kyle.ryan@LIGO.ORG - posted 11:47, Wednesday 02 October 2013 (7960)
Changed CP5 PID proportional gain from 1.3 to 1.5
We placed Mode Master downstream of three-mirror Gouy phase matching telescope comprising two tip-tilts and one fixed mirror that is used for REFL WFS. (See the last picture for layout and distances.)
Note that the measured TT1-TT2 distance is about 1cm shorter than nominal described in Sam Waldman's document (http://dcc.ligo.org/T1000247), TT2-M5 distance is about 14mm longer than nominal, both of which should have been quite acceptable.
Anyway, we made this measurement and the beam was much smaller than what was expected. The first plot as well as the table below show the measured VS the expected mode profile coming out of HAM1 propagated through the telescope with the measured mirror distances.
| measured, x | measured, y | expected | |
| M^2 | 1.04 | 0.98 | 1-ish |
| Waist radius | 1.38 mm | 1.15 mm | 1.92mm |
| Waist position (away from MM head into HAM1) | 4.31 m | 4.35 m | 1.78 m |
| Mode overlap between measured and expected | 0.872 | 0.753 | 1 |
The total mode overlap between the actual beam and what is expected is somewhere between 0.75 and 0.87 (sort of tedious to do the real calculation so I leave it).
The 2nd plot shows that IF the incoming beam from HAM1 is as expected, in order to explain the measured mode the TT1-TT2 distance labeled as delta1 should be shorter by 4.5cm than was measured for X, or by 5.7cm for Y. This is a huge number, there's no way my distance measurement was that much off.
The 3rd plot shows the Gouy shift between TTs (i.e. actuation orthogonality) and WFSs for the WFS sled (i.e. sensing), and it seems like both are quite poor for the measured mode, 26deg for actuation and 35 for sensing are sad though not a complete disaster.
Anyway, since it's hard to imagine that the ROC of TT1 (+1.7m), TT2 (-0.6m) and M5 (+1.7m) are grossly wrong, and since it's hard to imagine that the distance measurement has a 5 to 6cm error, this should mean either (or some) of the followings:
The third one doesn't sound likely, but neither Sam nor I have thought about this.
One quick thing to do is to measure the beam before it gets to the telescope by inserting M6 upstream of the TT1 to direct the beam to the Mode Master.
Yes, please, measure the beam before the TTs.
The original calculations were done by assuming that beam reaching HAM1 was perfectly matched to PRM.
I don't think we have reasons to believe that's true..
The "nominal" q of the beam right before the first tip-tilt RM1 is:
% REFL in-vacuum path beam propagation, HAM1 drawing v10
% https://dcc.ligo.org/LIGO-D1000313-v10
% LisaBar, August 14, 2013
q_in = 1.03+13.1i; % Beam on HAM1 calculated from CalculatePRM.m
% Lisa: we don't have a measurement yet which confirms
% this number!
I don't think the table in T1000247 is correct. The beam from PMMT2 goes through the Faraday, hits PMMT1 and is then send to HAM1. This is a) longer than 2.5m and b) adds PMMT1's curvature to it. Did you include this?
Yes, PMMT1 is included, it is just a typo in the note (there are two PMMT2!). Anyway, let's redo the calculations with the as-built parameters, and cross check with the measurements before the REFL telescope.
Kiwamu and Pablo and I measured the mode before the TTs by moving the BS for the RF detector to 16 inches after M2, with the front of the mode master 40 inches from the BS we measured:
| x | y | r | |
| M^2 | 0.97 | 1.03 | 1.00 |
| 2Wo (mm) | 3.588 | 3.532 | 3.567 |
| Z0 (m) | -2.387 | -3.578 | -3.026 |
The overlap between the mode measured before the Tip tilts and the mode measured after is 93% for X, 87% for Y. I used Lisa's alm mode model attached to D1000313, added Keita's measurements of the distances from RM1 to RM2 and M5, but didn't include the tilt of the optics. From this measurement before the tip tilts (projected through Keita's measurements of distances), the gouy phase separation is a little better than from Keita's measurement, WFS X=65 degrees, WFSY 60 degrees, TT x=56 TT y 50 degrees.
I checked to see how far wrong things in HAM2 would have to be in order to explain the beam waist sizes measured by Sheila before the tip-tilts.
I used the design parameters for IM2 and IM3 Rcs (except where varied), design parameters for HAM2 optics placement as found in E1200616 (except where varied), the measured value of PRM HR Rc of -10.9478m, and the design IMC parameters to get the starting beam parameter. The attached plots show the forward beam waist size (identical to the IMC waist size) and the return from PRM beam waist size, over variations in IM2 and IM3 Rc, and IM2->IM3 and IM4->PRM distance. At the design values (at the x-axis midpoint), the return x-waist size matches the forward waist size.
It looks like things in HAM2 would have to be further off from the design than is probably likely, in order to explain the measured beam waist size before the tip-tilts.
Propagating the IMC transmission beam through the "as-built" IMs, back from the PRM, off the FI rejected beam pick off mirror and onto HAM1 to the location where Sheila measured gives:
| axis | parameter | value |
| x | w0 | 2.123mm |
| y | w0 | 2.101mm |
| x | z | -2.469m |
| y | z | -2.150m |
| x | q | -2.469+13.310i |
| y | q | -2.150+13.035i |
| x | w | 2.159mm |
| y | w | 2.129mm |
| x | Rc | -74.21m |
| y | Rc | -81.16m |
I did not yet consider the calcite wedge polarizer effect on the beam parameter, and I didn't account for the thickness of the septum viewport.
The overlap of these beam parameters with Sheila's measured parameters are:
x overlap = 0.945
y overlap = 0.934
I'm including the Finesse kat file I used for the calculation, which has a list of all the parameters I used at the top. I also include that list here for convenience:
# H1_IMCtoPRC_matching.kat
# A file for checking the expected beam parameter in direct reflection from the PRM
# as a function of HAM2 optic RCs and placement positions
#
# Mirror curvature parameters taken from the nebula page, except IM2 and IM3 for
# which the design values were taken
#
# Distances taken from E1200616_v7 except where otherwise noted
#
# IMCC Curvature = 27275mm
# MC1->MC2 = 16240.6mm
# MC2->MC3 = 16240.6mm
# MC3->MC1 = 465mmm
# MC3 substrate path length = 84.5mm
# MC3-AR surface to IM1 = 428.2mm
# IM1->IM2 = 1293.8mm
# IM2 Rc = 12800mm
# IM2 AOI = 7deg
# IM2->IM3 = 1170.4mm
# IM3 Rc = -6240mm
# IM3 AOI = 7.1deg
# IM3->IM4 = 1174.5mm
# IM4->PRM-AR surface = 413.5mm
# PRM substrate path length = 73.7mm
# PRM Rc = 10947.8mm (from Rodica's measurement value)
# IM2->FIrejected pick off mirror = 1.012m (From Luke Williams)
# FI rejected pick off mirror->HAM1 mode master location =3.0175m (Estimated from
# Sheila's alog entry, HAM2 drawing, and 27.6" for HAM1 table edge to HAM2 table edge)
#####################################################################################
If anything, my measurement is a bit more suspicious than Sheila's, as mine is downstream of TTs in air and they are moving (mostly in PIT).
| axis | parameter | value |
| x | w0 | 2.121mm |
| y | w0 | 2.101mm |
| x | z | -2.583m |
| y | z | -2.154m |
| x | q | -2.583 + 13.29i |
| y | q | -2.154 + 13.04i |
| x | w | 2.161mm |
| y | w | 2.130mm |
| x | Rc | -70.95m |
| y | Rc | -81.05 |
Apparently I posted the last comment as Giacomo, sorry about that!
After discussing with Lisa about sign conventions for the beam waist position parameter, I realised that there are errors in some of the parameters I posted above. The mode master gives results as "z0" for waist position relative to the measurement position (z0-z), whereas Finesse gives results as "z" for the measurement position relative to the waist position (z-z0).
I had thought the convention was different, so I flipped my results to match the mode master convention. This was a mistake, because the conventions are the same, they just give different outputs. To get the q-parameter from the mode master results one should use the formula q = -z0 + i*zR. From the Finesse results one should use the formula q = z + i*zR.
This means that the z-values, Rc values and the real part of the q-parameters I posted should all have their signs flipped. Apologies for any confusion I caused here.
(Kiwamu, Stefan)
IMC demodulation phase rotated again for the 4th time...
After the IMC sideband sweep measurement this morning we noticed that the IMC WFS were no longer stable, and the IMC locking was a bit shaky. Sure enough we found that the RF phase rotated again, with most of the signal back in the I-phase (we use the Q-phase for feed-back.)
The 1st attached picture shows the I signal along the x-axis, and the Q signal along the y-axis. Also note that the size of the signal is not much smaller than in the picture from alog 7181 (and we currently has a slightly reduced PSL input power due to the installed 10% and 30% BS for the FI isolation measurement).
For now we again adjusted the phase of both length and angle sensors.
The new delay setting is in the 2rd attached picture (the old one is in alog 7119 - note that in alog 7119 we used the I-phase for feed-back). Picture 3 shows the I signal along the x-axis, and the Q signal along the y-axis after the LO delay change of 9.75nsec (~85deg).
The new WFS phase settings are the same as back in alog 7119 :
H1:IMC-WFS_A_SEG1_PHASE_R = -185
H1:IMC-WFS_A_SEG2_PHASE_R = -112
H1:IMC-WFS_A_SEG3_PHASE_R = -185
H1:IMC-WFS_A_SEG4_PHASE_R = -185
H1:IMC-WFS_B_SEG1_PHASE_R = -80
H1:IMC-WFS_B_SEG2_PHASE_R = -132
H1:IMC-WFS_B_SEG3_PHASE_R = -66.5
H1:IMC-WFS_B_SEG4_PHASE_R = -173
Before I changed them, the phases were
H1:IMC-WFS_A_SEG1_PHASE_R = -90
H1:IMC-WFS_A_SEG2_PHASE_R = -17
H1:IMC-WFS_A_SEG3_PHASE_R = -27
H1:IMC-WFS_A_SEG4_PHASE_R = -22
H1:IMC-WFS_B_SEG1_PHASE_R = +15
H1:IMC-WFS_B_SEG2_PHASE_R = -34
H1:IMC-WFS_B_SEG3_PHASE_R = +28.5
H1:IMC-WFS_B_SEG4_PHASE_R = -81
In conclusion - we are back in the same "RF phase state" as in elog 7119.
I've aligned the REFL beam from RM2 through the ISC sled. The beam from the pick-off BS is temporarily dumped in a spare black glass V-dump. The beam in the sled is well aligned through the first two lenses and the first 2 turning mirrors but is about 8mm high on the last turning mirror. It seems that the turning mirrors on the sled need to be adjusted to fix this but I wanted to consult with Keita about this first as it was my understanding that these had already been aligned in the lab.
We could not retreive data for the transfer functions that ran overnight on ITMX.
Run_Get_Batch.m, the generic script that the seismic team uses to get data from the frames, would systematically crash when collecting data for Stage1-V1 excitation, in the 500Hz-1000Hz frequency range (see attachement #1). It would also crash when trying to collect data for the other frequency bins.
We looked at the data stored in the frames (DaveB, and ArnaudP helped), and compared it with what was in the slow channels.
- The actuation signals were sent to the correct channels and witnessed by the related slow channels (see attahchement #2)
- However, the daq channel for the excitation along Stage1-V1 does not recall any excitation (see attachement #3), while one was recorded by its slow channel twin (see preious comment).
New channels were added to the master model, and h1isitst.mdl was not restarted since. When JimW and I restarted the TST model yesterday night, those channels were added to the .ini file. JimW and I did not dare restarting the DAQ without CDS people around. This is likely to be the reason why the data in the frame was corrupted.
A couple DAQ restarts were performed as part of the maintenance day today. Last one was around 3pm. We then started to run a quick set of high frequency transfer functions, and made sure that the data collection process went well. It did.
Transfer functions will be running ovenight on ITMX (currently on the test stand, using TST model)
** Work permits signed by ops today: 4157 (EY one-stop cables), 4158 (FW1 reconfigure SSD disks), 4159 (online detchar channel) ** LN2 delivery to CP3 (MY) ** Roofers moved a lot of material and equipment onto the Corner Station roof; also worked on the roof at MY ** Two DAQ re-starts, morning and afternoon ** A number of H1lsc CDS overflow alarms; I checked with Dave and disabled this alarm ** Lots of work at/near HAM1 today ** Usual Tuesday morning vendors on site ** EX spool clean room was cleaned this morning ** Cheryl worked in the EX TMS lab ** Dust monitor 9 continues to alarm in the white condition ** Lots of dust alarms at EX today as personnel were working in the VEA. 12-hour trend attached. ** LVEA has been in laser hazard all day and remains in laser hazard at 17:20 local.
HughR, GregG, JimW
Today, we managed to get most of SEI's cables sorted and connected. Cable brackets were installed, unfortunately I forgot that the GS-13's need to be shorted to the ISI, until Hugh reminded me. Still need to fix corners 2 and 3. Otherwise, it went well, seismometer cables (unplugged at the pods) and CPS's are plugged into the chamber. I watched MEDM as Greg connected CPS's, and we ran an emulator on the seismometer cables, so we are pretty sure the right sensors are plugged into the right spots. Now, we are ready for TMS and SUS to go in, uncover, add the last of their hardware and plug in before SEI can float and balance.
Doug and Jason We are setup and ready to start the in situ position alignment of the ETMx and relay the results to Hugh for ISI tweaks. We will need 30min in the morning to make sure none of out equipment has moved over night. Scott and Randy (Apollo) rechecked and verified the elevation monuments based on BSC9 chamber centering.
The CPS on board target ground lugs are tied to chamber ground. All sensor cables are strain relieved at the feedthru protection shrouds. The EM actuator cables still need to be strain relieved.
(Rich, Alexa, Daniel)
We connected the outside cables on HAM1, labeled them and mounted the feedthrough protectors. The RF cables were routed in the cable tray, but still need to be terminated on the rack side. The only missing cables are the LSC PD DC supplies which we were unable to locate.
We also mounted the RF cables on HAM6, but they are not routed yet.
WP 4157 Moved One-Stop cables at computers and I/O Chassis for h1susey, h1susauxey, h1seiey, and h1iscey computers. One-stop cables are now in numerical order according to the location in the equipment rack of h1iscey, h1susey, h1susauxey, and h1seiey.
Completed reconfiguring the external RAID array attached to FW0 under WP 4158, to match the configuration on FW1. (Note that I had the two FW designations reversed in the original work permit text - it was in fact FW0 that was reconfigured, FW1 was untouched.) It took approximately 3.5 hours to backup the minute trends to the SATABoy, with the SSD filesystem at 40% utilization. For a nearly full SSD filesystem, expect the backup to take the better part of a day.
(Kiwamu, Paul, Stefan) This morning we found the back-reflection from the PRM, leaking through the Faraday, back on the PSL table. We measured the following powers: - direct beam, sampled by ~30% BS: 339mWatt - return beam, sampled by the same ~30% BS: 37.0uWatt - as reference, we also measured the power on the REFL beam on ISCT1, just after the periscope: 6.94mWatt Faraday isolation ratio: 37.0uW/339mW, minus other losses (IMC visibility, PRM reflectivity)
Some more small information regarding to this measurement:
The "good" alignment in PRM is :
Patrick T., Thomas V. Last night Thomas and I swapped the temporary cables being used to test the rotation stage in the CSR with the ones made for the final installation. These are not pulled yet, but are coiled in front of the rack holding the Beckhoff PSL environmental chassis and attached to a rotation stage sitting on a rolling table nearby. For some reason two cables had been unplugged from the controller box (goes between rotation stage and Beckhoff module). One was power and the other was a control cable. I'm not sure why they were unplugged, but we reattached them. I was hoping this would address problems we were having getting the rotation stage to move, but they have persisted.
Patrick T., Thomas V., Vern S. It would appear after testing that the rotation stage itself is burned out.
The "failure" of the Newport URS50BCC rotation stage was of concern to me as we have three of them in each IFO controlling significant amounts of laser power. These were new units and we had been reasonably careful with them. Why should this one die all of a sudden? This is what I found on investigating our broken rotation stage, S/N B12 6940 (Newport's serial number, not the ICS or DCC number).
The rotation stage's angular encoder was working. The TwinCAT2 control software for the rotation stage was showing angle and the "Mechanicsl Zero" signal was present (a high to low transition on moving from 350 deg to 5 deg). This indicated that the electonics was working and not blown. However, the resistance across the motor terminals (at the DB15 connector, pins 2 and 10) was infinite. Opening the housing that held the DB15 connector and printed circuit while monitoring the motor resistance, I found that it would intermitantly read 57.4 ohms, the proper motor resistance. The problem was traced to a bad connection of the upper ribbon cable which went from the printed circuit board to the motor and shaft angle encoder. The connection was a leaded connector designed for through-hole mounting and soldered onto surface-mounting pads. This is not a method of assembly I would recommend. I patched it back together and confirmed that the stage works. I'll use this for debugging and testing and assign it to our spares.
