We need a distribution unit in the LSC rack to: 1) collect the demod signals coming from the Frequency Generation Box 2) adjust the power level 3) generate 2nd harmonics (for POP) 4) distribute the demod signals to the single demodulation boards.
The base line plan is the following:
The box can be build up gradually, but the priority goes to these parts:
I need help for this work. I know exactly how to do it, I just don't have the time to do it all by myself.
Besides the Distribution Box, the demodulation part of the upgrade would still require two steps:
1) upgrade the Band Pass Filters of the demodulation boards (I have all the parts)
2) cabling from the distribution box to the demod board (one-afternoon kind of job)
The Nodus connection to the Martian network stopped working after someone switched cables on the Netgear router. Apparently that router doesn't like to have the 23 and 24 ports connected at the same time.
Joe fixed the connection just freeing either the 23 or the 24 port.
I measured the amplitude noise of the source outputs and the EOM outputs of the Frequency Generation box.
the setup I used is shown in this diagram:
(NB It's important that the cables from the splitter to the RF and LO inputs of the mixers are the same length).
The results of the measurements are shown in the following plot:
1) both Crystals (29.5MHz and 11MHz) have the same noise
2) the 55MHz source's noise is bigger than the 11 MHz (~2x): the frequency multiplication and amplification that happen before it, add extra noise
3) the noise at EOM outputs is ~2x bigger than that of the relative sources
When I have the chance, I'll plot the results of my calculations of expected noise and compare them with the measurements.
I stored the Busby Box, the Rai's Box and the SR554 preamp in the RF cabinet down the Y arm.
I uploaded all the material about the RF frequency Generation Box into the SVN under the path:
I structured the directory as shown in this tree:
I'm quickly describing in a section of the Rf system upgrade document with LIGO # T1000461.
I completed a LIGO document describing design, construction and characterization of the RF System for the 40m upgrade.
It is available on the SVN under https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/RFsystem/RFsystemDocument/
It can also be found on the 40m wiki (http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_09/RF_System#preview), and DCC under the number T1000461.
As the suspension work winds down (we'll be completely done once the ETMs arrive, are suspended, and then are placed in the chambers), I'm going to start working on the RF system.
Step 1: Figure out what Alberto has been up to the last few months.
Step 2: Figure out what still needs doing.
Step 3: Complete all the items listed out in step 2.
Step 4: Make sure it all works.
Right now I'm just starting steps 1 & 2. I've made myself a handy-dandy wiki checklist: RF Checklist. Hopefully all of the bits and pieces that need doing will be put here, and then I can start checking them off. Suggestions and additions to the list are welcome.
There's also a page dedicated to the progress in the PD upgrade process:
There you can find a pdf document with my notes on that.
ELOG reverted to 2.7.5 due to editing difficulties
- /cvs/cds/caltech/elog/start-elog.csh reconfigured to launch 2.7.5
- /cvs/cds/caltech/elog/elog is linked to ./elog-2.7.5
- logbook dir of 2.8.0 was copied in the dir of 2.7.5. The old and obsolete 2.7.5 was discarded.
I think I had the same problem when I switched to 2.75 from 2.65.
Then the problem was FCKeditor.
We should try the solution I put in the elog page of the wiki.
[Koji and Kevin]
I was trying to characterize the REFL11 photodiode by shining a flashlight on the photodiode and measuring the DC voltage with an oscilloscope and the RF voltage with a spectrum analyzer. At first, I had the photodiode voltage supplied incorrectly with 15V between the +15 and -15 terminals. After correcting this error, and checking that the power was supplied correctly to the board, no voltage could be seen when light was incident on the photodiode.
We looked at the REFL55 photodiode and could see ~200 mV of DC voltage when shining a light on it but could not see any signal at 55 MHz. If the value of 50 ohm DC transimpedance is correct, this should be enough to see an RF signal. Tomorrow, we will look into fixing the REFL11 photodiode.
I just wanted to remind you that the most up to date resource about the RF system upgrade, including photodiodes, is the SVN.
Because I was doing new things all the time, the wiki is not up to date. But the SVN has all I've got.
For those of you who spend annoying amounts of time looking for tools, fear no more. Toolboxes for each optical table are coming!
They will probably have:
IR Viewer (a few optical tables will have IR viewers, these specific tables will be labeled in the diagram coming out later)
Ball screw drivers (3/16 in.) 6-8 in. handle
Various Connectors (I'll find out what's needed at some point)
Small flat screwdrivers (for adjusting camera gains)
Please suggest what else may be needed in these boxes.
The boxes will be held to the side of the tables, either by magnets or screws. A diagram of where they will be placed on each optical table in order to minimize obstruction of walkways will be distributed soon. Any objections can then be noted.
A heavy duty plastic box is the likeliest candidate for the optical table toolbox. It measures 5 9/16 in. x 11 5/8 in. x 4 5/8 in. and fits all the tools comfortably. ( http://www.mcmaster.com/#plastic-bin-boxes/=m4yh4m , under Heavy Duty Plastic Bin Boxes)
The list of tools has been updated to include a pen and a wire cutter as well as everything previously stated.
In addition, Steve has recommended that boxes should be secured to the walls or surfaces near the optical tables as opposed to the optical tables themselves, as to keep the tables from wobbling when tools are being exchanged.
A diagram of tentative box placements will go out soon.
I also took every allen key I can find so they can be sorted. They will be back in the appropriate drawer locations soon.
No, the small boxes must be attached to the optical tables. They won't be heavy enough to change the table tilt.
Also, all tools must be color coded according to the optical table using the 3M Vinyl table color code:
So the new tentative plan on the boxes is to bolt them (magnetic strips were proposed but overruled on the grounds that they're not strong enough to withstand being knocked down by accidents).
The boxes are going to be a mix of the Thorlabs Benchtop Organizer (http://www.thorlabs.com/thorProduct.cfm?partNumber=BT17) and the original box. The box will have a region covered in mesh, so tools can be placed and held there. The box will also have a spacer at the bottom, with another mesh right above it, lined up. However, this double-mesh will only cover half of the box. The other half of the box will be compartmentalized to hold things such as screws, connectors, etc. I will talk to Steve about building the boxes.
Also, using nail-polish to coat the Allen wrenches is not going to work. Nail polish does not stick easily enough. The tentative new plan is oil paint, but this is to be reviewed.
Finally, the diagram with the placement of the boxes relative to the optical tables has been put on paper, but needs to be computerized so it's easier to read. This will be done as soon as possible.
There are some tips for how to appy nail polish on YouTube from MKNails and MissJenFABULOUS. Their tips on how to prepare the site for a strong bonding strength are probably helpful for our gold/nickel coated tools. For chrome tools we may need to abrade the surface with a stone or fine sandpaper for it to take the layer better. IF the YouTube videos don't do it for you, then I suggest contacting Tom Evans at LLO to find out what kind of nail polish he uses.
This is the tentative box placement per optical table. The toolboxes are going to be color-coded by a combination of two colors (the order won't matter). The side of each toolbox will have a little panel to let you know which box corresponds to which set of colors.
On the diagram, the set of colors is simply the color of the box border and the color of the text.
If anyone has a problem with any of the colors or the box placement let me know before they are installed and become an annoyance:
ETMY: Box will be attached to the underside of the table by magnets. The box will be on the north side of the optical table.
POY: Box will be attached to the side of the optical table by magnets. The box will be on the west side of the optical table.
BSPRM: Box will be attached to the side of the optical table by magnets. The box will be on the west side of the optical table.
AS: Box will be attached to the side of the optical table by magnets. The box will be on the north side of the optical table.
PSL1: Box will be inside the optical table, in the northeast corner.
PSL2: Box will be inside the optical table, in the southwest corner.
POX: Box will be attached to the side of the optical table by magnets. The box will be on the south side of the optical table.
MC2: Box will be attached to the side of the optical table by magnets. The box will be on the south side of the optical table.
ETMX: Box will be attached to the side of the optical table by magnets. The box will be on the east side of the optical table.
I decided to go see what the electrical tape looks like on the other tools.
These are the tools I felt were necessary to label with tape: (the others don't seem to be terribly important in terms of not interchanging between boxes)
On another note I'm not sure why electrical tape can't be used on the Allen Wrenches too.
I also plan on ordering smaller flash lights for each table (this one is bulky and unwieldy), and filling in the gaps of the Allen Wrench sets as soon as I get the go-ahead.
Albert, our new undergrad work force received 40m specific- basic safety training last week. Please read and sign 40m procedures booklet.
These are the tentative box placements. Roughly. I don't actually have the box finalized yet, but the box should be around that size.
How do I perspective ._.
Thanks for the loan guys. I do have a lot of warm weather clothing at home that is not so necessary in the California climate. I will find some suitable attire for the Rb clocks there.
The rubidium clocks are still not quite locked together, though it is clear that the beat frequency has dropped a lot since yesterday.
I checked on the clocks and the 1pps sync light is on. The clocks are really hot again though despite the gap left at the bottom of the igloo. The side of the clocks were hot enough to not be touchable.
I made the executive decision that I would remove the hut just now. We can let the clocks lock together and then put the hut back on just before measuring. This way the hut will isolate from temperature fluctuations during the measurement but it won't be running at the hotter equilibrium temperature. I hope that the temperature won't change too much during the measurement if we put the hut back on.
RA: Attachment deleted because it was in Postscript format. Also not allowed here are the Stone Tablet and Cave Painting formats.
...I restarted it.
I restarted it using start-elog-nodus and this worked out fine - even though I did it from Pete's on my phone ;-)
The ATF wiki page doesn't seem to be working any more. Does anyone know where this is held so we can try to get it back online? Thanks
I phoned Phil Ehrens and found out that all these wikis have been moved to a new wiki site
The ATF wiki can now be found here
I have updated the link from the 40m wiki to reflect this
Elog was down, I restarted it.
...was down. Have restarted it.
was down. I restarted the version in the 2.7.5 folder. It went down again almost immediately but stayed up after the second restart.
40m wiki seems to have been down for quite a while now but I can't see any info in the elog about it. Is there some ongoing problem?
There was an email from Dave Barker about this. They had to reorganize the DNS at LHO. The URL that should be used is: http://blue.ligo-wa.caltech.edu:8000/40m
Thanks Jamie, I've updated the links from the ATF wiki to reflect this.
The manual instructions on the 40m wiki for restarting wouldn't work. I killed the process okay, but then I got an error saying it "couldn't bind to port 8080, please try again using -p to select port". The automated script worked though.
After the boot-fest, the nightly backup to Powell-Booth failed, and an automatic email got sent to me. I restarted the ssh agent, following the instructions in /cvs/cds/caltech/scripts/backup/000README.txt .
Restarted backup since fb40m was rebooted.
The fb40m just went out of order with status indicator number 8
It recovered on its own five minutes later.
Backup script restarted, backup of trend frames and /cvs/cds is up-to-date.
We have been waiting for this for 20 some years. Arrowhead water with cooler. AWESOME
Happy holidays, everyone!
To interface the Mini Circuits RF Frequency Counter(FC) Model UFC-6000 with Raspberry Pi on Linux platform. Also to create a User friendly interface, to control the FC with command lines.
Highlights of the Code(script attached):
The code enables the user to communicate and control different parameters of the UFC like:
1)Frequency Range Selection( for the device to read different frequencies, AutoRange is set by default).
2)Sampling Time (The time intervals for which the data will be retrieved)
3)Read Device Status(Whether the device is reading data or not).
Description of the Code:
HID USB Interfacing by sending byte Values.
1)Read The Freq or Range
Reading the Freq is done by reading the 1st and 2nd LCD of the Frequency counter.
1st line containing Range information, 2nd line is the Frequency result
the code should be send is 2
1st byte: 2
The returned 64 byte array is as follows:
2nd byte to Byte17 the ascii value of 16 characters of the 1st LCD line
Byte18 to Byte33 the ascii value of 16 characters of the 2nd LCD line
2) Set the Range
By default Freq Counter is in "AutoRange" mode.
To set the range manually send the code 4
1st byte: 4
2nd byte: the range value. can be any legal range value. for auto range need to be 255.
the 64 byte array is:
3)Set the Sample Time
By default Freq Counter Sample Time is 1 sec.
you can set the sample time from 0.1 sec and up in step of 0.1 sec.To set the Sample Time send the code 3
1st byte: 3
2nd byte: the sample value in sec double 10.
for example: to set the sample time to 0.4 sec 2nd byte need to be: 4
These bytes can be changed by changing the values of buffer and buffer in function /*Send Report to the device*/ in the main program.
The data is written into a .txt file(example attached) and the user can control the recording of data. The frequency data can now be made to talk to EPICS through slow channels.
The data from the .txt file can be used for error analysis at different sampling periods.
The interface of the FC with the Pi is now complete.
Make this FC talk to EPICS through slow channels.
To characterize the Mini-Circuits RF FC (Model UFC-6000) and plot Bode Plots at varying Modulation frequencies.
Here are the list of measurements(files attached) taken from FC using SRS(Model DS345) Synthesized Function Generator for a Sinusoidal signal at different Modulation Frequencies ranging from 0.01 Hz to 1 KHz:
Carrier Frequency Modulation Depth Attached measurement Folder
5 MHz Δ f = 5 MHz Bode_5
10 MHz Δ f = 10 MHz Bode_10
20 MHz Δ f = 20 MHz Bode_20
The measured data will be used to estimate:
1) Transfer Function of FC
2) Quantization noise from Power Spectral Density(PSD) vs Hz
To Do Next:
1)Complete interfacing the Pi with EPICS.
2)Make bode plots (Matlab script attached) and PSD plots and estimate the control parameters for optimal design of FOLL PID loop.
The goal is to characterize the Mini-Circuits RF FC (Model UFC-6000) by plotting Gain Plots.
The sampling rate of the UFC-6000 RF FC is 1s (should look into making the sampling time smaller). So to satisfy Nyquist criterion, the maximum modulation frequency is 0.5 Hz beyond which aliasing effects are seen.
The measurements taken (mentioned in my previous elog) are used to plot Gain vs Modulation frequency for carrier frequencies of 5 MHz and 25 MHz.
A modulated signal can be represented as X(t)= A*sin (Fc*t+D*sin(Fm*t+phase1)) where Fc and Fm are carrier and modulation frequencies respectively and D is the modulation depth.
This signal Y(t) is input to the FC and the output frequencies of the FC are recorded.
Let the output of the FC is Y(t)= A'*sin(Fc*t+D'*sin(Fm'*t+phase2));
Gain = D'/D;
phase = phase2 - phase1;
D' is calculated by subtracting the carrier frequency from the output frequency and calculating the amplitude of the resulting fitted sine wave.
The phase can be calculated if the phase of the input is known(which will be done next).
Plotting the Bode plots would give response of the FC to modulation.
The plots generated will be used to estimate:
1) Transfer Function of FC to be known to build an FOL-PID loop.
2) Quantization noise from Power Spectral Density(PSD) vs Hz.
1)Calculate the phase difference to complete the Bode plot. This would require interfacing of the ADC on raspberry pi.
2)Estimate the quantization noise from the digital output.
Plans for the Week:
Progress and Problems Faced:
Work Inside the Lab:
Goal- By the end of the week:
I have been trying to use an ADC with the Raspberry Pi to be able to measure the phase difference between FC input and output signals.I had a hard time interfacing the ADC with the Pi (setup attached) even after trying to debug the issue for last two days. So I and Eriq Q performed a system reboot on the Pi and tried all the possible ways for the Pi to detect the ADC but we were not able to. At the end we decided to order another IC(Microchip MCP 3008) which we hope can be interfaced with the Pi. Till then I will finish to write data from the FC into pipes so that the control computers can access the real time data. I will also look the correctness of the sampling time that is provided by the spec of the MCL-Mini circuits that is if we could really achieve 0.1 s sampling time with the FC.
Finally, the 0.1s sampling rate of the frequency counter(FC) has been achieved. For this I had to :
Send in byte codes to set a particular range of the frequency counter.
I was digging in to find how exactly the circuit inside the frequency counter works and how the processor inside is able to read and write bytes through a HID-USB interface. I found out that the 'AutoRange' setting (which I have been using so far) has an independent multiplexing circuit which consumes some time(that varies with the drift in frequencies) and thus, the the processor waits for some specific time for this process and cannot reach the minimum 0.1 s sampling time. To mitigate this issue, I set the range bytes to the appropriate range of frequencies so that I can bypass the MUX delay. Here is the list of Range and frequencies for the FC:
Range 1: 1 - 40 MHz
Range 2: 40 - 190 MHz
Range 3: 190 - 1400 MHz
Range 4 : 1400 - 6000 MHz
I then took measurements for sampling time of 0.1 s at carrier frequencies of 5 MHz and 25 MHz from SRS DS345 and plotted the improvised gain plots(attached) to those in my previous elog(10070) with the same procedure mentioned before.
To do Next:
Plot the gain plots for higher carrier frequencies till range 3 using Marconi Function generator.
Write the data from FC into C1: ALS-Y_SLOW_SERVO1_OFFSET EPICS channel.
The attached are the gain plots at carrier frequencies of 100 MHz, 500 MHz and 1 GHz measured using IFR 2023B (Marconi).
To complete the characterization of the Mini Circuits UFC-6000 RF Frequency Counter to be used for beat note measurement as a part of frequency offset locking loop. The aim of this setup was to obtain the bode plots and PSD plots for the FC.
Detail about the Setup:
UFC RF Frequency Counter: Described in detail in one of my previous elog (http://nodus.ligo.caltech.edu:8080/40m/10020)
Raspberry Pi: Raspberry Pi will be running Raspbian which is a version of Linux, and not a RTOS. When sampling data at a certain frequency we want samples to occur at fixed time intervals corresponding to the sampling period. A normal operating system cannot provide us with this functionality, and there will be jitter (variation) in the time difference between consecutive samples. Whether this is an issue depends on how much jitter we have and what the specific application is. In our application(measuring phase and noise), the jitter has to be taken into consideration. Hence for data acquisition we need to sample with much more tightly defined sampling periods (reduced jitter) which can be done by providing an external timing standard(Like a square pulse of the frequency same as the sampling rate of the FC ).
ADC : The ADC serves for two different conversion processes in the setup:
1) For converting modulating analog signal(from SRS 30 MHz Wave Generator) into digital signal for data analysis on Raspberry Pi.
2) To provide an external clock reference to the Raspberry Pi.
Interfacing ADC(ADS1115) with Pi:
In order to set the modes of operation defined above we must set the config register within the ADS1115. A register is simply a memory location within the chip. Registers are made up of bytes (8 bits) of data. Registers are typically either one or two bytes long. The bits are:
Bit  This bit is used to start a conversion, by setting this bit to 1 a conversion is initiated. When reading the config register this bit remains equal to 0 while the conversion is carried out, and is set to 1 once the conversion is complete, we can monitor this bit to find the status of a conversion
Bits [14:12] These bits set which pin to use as input to the ADC. Note that we can choose either single ended or differential mode through setting these bits. Note that each configuration has two inputs AIN~p~ and AIN~n~. By setting AIN~n~ to GND we obtain a single ended input with AIN~p~ as the input.
Bits [11:9] These bits set which setting of the programmable gain amplifier to use
Bit  Continuous conversion / No Continuous conversion
Bits [7:5] Set the samples per second (sps) value
Bit [4:2] Comparator setup, we will not use the comparator so these bits are irrelevant
Bit [1:0] Comparator mode, set to 11 to disable the comparator.
Four channels are used in differential mode for A-D conversion of two analog signals, one the slow modulating signal input and the other for a square signal of 10 Hz (same as sampling rate of FC(0.1 s)).
The raspberry Pi reads the external trigger from ADC and starts reading input from the FC only when the square signal is 1. Thus in this way we can avoid the clock jitter and timing can be as accurate as the RTOS.
Three function generators are used in the setup:
The setup is attached as pdf. The computer scripts will follow this elog.
The input and output modulated signals are recorded and the delay and noise of the FC are to be estimated.
When I was trying to plot PSD of the measurements, I still couldn't get better resolution. There still seems to be a problem with timing and synchronization of the R Pi with the FC even after addition of the external trigger circuit. Now, I am looking to debug this issue. Attached are the plots showing missing data points and data from the FC at uneven spacing(zoomed in plot).
Although there were few timing issues with the FC and the Raspberry Pi at the lowest sampling time of the FC (0.1s) even after adding an external trigger circuit, it turned out that most of these issues are not prevalent at higher sampling times(>0.5 s)(narrow peaks of PSD seen for higher sampling times). Rana suggested me to look at the PSD plots at different sampling times of the FC so that we can decide which would be the optimal sampling time to work with the FC before replacing the spectrum analyzer. I took the measurements with the setup discussed in my previous elog(http://nodus.ligo.caltech.edu:8080/40m/10129) . However, the noise of the R Pi- FC interface should be taken care of (I will discuss it with my mentors).
Attached are the plots at 100 MHz carrier frequency at different sampling times of the FC( 0.1s, 0.2s, 0.3s, 0.5s, 1s) (pdfs and code attached in a zip file)
RXA: Put all the plots in a single PDF file and use the same axis limits for all plots so that its easy to compare. (Attached in PSD.pdf)