I finished analyzing the results of the five optically contacted samples that I have tested:

1.0972  0.3503 (W/m*K) : High temp, 3kg weight sample

0.5365  0.0928(W/m*K)  : Low temp, 1kg weight sample

0.1344  0.0233 (W/m*K) : only heated sample

0.1275  0.0211 (W/m*K) : only weighted sample

0.0970  0.0132 (W/m*K) : null sample

These results refelect what we expect (highly weighted and heated sample has the best thermal conductivity and the null sample has the worst). To analyze the data, I fit an exponential to the data outputted by each temperature sensor and exptrapolated to find the 'final' temperature of each sensor. I used this temperature difference to calculate the conductivity (k_sample = (Q_SteadyState * thickness) / (Area_sample * TempDifference)). I also accounted for the heat power lost to the stainless steal weight on top of the assembly (about 0.017 W) as well as the small amount of heat radiated from the top sensor plate to the bottom sensor plate (about 0.0015 W).

I am currently re-running thermal conductivity tests on the copper / silicon interface at LN temperature. The first run of tests gave results that were opposite of what I expceted, and so I want to improve the setup and see if I get the same results. I attached a thermal strap from the cold plate to the working plate so that the assembly would cool down faster and farther (figure 1). I also cleaned the copper samples with a mixture of water, vinegar and salt to eliminate any oxidation on the copper. There was a visible difference in the cleanliness of the copper samples. Figure 2 (dirty copper) order: brush, polish, mirror finsih. Figure 3 (clean copper) order: mirror, brush, polish finish. 

shit happens:

1. It's reading funny numbers but if i reset the device and turn the source off, then on in reverse direction and then to AC excitation everything is working fine.
   
   
   
2. If you hard-reset the device it's showing funny numbers after it comes back
   
   
    
3.  I actually could break the device by killing the epics IOC while reading from the device . Device kept bitching and resetting itself . Opened it and removed the backup battery and used the reset jumber on the mainboard. Device is working again now. Have contacted SRS to see what we can do to fix some of the problems (there are many more)
   
   

I made a list of the balls currently in the air, which I will parse into an action plan with near term milestones after more calories are ingested.

The list:

Dewar (NOW AND SOON)

• Get shell back from Mike G
• Measure gaps in "normal orientation"
• Get 1" 10-32 screws?
• Clean screws
• Check on viton cord
• Get fatter indium wire (1/16")?
• CHECK THAT ALL SCREWS CAN GO IN SIMULTANEOUSLY
• MAKE THE INDIUM SEAL FOR BAKING - CHECK PRESSURE -> consider leak checking if can't hold pressure
• Figure out long term dewar lifting scheme - rope gets in way of stuff
• Check outgasing rates (pressure vs time when we close the valve)
• Get a quick run through on the backing heater setup in the PSL lab from Frank
• Wrap the Dewar and heat it
• Bake dewar for a while at 80C (days)
• Check outgasing rates

Dewar Guts

• Compare gap in 0 degree and 90 degree orientation
• Choose orientation based on acceptable stress to weld joints from clamping
• Come up with some internal wiring routing scheme based on orientation (possibly redoing Frank's 90 degree scheme)
• Check room temp position of dummy cavity w.r.t
• Get a dummy cavity with real dimensions (1.9" x 3.9"?)
• Progress on fixing the cavity support?
• Making cabling for dewar guts

Cavity

• Characterize mirrors before contacting?
• Clean mirrors?
• Silicon wafer / glue dunk testing
• Glue mirrors to cavity
• Send windows to coastline for annulus polishing

Temperature Sensing and Control



Electronics

• Low noise current driver
• Finish characterizing low noise current driver
• Get v2 of current driver in progress
• PDHv2 - guess feedback shape and stuff/test accordingly
• Photodiodes
• Make MOD plan for PDs
• Oscillator - CHOOSE LOW NOISE OSC FOR SIDEBANDS

Tabletop setups

• Sidebands on PLANEX with current mod
• PLANEX locked to room temp in air cavity with current modulation
• PLANEX transfer functions finished (most of data exists - need to write up)
• Finish finding best 1550 viewer (least bad one)
• Planex freq noise compared to in - air cavity
• Planex locked to suspended Si cavity @ room temp

While checking the firmware version i've found proof for my feeling that we must have gotten one of the first models of the cryo temp controller.  But i didn't expect #0
The individual modules are the same as in the room  temperature multiple channel temp controller they sell (PTC10)

a

TIME:

• Wall Clock: 2:31:30 PM Tue Jan 31
• Dataviewer: 12/1/31/22/32/12      // GPS: 1012084345

ACETONE SPRAY TESTING:: done

(an unknown time) after the acetone test, I valved off the exp chamber, so we can look back and get a leak rate if we want to later.

gave Tara the OK to take the valves from the optics table as he couldn't find any spares somewhere else (incl. 40m) . We don't need to float the table very soon and it is easier to replace those old legs with newer ones compared to the PSL lab. They don't make 13in legs anymore, the shortest ones are 16in, which makes it a lot more difficult to replace the legs in the PSL because of all the framing around which we would have to modify. We probably have to do so anyway but for now taking off the valves is the fasted way to get new results. However changing the legs for the cryo table to 16in height would not be a problem at all.

 Where are the undergrads?

< crickets >

When I went to move one of the lasers to the PSL lab bench from teh cryo lab, and noticed an error on one of the temperature controllers.

The current switch had been hit to "on" by someone working around the rack at some point. I do not know how long it was like this. I promptly turned them off, and am now going to test to make sure both lasers still lase. In retrospect, I probably should have checked to see if a beam was coming out first.

The diode which was set to "on" was 102068

I turned them on, let them warm up for 15 minutes, and measured the output power.

Testing (compare with elog:338)

Diode 102068

• R_therm = 9.002 k
• I_set = 105 mA
• P_meas = 12.98 mW

Diode 102085

• R_therm = 8.106 k
• I_set = 135 mA
• P_meas = 9.96 mW
  
  • Old recorded value at these parameters is P_old ~ 13mW

The above is not good. It should be higher.

Investigating further in the next elog.

Measured the hysteresis curves for the diodes as a function of temperature. This will be my basic benchmark for monitoring state change for now.

Manual data entry, so the rest of the plots following tomorrow.

I will also turn R_thermistor into temperature.

To get on fb, you now need to go through the cymac. You can also get to gaston.

For fb:

ssh -X controls@cymac1.caltech.edu
ssh -X controls@10.0.5.10

for gaston:

ssh -X controls@cymac1.caltech.edu
ssh -X controls@10.0.5.21

I made a cable to get the 2nd gold PD (which Rana so benevolently fixed for us) up and running;

Both cavities are now locked with the Gold PDs!

We made some progress on the temperature actuation front as well - We put a mirror by the input beam and bounced a 40 mW  405 nm laser off its edge to see if we could heat the cavity.

We also re-arranged the furniture when we were putting the lab back together, and moved the CyMac where the blue cryo parts cabinet used to be.

I got the beat realigned (we took it apart when trying to find a place to inject the heating beam), and the DFD signal back into the cymac

I turned the laser pointer on and off, there was a BOOMING SUPER FAST RESPONSE in the cavity cavity beat. The time constant at room temperature seems to be ~5 seconds (eyeballed in StripTool from the rate at which the beat signal asymptotes after giving it a heat pulse)

GOOD NEWS! We have a "way too much power" problem. This is much better than the opposite problem, and very promising for the prospect of using 

Next up:

We use the sweet sub Hz chopper that Steve brought in, and find out how small of a signal we can put in yet still extract via the spectrum (I guess we will want SNR(P_in), and for the final version SNR(P_in,T))

This is a shitty effect that Nic has found and mentioned before. The output stage of the PDH2 is a fancy-pants thing that was copied from the Rich uPDH design, and then we thought it would be fine to add the DAC_EXC injection without having any problems. We were wrong, in general, because adding a path to ground from this point through a resistance comparable to or smaller than the others in the stage's network changes the gain in the non-inverting configuration. This can be fixed by making R26 >> R24,R25 at the expense of lower excitation range.

There also appears to be a parasitic high-frequency path when the port is left open, which leads to a bump in the TF at 10 MHz, regardless of the INV setting. Therefore, it also creates a notch when out of phase with the main path. We don't know exactly how this happens, but clearly it's affected by what is connected to the DAC EXC input, so we terminate it.

Note that the former effect is what caused the oscillation when you plugged in the 50 ohm terminator (by changing the gain), while the latter is what caused it when you plugged in an open cable (by opening the parasitic path or by affecting the notch via the capacitance).

So, I would replace R26 with something bigger than 2.2k and terminate DAC_EXC when not in use.

I brought the cyrostat up to room temperature today to do some work inside, and there appears to have been a minor disaster.

The 100-Ohm heater was was glued to the large steel clamping block with (I'm assuming) conductive epoxy, and it appears as though there was enough heat to dissociate it at some point during the latest run.

When I opened the cryostat, there was a strong noxious smell, which was my first indication that anything had gone wrong. Upon opening the top of the can, I found that the power resistor was now attached to it and not the block (the whole thing hangs upside down, so the resistor fell of, then grabbed onto the lid as it cooled).

It's unclear when this happened. I had been running the cantilever at constant amplitude over varying temperature over the last 2-3 days and there was no significan event to indicate the time when the resistor must have fallen. My best guess was that it happened as I provided a steady power of ~10 W to it this morning to speed up the heat-up. The RTD, located on an adjacent side of the block some ~3 cm away, never registered above room temperature, and that was at the very end before I vented the chamber.

Thankfully, this stuff dissolves readily in isopropanol. I've been going through the entire system, starting with the Taiwan cantilever itself, and cleaning everything. There is a very slight (and typically invisible) residue apparent on most parts of the chamber, so I'm getting that all off.

The power resistor on the smaller (radial) clamp is screwed on, which I think is a better solution in light of this.

I powered up the Marconi that's been sitting at the bottom of my rack tonight and it did NOT like being awakened from its hibernation (see attached video).

The screen flickers and some internal clicking can be heard. What to do?

That's not good... The one on the cart next to Gaston is not used by anyone else, so you can use that for the time being. I have another one in the rack, that covers our needs for now, but we better get it fixed.

Jordan ran into some weird problems with the Keithley 2450 sourcemeter he's been using this morning. He posted some questions to the Tektronics forums this morning, and I just added my own notes. It appears the problem is a 41V offset in the box's measured voltage. Full details below:

https://forum.tek.com/viewtopic.php?f=263&t=139935&p=283529#p283529

One more update I didn't mention, 41V is very close to the maximum voltage imposed by the interlock setting (that would be 40V)--that is the setting that keeps the voltage from entering the widest range available by the 2450, 200V. Changing the state of interlock does not seem to change this offset, but it seems an odd coincidence that somewhere in this box is a voltage limiter at about 40V and we have an about 40V offset in our measured voltage. Maybe related? Unfortunately the pop makes me suspect a hardware problem... I suppose the next step would be to contact Tektronics to see if they can fix our box or if it's something we can swap out. Maybe we'll have some action on the forums, but I'm not hopeful.

The IFR 2023A by the entrance to the lab does not power up properly. With power switched on, the screen flickers between blank and off, and there is a popping or clicking sound at the same frequency. The fan also starts in bursts at this frequency until it is nudged from its initial position, so it is receiving some chopped power.

I opened up the box and tried to get my bearings with the service manual, which can be found here:

http://www.download-service-manuals.com/en/manual.php?file=Aeroflex-8780.pdf

Since the unit does not power up properly, I'm following mostly the section 'initial repair'.

1. The 2A fuse for the AC line is intact.

2. The DC outputs initially seemed to be all over the place, but I noticed they were actually being chopped at the frequency of the popping sound. I suspected there was some capacitor discharging somewhere on one of the boards, so I disconnected the connector from the power supply unit to the rest of the boards (so now the AC line just goes to the power supply's board, and the DC outputs don't go anywhere). Sure enough, the popping stopped, so the discharge is probably not on the power supply unit. However, pin V2, which should output +12V, is only giving +10V. Perhaps this is not enough voltage for whatever is expecting 12V, so I'll check out where that pin leads.

3. The relevant description of how the power is handled is on page 1-38 of the service manual.

to be continued

I think Zach already did the similar analysis (no elog?). Don't bother yourself for fixing. Give it to Steve and ask him to contact the manufacturer.

The problem is on the RF board. When it is unplugged, the clicking goes away and the control menu displays properly.

I found the relay that was clicking on the RF board and attempted to do some troubleshooting in that area with no luck. I put the unit back together the way I found it.

I planned to bring it to Steve to have it sent off---hence no elog---but I hadn't gotten around to it yet.

Gaston was unresponsive when I came to the lab today and I had to reboot it. It booted just fine, without any alarming notifications.

Needed to restart the front end because the excitation channel was not being driven. This was the same problem Aaron had a couple weeks ago. We followed all the commands that Chris outlined in elog 1793. Drive signal now works again.

Note : In the X1IOP_GDS_TP screen there are two things indicated in red that may need some attention

• Sync Source says 'NO SYNC"
• IRIG-B = 0

We have 7 SR560 in the cryo lab, and none of them have working batteries. I was using 4 for the ISS, there was one under the SR785, and two more in Zach's rack.

Andrew offered to take some over to the 40m to have the batteries replaced, which will take about a week, so
I handed 5 of our 7 SR560s to him, keeping two in the lab just in case.

They can be repaired later. One of the units I gave to Andrew also has a loose BNC output port. which will get fixed.

I installed Anaconda2 on Gaston and had to log out and back in to confirm that some manual configurations I made work as intended. I checked all the workspaces and made sure there was no unsaved work before I did so.

The upside is that we can now run jupyter notebooks no Gaston

Some of these units have now been returned.

They are stacked up in the EE workshop. The ones from the Cryo lab are labeled as such.

The remainder of the units (including the one with loose BNC) are still out being serviced by SRS or steve.

Borrowed the N2 ion gun rig.  Moved to the QIL lab for some optics cleaning.

The EEshop SR785 had no network access.  I've bought an iocgear ethernet-to-wifi adaptor and connected it to the cry-fi network as it is the closest to EEshop.  

In case you guys have an IP allocation protocol for your lab I've added the ethernet adaptor to 10.0.5.5 (close to other routers' IPs) and the prologix GPIB-to-ethernet adaptor to 10.0.5.224 (to be close to the other prologix devices in the lab).  

The devices are attached to the 'crackle lab' SR785 located in the EEshop with device IPs and credentials printed on the unit itself.  Its tested and working on your network; feel free to wheel it into your lab and use it too.

I don't think there is a protocol, and no allocation table or the likes. Most IP addresses are just set in the devices themselves. The router can use the address space above 200 for dynamic allocation, that's about it.

Not sure if this is related, but I couldn't switch on/off any of the filter modules for x1cry. Cymac crashed when I tried to unload/reload models and I had to hard reset it.

This just in: latest polls have shown that two out of three CryoLab Marconi's have power-up issues with flickering displays and clicking noises on startup. I will turn both over to Steve to get them fixed.

The Marconi that was sitting just above the Rubidium clock is showing the same symptoms the other one had.

As a part of the ongoing War On Noise™, I've borrowed Marconi 2023A (SN 202304/136) from the cryo thermal noise setup to PSL lab.

There might have been a short interuption to power to the thermal senor that was powered from the SR560 sitting on top.  Marconi was not plugged into anything so assumed it was good to take.

Adding to list of things PSL has taken:

1) HP4395A Spectrum/Impedance/Network Analyzer  (tagged C30602)

2) SRS FS725 Rubidium Frequency Standard

I have a directory on Gaston: /home/controls/duo/. It has my script to download data. Now the directory disappeared. I was wondering, maybe, does Gaston restore the machine somehow when it restarts? Or someone deleted the directory by accident?

I found duo/ it in the /users/ directory.

They are in QIL.

I disconnected the SS-8BS leak valve from the shutoff valve so I could bake it, but found an unpleasant surprise. The photos probably tell it best. The labelled parts in attachment 1 are:

There was a glass sleeve of some kind inside the valve, shattered; I can't find mention of it on the elog, but maybe I don't know what it was used for in the past?

The +18V Sorensen power supply in the cryocav rack was not working, which means all the CDS electronics were not powered properly. I'm not sure how long this was going on. The symptom was that the Sorensen front panel read 0 volts, and its remote operation LED was lit.

The fix: Sorensens have a connector in the back with jumpers that programs remote/local operation. After reseating that connector, the supply came back to life.

Not sure how, but none of the drawers of the blue optomechanics cabinet are opening. I don't have a key. Here's what happened

1. I closed one drawer ("A") and opened the drawer below it ("B")
2. Closed B
3. Opened A and B simultaneously; I could not open only B, only A and B together. Close A and B.
4. Open both A and B. Close only A.
5. Close B
6. None of the drawers now open, even A and B together. seems locked

Found someone who's had this problem before, might give it a try...

[update]

This worked, I used the metal meter stick to unlock the drawer.

[Stephen's updates]

--> note that link formatting breaks link for me, so here it is - https://www.practicalmachinist.com/vb/general/help-my-lista-locked-me-out-how-do-i-open-201606/

--> wrote up a similar experience with additional detail ENG_Labs/260

enter Wed Mar 17 12:55:44 2021

Grabbed the Marconi from cryo lab.

I left some of the current noise data on the moku ipad, so I transfer that over to spirou to plot the current noise.

Thought about filters for a while. Stuffed an RC low pass in a pomona box, but realized an LC would be better for the job.

exit Wed Mar 17 17:13:55 2021

I went digging for what TEC settings Johannes had been using for those lasers, and what x1cry channels I might use to measure their PV curve to get a current noise.

Strangely, I can't find the x1cry medm master files. I recently copied over these files into the x1oma medm directory, then made some modifications (rm'ed some files unnecessary for x1oma). I'm seeing those modifications reflected in the medm/x1cry/master directory, as well as medm/x1oma/master. Here's my bash history

I might not have actually lost data, since it looks like x1cry/master contained the actual master crymaster.adl, plus several backups. However, any changes I make in x1cry/master (eg, renaming the file) are reflected not only in x1oma/master, but also in the backups in medm/archives/x1cry_*/master. The files I'm working on are not linked, and the archives certainly shouldn't be affected by updates to the main files, so I don't know why this should happen.

Ah, I didn't realize x1cry/master was linked to some other directory. Now x1oma/master is linked to its own directory.

We got a new HEPA FFU yesterday. I wanted to see if the particle count has dropped as a result, but the minute and longer trends are not available... apparently no trends have been logged for about three weeks. I see from systemctl that the rts-edc (realtime system EPICS data concentrator) loaded but failed to run. Restarting that service eventually restored the frames. We should get an email when this happens.

I broke the cantilever while fastening the fork clamp. Afterwards, I used methanol to remove the varnish and separate the mirror from the cantilever shard. I then used a cotton-tipped swab soaked in methanol to clean the varnish from the sides of the mirror. I drag wiped the HR and AR surfaces of the mirror with methanol followed by isopropyl alcohol. Finally, I bonding the mirror to a different cantilever (this one with somewhat more pitting than the previous) -- again bonding with cryo varnish at four points on the sides of the mirror, but on recommendation from Chris this time with the mirror AR surface touching the cantilever.

Backups were restarted for the cryo lab computers gaston, spirou, and cominaux. A 4TB USB drive was connected to cominaux, mounted under /backup, and rsnapshot was configured to run on a nightly basis. It does not back up the full disk, but only those directories where user-generated files are kept (/home, /etc, /usr/local, /opt, /ligo). rsnapshot's configuration files are: /etc/rsnapshot.conf and /etc/cron.d/rsnapshot.

For the cymac, configuration and minute trend files are backed up by rsnapshot to a 1TB disk, mounted as /backup on cymac1.

For thermal design, we need to know specific heats of materials.   I looked up the basics in the cryogenics book by Guy White, 3rd edition.  You need to do some simple calculation to get the needed numbers for the entire temperature range.   I did this for the three dominate materials in the cryostat: copper, aluminum, and silicon, and plot the results below.   The programs that do it are attached.   

a few links to documents containing data about thermal expansion coefficients at low temperatures and other stuff. A copy of the pdf's is in the doc folder on the svn.

http://digicoll.manoa.hawaii.edu/techreports/PDF/NBS29.pdf

http://www.bnl.gov/magnets/Staff/gupta/cryogenic-data-handbook/Section11.pdf

http://reference.lowtemp.org/alkappa.html

from "PRE-AMPLIFIER IMPEDANCE MATCHING FOR CRYOGENIC BPMs" (http://adweb.desy.de/mpy/DIPAC2011/posters/tupd20_poster.pdf)

We have recently realized that we have not yet calculated the thermoelastic noise of the reference cavity spacer.

Naively, we can assume that this would be zero since we would operate at a zero CTE temperature. However, we will likely have some constant offset or fluctuating RMS offset from the true zero point. As a guess, we may assume this to be 1-5 mK.

Some relevant papers:

1. "Thermal Noise in Mechanical Experiments", P. Saulson, PRD (1990)
2. "Thermorefractive noise of finite-sized cylindrical test masses", Nawrodt, Vyatchanin, PRD (2011)
3. "FD Theorem for Thermo-Refractive noise", Y. Levin, PLA (2008)
4. "Thermodynamical Fluctuations and Photothermal noise", Braginsky, Gorodetsky, Vyatchanin, PLA (1999)

I modified the Comsol model CryoLab/comsol/cryo_cavity_sagging/cryo_cavity_sagging.mph (previously used to compute vertical acceleration coupling; see elog:843 et seq.) to compute the eigenfrequencies of the silicon cavities assuming fixed four-point contact. Comsol gives the frequency of the first longitudinal mode as f = 35 kHz [shown in the first attachment]. There are a number of lower-frequency modes (from 4 kHz to 8 kHz) in which the cavity rocks and rolls on its supports, but does not really change length. At 22 kHz there is a vertical bending mode [second attachment], and at 23 kHz there is the analogous horizontal bending mode. We should perhaps analyze whether these modes will interfere with our study of the longitudinal mode.

We can compare the Comsol result with the theoretical prediction. Problem 1, section 25 of Theory of Elasticity by Landau and Lifschitz gives the lowest longitudinal vibrational frequency of a bar with one end fixed and one end free:

f = (E/ρ)^1/2/(4L).

For a monocrystalline silicon cavity cut with its axis along the [100] axis of the silicon, the longitudinal elastic modulus E is 130 GPa [see eqs. 7 and 8 of What is the Young's modulus of silicon? by M. Hopcroft]. The mass density ρ of silicon is 2330 kg/m³. The spacer length is 4 inches (=10.2 cm), but we must take L = 5.1 cm, since in our case the center of the spacer is fixed and both ends are free. This gives f = 37 kHz, in good agreement with the Comsol result.

Si Young's Modulus:

Warren provided a reference for the Young's mod of silicon with less words by the same author (link here), maybe it is easier to read? The take away point is that the Young's mod is significantly different along the different crystal axes. In terms of using a numerical formula such as the one from L&L, can we just use E[100], or would we need to take all the E into account because Poissons ratio is a thing and when the spacer stretches, it squishes too? 

We would like to have calculations / estimates for the body modes of the spacer at both 300K and 120K, which means we need material properties at 120K as well. I looked around for E[axis;Temp] and eventually gave up and paged Warren. The reference he produced was this paper about Si cantilever frequency temperature dependance. Looking at equation 2, we see the eigenfrequency of the first mode go as sqrt(E). Looking at Fig 2, we see f(300)/f(120) ~ 10765/10815 = 0.995 ~ sqrt(E[300]/E[120]), or E[300]/E[120] ~ 0.991. Changes to the eigenfrequency of the spacer due to changing Young's modulus at 120K can probably be ignored as a ~0.5% effect.

What seems reasonable: have COMSOL use the 300K elasticity matrix for Si at both 300K and 120K.

Si Density:

The density change due to Si contracting is fairly small. V(300K)/V(120K) = [L(300K)/L(120K)]^3 = [integral(120->300) of alpha(T) dT]^3. This is roughly the area under a triangle with base = 180K and height = 2.6e-6 K^1, or just 1/2*180*2.6e-6. V(300K)/V(120K) = 1.3e-11. Completely negligible 

Dimensions:

We should use 3.9" length and 1.9" diameter with a 1/2" bore hole for all cavity calculations (as those are the actual cavity dimensions).

If we are interested in the longitudinal strain u_xx, then this is related to the stress T_ij by the compliance tensor: u_xx = s_xxij T_ij. Ignoring gravity and the supports, a pressure applied to the mirror faces produces (to first approximation) a stress whose only nonzero component is T_xx. Then u_xx = s_xxxx T_xx, and we only need the component s_xxxx of the compliance tensor, which is 1/E_[100] assuming x lies along the [100] axis of the silicon. Nothing here requires the material to be isotropic.