Replacing a Ta Shutter in a Glovebag
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Replacing a Ta Shutter in a Glovebag
Written by NTS from email 5/31/2016.
This is a serious procedure for which we must thoroughly plan and prepare.
This procedure was done for the In cell, and we will speak in terms of both the In shutter and a Ta Shutter.
Timeline
Timeline of Successful Ta shutter replacement action
Day 1: Prep for trimming new Ta shutter, and Trim new Ta shutter using tin snips and small, full cuts.
Day 2: Acetone and isopropanol sonication treatment on shutter blade (standing on blade in Treatment beakers), put shutter on Bravo trolley and pump down to UHV in LC (secure with Ta wire on pins), pump purge LC and RM, LC lamp bake on LC (only), BOS bake shutter bellows, review plan.
Day 3: Replace Ta shutter
Plan for Replacing Ta Shutter
Discuss how to replace a tantalum (Ta) shutter without taking off the SF.
Get a Ta shutter, trim it a bit so it will fit in through the In source port, clean it before install.
Trim shutter make sure it will fit into SF cell port; we have a spare SF panel somewhere to practice.
Trying this is desirable compared to pulling the SF, in both time and money. Likely in contamination risk as well.
Taking off the SF is a major maintenance that requires baking of the Growth chamber and would add a lot of time to this maintenance cycle.
Finish shutter-dangerous work on the port whose shutter we want to replace.
Installing a new shutter and then scraping more would be a risky, bad idea.
Normal cell maintenance is fine to do before or after, if the old/new shutter won't be an issue.
Procedure requires some special ultraclean tools and techniques.
Summary for Replacing Ta Shutter
The new shutter will have to be trimmed and cleaned before install.
We will assume the GC is vented and pumped as proper when needed.
Trim Shutter
Use tin snips to cut the Ta shutter to a size that will fit into the source port.
Trim an edge of the shutter with two slight yet complete cuts, to trim a bit at a time and round corners.
After each cut or two, check to see if it goes into the SF via a source port with some wiggling.
Repeat a few times, as needed.
Test repeatability, because we want this to work the first time.
Clean Shutter
Clean the shutter blade with a partial Treatment (Acetone and isopropanol sonication).
Put it on Bravo's trolley using Ta wires to attach it to two pins of the Trolley. Use ultraclean pliers to make a few small snug twists to hold the shutter in place.
Put the trolley into the LC and pump down, all the way to UHV, under 1e-7.
Vent LC
Remove trolley and undo Ta wire
Put the shutter in an ultraclean foil pocket, and place it in the front desiccator.
Clean LC, trolley, RM with pump-purge x3 and LC lamp bake (RM isolated)
NOTE FROM RCW 5/2022: ALSO RUN A SAFE LC BAKE ON THE SHUTTER/TROLLEY IN THE LC AND IF INSTALLING NEW BELLOWS, BAKE THOSE ON THE BOS
Remove the old shutter
Currently, the shutter rod is attached to the adjustable shutter bellows with a set screw, and attached to the current shutter.
Unbolt and slightly remove the bellows, and grab onto the shutter rod through the bellows port.
Undo the set screw on the SF side while holding the bellows and shutter, then remove the shutter rod from the bellows female end.
We can then extract the shutter out of the GC through the In port, passing off the shutter rod from one ultraclean long forceps to another.
Install the new shutter
Put the new trimmed shutter into the GC through the In cell port
Get the shutter rod in the GC then out of the bellows port, using two ultraclean long forceps.
Hold the shutter bellows next to its port at an angle, put a gasket onto the bellows
Simultaneously tilt up and insert the shutter rod into the bellows rod holder/female end.
Tighten the shutter rod set screw.
Raise the gasket with an ultraclean fingertip, contact the bellows to its port, and make sure the shutter is oriented correctly.
Put in top and bottom bolt loose fingertight.
Check alignment with viewports and slow manual actuation.
Do more minor adjustments, the shutter bellows flange is rotatable, which simplifies rotational adjustments.
When good, finger-tighten top and bottom bolts, and put in the rest fingertight, while watching the shutter constantly.
Wrench tighten down the bellows
Check alignment
Prep for Replacing Ta Shutter
Trim Shutter
Use tin snips to cut the Ta shutter to a size that will fit into the source port.
Use a spare SF to test this (cleaned System Foxtrot Source Flange from the shed).
Trim an edge of the shutter with two slight yet complete cuts, to trim a bit at a time and round corners.
After each cut or two, check to see if it goes into the SF via a source port with some wiggling.
Repeat a few times, as needed.
After a few attempts, the shutter can be maneuvered into the source port.
Test repeatability, because we want this to work the first time-- make another tiny cut or two to ensure this, if needed.
Overall, less than expected needs to be cutoff. Also, a bit of the shutter near the rod fixture was snipped off once.
Clean Shutter
Clean the shutter blade with a partial Treatment (solvents).
Acetone and isopropanol sonication.
Use Treatment beakers and bucket.
Standing up on its blade in the bucket
Use Ta wires to attach it to two pins of Bravo's trolley.
The shutter kind of naturally rests on two pins and must be wired into place
Using ultraclean pliers, like the Al crucible, make a few small twists to hold the shutter in place. Tighten the twists such that they choke up on the shutter rod and trolley pins, but not so tight that anything bends. Now the wires are snug enough to hold the shutter in place.
Twists must be good enough to secure the shutter while moving the trolley-- test them.
Put the trolley into the LC and pump down, all the way to UHV, under 1e-7. Pumping on it like this can quickly draw out any residual moisture from the solvent clean.
Vent LC
Remove trolley and undo Ta wire
Put the shutter in an ultraclean foil pocket, and place it in the front desiccator.
Clean LC, trolley, RM with pump-purge x3 and LC lamp bake
Return trolley to the LC.
Pump-purge the LC-RM three times to clear it out, because some moisture may have been sucked into the RM (used to vent the LC).
The RM is left at rough vacuum and isolated from the LC.
Turn the LC lamp eurotherm to auto for running the LC lamp bake recipe.
Run the LC lamp bake.
Procedure for Replacing Ta Shutter
The new shutter will have to be trimmed and cleaned before install.
Complete any pocket scraping before installing a new shutter.
We will assume the GC is vented and pumped as proper when needed.
Glovebag SF - P1, P2, P3, Gas
Parts and Tools: new 3" adjustable Ta shutter (custom trimmed to fit into source port), new 3" adjustable shutter bellows (if replacing), ultraclean nitrile gloves, ultraclean long forceps x2, ultraclean allen keys, transit case for cell.
Remove the old shutter
Currently, the shutter rod is attached to the adjustable shutter bellows with a set screw, and attached to the current shutter.
Remove the In cell and transit case it, or remove blank if In cell is already off.
Foil In port, you can remove foil and replace as needed
Unbolt and slightly remove the bellows, have P2 hold bellows
Grab onto the shutter rod through the bellows port (P1) using an ultraclean (UC) tool (UC long forceps recommended if shutter must come out of In port)
Undo the shutter rod set screw (P1) on the SF side while holding the bellows (P2) and shutter (P1)
Remove the shutter rod (P1) from the bellows female end, and move bellows away from SF (P2)
P2 passes bellows to P3 or puts bellows in a UC foil pocket
Extract the shutter out of the GC (P1) through either:
The bellows port, if it fits (P1 already has a grip on the rod to do this)
The In port, passing off the shutter rod from one ultraclean long forceps to another.
Remove any In shutter
System is now open at the In port and In bellows port, and has no In shutter
Install the new shutter
To protect the shutter rod while wiggling the shutter into the In source port, put UC foil around the port flange, such that it was covering the non UHV side-- think of this as a reverse foiling of the port.
Put the new, trimmed shutter into the GC through the In cell port. P1 may use UC gloves to wiggle it in.
Get the shutter rod in the GC using UC long forceps, then out of the bellows port using a second UC long forceps (inserted into the bellows port) to grab the shutter rod and pull it out of the bellows port.
The shutter is now in the pocket, and the rod is coming out of the source port. It can be safely rested here, so continuous holding is not needed.
Hold the shutter bellows near its port at an angle and wipe the shutter bellows and port knife edges.
Put a clean gasket onto the bellows, with careful attention paid to the rotatable nature of the flange, meaning the flange can drop away from the knife edge, so gaskets can fall unexpectedly.
Hold the shutter rod out of the port with UC forceps and put the bellows next to the bellows port and tilted.
Simultaneously tilt up the bellows and insert the shutter rod into the bellows rod holder/female end. The gasket will be semi-secure (it's not in place yet, but it can't fall).
Tighten the shutter rod set screw/tighten the rod in its bellows home using the little clamp.
We thought this would be straightforward, but the clamp that would tighten it was very unruly, spinning around the bellows female connector, upon which it must be tightened, and going onto the rod.
With teamwork, Kyle and Siff got the clamp to behave and tightened down the set screw with an ultraclean allen.
However, due to the rotatable flange on the shutter bellows assembly, the shutter kept rotating and it looked like the set screw was not locked down. Even with Kyle really tightening it, the shutter would move.
This is because where you hold the shutter bellows assembly steady (the side hinges) is connected to the flange, not the bellows.
And the set screw Kyle was tightening and the shutter rod & shutter are connected to the bellows not the flange.
In this way, the rotatable flange made this part more difficult.
Raise the gasket with an ultraclean fingertip, contact the bellows to its port, and make sure the shutter is oriented mostly correctly.
Put in top and bottom bolt loose fingertight.
Check alignment with viewports and slow manual actuation, modify orientation as needed.
Do more minor adjustments, the shutter bellows flange is rotatable, which simplifies rotational adjustments.
When alignment is good, fully finger-tighten top and bottom bolts, and put in the rest fingertight, while watching the shutter constantly.
Check alignment again
Wrench tighten down the bellows
Check alignment again
Return In cell (or blank) to In port as needed
Pump down system and THOROUGHLY leak check (all of the bellows and bellow flanges, the HVP and nipple, and the In cell at minimum). Make sure it hits nice low values as it pumps down after leak checking.
Notes
Shutter won't fit in through SF water cooling panel from RHEED port side. The cryoshoud blocks part of the panel toward the outside, where it is wider.
CAR is kind of in the way.
Shutter won't fit into In source port til trimmed
Take this chance to evaluate the bellows' health
Be careful while working near, with bellows, holding them, installing them, etc.
The shutter rod was a bit hard to get into the shutter bellows female end.
The bellows locking clamp was spinning around.
It was hard to tell when the clamp was tight because the shutter bellows has a rotatable flange. When holding the flange or side hinges, the bellows and rod can rotate, making the shutter rod clamp look loose.
Rotating the shutter was hard at first, then we realized the bellows has a tail you can use to rotate it.
10. The bellows tail and rotatable flange made the replacement a little easier.
11. The camera idea worked very well for alignment of the shutter rotation.