jenne.driggers@LIGO.ORG - posted 12:51, Thursday 10 May 2018 - last comment - 10:50, Friday 11 May 2018(41938)
IMC locked, alignment not yet complete
[Sheila, Jenne]
When Sheila first opened the light pipe, we weren't seeing beam on IMC REFL camera. We went to the table with a card and moved the PZT until we were back on the camera. I had previously set the IMC optics back to the bottom stage OSEM positions from the last IMC lock. This got us flashes. The IMC is now locked, although the alignment is very poor - we'll continue to work on that after the meeting, but should be ready to send beam to HAM 6 this afternoon.
The IMC is locked with a build up slightly lower than what we had before this vent. On April 26th we had 165 counts on MC2_TRANS_SUM with 2 Watts input, we now have 67 counts with 0.85 Watts of input power. Some of the things that we ran into:
Craig and I re-phased the length demodulator as his comment says, and flipped the sign. We then added 219 degrees to the IMC WFS demod phases. We found that the LSC power normalization was not up to date (probably a consequence of using the rotation stage medm rather than the guardian to set the power) the gain of the IMC WFS was very low. We also reset the dark offsets for the MC WFS. SDF screenshot attached.
Keita found that there was angular feedback to M2 on MC2, which I don't think is correct. This was set this way on Feb 17th and accepted in SDF, we set it back to M2 off and accepted that in SDF.
We set the mode cleaner to offline for a jitter measurement using the IMC WFS DC starting at 1:04 UTC. The PSL is in science mode and there is 8.9 Watts injected.
On a small detour, I made some edits to the state generator for the OFFLOAD_ALIGNMENT_MANY state, bug fixes from the guardian re-work. The motivation for this is that the offload MCWFS script doesn't turn off the loops so it misaligns the IMC which the slow MCWFS loops take a while to recover from. I had intended to write a guardian state that uses this generator, however, this generic offload state relies on having the alignment intergators in the suspension top masses, which is not the case for the MCWFS. We also would need to edit the state to deal with the IMC PZT. There were a few bugs to work out with the generic offload script, I added fast_ezca to the list of things that are imported by ISC_GEN_STATES, and removed two variables which were just renamed in the state ie:
def gen_OFFLOAD_ALIGNMENT_MANY(dof,tramp,optics):
class OFFLOAD_ALIGNMENT(GuardState):
request = False
redirect = False
tramp = ramptime
optics = opticList
became
def gen_OFFLOAD_ALIGNMENT_MANY(dof,ramptime,opticList):
class OFFLOAD_ALIGNMENT(GuardState):
request = False
redirect = False
Attached are data taken with the IMC unlocked with 8.5Watts input power, compared to the data attached to 39434 which was taken with the HPO and the IMC unlocked. Both are calibrated into beam diameters (normalized pit and yaw *sqrt(pi/8)). The 70W amplifier has lower jitter below 50Hz, but not above. This might be due to the high noise on the PSL table and periscope and the floor that Terra and Anamaria have pointed out (41707 and comments).
I did a quick summary page look at the HAM1 ground motion and PSL table motion from November jitter data timeframe and today. I also compared with LLO (used PSL table data from before install started, so August). Floor motion at LHO is slightly lower in the hundreds of Hz region now compared to Nov.
first plot: HAM1 ground, LHO on left, LLO on right
second plot: PSL table motion, LHO on left, LLO on right