normalized channel, so I will use these values here. We have been using 1.9W of input power for acquisition. Also note that the gains I have written here are the gains used once we have locked, some of the acquisition gains are different.
| PRMI no arms (POP18 = 30 counts) | PRMI with arms (POP18 = 55 counts) | |||||||
| trigger on | FM trigger | digital gain | ugf | trigger on | FM trigger | digital gain |
ugf |
|
| MICH | 8 (26%) | 24 | 2.8 | ~4Hz | 8 (14%) | 48 | 3.2 | 8 Hz |
| PRCL | 10 | ~45Hz | 5 | 30 Hz | ||||
| DRMI no arms (POP18 = 40 counts) | DRMI with arms POP 18 = 147 | |||||||
| MICH | 20 (50%) | 24 | 3 | 12Hz | 37 (25%) | 37 | 2.8 | 12 Hz |
| PRCL | 18 | 90 Hz | 3.5 | 8 | 70 Hz | |||
| SRCL | 10 (25%) | -33 | 50 Hz | 37 (25%) | -18 | 42 Hz | ||
The main thing to note is that the optical gain of MICH increased by a factor of 2.8 between PRMI and DRMI without the arms, and was similar to DRMI without arms in the PRMI with arms configuration. Based on this we guessed that the MICH gain might be too high with our normal settings (which used to work), and have reduced the MICH acquire gain for DRMI with arms from 3 to 1, which has given us several locks of a few seconds. for PRCL, there is not much of a change in optical gain between DRMI and PRMI and for PRMI with and without the arms. It is also interesting that we are able to acquire with rather different triggering configurations in terms of the percentage of the locked POP 18 build up.
In PRMI with the arms we are currently not able to get a build up of more than 60 in POP 18 counts, which before the vent Hang found that we had about 70 counts. All of this can be compared to the information in 44348, when DRMI acquisition was working better.
With PRMI locked and the arms held off resonance by ALS, Georgia centered the beams on POPAIRB, REFLAIR A and REFLAIR B. (this POPAIR B had been done since the ISCT1 move but not the refl air diodes). The other main change since the vent is the TCS preloading 45341 and 45523. THe other thing to note is that today we have no wind and microseism around 0.4 um/ second, which is a little high for Hanford but we have been able to lock in these conditions in the past.
We have been able to lock DRMI several times, although it seems to be very sensitive to alignment. We were able to transition to 3F, but lost lock when transitioning the BS ASC from 45 to 36 twice in a row.
The next time DRMI locked we skipped OFFLOAD_DRMI_ASC. The shutter guardian said that it failed it's test, so we ran the test manually and it passed.
Craig changed the ANALOG_CARM state to compensate for the factor of 2 less gain after the second photo diode was added by adding 6dB of gain in the summing junction.
We arrived on resonance with a recycling gain of 41 without any ASC other than DHARD, and manually engaged AS36 to BS loops. We stepped through the ENGAGE_REFL_POP_WFS step which was fine until we tried to engage PRC1 (POP QPD to PRM loop) which unlocked the interferometer.