Old MZ PD (InGaAs 2mm, @29.5MHz) has been modified for REFL33.
There has been no choice for the 11MHz notch other than putting it on the RF preamp
as the notch in parellel to the diode eats the RF transimpedance at 33MHz.
I wait for judgement of Rana if the notch at the MAX4107 feedback is acceptable or not.
REFL165 PD has been made from the old 166MHz PD.
As the required inductance was ~10nF level, the stray inductance of the circuit pattern was significant.
So, I am not so confident with the circuit functionality before the optical transfer function test.
I will test REFL33 and REFL165 with the Jenne laser to see how they work.
I vote for making an adapter plate between the sliding plate and the bottom base.
This morning, I realized that the current set-up of the horizontal shaker does not allow for the TT to be securely mounted. I was going to change the drill holes in the horizontal slider base (1 inch pitch). Jamie has suggested that it is better to make a pair of holes in the base larger. The circled holes are the ones that will be expanded to a 0.26" diameter so that I can mount the mirror securely to the horizontal slider base. There is a concern that a bit of the TT suspension base will hang over the edge of the horizontal sliding plate. We are not sure if this will cause problems with shaking the mirror evenly. Suggestions/advice are appreciated.
This REFL165 was good in terms of RF, but I forgot to make the DC path functioning.
I will try some ideas to fix this tomorrow.
REFL33 is ready for the installation
Characterization results of REFL33 is found in the PDF attachment.
Resonance at 33.18MHz
Q of 6.0, transimpedance 2.14kOhm
shotnoise intercept current = 0.52mA (i.e. current noise of 13pA/rtHz)
Notch at 10.97MHz
Q of 22.34, transimpedance 16.2 Ohm
Notch at 55.60MHz
Q of 42.45, transimpedance 33.5 Ohm
The shutter of the ABSL laser is closed for the vent work.
REFL165 PD was made and tested. The characterization results are in the PDF file.
Resonance at 166.12MHz
Q of 7.3, transimpedance 667Ohm (Series Resistance = Z/Q2 = 2.5Ohm)
shotnoise intercept current = 4.3mA (i.e. current noise of 36pA/rtHz)
As the circuit pattern had ~10nH level strain inductance, some technique was needed.
Now the size of the loop for the resonant circuit is comparable with the size of SOIC-8 opamp.
(Left-Top corner of the photo)
This improved the resonant gain by factor of 8.5dB at the test with TEST INPUT. (Analyzer photo)
There is no tunable component.
The resonant freq was adjusted by a parallel inductance (270nH) to the main inductor (15nH).
This morning Kiwamu and I have aligned the MC. Kiwamu aligned the last steering (on the OMC table) to recover the touch last week.
Then I have aligned the MC with MC1 and MC3 as the last steering did not help to get TEM00.
C1:SUS-MC1_PIT_COMM = 2.6587
C1:SUS-MC1_YAW_COMM = 2.7471
C1:SUS-MC2_PIT_COMM = 3.486
C1:SUS-MC2_YAW_COMM = -1.1592
C1:SUS-MC3_PIT_COMM = -1.876
C1:SUS-MC3_YAW_COMM = 1.2829
C1:SUS-MC1_PIT_COMM = 2.7596
C1:SUS-MC1_YAW_COMM = 2.6627
C1:SUS-MC2_PIT_COMM = 3.486
C1:SUS-MC2_YAW_COMM = -1.1592
C1:SUS-MC3_PIT_COMM = -1.697
C1:SUS-MC3_YAW_COMM = 1.2901
We will move on to the vertex region today.
The goal of the vertex region work is to get the pick-off beams out the chambers, including POX/Y and POP.
The work will be in parallel to the ETM woks.
The first step will be : lock and align MC with the IR beam.
[Rana Koji Jenne Jamie]
- The situation of the ETMY suspension is improved.
- The damping servos except for Pitch are now functional.
- We intentionally turned off the damping servos for the matrix measurements.
- Opened the light door of the ETMY chamber.
- We set up the CDS SUS lockin:
Excite UL/UR/LL/LR equally [by setting the output matrix (1, 1, 1, 1, 0)] at 3.12Hz with 2000 cnts
Put the OSEM PD outputs into lockin one by one. For the image rejection, 0.1Hz 4th order LPF has been used though we like to use a faster settling LPF.
- Found only UL was responding to the excitation. After fitzing with the cables and connectors, it was found that the DAC card was loose from the bus.
By pushing the card the responses have been back. [Note we had the reboot of c1iscey almost at the same time.]
- Checked the response in the I channel of the lockin.
UL -8ish / UR +7ish / LR +5ish / LL +2ish
- Tweaked LL sensor to get better response ==> in vain. Decided to move the lower OSEM plate for the better positioning of the LR/LL.
- Got reasonable (+5ish) response for LL.
- Confirmed that the POS/YAW/SIDE damping works with positive gains. PITCH did not work with the negative gain (but that could be a good sign.)
- Let the suspension freely swinging for a while (~30min). Checked the side/pos separation. They are not perfect but seemed diagonalizable.
- Closed the light door.
- Jenne will make a better kick/free-swing test later.
The entry was quite confusing owing to many misleading wordings.
- The PS2 should be calibrated "as is". (i.e. should be calibrated with the frame)
- The previous calibrations with the highly reflective surface were 0.32V/mm and 0.26V/mm, respectively.
This time you have 0.10V/mm (with an undescribed surface). The ratio is not 32 but 3.2.
- The DC output of PS2 on the shaking setup was 2.5V. The DC output seen in the plot is 3.5V-ish.
This suggests the possibiliteies:
1) The surface has slightly higher reflectivity than the frame
2) The estimation of the distance between the frame and the PS2 during the TF measurement was not accurate.
- The word "DC coupling level" is misleading. I guess you mean the DC value of the vbration isolation transfer function
of the suspension.
I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").
As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?
ITMX OSEMs were adjusted so as to have the right DC numbers and the more uniform response to POS excitation.
It is waiting for the free-swinging test.
- ITMX was moved from its position to the north side of the table.
- The table was rebalanced.
- We found that the output of the LR OSEM has an excess noise compared with the other OSEMs.
We tried to swap the LR and SD OSEMs, but the SD OSEM (placed at the LR magnet) showed
the same excess noise at around 10-50Hz.
- We found that one of the EQ stops was touching the mirror. By removing this friction, all of the OSEMs
come to show similar power spectra. Good!
- Then we started to use LOCKIN technique to measure the sensitivity of the OSEMs to the POS excitation.
Originally the response of the OSEMs was as follows
UL 3.4 UR 4.3
LL 0 LR 2.5
After the adjustment of the DC values, final values became as follows
UL 3.9 UR 4.4
LL 3.9 LR 3.2
- We decided to close the light door.
What are the parameters you are using? As you have the drawings of the components, you can calculate the masses of the objects.
Reducing the ECD resonance from 10Hz->6Hz looks nice.
The resonant freq of the ECDs are not (fully) determined by the gravitational energy but have the contribution of the elastic energy of the wire.
Q1: How much is the res freq of the ECDs if the freq is completely determined by the grav energy? (i.e. the case of using much thinner wires)
Q2: How thin should the wires be?
1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass
Complicated structure can be ignored. We need a rough estimation.
2) Your restoring force can have two terms:
- one comes from the spring constant k
- the other from the gravity
What are the reflected RF powers for those frequencies?
Is the 29.5MHz more problem than the 55MHz, considering the required modulation depth?
- We have checked the situation of the broken Piezo Jenna PZT (called PZT1)
- Tested PZT1 by applying a dc voltage on the cables. Found that pitch and yaw reasonably moving and the motions are well separated each other.
The pitch requires +20V to set the IPPOS spot on the QPD center.
- Made a high-voltage (actually middle voltage) amp to convert +/-10V EPICS control signal into -5 to +30V PZTout. It is working on the prototype board and will be put into the actual setup soon.
- The Piezo Jenna driver box has 4 modules. From the left-hand side, the HV module, Yaw controller, Pitch controller, and Ben abbot's connector converter.
- We checked the voltage on Ben's converter board. (Photo1)
It turned out that the red cable is the one have the driving voltage while the others stays zero.
- We hooked a 30V DC power supply between the red cable and the shield which is actually connected to the board ground.
- Applying +/-10V, we confirmed the strain gauge is reacting. If we actuated the pitch cable, we only saw the pitch strain gauge reacted. Same situation for yaw too.
- Kiwamu went to IPPOS QPD to see the spot position, while I change the voltage. We found that applying +20V to the pitch cable aligns the spot on the QPD center.
- I started to make a small amplifier boards which converts +/-10V EPICS signals into -5V to +30V PZT outs.
- The OPAMP is OPA452 which can deal with the supply voltages upto +/-40V. We will supply +/-30V. The noninerting amp has the gain of +2.
- It uses a 15V zener diode to produce -15V reference voltage from -30V. This results the output voltage swing from -5V to +35V.
The actual maximum output is +30V because of the supply voltage.
- On the circut test bench, I have applied +/-5V sinusoidal to the input and successfully obtained +5V to +25V swing.
- The board will be put on Ben's board today.
The PZT driver is now in place. The actual PZTs are not connected yet!
It is accommodated on Ben's connector adapter board.
The panel has additional connectors now: two inputs and a power supply connector.
The supply voltage is +/-30V (actual maximum +/-40V), and the input range is +/-10V
which yields the output range of -5V to 30V. The gain of the amplifier is +2.
It is confirmed that the HV outputs react to the epics sliders although the PZT connector is not connected yet
so as not to disturb the locking activity.
When we engage the PZT connector, we should check the HV outputs with an oscilloscope to confirm they
have no oscillation with the capacitances of the PZTs together with the long cable.
This modification of the LSC model made the rows of the LSC output matrix shifted. This caused the ASS scripts nonfunctional.
Kiwamu fixed the channel names in the ASS script.
[Jenne, Mirko, with supervision from Jamie]
I modified the c1lsc model to have shmem outputs that go from the degrees of freedom to the OAF, and shmem inputs from the OAF's output to sum into the DoFs, just like Yoichi's FF stuff. I also removed the old OAF_OUT, because it would only allow me to select one DoF at a time, and I will eventually want the ability to do multiple amounts of OAFing at the same time. Hopefully.
The pzt driver for PZT1 has been installed.
As there was unknown resistive connection in the vacuum chamber as described below,
the PZT out cable at the PJ driver module should always be disconnected.
The sensor cables have no problem to be connected to the controller.
In fact, they are a good monitor for the state of the PZTs.
In this configuration, Pitch and Yaw direction of PZT1 is under the control of the EPICS value as we expected.
- At the beginning, we tested the PZT driver output with low voltage level (~10V). We did not see any oscillation of the opamps.
The pitch output was observed to be OK, while the YAW output exhibited a half of the expected output voltage.
The opamp was holding correct voltage, however the voltage after the 1K output resister was about a half.
This indicated there was a voltage division happening.
- The cause of the voltage division was tracked. We found that the yaw red (=hot) line is connected to pitch black
in the vacuum chamber with a resistance of 1.4kOhm. The black cables are shorted to the ground level in the PJ driver.
- We decided to unplug the PJ's cable so that we can isolate the black cables while hoping the PZTs were drived only
by the red and white cables. And they did.
- This means that we should not connect the PZT driving cable to the PJ's driver. The sensors have no problem to be connected.
|. o| 5
|o | 17
| o| 4
|o | 16 Yaw Black
| o| 3 Pitch Black
|o | 15 Yaw White
| o| 2 Yaw Red
|o | 14 Pitch White
\ o| 1 Pitch Red
* Pitch White and Yaw White are connected to the ground at the amplifier side.
* Yaw Red and Pitch Black is connected with 1.4kOhm and isolated from the others.
Mess in the lab is increasing. Kiwamu and I had to clean up some stuffs to continue our work.
(i.e. some components were disturbing to open the lid of the tables.)
Basically the tools/equipments/component/cables/digital cameras/lens caps/IR viewers
you have used for the day should be cleaned up at the end of the day.
If one likes to leave a temporary stuff, leave a note to indicate by whom, for what, how long
it will be kept like that, and when one is going to back there with contact info like the cell phone #.
I have made some cleaning up of the LSC-related MEDM screens.
- LSC overview screen: ADC OVFL and WFAA indicators are now correctly matched to it associated PD signals.
- Whitening screens now have the correct indication of the associated PD signals.
- LSC Ctrl screen, which is invoked from the overview screen by clicking the servo filters, now has the switches of the servo filters.
- LSC tab of the sitemap was cleaned up by removing the broken links.
Can't we use Yuta's auto-Q adjust script?
Edit by KI :
Of course we can use it but first we have to fix some pynds sentences since his script was written for the OLD pynds.
DRMI team needs to use at least three lockins on LSC
- The code was modified, compiled, and installed.
- The code is now running. FB was restarted to deal with the change of the channel names.
- Now we have LOCKIN1, 2, and 3. This required the change of the names from C1:LSC-LOCKIN_.... to C1:LSC-LOCKIN1_...
- The LSC screen has also modified. It has three lockins on the screen.
- The corresponding matrix screens have been modified/created and linked from the main screen.
- I need to make the screens more cool but the locking team can start to use those lockins.
Both loops basically have no phase margins. i.e. unstable. How can you lock PRMI with these servos?
The following rough swept sine plots are the OLTs for MICH and PRCL. The gain setting was -10 and 0.5 for MICH and PRCL, respectively. Integrators were off. Looking at the measured plots, MICH has about 300 Hz UGF, when the gain is -20, and PRCL has about 300 HZ UGF, too, when the gain is 0.8.
As per the request of Anamaria, I have added the slider of the demodulation phase for each RF PD screens.
C1LSC_RFPD.adl screen was modified to have more information.
Activity on Friday evening
- The REFL path has been thoroughly aligned
As I did not like the REFL spot misaligned on the REFL CCD, we went to the AP table.
Many optics had the spots not on the middle of the optic, including the PBS whose post was not fixed on the post holder.
We aligned the optical paths, the RF PDs, and the CCD. The alignment of the PD required the use of the IR viewer.
One should not trust the DC output as a reference of the PD alignment as it is not enough sensitive to the clipping.
We aligned the optical paths again after the reasonable alignment of PRM is established with the interferometer.
"Next time when you see REFL spot is not at the center of the camera, think what is moved!"
- The REFL165 PD is disconnected from the power supply
I found that the REFL165 PD is producing 7.5V output at the DC monitor no matter how the beam is blocked.
As I could not recover this issue by swapping the power connector at the LSC rack, I disconnected the cable
at the RFL165 PD side. I need to go through the PD power supply circuit next week.
- PRMI alignment policy of the night
Kiwamu has aligned Y-arm some time ago (Thursday evening?). I decided not to touch ITMY.
So the Michelson is aligned by ITMX, PRC is aligned by PRM.
- Michelson locking
The short Michelson was locked with AS55Q and the MICH filter. We could use the gain of +/-20 for locking,
and could increase it up to ~+/-250. At the max gain, the all three integrators and the two resonant gains
could be activated. The sign depends on which fringe you want at the AS port (bright or dark).
In this condition, the output of the POXDC channel (which is actually the POY DC out -- c.f. This entry)
is used to determine the internal power. It was ~70cnt.
- PRMI locking
Then the PRMI was locked. There was some confusion of the gains because of the limitters at the servo filters
(which yielded the locking with 1bit outputs no matter how much the gains were....)
After all, I decided to use REFL33I for the PRCL for the test. The PRCL gain was -0.3~-1.0 for the carrier lock, but
was highly dependent on the alignment. i.e. if accidentally hit the high power recycling gain, it oscillated easily
and the lock was lost. Probably this was the first 3f locking at the 40m in the current optical config, if
Kiwamu did not do that secretly. The SB lock was also obtained by flipping the sign of the PRCL servo.
The difficulty we had was the instability when the recycling gain became big. We were monitoring the POXDC
(i.e.DCout of the POY PD). When this exceeds 5000, many glitches appears in the LSC signals and disturbs the lock.
This was not the fringes from neither the arms nor the SRC.
The observed POY DC with the carrier resonant PRMI was 5000~8000vcnt (momentary).
POXDC (i.e. POY DCout)
PRM misaligned: 70cnt
CA resonant PRMI: ~8000cnt (max)
PRMI antiresonant = 5200cnt
PRMI resonant = ~3000cnt
==> Visivility = 0.6
Transmissivity: TR=0.0575, tR=sqrt(TR)
Rough estimation of the power recycling gain (assuming perfect mode matching)
PPRM_mialign = Pin tR2
PPRM_resonant = Pin [tR/(1-rR rMI)]2
G = tR2 PPRM_resonant / PPRM_mialign = 8000/70*0.0575 = 6.5
This is way too low compared with the design (G>40)
This corresponds to rMI2=0.885 (loss of 10%) in the power recycling cavity.
But this yields visibility of 16%, instead of 60% which we saw. This is inconsistent.
If mode matching is not perfect, effective incident power of PRMI decreases
and this discrepancy may be explained
Pin = Pjunk + (Pin-Pjunk)
PPRM_mialign = Pin tR2
PPRM_resonant = (Pin-Pjunk) [tR/(1-rR rMI)]2
PREFL_antires ~ Pin
PREFL_resonant = Pjunk+(Pin-Pjunk)[-rR+(tR2 rMI)/(1-rR rMI)]2
PPRM_resonant / PPRM_mialign = (1-Rmm) /(1-rR rMI)2=8000/70
PREFL_resonant /PREFL_antires= Rmm+(1-Rmm)[-rR+(tR2 rMI)/(1-rR rMI)]2=0.6
here Rmm= Pjunk/Pin is the mode matching ratio
Solving the last two equations, we obtain
rMI2= 0.939 (loss of 4-5%)
Can we believe that the mode matching is 60% and the loss is 5%???
c1psl has got frozen during our ezcaread/write business.
After the target was rebooted and we lost the previous setting as there was no burt snapshot for the slow targets since Dec 13, 2010.
It seems that burtrestore is essential for the bootstrapping of the MC servo, as the auto locker script refers the locking parameters
from the PSL setting values (C1PSL_SETTINGS_SET.adl).
Jenne is working on the recovery of the snap-shotting for the slow targets.
[Kiwamu Suresh Koji]
Some main parameters of the PSL has been recovered using Dataviewer and some screen snapshots, as seen in the screenshots below.
I came to the control room and found the PMC and IMC were unlocked. ==> Relocked
I found the watch dogs of the vertex suspensions are tripped.
I checked the data for the past 6 hours and found they are independent events.
The unlock of the MCs occured 4 hours ago and the watchdogs tripped 2 hours ago.
The suspension damping was restored at around 7:50PM PDT.
Tip-Tilts has almost no isolation up to 3Hz, and isolation of about 0.5 up to 10Hz.
They have vertical resonances at around 20Hz.
See Nicole's entry
The lasers were shutdown
The racks were turned off
We could not figure out how to turn off JETSTOR
The control room machines were turned off
FInally we will turn off nodus and linux1 (with this order).
Hope everything comes back with no trouble
[Steve Koji Kiwamu]
- The storage on linux1 and linux1 itself (with this order) were turned on at 10:30am
- Kiwamu restored the vacuum system
=> opened V4, started TP1 (maglev) and opened V1.
The pressure went downfrom 2.5 mTorr to the normal level in about 20 minutes.
- A regular fsck of linux1 was completed at 5pm
- Nodus was turned on. Mounting /cvs/cds succeeded
- The control room computers were turned on
- The rack power for FB turned on, FB and megatron started.
- HVs on 1X1 were turned on. The are not vacuum HV, but used only in the air
- Turned on the RF generation box and the RF distribution box
- burtrestore slow machines (c1psl, c1susaux, c1iool0, c1iscaux, c1iscaux2, c1auxex, c1auxey)
The shutter before the MC was closed at 3:30 as I started working on the RFAM.
MC REFL (INLOCK): 0.6~0.7
MC REFL (UNLOCK): 6.9
MC TRANS: 50000~52000
Finished the work at 6:30
MC REFL (INLOCK): 0.50-0.52
MC REFL (UNLOCK): 6.9
MC TRANS: 54400~547000
Before the work: -48.5dBm for 1.07VDC (both 50Ohm terminated)
Right after the work: -80dBm for 0.896VDC (both 50Ohm terminated)
10min after: -70dBm
1hour after: -65dBm
3hours after: -62dBm
1day after (Oct 5, 20:00): -62.5dBm
2days after (Oct 6, 23:20): -72.5dBm
3 days after (Oct 7, 21:00): -57.8dBm
MC REFL (INLOCK): 0.6~0.7
MC REFL (UNLOCK): 6.9
MC TRANS: 50000~52000
POY11 PD was installed last night. The lock of the Y arm was confirmed with the POY11I signal.
- The DC transimpedance was modified to be 1010V/A as the incident power is tiny.
- The demodulation phase of the roughly adjusted (148deg) to have PDH signal at the I-phase.
The comparison with AS55I signal exhibits that POY11I have ~150 times weaker signal with 45dB whitening.
(In total 25000 times weaker.)
On the way to make POY11 functioning, there were many fixes at the LSC rack...
- The PD interface cards (power supply for the RFPDs) were checked:
So far the two card at the right hand side were checked.
Desipite the previous entry reported the issues on those boards, they did not show any problem yesterday.
One hypothetical possibility is the enabling switches that is controlled from the old slow epics targets.
- POY55 was removed
This 55MHz PD is supposed to be installed at POP.
The PD, an RF cable, an RF amp, the power supply of the RF amp were removed.
- POY11 was installed
The PD was placed where the 55MHz was placed.
The beam was aligned on the diode using the IR viewer and the digital multimeter.
The power supply cable and the RF cable for POY on the ITMY table were used.
There were an ND filter on the POY beam path. It was removed.
- On the LSC rack
The PD RF was connected to the patch panel at the top of the rack.
There were loose connectors on the patch panel. Some connectors were tightened on the panel.
I found that POY11 and POX11 had I&Q signal reversely connected to the whitening board.
==> These were fixed but require the orthogonality test again for those channels.
The I phase output of the AS11 demod board had a broken connector.
The onboard SMA has got disintegrated because of too much twist on the connector.
The board was once removed from the rack and the connector was fixed using a heat gun and soldering.
The DC signals were checked. POYDC was not correctly connected. POYDC were correctly connected to the POYDC channel.
c1lsc was found with the RFM frozen.
The c1lsc machine was soft-rebooted after stopping all of the RT processes.
Once the RT processes came back, they were all burtrestored.
- PDH locking
Restored Y-arm. Locked it with AS55Q.
Ran ASS alignment for Y-arm.
100cnt 150Hz sinusoidal signal is applied to ETMY
Measured the PSD of AS55Q, POY11I, and POY11Q.
Adjusted the demod phase so that the excitation could be minimized in POY11Q.
- REFL165 PD to be fixed (shows constant high voltage at the DC out)
- Make POP22/110 PD
- Install AS11? or use it as POX11?
- Install POP55
Script backup regularly runs on op340m by crontab,
but the true backup were not taken since Oct 16, 2010
as the backup program was looking at the old script directory.
/cvs/cds/script/backupScripts.pl was modified to look at the new script directory.
Script backup regularly runs on op340m by crontab,
but the true backup were not taken
$command = "cd /cvs/cds/caltech; /usr/sbin/tar cfX - $EXCLUDE_LIST scripts | bzip2 > $ARCHIVEDIR/scripts_$curdate.tar.bz2";
$command = "cd /opt/rtcds/caltech/c1; /usr/sbin/tar cfX - $EXCLUDE_LIST scripts | bzip2 > $ARCHIVEDIR/scripts_$curdate.tar.bz2";
"^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.)
The steering mirrors for PMC were aligned. The transmission went up from 0.779 to 0.852.
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.
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???
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.
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.
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.
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.
I have modified all of the three RFPD interface cards to be enabled permanently.
This prevents an accidental disabling caused by a stray voltage of the logic input (or whatever),
which was reported in multiple occasions by Anamaria and me.
The logic ICs (74LS04) for buffering of the EPICS switches were removed by 14pin sockets with additional wires soldered.
The modification shorts the inputs to the second logic chips, resulting in the permanent enabling of the PD circuit.
There looks some activity at around MC2 on Wednesday afternoon.
It caused the misalignment of MC2. Misalignment was not found in MC1/3.
It seems that the incident beam on the MC was aligned in the evening.
This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center.
We need an action on this issue tomorrow in the daytime.
The following directory exists. We can apply this convention to all of the models.
While trying to implement the regular yellow shell script button in MEDM for my new OAF screen, I noticed that the update snapshot stuff in all of the buttons that I checked (including IFO Align and LSC Overview) are pointing to folders in the old /cvs/cds/caltech/ area. Also, I think some of the folders that it's looking for don't exist anymore, even in the old system. So. Has anyone thought about where the snapshots should live in the new world order? Previously they were in ...../medm/c1/subsystem/ . Maybe we should make a snapshots folder in each subsystem's medm folder, at the same level as the 'master' folder for the custom screens? This is my current proposal.
Unless someone objects / has a better plan / knows why they're still pointing to the old place, I'll do this in the morning, and work on changing all the buttons to point to the new place.