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Message ID: 2530     Entry time: Fri Jan 29 10:14:16 2021
Author: Stephen 
Type: DailyProgress 
Category: Cryo vacuum chamber 
Subject: Restarting Cryo vacuum chamber effort 

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.

Attachment 1: CryoLabImages_QILelog2530.zip  62.317 MB
Attachment 2: IMG_8019.JPG  3.578 MB  | Hide | Hide all
Attachment 3: IMG_8024.JPG  2.392 MB  | Hide | Hide all
Attachment 4: IMG_8020.JPG  2.593 MB  | Hide | Hide all
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