L–Checklist for Changing Components in an evacuated UHV Chamber
Targeting pressure at around 10⁻¹¹ mbar.
1. Preparation
[ ] Notify Personnel:
Inform all relevant team members about the planned maintenance.
[ ] Gather Necessary Equipment:
Replacement component.
Clean, UHV-compatible tools.
New gaskets or O-rings if needed.
Cleanroom-grade gloves (powder-free nitrile or latex).
Cleanroom wipes and high-purity solvents (e.g., isopropanol).
[ ] Prepare the Environment:
Ensure the workspace is clean and free from dust.
Minimize airflow to prevent contamination.
Set up a clean surface to place removed components.
[ ] Personal Protective Equipment (PPE):
Wear cleanroom gloves and a lab coat or cleanroom suit.
2. System Verification
[ ] Confirm System Status:
Verify the status of the UHV chamber: Ion getter pump and pressure gauge need to be operational.
Confirm that the pump stand (roughing pump and turbo pump) is available.
[ ] Plan Venting Procedure:
Determine the safest method to vent the chamber without introducing contaminants.
Ensure high-purity nitrogen gas is available for venting.
3. Connecting the Pump Stand
[ ] Inspect the Pump Stand:
Check that the roughing pump, turbo pump, pressure gauge, and automatic flooding valve are operational.
Ensure all seals and connections on the pump stand are intact. Check that it is clean and its recent history.
[ ] Connect the Pump Stand to the Chambers Corner Valve:
Clean all mating surfaces and seals to prevent contamination.
Securely attach the pump stand to the chamber via the corner valve flange.
Tighten bolts uniformly in a crisscross pattern to ensure even pressure.
[ ] Verify Connections:
Ensure all connections between the pump stand and the chamber are leak-tight.
4. Evacuating and final test of the Pump Stand
[ ] Start the Roughing Pump:
Turn on the roughing pump to evacuate the pump stand and its lines. The Turbo pump will start automatically.
Monitor the pressure gauge on the pump stand.
[ ] Wait for Initial Vacuum:
Allow the pump stand to reach a high vacuum of lower than ~1×10⁻5 mbar.
[ ] Prepare Nitrogen Venting:
Ensure high-purity nitrogen gas (dry, oil-free) is connected to the automatic flooding valve.
Ensure proper pressure levels – about 10 % above atmosheirc pressure levels.
NOTE: CF flanges cannot handle large pressure differences!
[ ] Activate the Flooding Procedure:
Swtch off of the pump stand will automatically initiate flooding via vent, when turbo pump reached safe rotation speeds.
Test vent this section, while the corner valve to UHV chamber is still closed!
[ ] Restart the Pump Stand:
Check vacuum levels again.
5. Venting the Chamber
[ ] Open the Corner Valve Gradually:
Slowly open the corner valve to equalize pressure between the pump stand and the chamber.
[ ] Monitor Pressure and Current of the Ion Getter Pump:
Use the pressure gauges and the current monitor of the IGP to track the chamber and pump stand pressures for a few minutes.
[ ] Turn off the ion getter pump and main champer pressure gauge:
To prevent damage during flooding turn all main chamber equipment off.
[ ] Activate the Flooding Procedure:
Monitor pressure levels and pump status.
[ ] Equalize to Atmospheric Pressure:
Continue venting and keep N2 flow on during maintenance work.
6. Accessing the Chamber
[ ] Confirm Atmospheric Pressure:
Double-check that the chamber is fully vented and at or slightly above atmospheric pressure.
[ ] Open the Chamber Carefully:
Remove flanges or viewports as needed, placing them on clean, lint-free surfaces.
[ ] Maintain Cleanliness:
Avoid touching internal surfaces with bare hands.
Use clean tools and handle components with care to prevent contamination.
7. Removing the Old Component
[ ] Document the OLD Setup:
Take photos or detailed notes of the component's position and connections.
[ ] Remove Gently:
Carefully disconnect any electrical or mechanical connections.
Detach the component without applying excessive force.
[ ] Inspect for Contamination:
Check the surrounding area for any signs of debris or residue.
8. Installing the New Component
[ ] Final clean of the New Components if neccessary:
Check all components and tools before bringing them into cotact with clean UHV chamber.
Use cleanroom wipes and appropriate solvents to remove any contaminants if neccessary.
[ ] Install with Care:
Position the component precisely where the old one was located.
Reconnect any electrical or mechanical interfaces.
Document the NEW Setup:
Take photos or detailed notes of the component's position and connections.
[ ] Replace Seals:
Install new, clean gaskets compatible with UHV conditions.
[ ] Reassemble the Chamber:
Reattach flanges and viewports.
Tighten bolts in a crisscross pattern to ensure even sealing pressure.
9. Initial Pump Down
[ ] Verify All Seals:
Inspect all flanges, ports, and connections for proper sealing.
[ ] Start pump stand:
The roughing pump begins evacuating the chamber.
Ensure the nitrogen flooding valve is fully closed.
Watch the pressure gauge as the chamber pressure decreases.
Monitor the turbo pump current and rotational speed for proper operation.
10. UHV Pump Activation
[ ] Reach Crossover Pressure:
Continue pumping until the pressure is suitable for activating UHV pumps (~1×10⁻6 mbar).
[ ] Start the Ion Getter Pump:
Follow the manufacturer's procedures to activate the ion pump.
Monitor current and pressure to ensure proper operation.
[ ] Activate the Titanium Sublimation Pump:
Wait until pressure is below ~1×10⁻9 mbar.
Heat the titanium filament according to guidelines to deposit fresh titanium.
[ ] Monitor System Performance:
Regularly check pressure readings and pump statuses.
[ ] Close the Corner Valve:
Once suitable conditions are achieved, you may isolate the chamber by closing the corner valve.
Final Checks
[ ] Achieve Target Pressure:
Verify that the chamber reaches the desired pressure of 1×10⁻¹¹ mbar.
[ ] Gett ready for bakeout (if required)
[ ] Leak Testing:
Perform a helium leak test around all seals and connections.
Use a mass spectrometer leak detector for accurate results.
[ ] System Verification:
Check that all pumps are operating within specifications.
Ensure that gauges and sensors provide accurate readings.
[ ] Documentation:
Record all procedures, settings, and any issues encountered.
Update maintenance logs and component inventories.
Safety Considerations
Handling UHV Components:
Wear appropriate PPE to prevent contamination and injury.
Handle delicate components with tools designed for UHV applications.
Nitrogen Gas Use:
Ensure adequate room ventilation when venting with nitrogen.
Be aware of asphyxiation hazards due to nitrogen displacing oxygen.
Electrical Safety:
Be cautious of high voltages associated with ion pumps.
Lockout/tagout electrical equipment before maintenance.
Thermal Hazards:
Use insulated gloves when handling hot components during bake-out.
Allow sufficient cooling time before touching heated areas.
Vacuum Safety:
Never vent the chamber rapidly; rapid pressure changes can cause damage.
Be cautious of mechanical movements due to pressure differentials.
Note: Maintaining strict cleanliness protocols is crucial for achieving ultra-high vacuum conditions. Even minor contaminants can significantly impact vacuum levels and system performance. Avoid that UHV chamber is exposed to air for more than 1 hour – keep flooding with clean N2.
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