(Filiberto, Gerardo)
We turned ON the cleanroom that is on top of HAM1 and HAM2, time 11:48 am.
I've been trying to turn on Sensor correction at HAM2 & HAM3 on the ISI's. HAM2 works as expected, but HAM3 gets almost nothing from turning it on. So far I've look at the the input filters (HAM3 was looking at the wrong STS originally, and the cal filter had a pole and zero at 1), the Hua filters (which all look the same) the input and output spectra at various places on the STS signal path (which all look the same, that I've found) and the chambers isolation filters (which, again, look very similar). Not sure what's going on.
Seismic:Installing Guardian changes for commissioning group Testing sensor corrections HAM2 and HAM3 CDS: Cabling work at the HAM3 area PCal: Camera work at End-Y and End-X FMP: Trenching/road work between H2 enclosure and VPW GC: Monday 06:00 to 07:00 ISP outage, limited INet access.
The display of seismic FOM's on projector0 in the control room is now accurate. This follows a change of operating systems for the dmt computers performed yesterday.
model restarts logged for Thu 04/Dec/2014
2014_12_04 17:42 h1fw0
unexpected restart of fw0. Conlog frequently changing channels list attached.
Dave, Elli, Alexa, Evan
We are trying to decrease the observed loss in the Y arm by changing the position where the cavity mode falls on the test masses.
We have done the following things:
Dave, Evan
We found a sign error in the script, but it doesn’t matter because the Y arm broke lock soon after we started the script so there is no data.
We have tried to relock the Y arm, but have not been able to. Maxium buildup on the TRY PD is about 3 cts (I expect we should se flashes of 6 cts or so). We've left the Y arm test masses "aligned" as determined by their saved guardian values.
It seems there is no green light anywhere in the arm. The ALS Y camera is completely dark, the REFL PD is completely dark, and I cannot move the TMS (either by hand or with the baffle script) to put light on the ITMY baffle PDs. Perhaps there is an issue with how the green light is being launched into the TMS, but I cannot diagnose it.
Ryan called and walked me through unsticking the green QPD loops at the Y end, which had become railed.
We're leaving the rest of the work for the morning.
I and Alexa looked at the video image of ETMY and ITMY.
We confirmed that the green and the IR are on top of each other on ITMY when the alignment was good-ish for green and IR. There's no particularly bright spot.
We couldn't tell if the green and the IR are on top of each other on ETMY. But there are two bright spots on the ETMY camera that only appear when the arm is locked. See attached images (green was misaligned for these images so you only see IR).
The ETMY camera is looking at the ETMY from HR side. These spots could be something on the HR coating itself, or could be an image of something else (e.g. some scattering and ACB or some unknown ghost beam hitting near by structure?) reflected by the HR coating. This cannot be behind the HR coating, but it's still not impossible that these are some ghost beams from TMS structure taking strange path and coming into the camera at a large angle.
While Dave was walking the beam in PIT, the high spot became brighter or weaker but the lower spot didn't change much (the first three images).
When the beam was moved in YAW the lower spots got brighter (the 4th image).
Update:
This morning I locked green to Y arm without IR, and I can see bright spots on the same position (5th picture), so now it seems more likely that they are on the HR of the mirror.
The sixth picture is taken with green and IR both locked.
If these are on the mirror, the low spot is somewhat low and somewhat to the right left to the center of the HR.
Update 2: Is the loss by shmutz big?
To see if the loss caused by the shmutz is significant, Alexa and I moved the beam about +-3cm in YAW on the ETMY without moving ITMY position: (ITMY, ETMY)= (-7.5, +5.88) urad in YAW moves the beam on ETMX to the right, flip the sign to move to the left.
We saw an improvement in both of the cases but it was better when we moved to the left. This is probably because the shmutz is to the right to the center of the mirror.
Alexa will post the StripTools plot, Dave is working on the loss number.
In the attached picure, the first one is when the beam was moved to the right, the next one is when it was moved to the left. Ignore the bright thing at the center of the shmutz as that's just green, look at the halo, and you can see that the IR is indeed dimmer than the last picture from my previous entry.
Keita and I had intentionally misaligned the green PZTs to examine the ETMY and ITMY camera with only the IR beam, and we never realigned it. This is why Evan found the EY green QPDs railed.
Also I found that one of the two IR input pointing WFS had not been cleared, which also explains why the IR beam was not flashing in the cavity.
| ITMY YAW | ITMY PITCH | ETMY YAW | ETMY PITCH | ASAIR | |
| Original | -152.9 | 209.5 | -58.7 | 93.93 | 1068 cnts |
| Right 3cm | -160.4 | 209.5 | -52.82 | 93.3 | 1117 cnts |
| Left 3 cm | -145.4 | 209.5 | -64.58 | 93.3 | 1129 cnts |
The above tables lists the positions and the counts on ASAIR. When the IR is not resonanting in the arm, ASAIR reads about 1360 cnts.
In the StripTool I have shown ASAIR_LF_OUTPUT which we are using to measure the power loss, and LSC-Y_TR_A_LF_OUT which measures the IR transmitted power.
At -75 min the IR is flashing in the arm cavity, and ASAIR is about 1360 cnts. Shortly after the IR locks, and then the input pointing WFS engage, as seen by the power build up in IR.
At -70 min we have full IR buildup (TR is about 11 counts), meanwhile ASAIR has dropped to about 1068 cnts.
At -45 min I begin to move the beam to the right; this is completed at about -40 min. At this point the transmitted power has remained the same and ASAIR is now up to around 1117 cnts
Shortly after we lose lock, and I recover the lock.
At -30 min I begin to move to the left; this is completed at about -20min. Again the tranmistted power has stayed the same, and now ASAIR is at 1129 cnts. Eventually we lose lock again.
Mirror cage outline and guesstimated mirror center line.
Note that we are looking the mirror from the left at a big-ish angle.
Blue lines are inner edges of the cage.
Using the ASAIR data in LHO#15467, the loss 850 ppm for original, 690 ppm for left 3 cm, and 655 ppm for right 3 cm, again ignoring mode-matching issues.
The formula I’m using is as follows:
where , and
.
Rick sent us this picture of Pcal camera. We can clearly see bright spots, which I assume is caused by the IR.
Note that pcal camera is looking at the optic from the right.
The license file for Matlab (Ubuntu) has been updated on the DAQ test stand, Matlab should work properly.
I looked at past data from two weeks ago in which we were locking the Y arm without recycling.
Two weeks ago, the Y arm was as lossy as it is now, .
A good data set was found in Nov-21 08:44:55 - Nov-21 8:59:54. According to conlog, this is the last time when we changed the normalization factor for TRY to set it to 1. Here are the values for ASAIR_LF:
Compared with the data from yesterday (alog 15432), which gave a ratio of 0.82 at ASAIR_A, I don't see a big difference. Also, a plot from dataviwer is attached. Note that TRY dropped in the middle of the locking because we set the TRY digital gain such that it becomes 1 (although the one shown in the plot is without the PSL normalization which is 10.
Apart from this past data, I found another good data set from approximately two months ago in Oct-3 23:35:44 - Oct-4 02:34:44 when Sheila and Alexa were working on the Y arm IR WFS (alog 14296). However. I am having difficulty in getting the relevant data in second trend or full rate for some reason. I could get minute trend, but they were not helpful.
I managed to find the missing data frames on the Caltech cluster. The results for a lock on 3 Oct 2014 at around 23:18 UTC (1096413500) are very much the same:
H1:LSC-ASAIR_A_LF_OUT_DQ
locked = 1057.0
unlocked = 1226.4
ratio = 0.86
H1:LSC-ASAIR_B_LF_OUT_DQ
locked = 303.2
unlocked = 357.5
ratio = 0.85
A plot of the channels is attached (the x-axis is seconds). So, it seems the y-arm losses have not significantly changed in the past two months.
I briefly ran an Optickle simulation to see if we can explain the observed low recycling gain by the 750 ppm Y arm intracavity loss.
According to the result, I am concluding that the loss is the cause of the current low recycling situation.
(Some details)
I set loss of ETMY to 750 ppm such that it does not ruin the SB build up in the DRMI. For the X arm, I assumed a round trip loss of 60 ppm for now. Then I ran the same code as the one I did the day before yesterday (alog 15389).
According to the resultant plots (see the attached), both TRX and TRY went up to only 166 which is close to what we observed yesterday i.e. 140-ish. This corresponds to a recycling gain of roughly 5. Even with this amount of loss, REFLDC dropped to 35% which does not contradict what we observed i.e. 50-ish%. Due to the low TRX and TRY, the CARM signal synthesized by sqrt(TRY +TRY) can be a good linear signal only up to an offset of 15 or so at which point sqrt(TRX+TRY) starts loosing the sensitivity because we are running into the plateau region of TRX and TRY. Indeed we needed to hand the CARM from the sqrt signal to REFL9 at an offset of -15 yesterday.
Interestingly, ASDC does not increase so much between off-resonance and on-resonance points even though we, at the beginning, speculated that differential losses would show up at the dark port as a large contrast defect. So it means that the light at the dark port is still dominated by the 45 MHz SBs which qualitatively agrees with the observed ASDC from yesterday. I am guessing that the reason why the carrier defect is so small is that the power recycling gain is already so low in the first place that the whatever carrier components at the dark also result in a low power.
Sorry, Evan. Fig files again.
Can you please post PDFs of the plots as well?
