[Steve, Manasa]

We ran power cables and sma cables for the FOL fiber module from the PSL table to the IOO rack.

Overall Design

A schematic of the overall subsystem diagran in attachment.

RF and Optical Connections

Starting at the top left corner is the diode laser module.  This laser has an input which allows it to be amplitude modulated.  The output of the laser is coupled into an optical fiber which is connectorized with an FC/APC connector and is connected to the input port of a 1 by 16 Optical Fiber Splitter. The Splitter produces 16 optical fiber outputs dividing the input laser power into 16 roughly equal optical optical fiber outputs.  These optical fibers are routed to the Photodiode Receivers (PD) which are the devices under test. All of the PDs are illuminated simultaneously with amplitude modulated light. The Optical Fiber outputs each have a collimating fiber telescope which is used to focus the light onto the PDs. Optical Fiber CH1 is routed to a broadband flat response reference photodiode which is used to provide a reference to the HP-4395A Network Analyzer.  The other Channel outputs are connected to an RF switch which can be programmed to select one of 16 inputs as the output.  The selected outputs can then be sent into channel A of the RF Network Analyzer. 

RF Switch

The RF switch consists of two 8 by 1 Multiplexers (National Instruments PXI-254x) slotted into a PXI Chassis (National Instruments PXI-1033).  The Multiplexers have 8 RF inputs and one RF output and can be programmed through the PXI Chassis to select one and only one of the 8 inputs to be routed to the RF output.) The first 8 Channels are connected to the first 8 inputs of the first Multiplexer.  The first Multiplexer’s output is then connected to the Channel 1 input of the second Multiplexer. The remaining PD outputs are connected to the remaining inputs of the second Multiplexer. The output of the second Multiplexer is connected to the A channel of the RF Network Analyzer.  Thus it is possible to select any one of the PD RF outputs for analysis.

Software

Something on this tomorrow.

I've taken over one of the SENSMAT oscillators for a test of the EPICS system.

These are the channels I've modified, with their original and current settings:

controls@donatella|~ > caget C1:LSC-OUTPUT_MTRX_7_13 C1:CAL-SENSMAT_CARM_OSC_FREQ C1:CAL-SENSMAT_CARM_OSC_CLKGAIN
C1:LSC-OUTPUT_MTRX_7_13          -1
C1:CAL-SENSMAT_CARM_OSC_FREQ    309.21
C1:CAL-SENSMAT_CARM_OSC_CLKGAIN   0
controls@donatella|~ > caget C1:LSC-OUTPUT_MTRX_7_13 C1:CAL-SENSMAT_CARM_OSC_FREQ C1:CAL-SENSMAT_CARM_OSC_CLKGAIN
C1:LSC-OUTPUT_MTRX_7_13           0
C1:CAL-SENSMAT_CARM_OSC_FREQ      0.1
C1:CAL-SENSMAT_CARM_OSC_CLKGAIN   3
controls@donatella|~ >

 I put some optics to get the green SHG on the PSL table.

Now a green light successfully comes out from the doubling crystal.

Since the optical layout of the PSL table was dramatically changed, I had to re-setup the green SHG stuff. 

 - what I did

I put a steering mirror after the 90/10% pick off mirror, and then a half wave plate and a convex lens.

The lens is approximately on the right place.

 To get the green beam easily, temporarily I raised the current of the NPRO up to 2 A.

I connected the oven to the heat controller, set the temperature to 36.8 deg which is the set point previously used.

After putting and aligning the oven, I finally obtained the green beam.

At the end of the work I set the NPRO current back to 0.9 A and relocked the PMC.

- things to be done

 1. more precise mode matching

 2. optimization of the temperature 

In order to increase the green power on the PSL table, I moved the position of the Second Harmonic Generation (SHG) crystal by ~5cm.

After this modification, the green power increased from 200 uW to 640 uW. This is sufficiently good.

     As I said in the past elog entry (# 3122), the power of the green beam generated at the PSL table should be about 650 uW.

I measured the green power by the Ophir power meter and found it was ~200 uW, which made me a little bit sad.

Then I performed the beam scan measurement to confirm if the crystal  was  located on the right place. And I found the postion was off from the optimum position by ~5cm.

So I slided the postion of the SHG oven to the right place and eventually the power got increased to 640 uW.

some notes: 

(power measurement)

        The outgoing beam from the SHG crystal is filtered by Y1-45S to eliminate 1064nm.

According to Mott's measurement Y1 mirrors are almost transparent for green beams (T~90%), but highly reflective for 1064nm (T~0.5%).

All the green power were measured after the Y1 mirror by the Ophir configured to 532nm, though, the measured power might be offseted by a leakage of 1064nm from the Y1 mirror.

I didn't take this effect into account.

(beam scanning and positioning of crystal)

          Here is the properties of the incident beam. These numbers are derived from the beam scan measurement.

w0h             = 52.6657      +/- 0.3445 um

w0v             = 52.4798      +/- 0.1289  um

z0h             = 0.574683         +/- 0.001937 m

z0v             = 0.574325         +/- 0.0007267 m

Where the suffixes "h" and "v" stand for "horizontal" and "vertical" respectively.

The distances are calibrated such that it starts from the lens postion.

Both waist size are already sufficiently good because the optimum conversion can be achieved when the waist size is about 50um ( see this entry)

The measured data and their fitting results are shown in attachement 1.

         According to my past calculation the center of the crystal should be apart from the beam waist by 6.8mm (see this entry). 

So at first I put the oven exactly on the waist postion, and then I slided it by 6.8mm.

(to be done)

        I need to find an optimum temperature for the crystal in order to maximize the green power.

Previously the optimum temperature for the crystal was 38.4 deg. But after moving the position I found the optimum temperature is shifted down to around 37deg.

The optimum temperature for the doubling crystal on the PSL table was found to be 36.8 deg.

I scanned the temperature of the crystal from 44 deg to 29 deg, in order to find the optimum temperature where the frequency doubled power is maximized. 

(method) 

The method I performed is essentially the same as that Koji did before (see this entry).

(1) First of all, I enabled the PID control on the temperature controller TC200 and set the temperature to 44 deg.

(2) After it got 44 deg, I disabled the PID control.

(3) Due to the passive cooling of the oven, the temperature gradually and slowly decreased. So it automatically scans the temperature down to the room temperature.

(4) I recorded the power readout of the power meter: New Port 840 together with the temperature readout of TC200. The power meter was surely configured for 532 nm.

(result)

The measured data are shown in the attachment. 

The peak was found at T=36.8 deg where the power readout of  532 nm was 605 uW.

Compared with Koji's past data (see this entry), there are no big side lobes in this data. I am not sure about the reason, but the side lobes are not critical for our operation of the green locking.

 (to be done)

 Adjustment of the PID parameters

 It seems like you might inherit an offset by using step (3) b/c of the temperature gradient between the crystal and the sensing point. Depending on how large this gradient is you could increase the linear coupling from temperature to intensity noise from zero to a significant number. Phase noise should not be effected.

SInce these things (ovens) are so low time constant, shouldn't we

1. Lock to a temperature
2. Let the oven equilibrate for however long - a few tau maybe - my oven has a time constant of 60 sec, don't know if this is fast or slow compared to that
3. Measure P_532/P_1064
4. Change the setpoint
5. Go back to step 1

Plugging in the thermal feedback BNC cable to the laser reduced the DC voltage of the green PDH photo diode from 3.12 V to 1.5V off resonance.

The power emitted by the laser was the same as in the case without that cable. Note LT, i.e. measured crystal temperature, of the laser show a

different value when the BNC is connected, but the manual clearly states that this display does not work properly if a cable is connected to the

slow BNC plug, an offset is added.

The power of the 532nm light behind the SHG oven has been reduced from 1mW to 0.4mW. I changed the crystal temperature such that the power

of the green light is 1mW. With this new temperature setting the laser can be locked again.

Changing the crystal temperature changes the laser frequency. This will causes the beat note missing at the vertex.

In other words, you will find the beat note at the vertex when the actual temperature of the crystal is reproduced as before,
no matter how the dial setting/temp voltage input is.

I must confess that I changed the temperature of the laser via the dial yesterday. I believe the initial (displayed) temperature was ~19^o, whereas it is now probably in the high 20s. Sorry.

Okay, my elog entry was not clear I changed the temperature of the SHG which only changes the conversion efficiency. 

Anyhow, since the laser set temperature and thus the laser frequency has been changed by Zach and I couldn't find a note

of the original laser crystal temperature, my plan is to reset the SHG temperature to the old value, set the laser crystal temperature

around 19°C and do fine adjustment of that temperature by optimising the doubling efficiency. Okay?

Last night we finally got some online subtraction going. The filter used is described in the post this eLOG is @eLOG 11488. 

The results were as follow:

The filter worked as expected when subtracting noise out of MCL,

There is about a factor of 6 subtraction at the ~3Hz resonant peak. The static IIR filter predicted a factor of 6-7 subtraction of this peak as well.

The 1.2 Hz resenonant feature improved by a factor of 3. This should improve quite drastically when I implement the y-channel of the T240 seismo.

There is some high frequency noise being injected, not very noticeable, but present. 

We then took a look at the power in the MC when the filter was on,

The power being transmitted in the cavity was not as stable as with the feedforward on. We believe that the filter is not at fault for this as Eric mentioned to me that the MC2 actuator lacked some sort of compensation that I need to understand a bit better.

YARM was then locked when the filter was on and we took a look at how it was doing. There was stationary sound arising from the locking of the YARM, leading us to believe that the filter might have injected some noise in the signal. IT DID.

The filter injected nasty high frequency noise at YARM from 11 Hz and on. This is to be expected since the filter did not roll off to zero at high frequencies. Implementing a 1/f rolloff should mitigate some of the injected noise.

 Also, as one can see above, subtraction by around a factor of 2 or so, was induced by the mode cleaner feedforward subtraction.

For the future SLOW controls our current plan is to keep using the VME based stuff and associated processors (Baja, Motorola, etc.). This is not

a sustainable plan since these are obsolete and eventually will die. One option is to use these boxes from Diamond Systems:

http://www.diamondsystems.com/products/octavio

 All of the SLOW computers were in limbo since the fileserver/nameserver change, but me and Zach brought them back.

One of the troubles, was that we were unable to telnet into these computers once they failed to boot (due to not having a connection to their bootserver).

1. Needed special DB9-RJ45 cable to connect from (old) laptop serial ports to the Motorola VME162 machines (e.g. c1psl, c1iool0, c1aux, etc.); thanks to Dave Barker for sending me the details on how to make these. Tara found 2 of these that Frank or PeterK had left there and saved us a huge hassle. Most new laptops don't have a serial port, but in principle there's a way to do this by using one of our USB-Serial adapters. We didn't try this, but just used an old laptop. The RJ45 connector must go into the top connector of the bottom 4; its labeled as 'console' on some of the VME computers. Thanks to K. Thorne for this very helpful hint and to Rolf for pointing me to KT.
2. Installed 'minicom' on these machnes to allow communication via the serial port.
3. Had to install RSH on chiara to allow the VME computers to connect to it. Also added the names of all the slow machines in /etc/hosts.equiv to allow for password-less login. Without this they were not able to load the vxWorks binary. It was tricky to get RSH to work, since its an insecure and deprecated service. 'rsh-server' doesn't work, but installing 'rsh-redone-server' did finally work for passwordless access. Must be that linux1 has RSH enabled, but of course, this was undocumented.
4. Some of the SLOW machines didn't have their own target names or startup.cmd in their startup boot parameters (???). I fixed these.
5. For C1VAC1, I have updated the boot parameters via bootChange, but I have not rebooted it. Waiting to do so when Koji and Steve are both around. We should make sure to not forget doing this on C1VAC2. Steve always tells us that it never works, but actually it does. It just crashes every so often.
6. Leaving C1AUXEX and C1AUXEY for Q and Jacy to do, to see if this ELOG is good enough.
7. The PSL crate still starts up with a SysFail light turned on red, but that doesn't seem to bother the c1psl operation. We (Steve) should go around and put a label on all the crates where SysFail is lit during 'normal' operation. Misleading warning lights are a bad thing.

We still don't have control completely of the MC Servo board, so we need the morning crew to start checking that out

An example session (using telnet, not the laptop/serial way) where we use bootChange to examine the correct c1aux config:

controls@pianosa|target> telnet c1aux
Trying 192.168.113.61...
Connected to c1aux.martian.
Escape character is '^]'.

c1aux > bootChange

'.' = clear field;  '-' = go to previous field;  ^D = quit

boot device          : ei
processor number     : 0
host name            : chiara
file name            : /cvs/cds/vw/mv162-262-16M/vxWorks
inet on ethernet (e) : 192.168.113.61:ffffff00
inet on backplane (b):
host inet (h)        : 192.168.113.104
gateway inet (g)     :
user (u)             : controls
ftp password (pw) (blank = use rsh):
flags (f)            : 0x0
target name (tn)     : c1aux
startup script (s)   : /cvs/cds/caltech/target/c1aux/startup.cmd
other (o)            :

value = 0 = 0x0
c1aux >

 I have brought back c1auxex and c1auxey.  Hopefully this elog will have some more details to add to Rana's elog 10015, so that in the end, we have the whole process documented.

The old Dell computer was already in a Minicom session, so I didn't have to start that up - hopefully it's just as easy as opening the program.  (Edit, JCD, 9July2014:  Startup a terminal session, and then type "minicom" and press enter to get a Minicom session).

I plugged the DB9-RJ45 cable into the top of the RJ45 jacks on the computers.  Since the aux end station computers hadn't had their bootChanges done yet, the prompt was "VxWorks Boot".  For a computer that was already configured, for example the psl machine, the prompt was "c1psl", the name of the machine.  So, the indication that work needs to be done is either you get the Boot prompt, or the computer starts to hang while it's trying to load the operating system (since it's not where the computer expects it to be).  If the computer is hanging, key the crate again to power cycle it.  When it gets to the countdown that says "press any key to enter manual boot" or something like that, push some key.  This will get you to the "VxWorks Boot" prompt. 

Once you have this prompt, press "?" to get the boot help menu.  Press "p" to print the current boot parameters (the same list of things that you see with the bootChange command when you telnet in).  Press "c" to go line-by-line through the parameters with the option to change parameters.  I discovered that you can just type what you want the parameter to be next to the old value, and that will change the value.  (ex.  "host name   : linux1   chiara"   will change the host name from the old value of linux1 to the new value that you just typed of chiara). 

After changing the appropriate parameters (as with all the other slow computers, just the [host name] and the [host inet] parameters needed changing), key the crate one more time and let it boot.  It should boot successfully, and when it has finished and given you the name for the prompt (ex. c1auxex), you can just pull out the RJ45 end of the cable from the computer, and move on to the next one.

I ran (script dir)/PSL/FSS/SLOWscan on op440m from 11:30 to 12:30 on 27th. Although Rana and later I myself set "timed bombs" for the scan, they did not work as they have probably been ran on Linux. After the scan I relocked PMC, FSS, and MZ . MC locked automatically.

Observation:

1. To keep away from the mode hop, FSS_SLOWDC is to be at around 0. The values -5 ~ -6 is the place for the power, which is my preference for now. BTW, the mode hop only appears to the PSL output (=AMPMON) is this normal?

2. The PSL output looks dependent on the NPRO wavelength. The NPRO output and the PSL output tends to be high when the FSS_SLOWDC is low (= LTMP: Laser Crystal Temp is low). Also there is a step at the LTMP where we think the mode hop is present. This may cause the daily PSL output variation which induced by the daily change of the reference cavity length.

My naive speculation is that the NPRO wavelength is too long (= hot side) for the MOPA absorption as the MOPA heads are cooled to 19deg.

3. Scanning of -10 to +10 changes the LTMP from 42-49deg. This is almost 1/10 of the NPRO capability. The manual told us that we should be able to scan the crystal temperature +/-16deg (about 30deg to 60deg).

What I like to try:
a) Change the NPRO temp to more cold side.
b) Change the MOPA head temp to a bit hot side.
c) Tweak the MOPA current (is it difficult?)

 I think that the AMPMON ND problem was just that the responsivity changes with angle. So when I aligned it a little we got some few% improvement in the signal which is not a real power increase.

I don't think we can adjust any of the MOPA parameters because the controller is broken, but we can try the NPRO crystal temperature.

After fixing multiple issues, the model webviews are updating, should be done by tomorrow. It should be obvious from the timestamps on the index page which are the new ones. These new screens are better than the old ones and offer more info/details. Please look at them, and let me know if there are broken links etc. Once we are happy with this new webview, we can archive the old files and clean up the top directory a bit. I don't think this adds anything to the channel accounting effort but it's a nice thing to have up-to-date webviews, I found the LLO ones really useful in setting up the AS WFS model.

BTW, the crontab on megatron is set to run every day at 0844. The process of updating the models is pretty heavy because of whatever MATLAB overhead. Do we really need to have this run every day? I modified the crontab to run every other Saturday, and we can manually run the update when we modify a model. Considering this hasn't been working for ~3 years, I think this is fine, but if anyone has strong preference you can edit the crontab.

If someboy can volunteer to fix the MEDM screenshot that would be useful.

The simulink webview generation cronjob on megatron was not working, apparently due to a matlab license problem. I switched it to matlab 2019a (the current CDS standard), and added a script to generate medm screens from the webview. This can help with keeping hand-made screens up to date, or be a substitute for hand-made screens if the model is simple.

I have added/modified SMOO settings to all of the records in psl.db appropriately. Changes checked in to SVN.

As a reminder, you should check in to the SVN all changes you make to any of the .db files or any of the .ini files in chans.

I repeated the measurements using NPRO instead of Crystalaser. I am attaching optical layouts for these measurements for future reference. 

Lesson learnt : Do not use Crystalaser for transmission measurements and always separate the transmitted main beam from other beams that result from the wedged surface of the mirror. 

Measurements match specs provided by Laseroptik

p-polarization

T percentage = 0.10% 42 deg
                            0.092% 44 deg
                            0.086% 46 deg
Minimum transmittance = 0.081% 52deg

s-polarization

T percentage = 0.048% 42 deg
                            0.047% 44 deg
                            0.047% 46 deg
Minimum transmittance = 0.047% 46 deg

The two 40 mm apeture baffles at the ends were replaced by 50 mm one. ITM baffles with 50 mm apeture are baked ready for installation.

A concern was raised about the two ETMs and ITMX having the opposite response (relative to the other 7 SOS optics) in the OSEM PDmon channel in response to a given polarity of PIT/YAW offset being applied to the coils. Jon has factored into account all the digital gains in the actuation part of the CDS system in making this conclusion. I raised the possibility of the OSEM coil winding direction being opposite on the 15 OSEMs of the ETMs and ITMX, but I think it is more likely that the magnets are just glued on opposite to what they are "supposed" to be. See Attachment #6 of this elog (you'll have to rotate the photo either in your head or in your viewer) and note that it is opposite to what is specified in the assembly procedure, page 8. The net magnetic quadrupole moment is still 0, but the direction of actuation in response to current in the coil in a given direction would be opposite. I can't find magnet polarities for all the 10 SOS optics, but this hypothesis fits all the evidence so far..

Summary:

• SOS solidworks model is nearly complete
  • Having trouble with the design of the sensor/actuator head assembly and the lower clamps
• After Gautam's suggestion, installed Abaqus on computer. Teaching it to myself to eventually do FEM analysis and find resonant frequency of the system
  • Goal is to replicate frequency listed in the SOS documents to confirm accuracy of computer model, then replace guide rods with sapphire prisms and change geometry to get same results

Questions:

• How accurate do the details (like fillet, chamfer, placement of little vent holes), and material of the different SOS parts need to be in the model?
• If I could get pictures of the lower mirror clamp (document D960008), it would be helpful in making solidworks model. Document is unclear. Same for sensor/actuator head assembly. 

If you go through this thread of elogs, there are lots of pictures of the SOS assembly with the optic in it from the vent last year. I think there are many different perspectives, close ups of the standoffs, and of the OSEMs in their holders in that thread.

This elog has a measurement of the pendulum resonance frequencies with ruby standoffs - although the ruby standoff used was cylindrical, and the newer generation will be in the shape of a prism. There is also a link in there to a document that tells you how to calculate the suspension resonance frequencies using analytic equations.

In the cleanroom, I opened the nickel-plated SmCo magnet box to take a closer look. I handled the magnets with tweezers. I wrapped the tips of the tweezers with some Kapton tape to prevent scratching and magnetization.

I put some magnets on a razor blade and took some close-up pictures of the face of the magnets on both sides. Most of them look like attachment 1.

Some have worn off plating on the edges. The most serious case is shown in attachment 2. Maybe it doesn't matter if we are going to sand them?

I measure the magnetic flux of the magnets by just attaching the gaussmeter flat head to the face of the magnet and move it around until the maximum value is reached.

For envelope #1 out of 3 the values are: (The magnet ordering is in attachment 3):

Going to continue tomorrow with the rest of the magnets. I left the magnet box and the gaussmeter under the flow bench in the cleanroom.

Continuing with envelope number 2

I think I have to redo envelope 1 tomorrow.

Redoing magnet measurement of envelope 1:

Moving on to inspect and measure envelope 3 (the last one):

Yehonathan noticed today that the silver plated hardware on the assembled SOS towers had some pretty severe discoloration on it. See attached picture.

These were all brand new screws from UC components, and have been sitting on the flow bench for a couple months now. I believe this is just oxidation and is not an issue, I spoke to Calum as well and showed him the attached picture and he agreed it was likely oxidation and should not be a problem once installed.

He did mention if there is any concern from anyone, we could take an FTIR sample and send it to JPL for analysis, but this would cost a few hundred dollars.

I don't believe this to be an issue, but it is odd that they oxidized so quickly. Just wanted to relay this to everyone else to see if there was any concern.

Yup this is OK. No problem.

Salvage these (and any other things). Wrap and double-pack nicely. Put the labels. Store them and record the location. Tell JC the location.

{Paco, Yehonathan}

BHD Optics box was put into the x-arm last clean cabinet. (attachment 5)

OSEMs were double bagged in a labeled box on the x-arm wire racks. (attachment 1)

SOS Parts (wire clamps, winches, suspension blocks, etc.) were put in a box on the x-arm wire rack. (attachment 3)

2"->3" optic adapter parts were put in a box and stored on the xarm wire rack. (attachment 3)

Magnet gluing parts box was labeled and stored on the xarm rack. (attachment 2)

TT SUS with the optics were stored on the flow bench at the x end. Note: one of the TT SUS was found unsuspended. (attachment 4)

InVac parts were double bagged and stored in a labeled box on the x arm wire rack. (attachment 2)

I set up a working area on the table next to the south flow bench (see attachment). I also brought in a rolling table for some extra space.

I covered all the working surfaces with a foil from the big roll between 1x3 and 1x4.

I took the SOSs, SOS parts and the OSEMS from the MC2 table to the working area.

I cleaned some LN Allen keys with isopropanol and put them on the working table, please don't take them.

You can remove the components of the optical table enclosure (black ones) and use the optical table as your working area too.

I gathered all the components I could find from the SOS towers and the cleanroom and put it all on the table next to the flow bench (See attachment).

I combed through the cleanroom cabinet for SOS parts but didn't find all the parts listed in the procurement spreadsheet. I did find some extra items that were not listed.

This table compares the quantities in the spreadsheet to the quantities collected on the table. Green rows are items I found more than in the procurement spreedsheet while red rows are items I found less.

Gautam pointed out that there are extra Sm-Co magnets stored in the clean optics cabinet.

I took the magnet box out and put it on the rolling table next to south flow bench. The box contains 3 envelopes with magnets.

They are labelled as following:

FLUX 94 - 50 parts

FLUX 93 - 10 parts

FLUX 95 - 40 parts

(What is FLUX??)

The box also contains some procurement documents.

The clean and bake dcc says :

1. Ultrasonic clean in methanol for 10 minutes

2. Bake in vacuum at 177 C° for 96 hours

Should we go ahead with the C&B?

The curie temp of SmCo seems about x2 (in K) of the one for NdFeB. i.e. 600K vs 1000K. So I believe 177degC = 450K is not an issue. Just make sure the curie temp, referring the specific property for the magnets from this company. (You already know the company from the procurement doc). It'd be great if you upload the doc on the 40m wiki.

Done.

Also, the magnets are nickel-plated. I guess that doesn't matter for the baking (Curie temp of 355 °C)?

A summary of things that need to be fabricated/purchased/done:

I measure some of the dowel pins we got from Mcmaster with a caliper.

One small pin is 0.093" in diameter and 0.376" in length. The other sampled small pin has the same dimensions.

One big pin is 0.187" in diameter and 0.505" in length. The other is 0.187" in diameter and 0.506" in length.

The dowels meet our requirements.

We got some dumbells from Re-Source Manufacturing (see attached). I picked 3 in random and measured their dimensions:

1. 0.0760" in diameter, 0.0860" in length

2. 0.0760" in diameter, 0.0860" in length

3. 0.0760" in diameter, 0.0865" in length

In accordance with the Schematics.

Today I assembled the skeleton of 6 towers, without clamps and sensor assembly (attachment 1).

Some of the side plates have this weird hole that doesn't fit any of the suspension blocks (attachment 2). I didn't notice when I counted the parts and now there are exactly enough side plates to assemble 7 towers.

Also found that one of the stiffener plates has a broken threading.

We will need more parts to go beyond the necessary 7 SOSs. I will do the recounting later.

Things to do next:

1. Find the capped spring plungers and send them to C&B.

2. Assemble the clamps onto the suspension blocks.

3. Push some Viton tips into the vented screws we got to make safety stops.

4. more C&B: Magnets, dumbells, dowel pins, OSEMs.

5. Push clean dowel pins into the last suspension block.

6. Assemble 7th Tower.

7. Assemble safety stops and clamps.

8. Glue magnets to dumbells.

Today, I screwed the plungers on the sensor plates and installed them on the Towers. I also installed the wire clamps on the suspension blocks (attachment).

I ran into problems in 2 separate suspension blocks: one had a dowel pin that was slightly too fat for the wire clamp. In another, the tapped holes were too short so that the 4-40 screws couldn't be screwed all the way.

I found a "vice" in the cleanroom (attachment 1). I used it to push dowel pins into the last suspension block using some alcohol as a lubricant.

I then assembled the 7th and last suspension tower (attachment 2).

Things that need to be done:

1. Push Viton tips into vented screws and assemble the earthquake stops.

2. Glue magnets to dumbells.

I tried to push the clean Viton tips into the vented screws just to find out that the vented holes are too small. We need to drill 0.1" diameter holes about 0.1" deep into these screws and clean them again.

Can you just cut the viton tips smaller? If you cut it to have some wedge (or say, taper), it can get stuck with the vent hole.

Today I glued some magnets to dumbells.

First, I took 6 magnets (the maximum I can glue in one go) and divided them into 3 north and 3 south. Each triplet on a different razor (attachment 1).

I put the gluing fixture I found on top of these magnets so that each of the magnets sits in a hole in the fixture. I close the fixture but not all the way so that the dumbells get in easily (attachment 2).

I prepared EP-30 glue according to this dcc. I tested the mixture by putting some of it in the small toaster oven in the cleanroom for 15min at 200 degrees F.

The first two batches came out sticky and soft. I discarded the glue cartridge and opened a new one. The oven test results with the new cartridge were much better: smooth and hard surface. I picked up some glue with a needle and applied it to the surface of 6 dumbells I prepared in advance. I dropped the dumbells with the glue facing down into the magnet holes in the fixtures (attachment 3). I tightened the fixture and put some weight on it. I let it cure over the weekend.

I also pushed cut Viton tips that Jordan cleaned into the vented screws. While screwing small EQ stops into the lower clamps I found some problems. 4 of the lower clamps need rethreading. This is quite urgent because without those 4 clamps we don't have enough SOS towers. Moreover, I found that the screws that we bought from UC components to hold the lower clamps on the SOS towers were silver plated. This is a mistake in the SOS schematics (part 23) - they should be SS.

Then, can we replace the four small EQ stops at the bottom (barrel surface) with two 1/4-20 EQ stops? This will require drilling the bottom EQ stop holders (two per SOS).

According to the schematics, the distance between the original EQ tap holes is 0.5". Given that the original tap holes' diameter is 0.13" there is enough room for a 1/4" drill.