ID |
Date |
Author |
Type |
Category |
Subject |
5639
|
Sun Oct 9 17:13:46 2011 |
kiwamu | Update | LSC | First attempt to estimate mode matching efficiency using interferometer |
The efficiency of the mode matching (MM) to PRC (Power-Recycling Cavity) has been estimated by using the interferometer.
The estimated MM efficiency is about 74 % when losses in the cavity are assumed to be zero.
(Motivation)
There had been an issue that the recycling gain didn't go to the designed high value of about 42 ( #5541).
One of the possibilities is a low efficiency in the MM to PRC ( also see #5541).
Although the MM efficiency had been measured using a beam scan ( see a summary on the wiki) a long time ago, it haven't been verified.
Therefore the MM has to be reviewed by using the real interferometer.
(Measurement)
The concept of this measurement is observe the amount of the reflected light from a power-recycled cavity and estimate the MM efficiency based on the measured reflectivities.
Since using the real PRC (consisting of BS, ITMs and PRM) could be a too complicated system for this measurement,
simpler cavities, namely Power-Recycled ITMX and ITMY (PRX and PRY), were used to examine the MM efficiency.
The measurement goes in the following order :
(1) Measurement of the amount of the single-bounce reflection from PRM with BS and ITMs misaligned.
(2) Lock PRX or PRY to carrier resonance.
(3) Alignment of PRX/Y to maximize the intracavity power. This time ASDC was used as a monitor of the intracavity power.
(4) Measurement of the amount of the reflected light when the cavity is in resonance. The value in REFLDC was averaged in 100 sec.
=> done by tdsavg 100 C1:LSC-REFLDC_OUT
The same measurement was performed for both PRX and PRY.
- locking parameters -
Sensor = REFL11_I
Whitening gain = 10 (30 dB)
PRCL_GAIN = 2
UGF ~ 200 Hz
(Analysis)
In order to estimate the relation between the MM efficiency vs. the reflected light, two models are considered:
(1) simple model => no loss and no sidebands
(2) sideband-included model => no loss but sidebands are taken into the account of the reflection.
(1) In the simple model the reflectivity Prefl / Pin is expressed by
[Reflectivity] = Prefl / Pin = Z * Rcav + (1- Z) * Rprm
where Z is MM efficiency and Rprm is the reflectivity of PRM
and Rcav is the reflectivity of PRX/Y when it's resonance and it is defined by
R cav = | r prm - r itm t 2BS| 2 / |1 -r prm r itm t 2BS | 2
Tprm = 5.75% and Titm = 1.4 % are assumed in all the calculations.
In the first equation the first term represents the mode matched light and hence it couples with the cavity through Rcav.
The second term is the non-mode-matched light and because they are not interacting with the cavity they will be simply reflected by PRM through Rprm.
(2) In reality two phase-modulated light (11 MHz and 55 MHz) will behave differently from the carrier.
For example when the carrier is in resonance the sidebands will be anti-resonance against the cavity.
So that the amount of REFLDC will be slightly bigger because of the reflection of the sidebands.
Prefl = Z * Rcav * Pc + Z * Ranti * Ps + (1- Z) * Rprm * (Pc + Ps)
where Pc and Ps are the power in the carrier light and the sidebands respectively.
And Ranti is the reflectivity of the anti-resonance PRX/Y, which can be obtained by replacing the minus sign by the plus sign in the equation of Rcav shown above.
It is assumed that the sum of the carrier power and sidebands power is the incident power Pin = Pc + Ps.
The power in the carrier and the sidebands were estimated based on the OSA measurement ( #5519), so that
Pc / Pin = |J0(0.14)|2 * |J0(0.17)|2 = 0.976
Ps / Pin = 2 * |J1(0.14)|2 + 2 * |J1(0.17)|2 = 0.024
(Results)
Here are the measured values in REFLDC
-- Measurement 1 : PRX
Single bounce from PRM = 4802.27 counts
==> the incident power = 5095.25 counts
Reflected light from PRX = 4433.88 counts
==> Reflectivity = 0.8702
-- Measurement 2 : PRY
Single bounce from PRM = 4833.05 counts
==> the incident power = 5127.05 counts
Reflected light from PRX = 4444.48 counts
==> Reflectivity = 0.86672
On average the reflectivity of power-recycled ITM cavity was 0.868 with a standard deviation of 0.001744.
Actually the standard deviation estimated here is not fair because the measurement was done by only twice,
but my intention was that I wanted to see how the error can affect the estimation of the MM efficiency.
Here is a plot comparing the model curves and the measured values with 5 sigma error box (5 times of measured standard deviation).

It is shown that the mode matching efficiency is 73.7 % when the sideband-included model is considered.
With the 5 sigma deviation it can go from 65% to 82% but it is still low and lower than the beam scan measurement ( see a summary on the wiki).
Anyways the estimated MM efficiency with the sidebands effect included and without loss effect is
MM efficiency = 73.7 +/- 1.7 % (1 sigma error) or +/- 8.7 % (5 sigma error) |
5640
|
Mon Oct 10 00:01:26 2011 |
Koji | Update | LSC | First attempt to estimate mode matching efficiency using interferometer |
"^2"s are missing in the second equation, but the calculation results seem correct.
PRX and PRY have different mode matching because of the Michelson asymmetry.
Are individually estimated mode matching indicates any sign of reasonable mode mismatch?
(The difference can be very small because the asymmetry is not so big.) |
5641
|
Mon Oct 10 10:14:43 2011 |
rana | Update | LSC | length fluctuations in SRCL |
How does it make sense that the motion at 0.1 Hz of PRC is 10x larger than MICH?
EDIT by KI:
That's actually the point which I was wondering at. One possible reason is that my actuator responses are not so accurate below 1Hz.
I will measure the DC response of all the actuators and it will completely determine the shapes of the actuator responses except for the region around the resonance.
In the process of producing the plot I was assuming that all the actuator response have a 1 Hz resonance with Q of 5.
However in reality this assumption is not true because the resonant frequency is different in each actuator. |
5642
|
Mon Oct 10 12:14:00 2011 |
Mirko | Update | Computer Scripts / Programs | IMC simulations |
[Mirko, Kiwamu]
I tried to answer two questions regarding the IMC:
1. What is the coupling of fluctuations in the SB freq. to SB transmitted power?
2. What (if any) is the influence of the IMC on the AM?
I ran into some weird things regarding the corresponding optickle simulations:
1. There seems to be some artifact at the beginning of every simulation sweep.
2. The position of features depends on the parameters of the sweep.
I mailed Matt asking if he sees some error in the simulations

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Attachment 2: DC_power.png
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Attachment 3: DC_power_B.png
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Attachment 4: IMC_simulation.zip
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5643
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Mon Oct 10 13:52:04 2011 |
kiwamu | Update | LSC | RE: First attempt to estimate mode matching efficiency using interferometer |
Quote from #5640 |
"^2"s are missing in the second equation, but the calculation results seem correct.
PRX and PRY have different mode matching because of the Michelson asymmetry.
Are individually estimated mode matching indicates any sign of reasonable mode mismatch?
(The difference can be very small because the asymmetry is not so big.)
|
- Thank you for the correction. The missing square operation has been added correctly on the last entry (#5639).
- As for the individual MM efficiency,
I was assuming that the MM solutions are the same for PRX, PRY and the real PRC, so I haven't carefully checked differences between those cavities.
However as you mentioned the difference in those cavities can be tiny due to the small 3 cm Schnupp asymmetry.
Anyway I will briefly check it to make me sure. |
5644
|
Mon Oct 10 15:41:56 2011 |
Koji | Update | PSL | PMC aligned |
[Koji Suresh]
The steering mirrors for PMC were aligned. The transmission went up from 0.779 to 0.852. |
5645
|
Mon Oct 10 16:32:18 2011 |
steve | Update | SUS | UL sensor of ETMY is recovered |
I lost UL osem voltage this morning when I was checking the actual connection at rack ETMY
This after noon I disconnected the 64 pins IDE connector from satelite amp at the rack, and the two 25 pins Dsubs at this juction board.
UL OSEM recovered after reconnecting these three connectors.
Atm3, bad connection.........noisy UL
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Attachment 1: ETMY_UL.png
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Attachment 2: ETMY_OSEM_UL.png
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Attachment 3: noisyETMY_UL.png
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5646
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Mon Oct 10 18:53:04 2011 |
Katrin | Update | Green Locking | Mirrors whose angle of incidence is not 45° |
The angle of incidence of light is for some mirrors on the YARM end table different from 45° even though the mirrors are coated for 45°.
The mirrors below are useful if there are plans to replace these mirrors by properly coated ones.
Mirror
|
Angle of incidence (degree) |
1st 1" mirror right after laser* |
10 |
2nd 1" mirror right after laser |
35 |
1st 2" steering mirror to vacuum system |
15 |
2nd 2" steering mirror to vacuum system |
28 |
* This is the new mirror as decribed on http://nodus.ligo.caltech.edu:8080/40m/5623
|
5647
|
Tue Oct 11 00:59:55 2011 |
Suresh | Update | IOO | Preliminary locking of WFS loops |
[Kiwamu, Koji, Suresh]
After correcting several errors in the WFS loops, we turned them on today and saw them working!
A while back (last week actually) I noticed that the WFS1 and WFS2 QPD segments were numbered in a different order but that their input matrices did not reflect this change. As result the WFS pitch and yaw definitions were pretty much mixed up. However even after clearing this up the signals still showed significant amount of cross couplings.
This problem was finally traced to the relative phase between I and Q channels of the WFS segments. Koji suggested that I check the relative phase between all the segments to be sure. I then repeated the procedure that Valera and I followed in our earlier elog # 5321 , and found that the phases indeed required to be adjusted. The excitation of MCL was at 6Hz, 100mVpp, as before. The WFS response after this was much improved i.e. the pitch yaw cross couplings were not visible when we misalign the MC with sliders in MC_ALIGN. And the magnitude of the response also increased since the signal was transferred from the Q to I channels. The the phases were tweaked by hand till Q< 1% of I. However when I repeated this measurement an hour later (I wanted to save the plots) I found that the phases had changed by a few percent!
Koji noticed that the MC_REFL camera image showed significant intensity fluctuations and advised that we try a higher frequency and lower amplitude to avoid nonlinear effects in the WFS and in the MCL to PSL lock. So we repeated the process at 20Hz and 20mVpp, introduced at the IN2 of the MC_Servo. The fig below shows the level to which we reduced the signal in Q.

We then checked the relative phase between various quadrants by looking at the time series in dataviewer. WFS2 Seg4 phase had to be flipped to bring it into phase with all the rest.

After this I tried to see the WFS response to moving the MC1 and MC3 with the sliders and determined the following relations:
Pitch |
WFS1 |
WFS2 |
MC1 |
+ |
- |
MC2 |
- |
- |
MC3 |
+ |
+ |
Yaw |
WFS1 |
WFS2 |
MC1 |
+ |
+ |
MC2 |
- |
- |
MC3 |
+ |
- |
Disregarding the MC2 for now and assuming arbitrary gains of 1 for all elements we inverted these matrices inserted them into the WFS_servo_outmatrix. We then found that the with a sign flip on all elements the loops were stable. In the servo filters we had turned on only the filter modules 3 and 4. There was no low frequency boost. We gradually increased gain till we saw a significant suppression of the error signal at low frequencies as shown below. There was also an associated suppression of Intensity noise at REFL_DC after a single bounce from PRM.

To see if the locks can actually realign the MC if it were manually misaligned, we turned the loops off and misaligned MC by moving MC3 pitch by 0.05 (slider position), and then turned on the loops. The locks were reengaged successfully and the MC regained alignment as seen on the StripTool below:

We can now proceed with the fine tuning the servo filters and understand the system better:
Q1: Does the WFS (I to Q) phase drift rapidly? How can we prevent it?
Q2: How is that we do not see any bounce or roll resonances on the WFS error signals?
Q3: How do we include the MC2 QPD into the WFS Servo?
I will proceed with determination of the actual transfer coefs between the MC DoF and the WFS sensors.
|
5648
|
Tue Oct 11 03:35:16 2011 |
kiwamu | Update | LSC | BS actuator reponse at low frequency : measured |
The response of the BS actuator in a low frequency regime has been measured.
After the measurement I did a coarse fit to see if the low frequency data agree with the high frequency response which I have measured two weeks ago ( #5583)
So far it shows a good agreement with the high frequency data (see the plot below). Tomorrow I will do a serious fitting.
Once the calibration of BS is done, the low frequency responses of ITMs, PRM and SRM will be done by simply exciting BS and comparing them (maybe at a couple of frequency points around 0.1Hz).
(Measurement)
+ With free swinging MICH, the sensor (AS55_Q) was calibrated into counts/m.
=> The peak-peak counts was about 110 counts. So the sensor response is about 6.5x108 counts/m
+ Locked Michelson with AS55_Q and the signal was fedback to BS.
+ Set the UGF high enough so that the open loop gain below 10 Hz is greater than 1.
+ With DDT's swept sine measurement, C1:LSC-MICH_EXC was excited with a big amplitude of 40 counts.
+ Took a transfer function from C1:LSC-MICH_OUT to C1:LSC-MICH_EXC.
+ Calibrated the transfer function into m/counts by dividing it with the sensor response.
Quote from #5641 |
One possible reason is that my actuator responses are not so accurate below 1Hz.
I will measure the DC response of all the actuators and it will completely determine the shapes of the actuator responses except for the region around the resonance.
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5649
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Tue Oct 11 15:14:50 2011 |
rana | Update | LSC | BS actuator reponse at low frequency : measured |
Quote: |
The response of the BS actuator in a low frequency regime has been measured.
|
This seems like an error prone method for DC responses due to the loop gain uncertainty. Better may be to use the fringe hopping method (c.f. Luca Matone) or the fringe counting method |
5650
|
Tue Oct 11 15:19:17 2011 |
rana | HowTo | Environment | 40m map |
The Kinemetrics dudes are going to visit us @ 1:45 tomorrow (Wednesday) to check out our stacks, seismos, etc.
 
I put these maps here on the elog since people are always getting lost trying to find the lab. |
5651
|
Tue Oct 11 17:32:05 2011 |
jamie | HowTo | Environment | 40m google maps link |
Here's another useful link:
http://maps.google.com/maps?q=34.13928,-118.123756 |
5652
|
Tue Oct 11 19:11:25 2011 |
kiwamu | Update | LSC | Re: BS actuator reponse at low frequency : measured |
I think the precision due to the loop gain uncertainty is something like 0.1% at 0.1 Hz. It's not the issue.
The real issue was the loud motion of MICH, which degrades the coherence of the measurement.
Also last night I tried the fringe hopping technique and gave it up for several reasons.
(uncertainty due to the loop gain)
When MICH is locked, the signal at C1:LSC-MICH_OUT can be expressed in frequency domain by
MICH_OUT = G / (1+G) * (1 / A) * X + G / (1+G) * (1 / H) * (1 / A) * S, [1]
where G is the open loop gain, A is the actuator response, H is the sensor transfer function (constant factor),
X is the natural (unsuppressed) motion of MICH and S is an excitation injected at C1:LSC-MICH_EXC.
When the natural motion of MICH X is smaller than the excited displacement S/H, dividing MICH_OUT by S gives
[Transfer function] = S / MICH_OUT
= (1+G) /G * H * A
At low frequency the open loop gain is always big, so that the transfer function can be approximated to
[Transfer function] ~ H *A
This approximation is valid with a precision of 1/G.
In my case yesterday, the open loop gain at 0.1Hz was about 103 or more than that, so the uncertainty due to the loop gain was 0.1% or even less.
(Effect from the MICH motion)
In the equation [1], it is shown that the MICH motion X shows up together with the excitation signal.
Actually this MICH motion term was not completely negligible and eventually this term disturbs the measurement resulting in a low coherence.
In order to get a high coherence in the measurement, X should be smaller than the excited displacement S/H,
X << S / H
This the reason why I had to inject a big excitation signal. Although the coherence around 1Hz turned out to be still low due to the loud natural motion in MICH.
The excitation was already close to 0.1 um level in terms of peak-to-peak displacement, and I wasn't able to increase it any more because the MICH signal would run into a nonlinear regime.
In the worst case I lost the lock due to a too much excitation.
(Fringe hopping technique)
Actually I tried and gave up this technique. That's why I did the in-loop measurement.
My feeling is that this technique is not suitable for the 40m.
What I tried was to flip the sign of the MICH control such that the fringe hops from the dark fringe to the neighbor bright fringe or vice versa.
Difference in the control signal (C1:LSC-MICH_OUT) was supposed to give us the amount of signal which drives the actuator by exactly quarter of the laser wave length.
However this technique turned out to be not good because
(1) BS actuator is too strong
=> expected difference in the control signal is quite small.
=> \lambda / 4 / A ~ 12 counts, where A is the actuator DC response of about 2.2e-8 [m/counts].
(2) MICH motion was too loud
=> I saw such a tiny 12 counts difference in the control signal, but once the hopping is done the control signal immediately fluctuated and it was really hard to precisely measure it.
=> It's simply because MICH was loud, and the actuator tried to suppress the motion and it resulted such an immediate signal fluctuation in the control signal
|
This seems like an error prone method for DC responses due to the loop gain uncertainty. Better may be to use the fringe hopping method (c.f. Luca Matone) or the fringe counting method
|
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5653
|
Tue Oct 11 21:23:51 2011 |
Jenne | Update | LSC | Arm absl lengths |
Quote: |
[Katrin, Jenne]
We took the data for the new absolute length measurement of both arms, after the latest vent and move. We will analyze soonly. We had done a round of analysis, but then Koji pointed out that our data wasn't so clean because the whitening filters were on (and saturated the ADC). We now have the data (but not the analysis) for the better data with the WF off.
So our dirty-data preliminary number for the X arm is 37.73meters, which is 14cm different from our old length. We were supposed to move by ~20cm, so....either this measurement is bad because the data sucked (which it did), or we are 6cm off. Or both.
I'll do another analysis with the clean data for both arms later today/tomorrow.
|
After analyzing the cleaner data, I get the following:
Y_Length_long = 37.757 meters
X_Length_long = 37.772 meters
As stated in the wiki, the goal arm length was L = 37.7974 m for each arm.
So we're within 2cm for X, and within 4cm for Y.
According to Kiwamu's awesome tolerance calculation, we need to be within 2cm for each arm. Given that we started out 20cm wrong for X and 25cm wrong for Y, we're a lot closer now, even though we aren't meeting our Yarm requirement yet.
Probably some Optickle action is in order, to see what these new lengths give us in terms of sideband phase and other stuff.
If you want more digits on my calculated numbers (which are probably meaningless, but I haven't done a careful error analysis), in my directory ...../users/jenne/Xarm and ..../users/jenne/Yarm run Xarm_find_peaks_and_length.m and Yarm_find_peaks_and_length.m respectively. These will output the lengths. |
5654
|
Wed Oct 12 00:35:42 2011 |
kiwamu | Update | LSC | TRY path realigned |
The TRY (TRansmitted light from Y arm ) path was a bit realigned because there had been a small clipping.
This clipping was introducing offsets on the error signals of the C1ASS servo.
(Story)
During I was running the C1ASS servo on the Y arm I found every time after the auto-alignment is done there still remained a slight offset in the beam pointing,
I looked at the CCD camera which looks at the transmitted light and then introduced an intentional misalignment in ETMY in order to find an obvious clipping.
Indeed there was a clipping in horizontal direction. I checked through the optics on the Y end optical bench.
On the second mirror (beam splitter) the beam was on a very edge. So I steered the first steering mirror to fix it,
In addition to that an iris which is placed between the first and second mirror was also clipping the beam,
So I fully opened the aperture of the iris. |
5655
|
Wed Oct 12 08:43:30 2011 |
steve | Update | SUS | ITMX oplev improved a bit |
Atm2 is before optical path adjustment. The idea was to remove possible clipping in vacuum.
Coherense significantly reduced below 4 Hz
Today I will replace the He/Ne laser 1125P with 1103P
|
Attachment 1: ITMXoplev.png
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Attachment 2: ITMXoplevservo_ON.png
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5656
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Wed Oct 12 17:53:01 2011 |
kiwamu | Update | LSC | BS actuator response : fitting done and histroy of delays |
An update on calibration of the BS actuator : A fitting has been done.
(Fitting)
I used LISO for fitting the complex transfer function.
Because the data points around 1 Hz didn't have big coherence a few data points, which had coherence of less than 0.9, were excluded.
Also the fitting of the Q-factor wasn't successful due to the lack of good data points around the resonance.So I left Q fixed to be 5 in the fitting.
(Fitting result)
G = 2.18060874008e-8 +/- 6.425e-10 (2.95%)
f0 = 1.0100491195 +/- 1.51e-2 (1.49%) [Hz]
Q = 5 (fixed)
delay = 423.2753462089e-6 +/- 4.989e-6 (1.18%) [sec]

(History of delay)
Because we have been observing several different amount of delays in different configurations, perhaps it is worth to summarize those numbers.
description |
delay [usec] |
elog entry |
MICH lock (BS actuation) |
423 |
this entry |
LSC feed forward path |
127 |
#5218 |
MICH lock (BS actuation) |
600 |
#4638 |
ALS on X arm (ETMX actuation) |
330 |
#4196 |
RFM (from c1lsc to c1sus) |
125 |
#4153 |
from ADC to DAC (all the front end machine) |
38-110 |
#3961 |
from ADC to DAC (c1sus) |
124 |
#3838 |
RFM (c1ioo and c1sus) |
8-62 |
#3855 |
Quote from #5648 |
Tomorrow I will do a serious fitting.
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5657
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Wed Oct 12 18:54:02 2011 |
Katrin | Update | Green Locking | 60 Hz oscillation due to broken BNC cable |
There was a 60 Hz and 120 Hz oscillation on the green PDH photo diode output. After a long search, I could identify that
the source was a broken BNC cable which was connected to the photo diode. I exchanged that BNC cable and the 60 Hz
and 120 Hz are gone :-)
With the new cable the PD output was less noisy so that it was easier to achieve a better alignment of the light to the cavity.
The reflected power could be reduced from 40% to 30%. For perfect alignment the reflected power would be 20%. |
5658
|
Wed Oct 12 19:58:32 2011 |
Katrin | Update | Green Locking | Power splitter is unbalanced |
The mini circuit power splitter ZFRSC-42S+ used at the YARM has no balanced output as it should have according to the data sheet.
@ 0.05MHz the amplitude unbalance should be 0.03 dB
A quick measurement shows that there is a LO amplitude dependent unbalance:
LO amplitude input (Vpp) |
unbalanced output (dB) |
1.3 |
3.66 |
1.4 |
4.08 |
1.5 |
4.28 |
1.6 |
4.36 |
So my question is, shall I replace the power splitter just in case it is further degrading? |
5659
|
Thu Oct 13 03:22:53 2011 |
kiwamu | Update | LSC | measurement of sensing matrix : just began |
- status update on LSC activity :
The measurement of the LSC sensing matrix has begun. But no useful results yet.
The measurement script (#4850) ran pretty well after I did some modifications to adopt the script to the latest LSC model.
However the SNR weren't so great particularly in REFL33 in the PRMI configuration.
So I will tune the amplitude of excitations and integration times tomorrow.
Currently the excitation is at 238.1 Hz, where no disturbing structures are found in the spectra. |
5660
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Thu Oct 13 14:23:09 2011 |
steve | Update | SUS | ITMX oplev with 3 mm beam on qpd |
I replaced the JDSU-Uniphase 1125P by 1103P He/Ne laser. This new laser had 2.8 mW output yesterday. It degraded to 0.5 mW by this morning.
The beam size on the QPD is ~3 mm This should give us better sensitivity. These are not the perfect lenses at all, but we have them here.
On the other hand, there are still some coherence below 1 Hz, so the laser intensity noise or clipping dominating this part of the spectrum.
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Attachment 1: ITMXoplev1103p#2.png
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Attachment 2: ITMXoplev.png
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5661
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Thu Oct 13 20:25:32 2011 |
Katrin | Update | Green Locking | LPF transfer function YARM |
It is a 4th order filter with cut of frequency of 120 kHz.
Design

Measurement

  

|
5662
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Thu Oct 13 21:40:59 2011 |
rana | Summary | VAC | Recovery from the power shutdown is completed |
As it turns out Steve is not crazy in this particular instance: the vacuum computer, linux3 , has some issues. I can login just fine, but trying to open a terminal makes the CPU rail and the RAM max out and eventually the machine freezes.
Under KDE, I can open a terminal OK as root, but if I then try a 'su controls', the same issue happens. Let's wait for Jamie to fix this. |
5663
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Thu Oct 13 21:44:48 2011 |
Mirko | Update | CDS | Seismic BLRMS channels, new RMS calculation |
[Rana, Koji, Mirko]
We looked into the CDS RMS block c-code as described in Rolfs RCG app guide. Seems the block uses a first order LP filter with a corner freq. / time of 20k execution cycles. There are also some weird thersholds at +-2000counts in there.
I was looking into implementing a hand-made RMS block, by squaring, filtering, rooting. The new RMS (left) seems nicer than the old one (bottom right). Signal was 141counts sinus at 4Hz.
Filters used: Before squaring: 4th order butterworth BP at given freq. & (new) 6th order inverse Chebyshew 20dB at 0.9*lower BP freq. and 1.1*upper BP freq. => about 1dB at BP freq.
After squaring: 4th order butterworth LP @ 1Hz.
C1PEM execution time increased from about 20us to about 45us.
Made a new medm screen with the respective filters in place of the empty C1PEM_OVERVIEW. Should go onto the sitemap.

Original RMS LP is slower than 0.1Hz, see below for single LP at 0.1Hz in the new RMS. Original RMS is faster than single LP @ 0.01Hz

Some of the channels are recorded as 256Hz DAQ channels now. Need to figure out how to record these as 16Hz EPICS channls. |
5664
|
Thu Oct 13 23:58:38 2011 |
Koji | Update | LSC | fixing REFL165 |
I already have reported in this entry that REFL165 shows too high DC output which does not depend on the light level on the diode.
Today I removed REFL165 from the table and inspected it.
The diode has been burnt as shown in the first picture (left).
The window is smoked, and the photo sensitive surface has been removed from its base. It moves in the can.
The burnt diode was replaced to the new one.
The new one shows ~30% better capacitance of ~50pF and I had to increase the inductance from 14nH (i.e. 15nH//220nH) to 18nH.
After some struggles to increase/decrease the stray inductance by moving the SMD capacitors a little, the resonance is reasonably tuned to 166MHz.
The comprehensive test will be performed shortly. |
Attachment 1: PA131612.jpg
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Attachment 2: PA131618.jpg
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5665
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Fri Oct 14 04:35:45 2011 |
kiwamu | Update | LSC | locking tonight |
The lock of DRMI wasn't stable enough to measure the sensing matrix. Failed.    
PRMI and SRMI were okay and in fact they could stay locked robustly for a long time.
I added a new option in the C1IFO_CONFIGURE screen so that one can choose Signal-Recycled Michelson in carrier resonant condition.

Additionally the orthogonalization of the I-Q signals on REFL55 should be done because it hasn't been done.
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5666
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Fri Oct 14 16:20:11 2011 |
Zach | Update | SUS | C1:SUS-ETMX_SPDMon fixed |
I offered to help Kiwamu with some of the 40m work. The first task was to figure out why the ETMX side OSEM monitor was so low, since we know that the depth is about right. It was showing ~0.13 V to the others' ~0.7 V.
TL,WR: There was a wire disconnected from the breakout panel on the side of the rack
I started by pulling the board out and checking to make sure that it was working properly. I injected a sine wave to the SIDE IN and found that it showed up in the signal coming out of the back (into the crate) just fine (see below). One strange thing I noticed while testing the board is that both inputs for each used channel of the MAX333 switches on the board are shorted to their respective outputs. That is, the switches seem to be open to BOTH 0 and 1 logic states. This seems counterintuitive, but perhaps there's something about how these work that I don't know.

Then I went about tracing the signal from the back of the crate to the breakout panel on the side of the rack. I opened it up, verified that the ribbon cable was transmitting correctly, and as I went to plug it back in I noticed that one of the wires---the correct one---had come completely undone.

The screw clamp appeared to be a bit finicky, as I had to loosen and tighten it a few times before it finally seemed to grab hold of the wire. It probably just wasn't tight in the first place and the wire was pulled out. Anyway, things are working now:

|
5667
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Fri Oct 14 18:38:41 2011 |
kiwamu | Update | SUS | C1:SUS-ETMX_SPDMon fixed |
Quote from #5666 |
Anyway, things are working now:
|
Good job ! Thank you so much  |
5668
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Sat Oct 15 04:53:41 2011 |
Suresh | Update | IOO | MC WFS Output Matrix determination |
After we had a rough idea of what the output matrix looks like (see this elog), I tried to measure the transfer function coefs (TFCs) between mirror degrees of freedom and the WFS sensors (WFS1, WFS2 and MC_Trans QPD) I found that the TFCs that I obtained at 10.15 Hz did not have any resemblance to the previously identified output matrix. The problem, I realised, arises because the various lockins used in the C1IOO model do not have the same relative phase; So if we try to excite a mirror with one of them and demodulate a sensor signal on any of the other lockins the resulting output would not have the correct phase (relative to the 1st lockin output). As a result unless we can reset the phase of all the lockins simultaneously, we cannot demodulate multiple signals at the same time. (Joe/Jamie, Is it possible to reset/reinitialise the phase of the CLK signals of the lockings? ) To get around this problem Koji suggested that I use just one lockin and determine all the 36 elements of the transfer matrix with it one at a time rather than six at a time. When I did that, I got results consistent with the previoulsly determined outmatrix. It, of course, takes six times longer.
The matrix I first got is this one
(Mag, Phase) |
WFS1P |
WFS2P |
MC_T_P |
WFS1Y |
WFS2Y |
MC_T_Y |
MC1P |
0.332 |
0.518 |
0.316 |
0.019 |
0.066 |
0.000 |
|
5.832 |
1.892 |
8.180 |
38.285 |
8.807 |
0.000 |
|
|
|
|
|
|
|
MC2P |
0.355 |
1.798 |
0.342 |
0.023 |
0.144 |
0.000 |
|
72.977 |
76.683 |
76.804 |
-16.364 |
77.451 |
71.579 |
|
|
|
|
|
|
|
MC3P |
0.352 |
0.394 |
0.254 |
0.036 |
0.023 |
0.000 |
|
2.005 |
3.249 |
6.249 |
5.712 |
26.349 |
NAN |
|
|
|
|
|
|
|
MC1Y |
0.051 |
0.055 |
0.058 |
0.788 |
1.024 |
0.001 |
|
15.979 |
-4.487 |
-9.707 |
2.642 |
1.276 |
0.000 |
|
|
|
|
|
|
|
MC2Y |
0.142 |
0.044 |
0.130 |
1.966 |
0.579 |
0.017 |
|
70.044 |
83.818 |
76.397 |
74.283 |
76.134 |
77.269 |
|
|
|
|
|
|
|
MC3Y |
0.044 |
0.052 |
0.022 |
0.080 |
0.948 |
0.194 |
|
22.932 |
14.227 |
-45.924 |
9.677 |
1.125 |
1.124 |
|
|
|
|
|
|
|
Which can be |
recast as below |
|
|
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|
Magnitude |
WFS1P |
WFS2P |
MC_T_P |
WFS1Y |
WFS2Y |
MC_T_Y |
MC1P |
0.332 |
0.518 |
0.316 |
0.02 |
0.07 |
0 |
MC2P |
0.355 |
1.798 |
0.342 |
0.02 |
0.14 |
0 |
MC3P |
0.352 |
0.394 |
0.254 |
0.04 |
0.02 |
0 |
MC1Y |
0.05 |
0.05 |
0.06 |
0.788 |
1.024 |
0.001 |
MC2Y |
0.14 |
0.04 |
0.13 |
1.966 |
0.579 |
0.017 |
MC3Y |
0.04 |
0.05 |
0.02 |
0.080 |
0.948 |
0.194 |
Phase |
WFS1P |
WFS2P |
MC_T_P |
WFS1Y |
WFS2Y |
MC_T_Y |
MC1P |
5.8 |
1.9 |
8.2 |
38.3 |
8.8 |
0.0 |
MC2P |
73.0 |
76.7 |
76.8 |
-16.4 |
77.5 |
71.6 |
MC3P |
2.0 |
3.2 |
6.2 |
5.7 |
26.3 |
NA |
MC1Y |
16.0 |
-4.5 |
-9.7 |
2.6 |
1.3 |
0.0 |
MC2Y |
70.0 |
83.8 |
76.4 |
74.3 |
76.1 |
77.3 |
MC3Y |
22.9 |
14.2 |
-45.9 |
9.7 |
1.1 |
1.1 |
Note that when MC2 is excited all the sensors showed a response about 75 deg out of phase with the reference (MC1 --> WFS1_PIT ) This was traced to the fact that while there is a 28Hz Elliptic LP filter on
both MC1 and MC3, while it is absent on MC2. The Transfer functions below show the difference in the phase of their response

Since the MC2 POS is used in servos involving MCL we cannot afford to install a 28 Hz LP filter into the MC2 coil drivers. However a module with the 28 Hz ELP was switched on, in each of the
MC2 PIT and YAW filter banks. I then checked to see if this has affected the relative phase of variour sensors. The Phase angle between I and Q on each sensor channel was checked and corrected.
Below are the spectra with the "before" and "after" correction of phases.
Before:

Obviously this needed adjustment to reduce Q phase.
After twealkng the angle "R":

And again determined the transfer matrix (below).
( I , Q ) |
WFS1P |
WFS2P |
MC_T_P |
WFS1Y |
WFS2Y |
MC_T_Y |
MC1P |
0.236 |
-0.300 |
0.229 |
0.049 |
-0.008 |
0.000 |
|
0.015 |
-0.004 |
-0.027 |
0.011 |
-0.019 |
0.000 |
|
|
|
|
|
|
|
MC2P |
-0.125 |
-0.962 |
-0.135 |
0.114 |
0.028 |
0.000 |
|
0.007 |
-0.052 |
-0.028 |
-0.004 |
-0.002 |
0.000 |
|
|
|
|
|
|
|
MC3P |
-0.225 |
-0.254 |
-0.255 |
-0.026 |
-0.010 |
0.000 |
|
0.004 |
-0.012 |
-0.010 |
0.009 |
0.002 |
0.000 |
|
|
|
|
|
|
|
MC1Y |
-0.059 |
-0.023 |
-0.040 |
0.460 |
0.705 |
0.001 |
|
0.004 |
0.003 |
0.009 |
0.009 |
0.017 |
0.000 |
|
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|
MC2Y |
0.030 |
0.190 |
0.040 |
-1.144 |
-0.296 |
0.015 |
|
0.007 |
0.006 |
-0.009 |
-0.038 |
-0.009 |
0.001 |
|
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|
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|
MC3Y |
0.018 |
-0.108 |
-0.018 |
0.134 |
-0.832 |
-0.001 |
|
0.017 |
0.005 |
0.001 |
0.006 |
-0.016 |
0.000 |
Magnitude |
WFS1P |
WFS2P |
MC_T_P |
WFS1Y |
WFS2Y |
MC_T_Y |
MC1P |
0.236 |
0.300 |
0.231 |
0.05 |
0.02 |
0 |
MC2P |
0.125 |
0.964 |
0.138 |
0.11 |
0.03 |
0 |
MC3P |
0.225 |
0.254 |
0.255 |
0.03 |
0.01 |
0 |
MC1Y |
0.06 |
0.02 |
0.04 |
0.460 |
0.705 |
0.001 |
MC2Y |
0.03 |
0.01 |
0.19 |
1.145 |
0.296 |
0.015 |
MC3Y |
0.02 |
0.11 |
0.02 |
0.134 |
0.832 |
0.001 |
Phase |
WFS1P |
WFS2P |
MC_T_P |
WFS1Y |
WFS2Y |
MC_T_Y |
MC1P |
3.694 |
0.784 |
-6.778 |
13.1 |
66.67 |
#DIV/0! |
MC2P |
-3.214 |
3.100 |
11.557 |
-2.05 |
-4.48 |
0 |
MC3P |
-1.020 |
2.665 |
2.158 |
-19.1 |
-10.76 |
NA |
MC1Y |
-3.96 |
-6.45 |
-12.14 |
1.085 |
1.357 |
0.000 |
MC2Y |
13.22 |
41.08 |
-2.6 |
1.887 |
1.706 |
4.987 |
MC3Y |
42.69 |
-2.56 |
-3.73 |
2.652 |
1.068 |
0.000 |
This time the signals are all nearly in the same phase and in agreement with the outmatrix estimate made earlier.
I plugged these TFCs into the matrix inversion code: wfsmatrix2.m. And get the following inverse:
|
WFS1P_Act |
WFS2P_Act |
MC_Trans_P_Act |
WFS1Y_Act |
WFS2Y_Act |
MC_TRANS_Y_Act |
MC1P |
1 |
-0.64 |
|
|
|
|
MC2P |
-0.27 |
-1 |
|
|
|
|
MC3P |
0.98 |
-0.65 |
|
|
|
|
MC1Y |
|
|
|
-0.26 |
-1 |
|
MC2Y |
|
|
|
1 |
0.12 |
|
MC3Y |
|
|
|
0.16 |
0.07 |
|
I have ignored the MC2_Trans_P and Y sensors for now. |
5669
|
Sat Oct 15 10:58:32 2011 |
rana | Update | IOO | MC WFS Output Matrix determination |
In order to save time and sanity, you should not measure the pitch ->yaw and yaw-> pitch. It makes things too complicated and so far is just not significant. In the past we do not use these for the matrix work.
i.e. there should just be a 3x3 pitch matrix and a 3x3 yaw matrix. Once the loops are working we could investigate these things, but its really a very fine tweak at the end. There are quite a few other, more significant effects to handle before then.
To make things faster, I think we can just make a LOCKIN which has 3 inputs: it would have one oscillator, but 6 mixers. Should be simple to make. |
5670
|
Sat Oct 15 16:01:26 2011 |
kiwamu | Update | IOO | about LOCKIN module |
Quote from #5669 |
To make things faster, I think we can just make a LOCKIN which has 3 inputs: it would have one oscillator, but 6 mixers. Should be simple to make.
|
I think the idea of having multiple inputs in a LOCKIN module is also good for the LSC sensing matrix measurement.
Because right now I am measuring the responses of multiple sensors one by one while exciting a particular DOF by one oscillator.
Moreover in the LSC case the number of sensors, which we have to measure, is enormous (e.g. REFL11I/Q, REFL33I/Q, REFL55I/Q, ... POY11I/Q,...) and indeed it has been a long-time measurement. |
5671
|
Sat Oct 15 16:42:08 2011 |
Koji | Update | LSC | Testing REFL165 |
Test results of new REFL165 (the first attachment)
- The resonant freq 166.2MHz, Q=57 (previous Q was ~7)
- If we believe the TF measurement, the transimpedance at the resonance is 7.8k [V/A] and the shotnoise intercept current of ~1mA.
The linearity of the peak was confirmed by changing the modulation level of the beam.
- There is a riddle: the white light test indicates 4.5k [V/A] and 2.8mA for those numbers.
There are big descrepancies from those by the TF measurements.
Further analysis of the descrepancies:
Using the noise measurements with different DC current levels, the transimpedance for each frequency can be reconstructed.
Does this indicate the satiration by the white light???
- The TF measurement shows consistent mag&phase relationship at the resonance (c.f. LISO fit).
So this steep resonance is not an artifact by a noise or glitch but the real structure of the electronics.
- The TF measurement has been done with the photocurrent of ~0.3mA, while the transimpedance measurement
with the white light illumination has the practical effect only when the DC photocurrent is larger than 1mA
because of the circuit noise. Does this higher photo current affected the resonance?
- The off-resonant transimpedance agree with the TF measurement as far as we can see with those measurements.
This may mean that the actual resonant structure has been affected in the white light measurement.
(i.e. not the saturation of the RF opamp which causes the change of the gain at any freq.)
Is the above mentioned higher DC current causing the change of the diode capacitance or other property of the diode or the inductors??? |
Attachment 1: REFL165_test_111014_KA.pdf
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Attachment 2: REFL165_transimpedance2.pdf
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|
5672
|
Sat Oct 15 17:06:20 2011 |
Koji | Update | LSC | Installation REFL165 |
REFL165 was installed on the AP table last night.
Meanwhile I found the DC power level at the REFL PDs were 0.8~1.2V if the PRM is aligned and the IFO is not locked.
This corresponds to 16~24mA (20~30mW). This is too big.
The HWP of the REFL path were adjusted so that we have 6~10mA (8~12mW) on each PDs. |
5673
|
Sun Oct 16 02:30:00 2011 |
rana | Update | Electronics | Testing REFL165 |
Unless the bias feedback circuit has been tuned for the 1 mm diode, its possible that you are seeing some C(V) effects. Its easy to check by looking at the phase response at 165 MHz v. the DC photocurrent. Then the feedback or feedforward gain can be tuned.
|
5674
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Sun Oct 16 05:35:18 2011 |
rana | Update | Computer Scripts / Programs | Failing to set SUS summary screen values |
Quote:
|
Quote: |
I am trying to run Rana's setSensors.py script, but am failing. Any inspiration would be appreciated:
rosalba:SUS_SUMMARY>./setSensors.py 1001708529 500 .1 .25
['./setSensors.py', '1001708529', '500', '.1', '.25']
/cvs/cds/caltech/apps/linux64/python/lib64/python2.4/site-packages/nds/__init__.py:28: RuntimeWarning: No protocol specified, attempting protocol nds_v2
super(daq, self).__init__(host, port)
Connecting NDS2 .... authenticate done
Traceback (most recent call last):
File "./setSensors.py", line 81, in ?
mean = acquire(x)
File "./setSensors.py", line 73, in acquire
daq.request_channel(chans[x])
Boost.Python.ArgumentError: Python argument types in
daq.request_channel(daq, str)
did not match C++ signature:
request_channel(_daq_t {lvalue}, daq_channel_t*)
I'm not exactly sure what the problem is. Line 73, looks like it should have 2 arguments in the daq.request_channel, but even if I put in the "daq" variable (which is set a few lines above), I get the exact same error. So...something else is wrong. Ideas from someone who "speaks" python??
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My guess is that this has something to do with the NDS client version you're using. Try running the script on a machine where pynds and nds-client are known to be compatible, like pianosa.
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Doesn't work on pianosa either. Has someone changed the python environment?
pianosa:SUS_SUMMARY 0> ./setSensors.py 1000123215 600 0.1 0.25
Traceback (most recent call last):
File "./setSensors.py", line 2, in <module>
import nds
ImportError: No module named nds
|
5675
|
Mon Oct 17 07:57:24 2011 |
steve | Update | SUS | ETMX sus damping restored |
|
5676
|
Mon Oct 17 10:43:14 2011 |
Mirko | Update | CDS | Commited changes to c1rfm |
I want to make changes to c1rfm. Found uncommited changes to it from Sept 27. Since we recompiled it since then it should be safe to commit them, so I did. See svn log for details. |
5677
|
Mon Oct 17 11:06:31 2011 |
Mirko | Update | CDS | Piping data from c1lsc to c1oaf |
Changed, recompiled, installed and restarted c1rfm and c1oaf to get the MC1-3 Pitch and Yaw data into the c1oaf model.
Also changed c1oaf to use MCL as a witness channel (as well as an actuator).
Added the changes to svn. |
5678
|
Mon Oct 17 11:40:44 2011 |
Koji | Update | LSC | REFL165 removed from the table |
REFL165 removed from the table for the C(V) test |
5679
|
Mon Oct 17 14:26:22 2011 |
Mirko | Update | CDS | Seismic BLRMS channels, new RMS calculation |
Quote: |
[Rana, Koji, Mirko]
We looked into the CDS RMS block c-code as described in Rolfs RCG app guide. Seems the block uses a first order LP filter with a corner freq. / time of 20k execution cycles. There are also some weird thersholds at +-2000counts in there.
I was looking into implementing a hand-made RMS block, by squaring, filtering, rooting. The new RMS (left) seems nicer than the old one (bottom right). Signal was 141counts sinus at 4Hz.
Filters used: Before squaring: 4th order butterworth BP at given freq. & (new) 6th order inverse Chebyshew 20dB at 0.9*lower BP freq. and 1.1*upper BP freq. => about 1dB at BP freq.
After squaring: 4th order butterworth LP @ 1Hz.
C1PEM execution time increased from about 20us to about 45us.
Made a new medm screen with the respective filters in place of the empty C1PEM_OVERVIEW. Should go onto the sitemap.

Original RMS LP is slower than 0.1Hz, see below for single LP at 0.1Hz in the new RMS. Original RMS is faster than single LP @ 0.01Hz

Some of the channels are recorded as 256Hz DAQ channels now. Need to figure out how to record these as 16Hz EPICS channls.
|
Channels are now going into EPICS channels (e.g. C1:PEM-ACC1_RMS_1_3 ). Adapted the PEM_SLOW.ini file. Channels don't yet show up in dataviewer. Probably due to other C1PEM maschine |
5680
|
Mon Oct 17 17:07:30 2011 |
steve | Update | SUS | ETMX oplev returning beam od 3 mm |
ETMX oplev had 6 mm diameter beam on the qpd. I relayed the beam path with 2 lenses to get back 3 mm beam on the qpd
BRC 037 -100 Bi _concave lens and PCX 25 200 VIS do the job. Unfortunately the concave lens has the AR 1064.
|
Attachment 1: ETMX-oplev.jpg
|
|
5681
|
Mon Oct 17 22:20:42 2011 |
Koji | Update | LSC | REFL165 removed from the table |
Quote: |
REFL165 removed from the table for the C(V) test
|
The PD was returned on the table.
The C(V) compensation path was modified and the change of the resonant freq was cancelled.
A more precise analysis comes later. |
5682
|
Mon Oct 17 23:28:32 2011 |
rana | Update | Electronics | StochMon |
To get to the bottom of the RFAM mystery, we've got to resurrect the StochMon to trend the RFAM after the IMC.
We will put an 1811 on the MC_TRANS or IP_POS beam (the 1811 has an input noise of 2.5 pW/rHz).
Then the Stochmon has an input pre-amp, some crappy filters, and then Wenzel RMS->DC converters. We will replace the hand-made filters with the following ones from Mini-Circuits which happen to match our modulation frequencies perfectly:
11 MHz SBP-10.7+
55 MHz SBP-60+
29.5 MHz SBP-30+
|
5683
|
Mon Oct 17 23:56:34 2011 |
Suresh | Update | IOO | MC WFS Integrators switched on and WFS_MASTER screen updated |
[Rana, Suresh]
To see if the loops will stay locked when the Integrators in the servo are switched on, we stayed with the same simple output matrix (just 1 or -1 elements) and switched on the FM1 on all WFS servo filter banks. We monitored the time domain error signals to see if engaging the locks made the error signals go to zero. Most of the error signals did go to zero even when an intentional offset was introduced into the MC pitch of the suspension.
We need to include TestPoints just before the Input Servo Matrix so that we can monitor the error signals without being affected by the gain changes in the WFS_GAIN slider. These are currently not present in the C1IOO model and the position of the WFS_GAIN also has to be shifted to the other side of the Input matrix.
The C1IOO_WFS_MASTER screen has been changed to the new one. This incorporates filter banks for the MC_TRANS_P and _Y channels. The screen is not yet fully functional but I am working on it and I it will continue to improve it.

|
5684
|
Tue Oct 18 04:04:27 2011 |
kiwamu | Update | LSC | measurement of sensing matrix : touchy SRM |
I made some attempts to measure the sensing matrix of the central part.
I could measure the matrix in the PRMI configuration but wasn't able to measure the matrix in the DRMI configuration.
=> I will report the result of the PRMI sensing matrix tomorrow.
The main reason why I couldn't lock DRMI was that the suspensions were touchy and especially the SRM suspension wasn't good.
Some impacts due to the feedback during the lock acquisition completely kicks SRM away.
The watchdogs' RMS monitor on SRM easily rang up to more than 10 counts once the acquisition started.This is quite bad.
Also the stability of the PRMI lock was strongly depending on the gains of the PRM oplevs.
I guess I have to revisit the vertex suspensions more carefully (i.e. f2a coupling, actuator output matrix, damping gains, input matrices, oplev filters)
otherwise any LSC works in the vertex will be totally in vain. |
5685
|
Tue Oct 18 10:04:41 2011 |
Koji | Update | LSC | REFL165 removed from the table |
The original REFL165 had ~50MHz/A dependence on the DC photocurrent.
The resistr R21, which was 2670 Ohm contrary to the original drawing, was replaced to 532 Ohm
to increase the feedforward gain by factor of 5.
The resulting dependence is reduced to ~0.5MHz/A although it has Q reduction of ~20% at 6mA.
Some concerns:
These transfer functions were measured between TEST IN and RF OUT while the diode was illuminated with the white light from a light bulb.
There looks some thermal effect on the resonant freq. If the white light illumination is suddenly removed, the bias compensation
is immediately removed but the resonance takes some time (~min) to come back to the original freq.
I am afraid that the light bulb gave too much heat on the surrounding PCB and lead unnecesarily high level dependence of the resonant freq on the DC current.
Or, if this thermal effect comes from the power consumption on the diode itself, we need to characterize it for aLIGO.
In order to check this, we need a test with the 1064nm illumination on the diode in stead of the light bulb. |
Attachment 1: REFL165_original.pdf
|
|
Attachment 2: REFL165_new.pdf
|
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Attachment 3: REFL165_schematic_111017_KA.pdf
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5686
|
Tue Oct 18 15:20:03 2011 |
kiwamu | Summary | IOO | RFAM plan |
[Suresh / Koji / Rana / Kiwamu]
Last night we had a discussion about what we do for the RFAM issue. Here is the plan.
(PLAN)
1. Build and install an RFAM monitor (a.k.a StochMon ) with a combination of a power splitter, band-pass-filters and Wenzel RMS detectors.
=> Some ordering has started (#5682). The Wenzel RMS detectors are already in hands.
2. Install a temperature sensor on the EOM. And if possible install it with a new EOM resonant box.
=> make a wheatstone bridge circuit, whose voltage is modulated with a local oscillator at 100 Hz or so.
3. Install a broadband RFPD to monitor the RFAMs and connect it to the StochMon network.
=> Koji's broadband PD or a commercial RFPD (e.g. Newfocus 1811 or similar)
4. Measure the response of the amount of the RFAM versus the temperature of the EO crystal.
=> to see whether if stabilizing the temperature stabilizes the RFAM or not.
5. Measure the long-term behavior of the RFAM.
=> to estimate the worst amount of the RFAM and the time scale of its variation
6. Decide which physical quantity we will stabilize, the temperature or the amount of the RFAM.
7. Implement a digital servo to stabilize the RFAMs by feeding signals back to a heater
=> we need to install a heater on the EOM.
8. In parallel to those actions, figure out how much offsets each LSC error signal will have due to the current amount of the RFAMs.
=> Optickle simulations.
9. Set some criteria on the allowed amount of the RFAMs
=> With some given offsets in the LSC error signal, we investigate what kind of (bad) effects we will have. |
5687
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Tue Oct 18 20:50:19 2011 |
Suresh | Update | IOO | C1IOO and WFS associated screens |
In keeping with the current protocol, I have started to move all the user-built medm screens associated with C1IOO into the $screens$/c1ioo/master/ directory.
I then edited the menu button in the sitemap.adl to point to the screens in the ..c1ioo/master/ directory. All the screens in $screens$/c1ioo/ directory have been backed up into bak/. I plan to edit the c1ioo model soon and at that time I will delete all the screens in the $screens$/c1ioo directory and let only the automatically regenerated screens stay there. If there are broken links to user-built screens associated with c1ioo, please copy the relevant screen to the master/ directory and edit the path in the menus.
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5688
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Tue Oct 18 21:19:18 2011 |
rana | Configuration | IOO | WFS disabled in SUS |
I found that the MC WFS had large offset control signals going to the MC SUS. Even though the input switch was off, the integrators were holding the offset.
I have disabled the ASCPIT outputs in the MC SUS. Suresh is going to fix the MC autolocker script to gracefully handle the OFF and ON and then test the script before resuming the WFS testing.
MCL data for OAF may be suspect from this morning. |