Vacuum procedures - Msluis87/Information GitHub Wiki

Venting

Before venting a system the following procedure should take place.
• Check if the N2 line is connected. If the N2 line is connected check if the valve is open at the column.
• If you want to vent a part of a system check if this part is completely closed.

If these two points are checked then we can start with the venting procedure.

• First turn of all the pressure gages.
• Turn of the Ion pumps
• Turn of the Turbo pump.
• SLOWLY open the N2 line tot vent the system. If the venting happens thru the Turbo you wil hear that it slows down.
• Turn of the prepump

The system is now being vented. When the pressure is 1atm you can start opening the system. The N2 valve shouldn’t be closed until the system is closed. The flow of N2 will prevent a large part of contamination

Maintenance of a vacuum system

Seals

There are currently two kind of seals used at M2N. These are O-rings and cupper gaskets. When a cupper gasket is used ALWAYS replace after opening the system.
O-rings are mostly reusable. Except in the following cases:
• When there are cracks visible in the rubber.
• When the O-ring is completely dried out.
• When the O-ring is no longer a O but a 0 after a couple of minutes.
The O-rings can be greased in. There is specific grease for vacuum purposes. When you grease in a O-ring you should put on as little as possible. After the greasing in take a clean napkin and clean the O-ring. You would think that there is no more grease on the seal, but there is more than enough!!!

LT-STM

STM Chamber
• Disconnect all electronics
• Position STM in bake out position. The handle on the top should be in between the two “pins”.
• Turn the pre pump ON and turn the Turbo pump ON
• When the turbo pump has reached his velocity then open the valve. The valve is electrically operated and the switch is placed in the rack of the VT STM.

! The valve has a timing switch. This will close the valve after 10 min if the pressure between the pump and system hasn’t reached the correct pressure!

• Place heating cord.
• Rap in alu foil
o Connect the regulator to mains.
o Set regulator temp to 140 degrees.
o Connect IR light with variac
o Set variac at 200V.
The maximum temperature of the STM chamber is 150 degrees. The minimum bake out time is 48h. The pressure that should be reached after baking is around 8-10mbar
• After the bake out turn the pressure should be around 2 x 10-8 of the IR light and turn the regulator temp down.
• When the overall temperature of the system is around 90 degrees, turn the Ion pump on. Due to impurities in the pump the pressure will rise to 5 x 10-7 The pressure will drop to the initial pressure and will drop further.
• When the pressure is below 8 x 10-9 close the valve, the Ion pump is will take it over.
• Turn of the Turbo
• Turn of the pre pump
Now the system is baked and ready for testing.