Noise below 10 Hz became larger again compared with the data before (see here #4352)
Note that the Y-axis is in MHz.
Ansell AccuTech 91-300 clean room gloves ONLY in the 40m lab.
Cleaning and preparation must be carried out in these gloves also.
The screens for the simplified c1spx model have been updated. I re-introduced the suspension point information into the sensor output matrix so we can take into account the fact that as the entire supporting structure moves, the osems moves relative to the optic.
Master screens for the noise filters (i.e. 60 Hz, suspension point motion, and optic noise) have been created.
I have currently set the matrix values of the c1spx model to handle just longitudinal motion. I.e. Coils drive only in the POS degree of freedom and sensor read outs are also only in the POS degree of freedom. I've turned off all the noise inputs.
I added a simple double pole at 1 Hz in the C1:SUP_ETMX_PL_F2P_0_0 filter bank.
Here is a diagram for our intensity noise coupling measurement.
The below is a plot for the intensity noise on the DCPD. (I forgot to take a spectra of the PD dark noise)
For some reason, the RIN spectrum becomes sometimes noisier and sometimes quieter. Note that after 10 pm it's been in the quiet state for most of the time.
An interesting thing is that the structure below 3 Hz looks like excited by motion of the MC when it's in the louder state.
A photo diode and an AOM driver have been newly setup on the PSL table to measure the intensity noise coupling to the beat note signal.
We tried taking a transfer function from the PD to the beat, but the SNR wasn't sufficient on the PD. So we didn't get reasonable data.
[Koji, Steve, Suresh, Kiwamu]
The following video cables have been newly laid down :
- MC1F/MC3F (65 ft.)
- PMCR (100 ft.)
- PSL spare (100 ft.)
- PSL1 (100 ft.)
- PSL2 (100 ft.)
Here is a new plot for the differential noise measurement. I plot a noise contribution from the intensity noise (brown curve).
If we believe this data, the differential noise is NOT dominated by the intensity noise of the PSL.
(intensity noise coupling measurement)
Here is a plot for the transfer functions (TFs) from the intensity noise DCPD to the beat signal.
In principle these TFs tell us how much intensity noise are contributed into the differential noise.
When I measured the spectra shown above, the frequency offset of the beatnote was at about 8 MHz from the zero cross point.
Keeping the same lock, I measured the transfer function (red curve) by using the swept sine technique on DTT. The setup for this measurement is depicted on the last entry (#4389).
Then I made the spectra above by multiplying the intensity spectrum by this TF.
Later I measured another transfer function when the beatnote was at about 2 MHz from the zero cross point.
According to this measurement, our MFD gets insensitive to the intensity noise as the beat offset goes close to the zero cross point. This is consistent with what we expected.
For some reason the c1ioo machine suddenly died just 30 miteus before.
It died after we added a DAQ channel for c1gcv and rebooted the frame builder.
It didn't respond to a ping command. Therefore I rebooted the machine by clicking the physical reset button.
Now it seems fine.
I measured the transfer function, shot noise, and dark spectrum of AS55.
From the shot noise measurement, the RF transimpedance is (556.3 +- 0.8) Ohms and the dark current is (2.39 +- 0.01) mA. The dark noise agrees with the approximate value calculated from the circuit components.
There are no anomalous oscillations when there is no light on the photodiode. I am working on fitting the transfer function in LISO but the other plots are on the wiki at http://blue.ligo-wa.caltech.edu:8000/40m/Electronics/AS55
To simulate digitization noise, the easiest way I found was to use the MathFunction block, found in the CDS_PARTS model, under simLinkParts.
The MathFunction block supports square of input value, square root of input value, reciprocal of input value, and modulo of two input values.
The last is useful because it casts the input values as integers before taking the modulo.By placing this block after the saturation block (set to +/- 32768), adding 32768.5, choosing the 2nd input to be larger than 2 * 32768 (100,000 in this case), and then subtracting 32768, we wind up with a rounding function.
The above method has been applied to the c1spy model in the CI and SO out sub-blocks.
We are limited by the intensity noise of the X arm transmitted green light.
Since the intensity noise from the PSL wasn't big enough to explain the differential noise (#4392), so this time I measured the noise contribution from the X arm transmitted light.
I performed the same intensity noise coupling measurement, but this time between the DC signal of the beatnote RFPD and the beatnote signal.
While measuring it, I excited the intensity of the PSL laser by using the same AOM like I did yesterday. This AM cause the observable intensity noise on the beatnote RFPD.
With the excited AM, we can pretend to have an excited AM on the green transmitted light from the X arm, of course assuming the intensity noise coupling from the PSL is less.
The next steps we should do are :
We can modify the freq divider circuit to make it a comparator.
There are 3 standard techniques to reduce this effect:
1) Stabilize the end laser by sensing the green light coming into the PSL before recombination and feeding back with SR560 (this is the only one that you should try at first).
2) Moving to the center of the MFD fringe via ETM steps.
3) Auto-alignment of the beam to the arm.
Aidan: Joe and I have added a channel that takes the DC output from the vertex beatnote PD and sends it, via RFM, to a DAC at the ETMX end. Immediately before the output is a filter C1GCX_AMP_CTRL. The output of the DAC is connected to the CURRENT LASER DIODE modulation input on the back of the Innolight driver. This will modulate the current by 0.1A/V input.
We should be able to modulate the green laser on the end now and stabilize the intensity of the amplitude on the beatnote PD at the vertex. (In this configuration, the ampltiude noise of the PSL laser will be injected onto the end laser - we may want to revisit that).
Joe's comments on model change:
I added a RFM connection at the output of the C1:GCV-XARM_BEAT_DC filter in the c1gcv model. The RFM connection is called: C1:GCV-SCX_ETMX_AMP_CTRL.
This RFM connection goes to the c1scx model and into Kiwamu's GCX box, which uses top_names. There's a filter inside called AMP_CTRL, so the full filter name is C1:GCX-AMP_CTRL. The output then goes to the 7th DAC output.
The reason that I chose this PD is that, apparently, the green light coming from the cavity is clipped when it is picked off for its DC PD.
Ridiculous and hacky. Digital stabilization removed as well as the old "leave a pile of equipment on a stool" strategy.
We used a a BNC cable to send a pickoff of the beam before the recombination to the end via an SR560.
While fixing up some medm screens and getting spectra of the simulated plant, I realized that the naming convention for the Matrices of Filter banks was backwards when compared to that of the normal matrices (and the rest of the world). The naming was incorrectly column, row.
This has several ramifications:
1) I had to change the suspensions screens for the TO_COIL output filters.
2) I had to change the filters for the suspension with regards to the TO_COIL output filters so they go in the correct filter banks.
3) Burt restores to times previous March 11th around noon, will put your TO_COIL output filters in a funny state that will need to be fixed.
4) The simplant RESPONSE filters had to be moved to the correct filter banks.
5) If you have some model I'm not aware of that uses the FiltMuxMatrix piece, it is going to correctly build now, but you're going to have to move filters you may have created with foton.
New Focus Servo Controller has just arrived. We have 25 days to evaluate this product.
It will have to be shipped back to the vendor on April 4, 2011 the latest in order to get full refund.
The FM1 filter module change for XXSEN was propagated to the ETMX suspension. This was a change from a 30,100:3 with a DC gain of 1 to a 3:30 which just compensates the hardware filter.
The good gains for the Sim damping were found to be: 100 for ETMX_SUSPOS, 0.1 ETMX_SUSPIT, and 0.1 ETMX_SUSYAW, ETMX_SUSSIDE is -70. Gains much higher tended to saturate the simulated coils (i.e. hitting 10V limit) and then had to have the histories cleared for the RESPONSE matrix.
These seem to work to damp the real ETMX as well.
I did some work on the ETMY real and Sim.
It seems like there is still a problem with the input whitening filters. I believe the Xycom logic is set such that the analog whitening of the OSEM signals is turned ON only when the FM1 is turned OFF. Joe has got to fix this (and elog it) so that we can damp the suspension correctly. For now, the damping of the ETMY and the SETMY require different servo gains and signs, probably because of this.
4. The blue Output Filters section has been changed to agree with the new filter of matrices row, column labeling. My fault for not testing it and realizing it was broken. The change was made in /opt/rtcds/caltech/c1/medm/master/C1SUS_DEFAULTNAME.adl and then ,/generate_master_screens.py was run, updating all the screens.
5. I have swapped the logic for the sensor filter banks (ULSEN, URSEN, etc). It now sends a "1" to the Binary Output board controlling the OSEM analog whitening when the FM1 filter is ON. This has been done for all the suspensions (BS, ITMX,ITMY, SRM, PRM, MC1, MC2,MC3, ITMX, ITMY).
I am also updating the first sensor filter banks for the BS, ITMX, ITMY, SRM, PRM,MC1,MC2,MC3, called "3:30", to match the Y and X ends.
8. I can't find any documentation on how to get a momentary button press to toggle states. I could stick a filter bank in and use the on/off feature of that part, but that feels like a silly hack. I've decided for the moment to split the TM offset button into 2, one for ON, one for OFF. I'll put in on the list of things to have added to the RCG code (either a method, or documentation if it already exists).
EDIT: TM offset still doesn't work. Will worry about it next week.
9. Fixed a connection in SPY/SPX models where the side senor path that was missing a constant to a modulo block.
Steve pointed out to me today he couldn't get trends for his PEM slow channels like C1:PEM-count_full.
I experimented a bit and found for long time requests (over 20 days), it would produce minute trends up to the current time, but only if they started far enough back. So the data was being written, but something was causing a problem for dataviewer/NDS to find it.
On further investigation it looks to be some incorrect time stamps at several points in the last few months are causing the problems. Basically when Alex and I made mistakes in the GPS time stamp settings for the frame builder (daqd) code, the wrong time got written for hours to the raw minute trend data files.
So Alex is going to be running a script to go through the roughly 180 gigabytes of affected trend data to write new files with the correct time stamps. Once it done, we'll move the files over. We'll probably lose a few hours worth of recent trend data, depending on how quickly the scripts run, but after which minute trends should work as they are supposed to.
Prior to the works on the Y end setup I propose to perform the temperature scan business like Koji and Suresh did before (see this entry).
This business will allow us to easily find a beatnote at 532nm after the installation on the Y end.
I guess the right persons for this work are Bryan and Suresh.
Bryan will have a safety guidance from Steve in this after noon. So after that they can start working on it.
/* - - - coarse plan - - - */
* remove Alberto's laser from the AS table
* setup Alberto's laser on the PSL table
* put some stuff such as lenses, mirrors and etc. (Use the IR beam picked off after the doubling crystal for the main laser source)
* mode matching
Which laser are we going to use, Alberto's laser or MOPA laser ?
We use Alberto's laser for the Y end Green Locking.
Which laser are we going to use, Alberto's laser or MOPA laser ?
The reason for using Alberto's laser is that some amount of work has already gone into characterising its phase noise. Ref elog entry 2788
I updated our lockin simulink pieces to use the newer, more streamlined lockin piece that is currently in CDS_PARTS (with new documentation block!). It means we are no longer passing clock signals through three levels of boxes.
In order to use the piece, you need to right click on it after copying from CDS_PARTS and go to Link Options->Disable Link. This forces the .mdl to save all the relevant information about the block rather than just a pointer to the library. I talked with Rolf and Alex today and we discussed setting up another model file, non-library format for putting generically useful user blocks into, rather than using the CDS_PARTS library .mdl.
The BS, ITMX, ITMY, PRM, SRM, ETMX, ETMY now have working lockins, with the input matrix to them having the 2nd input coming from LSC_IN, the 3rd from the oplev pitch, and the 4th from oplev yaw.
This necessitated a few name changes in the medm screens. I also changed the lockin clock on/off switch to a direct amplitude entry, which turns green when a non-zero value is entered.
Currently, the Mode cleaner optic suspension screens have white lockins on them. I started modifying a new set of screens just for them, and will modify the generate_master_screens. Unfortunately, this requires modifying two sets of suspension screens going forward - the main interferometer optics and the MC optics.
PMC TRANS/REFL on MEDM showed red values for long time.
TRANS (a.k.a C1:PSL-PSL_TRANSPD) was the issue of the EPICS db.
REFL (a.k.a. C1:PSL-PMC_RFPDDC) was not physically connected.
There was an unknown BNC connected to the PMC DC output instead of dedicated SMA cable.
So they were swapped.
Now I run the following commands to change the EPICS thresholds:
ezcawrite C1:PSL-PMC_PMCTRANSPD.LOLO 0.8
ezcawrite C1:PSL-PMC_PMCTRANSPD.LOW 0.85
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIGH 0.95
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIHI 1
ezcawrite C1:PSL-PMC_RFPDDC.HIHI 0.05
ezcawrite C1:PSL-PMC_RFPDDC.HIGH 0.03
ezcawrite C1:PSL-PMC_RFPDDC.LOW 0.0
ezcawrite C1:PSL-PMC_RFPDDC.LOLO 0.0
As these commands only give us the tempolary fix, /cvs/cds/caltech/target/c1psl/psl.db was accordingly modified for the permanent one.
field(DESC,"RFPDDC- RFPD DC output")
field(INP,"#C0 S32 @")
field(DESC,"PMCTRANSPD- pre-modecleaner transmitted light")
field(INP,"#C0 S10 @")
Bryan Barr is visiting us from Glasgow for a month. He received 40m specific safety training on Friday.
I added a new ADC channel for a DC signal from the X end green PD.
It is called C1:GCX-REFL_DC and connected to adc_0_1, which is the second channel of ADC_0.
By the way, when I tried connecting it to an ADC I found that most of the channels on the AA board on 1X9 were not working.
Since the outputs form the board are too small the circuits may have benn broken. See the picture below.
In addition to that I realized that the signal from the PDH box for the temperature actuation is limited by +/- 2V due to the range of this AA board.
In fact the signal is frequently saturated due to this small voltage range.
We have to enlarge the range of this AA board like Valera did before for the suspensions (see this entry).
A comparator has been installed before the MFDs (mixer-based frequency discriminator) to eliminate the effect from the amplitude fluctuation (i.e. intensity noise).
As a result we reached an rms displacement of 580 Hz or 80 pm.
As a result we reached an rms displacement of 580 Hz or 80 pm.
(differential noise measurement)
Here is the resultant plot of the usual differential noise measurement.
The measurement has been done when the both green and red lasers were locked to the X arm.
In the blue curve I used only MFD. In the black curve I used the combination of the comparator and the MFD.
Noise below 3 Hz become lower by a factor of about 4, resulting in a better rms integrated from 40 Hz.
Note that the blue and the black curve were taken while I kept the same lock.
A calibration was done by injecting a peak at 311 Hz with an amplitude of 200 cnt on the ETMX_SUS_POS path.
Yesterday Koji modified his comparator circuit such that we can take a signal after it goes thorough the comparator.
The function of this comparator is to convert a sinusoidal signal to a square wave signal so that the amplitude fluctuation doesn't affect the frequency detection in the MFD.
I installed it and put the beat-note signal to it. Then the output signal from the comparator box is connected to the MFDs.
The input power for the comparator circuit has been reduced to -5 dBm so that it doesn't exceeds the maximum power rate.
- Plan for tomorrow
* Video cable session (I need ETMY_TRNAS) (team)
* Characterization of the Y end laser (Bryan / Suresh)
* LPF for the X end laser temperature control (Larisa)
* Frequency Divider (Matt)
* X end mechanical shutter (Kiwamu)
Succeeded in handing off the servo from the green to the red.
This time we found that the fluctuation in the IR signals became lesser as the gain of the ALS servo increased.
Therefore I increased the UGF from 40 Hz to 180 Hz to have less noise in the IR PDH signal.
Here is a preliminary plot for today's noise spectra.
The blue curve is the ALS in-loop spectrum, that corresponds to the beat fluctuation.
The red curve is an out-of-loop spectrum taken by measuring the IR PDH signal.
Since the UGF is at about 180 Hz the rms is integrated from 200 Hz.
The residual displacement noise in the IR PDH signal is now 1.2 kHz in rms.
I am going to analyze this residual noise by comparing with the differential noise that I took yesterday (see the last entry ).
Solid door, numbered 4 at south west corner of PSL enclosure was replaced by laser protective window.
The carpenter shop's Mark is making 4 more identical ones for the east side.
The Lightwave NPRO126 of 700mW was moved from the AP-table into the PSL-enclosure temporarily.
It's emergency shutdown switch can be seen at the center bottom picture
Yesterday during the day, Alex ran a script to fix the time stamps in the trends files we had messed up back during the daqd change overs around Feb 17th and 23rd. See this elog for more information on the trend problem.
Due to how the script runs, basically taking all the data and making a new copy with the correct time stamps, the data collected while the script was running didn't get converted over. So when he did the final copy of the corrected data, it created a several hour gap in the data from yesterday during the day time.
The original files still exist on the fb machine in /frames/trend/minute_raw_22mar2011 directory.
[Steve, Suresh, Larisa]
The following cables were laid today: ETMYT, ETMY, IFOPO, MC1, OMCR, AS Spare, and MC2T.
Though the paper suggested 135' for the MC2T, we used a 110'. This is too short: need at least another 15' for the MC2T.
The RCR cable wasn't crossed off on the list, but a cable exists at the RCR cable which is black and is labeled (old label, 75 ohms)
There was no indication of which length was needed for MC1, so a 95' cable was used.
Kiwamu and I looked at all the electronics that are currently in place for the green locking on the X-arm and have made a set of block diagrams of the rack mounted units that we should build to replace the existing ... "works of art" that sprawl around out there at the moment.
1. "ETM Green Oscillator/PDH support box". Not a great name but this would provide the local oscillator signal for the end PDH (with a controllable phase rotator) as well as the drive oscillator for the end laser PZT. Since we need to hit a frequency of 216.075kHz with a precision that Kiwamu needs to determine, we'd need to be able to tune the oscillator ... it needs to be a VCO. It'd be nice to be able to measure the output frequency so I've suggested dividing it down by N times to put it into the DAQ - maybe N = 2^7 = 128x to give a measured frequency of around 1.7kHz. Additionally this unit will sum the PDH control signal into the oscillation. This box would support the Universal PDH box that is currently at the X-end.
2. "Vertex X-arm beatnote box" - this basically takes the RF and DC signals from the beatnote PD and amplifies them. It provides a monitor for the RF signal and then converts the RF signal into a square wave in the comparator.
3. "Mixer Frequency Discriminator" - just the standard MFD setup stored in a box. For temperature stability reasons, we want to be careful about where we store this box and what it is made of. That's also the reason that this stage is separated from the X-arm beatnote box with it's high-power amps.
4. RS232 and EPICS control of the doubling ovens
5. Intensity stabilization of the End Laser
P.S. I used Google Diagrams for the pictures.
I tidied up some of the stuff that was on the SP table. The ISS box that has been sitting on there for months is now underneath the X-arm on top of the spare Marconi which is stored there.
Last Friday, we discovered a bug in the RCG where the delay part was not actually delaying. We reported this to Alex who promptly put a fix in the same day. This allowed Matt's newly proposed frequency discriminator to work properly.
It also required a checkout of the latest RCG code (revision 2328), and rebuild of the various codes. We backed up all the kernel and executables first such as mbuf.ko and awgtpman.
We did the following:
1) Log into the fb machine.
2) Go to /opt/rtcds/caltech/c1/core/advLigoRTS/src/drv/mbuf and run make. Copy the newly built mbuf.ko file to /diskless/root/modules/18.104.22.168/kernel/drivers/mbuf/mbuf.ko on the fb machine.
3) Use "sudo cp" to copy the newly built mbuf.ko file to /diskless/root/modules/22.214.171.124/kernel/drivers/mbuf/
4) Go to /cvs/cds/rtcds/caltech/c1/core/advLigoRTS/src/gds and run make.
5) Copy the newly built awgtpman executable to /opt/rtcds/caltech/c1/target/gds/bin/
6) Go to /opt/rtcds/caltech/c1/core/advLigoRTS/src/mx_stream/ and run make.
7) Copy the newly built mx_stream executable to /opt/rtcds/caltech/c1/target/fb/
Koji was unable to build his c1lst model first thing this morning. Turns out there was a bug with RCG parser that was introduced on Friday when we did the RCG updates. We talked Alex who did a quick comment fix. The diff is as follows:
--- Parser3.pm (revision 2328)
+++ Parser3.pm (working copy)
@@ -1124,8 +1124,8 @@
print "Flattening the model\n";
print "Finished flattening the model\n";
- CDS::Tree::do_on_nodes($root, \&remove_tags, 0, $root);
- print "Removed Tags\n";
+ #CDS::Tree::do_on_nodes($root, \&remove_tags, 0, $root);
+ #print "Removed Tags\n";
CDS::Tree::do_on_nodes($root, \&remove_busses, 0, $root);
This was some code to remove TAGs from the .mdl file for some reason which I do not understand at this time. I will ask tommorrow in person so I can understand the full story.
Koji then rebuilt and started the c1lst process. This is his new test version of the LSC code. We descovered (again) that when you activate too many DAQ channels (simply uncommenting them, not even recording them with activate=1 in the .ini file) that the frame builder crashes. In addition, the c1lsc machine, which the code was running on, also hard crashed.
When a channel gets added to the .ini file (or uncommented) it is sent to the framebuilder, irregardless of whether its recorded or not by the frame builder. There is only about 2 megabytes per second bandwidth per computer. In this case we were trying to do something like 200 channels * 16384 Hz * 4 bytes = 13 megabytes per second.
The maximium number of 16384 channels is roughly 30, with little to no room for anything else. In addition, test points use the same allocated memory structure, so that if you use up all the capacity with channels, you won't be able to use testpoints to that computer (or thats what Alex has led me to believe).
The daqd process then core dumped and was causing all sorts of martian network slowdowns. At the same time, the c1lsc computer crashed hard, and all of the front end processes except for the IOP on c1sus crashed.
We rebooted c1lsc, and restarted the c1sus processes using the startc1SYS scripts. However, the c1susfe.ko apparently got stuck in a wierd state. We were completely unable to damp the optics and were in general ringing them up severely. We tried debugging, including several burt restores and single path checks.
Eventually we decided to reboot the c1sus machine after a bit of debugging. After doing a burt restore after the reboot, everything started to damp and work happily. My best guess is the kernel module crashed in a bad way and remained in memory when we simply did the restart scripts.
I measured some laser powers associated with the beat-note detection system on the PSL table.
The diagram below is a summary of the measurement. All the data were taken by the Newport power meter.
The reflection from the beat-note PD is indeed significant as we have seen.
In addition to it the BS has a funny R/T ratio maybe because we are using an unknown BS from the Drever cabinet. I will replace it by a right BS.
During my work for making a noise budget I noticed that we haven't carefully characterize the beat-note detection system.
The final goal of this work is to draw noise curves for all the possible noise sources in one plot.
To draw the shot noise as well as the PD dark noise in the plot, I started collecting the data associated with the beat-note detection system.
* Estimation and measurement of the shot noise
* measurement of the PD electrical noise (dark noise)
* modeling for the PD electrical noise
* measurement of the doubling efficiency
* measurement of an amplitude noise coupling in the frequency discriminators
In the last week Matt and I modified the MFD configuration because the mixer had been illegally used.
Since the output from the comparator is normally about 10 dBm, a 4-way power splitter reduced the power down to 4 dBm in each output port.
In order to reserve a 7 dBm signal to a level-7 mixer, we decided to use an asymmetric power splitter, which is just a combination of 2-way and 3-way splitter shown in the diagram above.
With this configuration we can reserve a 7 dBm signal for a mixer in the fine path.
However on the other hand we sacrificed the coarse path because the power going to the mixer is now 2.2 dBm in each port.
According to the data sheet for the mixer, 1 dB compression point for the RF input is 1dBm. Therefore we put a 1 dB attenuator for the RF port in the coarse system.
In the delay line of the fine path we found that the delay cable was quite lossy and it reduced the power from 2.2 dBm to about 0 dBm.
Using 2 dBm for a Level 7 mixer is so bogus, that I will dismantle this as soon as I come over.
PLEASE DO NOT DISMANTLE THE SETUP !
Actually we tried looking for a level-3 or a smaller mixer, but we didn't find them at that moment. That's why we kept the level-7 mixer for the coarse path.
As you pointed out we can try an RF amplifier for it.
I (think) I have finished the new PMC base riser. The eDrawing of it (so you can view it on any computer) has been uploaded to the PMC wiki page.
I also attach it here, for comments.
Its going to need some kind of way to locate the PMC on the top. In the previous design, we had the 3 balls to decouple the body from the base. That design was flawed due to the roughness of the holes in the PMC body.
Also probably need some kind of relief on the bottom. Its possible that it would be OK like this, but I am unsure if the shop can maintain the flatness we want over the whole length and/or the flatness of any given (OLD) optical table over ~8". Its probably not a good idea to have to torque this (aluminum?) to make it conform to the optical table's shape.
Hmmm, so, this was just meant to be a riser that goes underneath the old PMC mount, to raise it from 3" beam height to 4" beam height. I will make another one that is a complete mount, designed for 4" beam height. Please hold........... .......... ....... ..... ... .
This is the log of the work on Wednesday 23rd.
1. Power Supply of the freq divider box
Kiwamu claimed that the comparator output of the freq div box only had small output like ~100mV.
The box worked on the electronics bench, we track down the power supply and found the fuse of the +15V line
brew out. It took sometime to notice this fact as the brown-out-LED of the fuse was not on and the power
supply terminal had +15V without the load. But this was because of the facts 1) the fuse is for 24V, and 2)
the large resistor is on the fuse for lighting the LED when the fuse is brown out.
I found another 24V fuse and put it there. Kiwamu is working on getting the correct fuses.
2. MC locking problem
After the hustle of the freq divider, the MC didn't lock. I tracked down the problem on the rack and found
there was no LO for the MC. This was fixed by pushing the power line cable of the AM Stabilizer for the MC LO, which was a bit loose.
This is the continuation of http://nodus.ligo.caltech.edu:8080/40m/4402
The first picture is of the actual component, where the resistor is 1M and capacitor is 10uF.
But before the component can be put into place, its transfer function had to be checked to make sure it was doing what we calculated it would do. The results of these are in the graphs generated: frequency vs. gain, and frequency vs. phase.
According to these graphs, we are not achieving the targeted cutoff frequency: need to recalculate and compensate for the extra 100k resistance being encountered.
For bode plot:
USE LOG-LOG plot for the amplitude
USE LOG-LINEAR plot for the phase
Search "Bode Plot" on web