So the mystery 3com router on a floating DHCP address was actually the one in the TCS lab. I've given it an IP now listed on the ATF wiki.
The 3com switch that was unaccounted for is actually the one in the PSL lab. I've tried all the IP addresses it should be and it is compleatly unresponsive. Local devices that have been configered with manual IPs are accessing the wider network fine but anything set find an IP via DHCP is failing to get an IP address. We can't chage any of the settings unless we know the IP of the router.
Jon is similtinously working on getting a gateway PC up and running, but the only change there is that the main 10.0.1.1 router has been disconnected from the wall. I'll try running a deeper nmap scan over the PSL side of the network to find this 3com router.
Jon has been working on getting a gateway PC set up again so that we can ssh into the lab from outside the ATF network.
The old gateway computer has died. It looks like a dead power supply. The computer is an old Penguin tower box and is ~10 years old, its probably still good but is a lot of work to find a power supply on line to replace. Larry Wallace didn't have any power supplies so he gave me a low end dell computer and a spare Ethernet card/usb dongle to use instead.
Jon installed scientific linux and was trying to pass traffic through the computer from the outside world (from one Ethernet port to the other). From what I can gather he was able to get pings in and out to the internet but there was a problem with finding a way to configure DNS settings that would allow regular internet use resolving www requests. There isn't really enough support for these types of tasks for the Scientific Linux distribution, so instead we have install Debian and will try to configure that.
I'm now not sure that we want a computer firewall and all the configuration difficulty that entails. Its possible to configure the Linksys router to forward certain port requests at the outward facing IP address so that they get redirected to ports of particular IP addresses internal to the network. This can be found under the Applications & Gaming tab at the gateway router (10.0.1.1), under UPnP Forwarding ports requested from outside the network can be redirected machines inside the network. So, for example an outside ssh request to port 1234 can be redirected to port 4321 on machine ip 10.0.1.123. This is basically what we want, a single machine from which we can ssh to any of the lab computers for offsite maintenance and operation.
Applications & Gaming
So to access the ATF subbasement computers you need to know the labs outward facing IP address <IP>, port <port> and password to the gateway machine. Then simply run
ssh -Y controls@<IP> -p <port>
The -Y here is for window forwarding, you'll need xQuartz if you are on a mac.
If you can't see it you might need to ask someone in person to add you to the view list.
Jon's Edits to Andrew's Setup of the Linksys Router
Andrew is right that the Linksys router (10.0.1.1) can be configured to do everything we want from a gateway, namely providing password-protected ssh access into the LAN machines from the outside while blocking all other ports. I made some minor changes to Andrew's initial setup to balance security with ease of accessibility.
First, I made the Caltech-assigned IP address (22.214.171.124) discoverable on the ligo.caltech.edu network. This makes the gateway pingable, which is useful for determining whether the LAN is down. Note that this gateway is still only discoverable from inside the ligo.caltech.edu network, not from the outer Internet.
Second, I enabled the default port for SSH communications, port 22. I think this is fine security-wise because, again, the machine is only discoverable from within the ligo.caltech network and access is password-protected.
To connect to one of the LAN machines from another machine on the ligo.caltech.edu network with X11 graphics forwarding, you can add this script to your .bashrc file:
ssh -Xt controls@<IP> \
ssh -X email@example.com.XX
where 10.0.1.XX is the address of the machine on the local network. You'll be prompted twice for a password, first for the gateway and second for the inside machine.
To connect from outside the ligo.caltech.edu network, forward the connection through a network machine (e.g., I use my office desktop) by adding the line:
ssh -Xt USERNAME@MACHINE.ligo.caltech.edu \
I wanted another Debian computer around the lab to install LIGO tools on. ws1 was running Ubuntu 14 which is ok but less supported for all these LIGO CDS tools. Given that nobody uses this computer and there appears to be nothing on it I used this as a new Debian 8 box.
Same IP address 10.0.1.21 and same user name. As a bonus it now has an os that is more up to date.
The TCS lab did not get Internet back after the the ATF lab pipe work was done. I traced the problem back to the fiber connecting the TCS switch to the main switch in the ATF lab next door. It was plugged into the wrong slot. If anyone has network problems in other labs, check the fibers in the main switch because many of them are unlabelled.
Its now possible to install DTT (aka diaggui) ont your personal laptop using macports. This would allow you to access data from the LIGO sites, the 40m NDS, as well as the W. Bridge sub-basement labs (once Jon and I set up a way to move the data to the CIT cluster and NDS it).
as usual with MacPorts, YMMV, but this way works for me on more than one machine:
sudo port install gds
Error: Failed to archivefetch gds: root5 must be installed with +python27.
sudo port uninstall root5
sudo port install root5 +cocoa+gcc6+graphviz+gsl+http+minuit2+opengl+roofit+soversion+ssl+tmva+xml+python27
This works on my old laptop (El Capitan), but so far not on Sierra.
After that you can run diaggui to open up your old .xml files, look back at old data, etc.
Somehow I lost access to the 3com switch in the PSL lab. The default config IP was lost and from there we have been unable to edit its settings.
The 3com model 2920-SFP switches don't have a reset button. They can only be reset from the serial port. Larry Wallace lent me a USB serial to RJ45 cable but I have been unable to obtain a connection through a terminal PuTTY session until now.
The instructions for resetting the router can be found HERE
I found that serial connections through MacOs terminal 'screen' utility just returned random characters. It turns out that the problems with the USB serial connection were the baud rate. In this case it must be set to 38400.
To launch a serial USB session with a converter device. Run
> ls /dev/*usb*
then plug in the USB converter device (USB to serial DB9 + DB9 to RJ45) and run the above command again to see what appears when the device is initialized. You should see something like /dev/cu.usbserial-xyz appear, where cu.usbserial-xyz is serial converter you want to connect to.
Then launch screen with
> screen -L /dev/cu.usbserial-A4007BdM 38400 -L
Power cycle the 3com router and it should return a bunch of sensible startup dialog like
* 3COM 2920-SFP Plus BOOTROM, Version 113 *
Creation Date : Jun 1 2009
CPU L1 Cache : 32KB
CPU Clock Speed : 333MHz
Memory Size : 128MB
Flash Size : 128MB
CPLD Version : 002
PCB Version : Ver.B
Mac Address : 002473850035
Press Ctrl-B to enter Extended Boot menu...0
* 3COM 2920-SFP Plus BOOTROM, Version 113 *
Creation Date : Jun 1 2009
CPU L1 Cache : 32KB
CPU Clock Speed : 333MHz
Memory Size : 128MB
Flash Size : 128MB
CPLD Version : 002
PCB Version : Ver.B
Mac Address : 002473850035
Press Ctrl-B to enter Extended Boot menu...0
As instructed hit Control-b (Not command-b) then follow the instructions in the LINK above. Note that where they say "<blank>" for password they actually mean enter nothing.
From there you can configure IP addresses etc from command line. However, it is probably just easier to let the top level router DHCP allocate an IP address and then do it directly from the browser.
YOU MUST SET A NEW ADMIN PASSWORD
The old LinkSys router has been hanging every 48 hours or so. Also it is fairly slow. I've purchased a tp-link TL-R600VPN router to replace it.
I put the details of the configuration on the wiki atf Computing Network page. And posted the admin username and password physically on the unit.
Its important not to open up remote access to configuration settings for now (see security disclosure 2018/05/VPNFilter). Once a firmware patch fixes this we should be able to configure the router to give VPN access to the lab. For now you can access the lab through the ussual ssh method on the ussual ports, see the wiki for details.
FYI, I have hard reset the router, changed the password and updated the firmware since yesterday.
This afternoon Chris and I installed the ADC and DAC cards in fb4.
We may want to start with a fresh install of Debian 9 and just reinstall the LIGO binaries.
I know there is some CTN slow channel data on the disk. Is it at all possible to boot so that can be recovered?
This afternoon Chris and I installed the ADC and DAC cards in fb4. We connected them to the timing card adapters (left external to the computer chassis for now).
We found fb4 to be running Debian 8 so first attempted to upgrade to 9, as that is the version supported by Jamie's cymac binaries. However, we encountered problems during the upgrade, apparently with gdm (the linux GUI). By switching to consol mode and killing gdm, were able to proceed to the point of updating all the packages. It completed successfully, but then the system failed to reboot, even in recovery mode. During boot, the advligo-rts kernel fails to start, and then boot hangs completely at the point the graphical interface is started.
This post will host plots and trends from this radiative cooling run (QIL/2704).
Preliminarily, it looks like the reconfiguration to remove a hardware mistake or two led to a healthier run. The comparison below clarifies the two runs:
Run ended with cryocooler shutdown at 12:27 pm (actual duration just under 92 hours). System will warm up with pumps on for the rest of the break, unless I am inspired to come in and run one of the next intended runs discussed in QIL/2704. I did not run any heat input test for this data set, as I am not planning to come in frequently enough to monitor the heating safely.
Attachment 1 compares QIL/2704 (solid) to QIL/2702 (dashed). As expected, the outer shield temperature from the latter run stays warm since the conductive short was resolved. Due to the reduction of the inner shield's thermal load, the inner shield is able to cool faster and plateau at a colder temperature. As Stephen pointed out, however, the test mass is not cooled as efficiently compared to when the outer shield was conductively cooled.
Attachment 2 is a current model diagram of the various components being considered, and their thermal couplings. Attachment 3 plots the fitted model (dashed) over the temperature data (solid). The fit parameters were the following emissivities: aluminum foil, rough aluminum, and aquadag. Notes from the fit:
1. With the conductive shorting of the outer shield resolved, the model (which considers only radiative cooling of the OS) is well fit to the OS temperature data.
2. The inner shield model is missing some key term(s) affecting its time constant and steady state temperature.
3. The above error propagates to the test mass model (I believe).
Given these caveats, the fit results are as follows: aquadag e = 0.92, Al foil e = 0.04, rough Al e = 0.19. These all initially seem reasonable, and I'm happy to see that the aquadag emissivity is higher than previously estimated.
1. Separate the cold plate from the inner shield, and model their conductive and radiative link. Also model the radiative link between the cold plate and the test mass.
2. Cover the test mass in foil (to best of our ability) to refine the radiative link between the test mass and inner shield. Doing so will mean both elements have the same emissivity, so there is only one unknown parameter.
The top (seen with several threaded holes along with 16 through holes) and bottom (only 2 threaded holes for lifting and 16 through holes) plate for the vacuum chamber has arrived and I have moved them into the QIL optical bench/table. Using some aluminum struts/bosch, I am making a simple 3’’ tall spacer on top of which the bottom plater will be resting. After wiping them with solvents, I will start assembling the chamber and the plates.
The viton O-ring shipped by Nor-Cal fits the chamber groove, given below is the correct specification for future reference. I am buying few more for spares.
2-473 Viton , ID 23.940'' OD 24.490'' Width 1/4''
Aaron and Rahul - The bottom plate of the chamber was upside down (Gabriele and I did it as we were trying out few things during assembly last week). Now, the bottom plate has been inverted (using crane and trolley) and is ready for the chamber to be brought in. I am giving the chamber and the plates a thorough wipe (speckles of dust easily visible) and the grooves for the O-ring also looks slightly dusty. Probably I should get clean plastic sheets to cover the vessel when the top lid is open.
The vacuum chamber has 12 flanges (four 4-5/8 and eight 2-3/4 flange size). For the pump down test I will attach the pumping station to the 4-5/8 flange and close down the other three flanges with blank flange. Similarly out of the eight smaller flanges (2-3/4 size) five will have Tees (for 2 gauges), up to air valve, two optical windows, cryo-feedthrough and the remaining with blank flanges (or else I can change them with other feedthroughs to test them out for vacuum leakage). Just for information - the pumping station is attached to a reducer which will house the rotary valve. Reducer is requred to match the flange size of the pumps (4-51/2 siz - CF63 size) and the vacuum chamber (4-5/8 size). The rotary valve will be attached to the hose which will then be attached to the flange of the vacuum chamber.
Cold plate and the radiation shields have arrived. I will perform a mock assembly of these fabricated parts to check if they are as per our drawings. Next, the outer radiation shields will be shipped for gold plating the outer surface. Rest of the fabricated parts will be cleaned (lots of grease and finger marks visible) and then baked.
The bottom plate and the vacuum chamber (collar) has been assembled – thanks to Aaron for helping me out. The O-ring holds in well in the dovetail groove and makes it really easy (without falling off) to assemble the two components together.
The cold plate and radiations shields (100K, 50K and bottom 100K shields) are at 40m for cleaning and baking. The outer shields will be cleaned and then sent for gold plating. The inner shield and cold plate be baked after cleaning.
The radiation shields and the cold plate have been cleaned twice at the bath at 40m. They are currently undergoing baking for 12 hours, will pick them up on Wed morning once finished.
The radiation shields and the cold plate have been cleaned (class B) and baked and can be used in vacuum. I brought them back to the lab and will ship the outer shields for Gold plating.
The cryo vacuum chamber was closed yesterday (Thursday) for the 1st pump down test. The figure below shows various components which was attached on to the CF flanges. Later I will post the results of the ongoing pump down test.
I switched on the pumping station this morning at 10 am and roughly after 6 hours of pumping the pressure in the vacuum chamber is 8.2*10^-6 Torr. The pressure is being monitored using two gauges (wide range gauge and Ion gauge). However due to some reason the gauge controller is unable to switch on the Ion gauge (there is an inbuilt safety in the controller to protect the low pressure gauge, so this could be one of the reason).
I will keep the pumps running overnight and through out the weekend to monitor the pressure.
With the help from Chub, we opened the vacuum chamber. The procedures are not complicated. Here are some notes, both about the opening procedures and some other things I learned from Chub.
1) Vent the chamber by opening the venting valve slightly. The venting process needs to be slow - we cover it with a wipe, as shown in the photo 1. We stop opening the valve when we hear the air wheezing.
2) The thing with a screen is a gauge, which gives the pressure inside, but it is not quite working - always showing atmosphere pressure. Chub left me a document on it; I should be able to get it working.
3) We removed the screws of the top chamber. Correct hex keys is necessary - I was going to use one that loosely fits but Chub said it is not good.
4) We lifted the cover of the chamber with the crane and put it besides the chamber. We should release the break of the crane first and then break it again when we land the weight.
5) The pump connection is not very good - leaking oil both into the chamber and onto the floor.
6) The surface under the chamber (shown in photo 2) cover can only be cleaned by dry wipe or alcohol.
Next I am going to set up the optics, electronics and whatever inside before we close it and pump it down.
We closed the chamber without installing the radiation shields or cold plate in order to test the vacuum pressure of the empty system. Upon turning on the backing pump there was a fine oil mist from exhaust port, so the pump was turned off and an oil trap/filter has been purchased.
It was estimated that 12 inch/pound of torque is required for each of the top plate bolts in order to compress the 75 Shore hardness Viton o-ring by 20% (recommended by O'Hanlon).
Today we unpacked the radiation shields and started to puzzle out how to assemble them. Attached are photos of the parts as we guessed they are intended to stack up. We didn't see how the outer shield would be supported and isolated from the cold plate, so we are contacting Rahul to clarify.
One detail not shown in these photos is the rather poor weld quality on the interior of the outer shield.
We installed the oil filter/trap on the roughing pump and began pulling a vacuum. This was delayed due to the turbo pump flashing an error message and shutting off automaticallly after failing to spin up within its preset ramp-up time (error message 1221(3)). Upon restarting the system there were no ramp up issues, likely due to the chamber already having pumped down to ~0.5 Torr at the time of restart. Fix: need to increase the turbo pump delay start time, currently at 0 (immediately spins up). After 30 minutes of pumping the pressure reached ~4e-5 Torr in the chamber. (It reached 7e-6 torr after 3 days of pumping.)
We also tested an alternate internal configuration with the unwrapped components (see attached doodle, unlabelled green disc is the cold plate). This has the advantage of thermally isolating the outer radiation shield from the cold plate, but, we found, would slightly misalign the optical input ports.
Several ant traps were placed around the lab to combat the observed ant problem.
we'll suffer if we use a oil based pump long term - please find and order a dry pump to back this turbo. Not only is it bad for the vac chamber, its bad for other optics in the lab,
A historical note - electricians from Facilities visited the lab several weeks ago and installed new electrical service. To do this with a minimum of disruption to the lab, they de-installed some electrical outlets along the south wall and reused the conductors. They also taped up plastic sheeting to the table enclosure to protect the squeezing and laser stabilization experiments.
Ever since the initial pumpdown the pressure in the new cryo chamber has been stuck at ~6e-6 torr, so there's probably a small leak.
Our vacuum gauge controller has a serial communications port, which we can use to log the system pressure to aid in leak hunting. It's connected now to an unused port on fb4. A small python-based epics server queries the pressure gauges and makes the data available as two epics channels, C4:VAC-CRYO_PRES_P1 (wide range gauge) and C4:VAC-CRYO_PRES_P2 (ion gauge). These are recorded by the framebuilder. The script is stored under ~controls/services on fb4 and should start automatically on reboot.
Attached is a drawing of the first phase (minimal vibration isolation) cryocooler attachment, where the main tank connects via the blue rimmed feedthrough. Boxed/circled components are those that will require custom fabrication:
Currently there are only two connections that require viton o-ring rather than conflat connections (cooler to piece 1, piece 3 to HV feedthrough).
Tightened all of the vacuum ports on the chamber so that the flange interfaces are all now metal-to-metal, ie full copper gasket compression. All of the ports required at least two star pattern passes before reaching this point, except for the bellows line to the turbo/backing pumps which was already at complete compression. Prior to tighening, the wide range gauge gave a pressure reading of 5.8x10-6 Torr and the ion-gauge showed 5.75x10-6 Torr. After tightening the wide range flange the reading dropped to 5.6x10-6 ; after tightening the ion-gauge flange the gauge reading dropped to 5.69x10-6.
For future reference: the 4.625" flanges use 5/16" torx bolts and 1/2" nuts, and the 2.75" flanges use a 1/4" torx bolt and 7/16" nuts.
I've attached a photo of some changes to the cryocooler-tank connection design. We can save money and space by removing the 45 degree 1.33" conflat ports from the custom CH104 to 6" conflat adapter and using zero length conflat reducers at the unused 4 way cross ports, ie replace the 4-way piece blanks with holes for the vacuum line and gauge. The primary goal for these changes is to shorten the path from the cooler's heat station to the tank so that we keep the long thermal strap for use inside the tank. Also, the height is reduced from 89 cm to 59 cm.
A slightly different cupper adapter is needed to accomodate the thick strap, but no adapter will be needed anymore between the heat station and the thermal strap (same diameter round mates(new holes will need to be drilled though)).
Last week I moved the upper portion of the crane to the new, bolted crane support stand. Chub removed the wheeled lower section from the lab shortly thereafter. I also re-threaded the nylon lifting strap to remove slack and level the lid a bit better during lifting and moved one of the side tables next to the crane so the lid can be safely lowered after being lifted off the tank (see first photo).
Opened the tank today to check internal dimensions. It is now closed (top bolts finger tight) but not under vacuum. The diaphragm pump was dispatched today, so will replace the dirty pump and pull vacuum again upon arrival.
Attached a photo of the baseplate for future drill pattern reference. Note there are three anomalous holes, this is where the PEEK support poles should go. It was discovered today that these holes are 1/4-20 tapped but the PEEK pillars are dirlled/threaded for a smaller bolt.
I've attached a rough cartoon of the cold plate height relative to the optical ports and the tank wall. The outer rad shield is not shown and is slightly misaligned, but it can be easily aligned with a ~1.5 mm shim (better for thermal isolation anyways).
Update of our available electrical feedthroughs:
2 x 19 pin round with corresponding internal connectors and external connectors
2 x 15 D sub
- re-tapped the PEEK support pieces to 1/4-20 to match the bottom of the tank, added them with vented socket set screws. These will need to be replaced with brass or aluminum to better match thermal contraction (steel screws likely to crack the PEEK upon cooling)
- Drilled holes (attached, highlighted in orange) in the pump station base in order to utilize the more robust shock absorbers that came with the oil pump.
- Noticed significant flaking of the nuts/bolts when removing the tank lid. Suggested using anit-seize compound on the tank lid bolts but Chris advised against anything lube-like on the system. Just a note to remember to check the integrity of the bolts going forward before tightening the lid to avoid bolt seizing.
[Aidan, Chris, Ray]
don't we also want to record the dark noise spectrum as a function of T and V_Bias ? I would guess that the dark noise doesn't always scale with dark current at low frequencies since its probably more like a random walk than shot noise.
Torque driver set for QIL setup bolted joints, with range 15 in*oz - 50 in*lb, p/n WIHA 5HYL9, is on order from Grainger, with anticipated delivery in the week of July 20th. Refer to PO S477925. *update* Tracking Number UPS 1Z19W9330321365493
Cryo connection copper parts PO S475316 will be finished early next week by the machine shop in Torrance, I'll bring them to campus or to Raymond's place (TBD).
Copper parts picked up July 23rd and brought to QIL, now only waiting on PO# S477874 and the pirani gauge from Koji's bulk JPL order
Picked up the prototype shield panels from Hamilton Metalcraft 7/22 and brought them to QIL. All of the parts are wrapped by part number and in a bin (see attached photo). There are 6 sets of shield panels, but 2 full sets were removed for coating vendors. One full set is as follows (20 parts total):
All component #'s are preceded by 'D2000298-'. 031, 032, and 033 are 03 panels but with hole variations, same goes for 131, 132, and 133 with respect to panel 13
Used the 19-pin MIL feedthrough to run 4 platinum RTD's and a 25 Ω 100 W resistive heater to the cold head. Attachment 1 is the wiring diagram for the feedthrough and the D-sub connector to the CTC-100 temperature sensor. Attachment 2 shows the three RTDs placed on the cold head. It also shows the thermal anchoring of all lead wires. Attachment 3 shows the RTD attached to the cooler below the cold head using cigarette paper and cryo varnish (stored in the flammables cabinet in QIL).
The Al block is a premade PT-RTD integrated mounting setup, which was placed on some indium sheet bits and clamped down with a screw and belleville washer. The other two cold head sensors are pressure fit to the cold head by a spring loaded mini dog clamps, and one of the two has some indium underneath the RTD to see if there is any value in doing so going forward with these mounting springs. The glued sensor was attached by painting a thin layer of cryo varnish on the cooler, adding a strip of cig paper, layer of varnish, press in sensor, another strip of paper, paint over all of it with a last thin layer of varnish that reaches beyond the bounds of the paper strips.
The diaphragm pump was turned on earlier this week after finally closing up this external adapter tank. Out of an overabundance of caution the tank and cryocooler are supported by the skycrane and a number of posts to prevent it walking off the foam resting pad once the cryocooler is switched on.
All temperature sensors agree with each other within 0.1 K at room temperature
Cryopump is up and running. Initial attempts to run the cooler were stymied by an open circuit in the cold head to compressor connection caused by one of the two accessory port fuses (right, circled in attachment 1). The compressor would run but the valve motor wouldn't start in the cooler itself. I extended the spring in the fuse housing (attachment 2) and it seems to have fixed the problem, as now the valve motor starts at the same time the compressor is turned on. Attachment 1 also shows the highly technical cord management procedure done to reduce the trip hazard caused by the compressor power plug.
User manual recommendations*:
*Manuals for both the compressor and the cryocooler are linked on the West Bridge wiki manuals page
2020 Sep 01, StephenA with remote assistance from RaymondR
Came into lab today, with two main goals:
1) Bring Downs equipment for vibration measurements of cryo cooler during next operation
--> DONE, see photo
2) Assemble shields, with two layer scheme using electropolished and mill finish panels.
--> issue: the electropolished shield set was only partially shipped out in Ticket 15101 - unfortunately there was a misinterpretation by Logistics personnel regarding which parts to ship, due to the formatting of the ticket page. I will coordinate shipment of the balance of the panels to the vendor Able Electropolishing for completion of PO S479514
StephenA, RaymondR remotely assisting (off payroll haha)
It seems that we won't likely receive the intended hand-off resources (especially of note is that Raymond can't seem to find the videos he made, wherein he guides through operations of the vacuum system and cryocooler). Raymond has been kind enough to support via Zoom as needed so that things can progress with some sort of guidance.
I'll stay on top of the lessons learned and dump these, along with photos and other resources in the log. I'll also make weekly visits with the intent of making continued progress.
1) What is the current state of the QIL Chamber?
- Raymond left the vacuum line shorting the "external volume" with the cross, cryocooler, etc. directly to the "main volume" because the losses between the "external volume" and the feedthrough entering the chamber were too large. The system was down in the e-5 torr range. Ref IMG_8019, with flex hose connecting bottom of 4-way cross to side of chamber.
- To implement this vacuum arrangement, there was a key component put aside on the table - IMG_8024 is a T which connects the roughing line to both the external volume and the main volume, using the flex line from IMG_8019 and the components pictured in IMG_8020.
- The copper feedthrough has all clamps attached, such that temperature measurements are being made on the adapter copper rod, which has a bolt pattern for thermal straps. Sensor names reflect current locations.
- We inspected everything (cryocooler connections, vacuum gauges, temperature logging), and pronounced it "ready to go" at the end of my work day.
2) What did I learn today?
- Cryocooler has only one setting, and temperature control must be engineered at the output using thermal contact, emissivity, etc.
- Formatting of USB is the main error that can befall the CTC100 datalogger. If the red dot in the upper right corner of the screen does not light up bright when it is tapped (this starts datalogging), then there is something wrong. Easy enough to test by removing the USB when the red dot is dim (datalogging paused) and checking whether there are log contents.
- Raymond's focus with the QIL chamber had been on answering the question, "can we cool down the cryocooler's connection (copper linkage which passes into the chamber) adequately?" He had never successfully obtained a cooldown that was below 150 K, and the primary limitation appeared to be related to high pressures in the "external volume".
3) What are we up to next?
- The next time I come in, I will be turning on the cryocooler and datalogging first thing, and I will hopefully have cooldown trends to share in the log.
- If those trends are > 150 K, I was advised that the next thing to do would be to bring the "external volume" out of the equation, and directly attach the cryocooler to the copper feedthrough linkage. This would be one way to demonstrate the least-lossy, best case scenario.
- If < 150 K, I am told that Karthik may be ready to move in for some measurements. If not, I would be interested in dropping in the suspended, shielded Silicon dummy (currently standing by) and seeing if we can measure a successful (< 150 K) cooldown on the Si mass.
4) Can we increase the height of the chamber?
I've shared lots of images related to the question of extending the height of the chamber. Here are my thoughts:
- Raw measurements - Ceiling = 0", Crane ~ -12", Crane hook ~ -16", Chamber Lid ~ -26", Chamber Base ~ -40", Table ~ -43".
--> Not much space above the surface of lid, currently about 10" of range for a possible extension.
--> Actual useable range is less, due to real world limitations such as the height of lifting straps, interference with the angled crane arm, etc.
- It would require a clever solution to increase the crane height (spacer at base? extended height model?) or lower the lid height wrt the crane (position on lower table? lower the table on its leveling feet?) to buy a few more inches.
- Current allowed object height ~8" (could be extended to about 10" with modified PEEK spacers at base); would we benefit greatly from having a ~16" allowed object height? Or do we need to get more height out of this update?
- I need to follow up with my request for quote of an extension of ~10" height.
[updated with reference to data set, cleaner plot, images of chamber configuration]
Data - cooldown 20210205 (CSV = raw, XLSX = Stephen's plots) in Box Folder [Voyager\MarinerBox\CryoEngineering\CSVlogs]
Description - 5.5 hour cooldown with data, which was then allowed to continue for a total of 96 hours (but data collection failed for the long stretch, except for a snapshot of the final state). The cold flange was below 100 K after 6 hours, and leveled off at about 80 K. The vacuum pressure was steady at 3 microTorr throughout, via a roughing line connecting the external and internal volumes (mitigated losses in external connection volume, with no areas dramatically cold to touch). The cold flange was radiating to room temperature surroundings, as the radiation shields were not installed. The cryocooler was turned on/off at the start/end of the data collection, and the in-vac heater was not powered on at all.
is the x-axis in units of seconds? I think if we are clever, we should be able to look at a couple of the thermal time constants and figure out where the heat leaks are.
Link to ligo.wbridge QIL Cryostat HowTo Playlist Cryostat on youtube - not super user-friendly as of yet, but populated with a couple of videos so far.
Link to ligo.wbridge QIL Cryostat Photo Album on google photos - not well curated, currently just a dump.
1. Viewport swap to nozzle that is not occluded by cryo shield = complete. All bolts on both Active Ion Gauge and Viewport have been torqued gradually (about a half turn at a time, around the clock dial) until the conflat seal was metal-to-metal. Periscope on damped optical rod was rotated to make room for replacement.
Before viewport swap - IMG_8487
After viewport swap - IMG_8502
2. Cryo RTD repair = complete. Two RTDs had been damaged during prior mounting efforts by me. I was able to repair the clamped RTD at the single damaged solder joint. I was able to repair the former Al-Block RTD by replacing the RTD element, and making a new direct attachment (not preloaded, not varnished to the aluminum block anymore)
Materials and set-up for solder repair - IMG_8491
Repaired Clamp-2 RTD - IMG_8494
Damaged Al-Block RTD - IMG_8492 (note short length between kapton strain relief and aluminum block was not ideal, one lead had already fractured and the second soon followed at the slightest touch)
Repaired, remounted Al-Block RTD - IMG_8495 (heater sandwiched underneath threaded adapter, clamp threaded into adapter, sandwiching RTD at top plane)
Remounted Clamp-2 RTD - IMG_8496 (RTD clamped at cold flange, strap is mounted)
Remaining Clamp-1 and Varnish RTDs are free - IMG_8497
Current readouts of CTC-100 controller, with repaired RTDs now behaving (note need to rename the Al-Block RTD) - IMG_8501
3. Next steps:
- Karthik to install clamps, align in-air relay, and confirm positition of radiation shield aperture.
- Remaining free RTDs to be mounted; current RTDs are mounted at Heater and Cold Flange, would be good to mount RTD at Work Piece/Clamp and at Outer Radiation Shield.
- Radiation shield lids to be installed (might be easiest to install Outer Radiation Shield RTD after installing lid)
- Mount lid, install bolts, pump down, turn on cryo cooler, the usual!