Source Flange Prep for Opening
Day 1-3 - Prep Growth Chamber
Day 1
Cool the As and Sb sublimators and crackers using a recipe
Cool the other cells to a very low idle temperature (150 C).
As long as the water is flowing it will not be frozen by the LN2
for more info: Idling Cells for Opening
Day 2
Freeze Al using a recipe, per the combined instructions of the relevant Wiki page (Melting and Freezing Aluminum) and the last Al freezing recipe.
The recipe is a loop that decreases the power to the Al cell by 0.1% and waits 10 minutes to repeat. It lowers the temperature 1 C every ~2.5 minutes.
I will update the Wiki soon.
We also put the 2.75" viewports and new sapphire HVP on the BOS and will bake them tomorrow. This is a good activity for new students.
Day 3
The Al cell will be cold, other cells are still warm
Turn off the LN2.
When the LN2 is gone, we can turn all of the cells off (except Ga).
As the remaining LN2 in the cryoshroud warms up, it evaporates out of the shroud via the Return line. As the shroud warms, it no long freezes molecules onto it, and we lose its effective pumping ability. More importantly, everything that was cryo-adsorbed onto it will warm up, and effectively evaporate off (at well below room temperature). During this process, the growth chamber pressure will rise.
Take off the shutter wheel.
Disconnect the supply to shutter wheel connection (input pressurized air line and electronic control cable), as well as the pneumatics (supply the air for shutter operation), electronics (controls the pneumatic), and mechanical connection to the shutter bellows (move the physical shutter).
The pneumatic connections for most cells are self-contained on the shutter wheel, but the connections with non-SF components extend beyond. These are the deep upward looking (DUL) dopant cells, and RHEED screen.
The electronic connections are similarly mostly self-contained, but again the DUL dopant cells and RHEED are off the shutter wheel.
The mechanical connections are the physical shutter rods and where they attach to the shutters. The off-shutter wheel shutters are self-contained for this part. The other cells on the SF itself have shutter rods that must be carefully disconnected at the shutter.
They are joined by a pin and eye socket type connection.
The shutter wheel also has four posts which attach it to the SF, each with one set screw. The set screw must be loosened to pull it off. Once everything is disconnected (and double checked), you can pull off the shutter wheel (2-4 people recommended). You want at least one person pulling it off and one person keep lines and tubes out of the way. Use two and two for extra eyes and ease.
Tape down the shutters carefully and securely in a neutral/floating position using kapton, and avoid taping on the bellows welds.
Once the LN2 had evaporated out quite a bit, turn the cells (except for Ga) off.
Let the GC pressure stabilize before proceeding.
Day 4 - Draining Day
Wait for the growth chamber pressure to rollover and stabilize.
Cool Cells
Turn down the HVP to 0.0 first so it has enough time to cool to prevent burns while working on the flange!
Turn down all of the cells to 0 output power (except for Ga)
The cell setpoints are set to 10 C (below room temperature) so the output power will drop to 0 (if the Eurotherms are put into auto the cells won't re-heat) and the Eurotherms are put into manual (prevents accidental re-heating via Amber).
The substrate heater is also lowered to 10 and put into manual.
We keep Ga warm (at 100 C), we have an interlock override connector. We insert the overrides into the Ga Base and Ga Tip Eurotherms. The overrides are male end connectors with a short.
Once Ga is idled (~2.5% base, 3.5% tip), override the interlock by:
go to 'manual' mode on the Eurotherm
adjust the tip and base power to 0.0%
pull the Ga tip and base connections from the back of the Eurotherm box
In their place, install the shorted connectors
adjust the tip and base power back to their idle points
Override the AHS Eurotherm interlock too in preparation for draining cell and SF water (drop in water pressure caused AHS to shut off 8/28/2023 - AFR)
Drain Sources
Drain Sources Cooling Water
Note that the sources water is just water, can be put into milk jugs, and re-used in the chiller. The SF water is glycol/water and will be disposed of.
The hardware for water draining is kept in the white cabinet by the fume hood (tubing, caps, quick-disconnect fittings).
By stopping the flow of the source cooling water, we will trip the associated interlock. All of the cells (except Ga) and substrate heater are already cold and in manual (or overridden for Ga), so this has no effect.
The sources cooling water comes from a manifold near the ceiling equipped with self-sealing quick-disconnect fittings.
Check the cell water flow operating levels are currently correct and marked.
Turn down the cell water flow levels to off. This prevents water issues when we are reconnecting the lines.
We can disconnect the Supply and Return line from the manifold, and only a few drops of water might drip out.
Each line is now a tube connected to the appropriate cell water feedthroughs.
Some lines have multiple cells on the same line (a Cell Group), that are interconnected in series with short lines between cells. An example is Ga, In, Er, Bi.
Connect a quick-disconnect fitting to the Supply end of the water line and put it into a Water milk jug (our receptacle of choice) to contain draining water.
It won't drain til we open up the other end though, because it is sealed and draining water would create a vacuum in one end.
Connect a Clean Dry Air (CDA) line to the Return end of the water line and water will start draining out of the Supply into the milk jug.
The logic behind draining out of the Supply is below.
Let the air run for three minutes per cell to dry it out nicely.
Disconnect the tubing from the cell water feedthroughs, both the Cell Group supply and return and the smaller intercell tubing.
Cap the cell and nipple water feedthroughs to keep them sealed during glovebagging.
We can coil up the water lines, both the Cell Group supply and return and smaller intercell tubing, ziptie the Group together, and set it aside.
We repeat this for each Cell Group.
The As and Sb sublimators are different, they have to be blown out for ten minutes.
All of the drained Source water should be put back into the proper chiller for re-circulation before bringing the system back up.
Drain SF
Drain SF Water/Glycol
By stopping the flow of the SF water, we will trip the associated interlock. The cells and substrate heater are already cold, and Ga is interlock overridden, so we are fine.
First, look at the water flow level for the Echo SF, there is a gauge located at ceiling level near the middle of lab-- we will need to set it back to that level shortly. Echo and Bravo share a SF water chiller in the mezzanine, turning one on or off will affect the other's flow. The valves to turn the SF water on or off are located at ceiling level near the middle of lab and are labeled.
Turn off the Bravo flow of water, first the Supply, then the Return. We always turn off Supply first, then Return, to prevent a pressure build up (to turn flow on, open Return first, then Supply).
Adjust the Echo flow back to the proper operation level by adjusting the valve handle on the ceiling labeled Echo supply.
Note: glycol water is poison to humans, so clean up any spilled SF water and put any drenched cleanroom garments in the laundry if covered with the water. Frequently change gloves, especially if covered in water
Uncap the Bravo Drain line while someone holds a water catching bin (drip bin) underneath the Drain line connection (to catch and water that will drip out).
The drain line is next to the supply line on the bottom of the source flange. It is bent slightly downward on Bravo
The water shouldn't spray or splash out (that would create a vacuum up the line), but I've seen things, so use the bin and have cleanroom wipes on hand.
Attach draining tubing and put the tubing end into a carboy to collect the SF water
It is also a good idea to use a funnel if one is handy
Loosen the Return line (at SF top) to let some air leak in and get the draining flow started.
You should see bubbles moving up the return line and the water level in the return line slowly draining
Wait for the Return line to be empty, then Unscrew the Return line with a drip bin underneath.
Cap the Return tubing and leave the metal pipe open.
Let the water drain, it looked like 3/4 gallon.
When the water is drained, unscrew the Supply line (at bottom), cap the tubing, and leave the metal pipe open for a minute.
Cap the Return metal pipe and then the Supply metal pipe.
Disconnect the Drain line tubing, and cap the Drain metal pipe.
All of the drained water should be disposed of, it has glycol in it. We must top off the SF chiller before bringing Bravo back up.
Remove N2 station
Removing the Bravo Nitrogen System
Water Supply vs Return
If you want to ensure that a cup with a hole at the bottom is completely full, how should you fill it? Why should you care it is completely full?
Our cup is the Cell water feedthroughs and in-vacuum Cell cooling.
By having a full "cup," we avoid air pockets, hotspots, and areas with very different temperatures.
We fill that "cup" from the hole at the bottom.
Filling it from the top would cause the water to just go in and seek the drain hole without filling the volume and effectively cooling the cell.
By filling from the bottom, we ensure that the whole volume is full before the water finds the drain hole at top.
Each Supply water feedthrough is at the lowest point of the cell, and each Return is at the highest point.
Because the Supply is the low point, it is the best water line to drain, making the Return better suited for a CDA line to push water out and dry the lines.
Day 5 - Prep SF and Glovebag
Prep SF for Glovebag
Open As and Sb valves and remove valve motors.
Set Valves to 100 to make them nominally open.
Change valve motor controllers for both As and Sb for 'manual'
Disconnect power cables to each. The valve controller will freak out, this is normal. Keep it on!
Open the valves manually to about halfway to ensure openness. Both cells are labeled.
Both cracker valves move outward to open, so bellows move into cell body.
Loosen set screw on textured black piece over helical coupler and pull back gently.
There are two set screws. Only loosen the the one that is the most to the left/counter clockwise
Loosen set screw on on silver helical coupler to free it. Careful, helical coupler can slip.
You will know when it is loose if rotating the helical coupler does not appear to change the valve position
Loosen set screws of motor on cell and remove motor.
Tape down exposed valve motor axle on back of cell.
Disconnect power lines except Ga. Thermocouples then power lines (all cells are in manual receiving 0% power, but double check).
Zip tie down thermocouples and power feedthroughs, prevents extra loose things in the glovebag.
Double check all shutter tape jobs, fix as needed.
Cover pointy parts of system and surroundings with kimwipes (taped-on) to prevent sharp edges contacting the glovebag. Also cover the As sublimator top.
Close the GC to BC gate valve completely.
Prep Glovebag
Put up the glovebag(s): Glovebagging - On the day prior to opening
There are two tables to support glovebag setup and work. As of now, we use the GC table as just a tabletop and blue bins (three stacked upside down) and the Bravo frame as the legs.
Begin pre-purge with UHP N2. Fill up the bag and make sure it inflates and the tape job is good.
Prep tool bins for opening, the list of what to pack is on the Wiki under the opening checklist.
Prep glovebags for opening: put in other things that don't fit in tool bin, or are needed but not on opening checklist and not in a desiccator.
Misc
The transit case for the HVP and Al cell is in the front desiccator.
Ultra clean tools will be loaded for desiccation tomorrow morning.
Monitor the Ga temperature and power during Opening. We need to keep the Ga warm to prevent freezing, but running the cell filaments at non-vacuum pressures can prematurely age or damage them. We strike a balance by turning the power to 0%, and raising it slightly as needed during opening to keep the Ga molten. We want to keep the tip warmer than the base, and not exceed 1 A to either filament. Recall it idles at 100-150 C for maintenance.
Review how to pump down the growth chamber with the new turbo pumps.
Remember to override cryopump interlocks for GC IG after pumping down GC after venting.
. Turn Ga power up manually to prevent freezing, or set to Auto, after pumping down GC
. Keep the cell between 100-150 C, and the tip warmer than the base.
. Manual: Set the tip to 3.5% and base to 2%. This may need to be modified slightly based on how much Ga is in the cell.
. Auto: Determine by setting to manual overnight and seeing at what temperature Ga cell stabilizes.
. Auto (full cell): Tip: 139.8 C (~3.2% power); Base: 129.6 C (~2.2% power)
. Auto (low Ga): Tip: 135 C (~3.5% power); Base: 105 C (~1.0% power)
Bravo bring down procedure (Venting for maintenance)
Quick notes, only use if you know what you are doing
More complete procedure is here: Venting and Pumping the MBE System
Make sure both the GC and roughing manifold/LC are at UHV, and the Buffer chamber is isolated. Get roughing manifold to UHV if needed.
Do RGA scan before venting Bravo and save it. Then turn off the filament, unplug the RGA serial connector, and turn off the RGA.
Turn off the beam flux ion gauge;
Turn off/Close the gate valves of two cryopumps. You will see the pressure increase on GC ion gauge;
Turn off the GC ion gauge;
Open the All Metal valve between GC and roughing manifold;
Turn off the LC ion gauge;
Turn down the Gallium Tip and Gallium Base Power Output to 0 (monitor Ga temperature at all times);
Turn off the Turbo Pump. Wait for the turbo to fully spin down;
Open the Viton Seal on roughing manifold; (If Green valves(¼ valve) is open to purge line, make sure to close ¼ valve first before open the Viton Seal)
Close the All Metal valve between roughing manifold and LC;
Close the scroll pump VPI;
Turn off the scroll pump;
Gradually Open the Green valves(¼ valves) to vent the GC (and fill it with N2).
Check the pressure gauge on the roughing manifold and close the ¼ valve if/when the GC is at atmosphere;