Procedure Regenerate P20

used so far

• Isolate P20 from the system (close valve)
• Open valve between line segments pumped by P20 and P30 (so line segemnt P20 will be pumped by P30)
• Shut down P20
• Hook up turbo pump cart to P20. If possible, take the one with the turbo pressure gauge.
• Evacuate the bellows with the turbo pump cart
• Open valve between turbo pump cart and P20
• Plug in heater of P20
• Wait
• Close valve between turbo pump cart and P20
• Turn off heater of P20
• Decouple turbo pump cart
• Wait until P20 has cooled down (several hours?)
• Start P20
• If pressure is ok; open valve between P20 and the line

additional info found on internet

1. Bakeout temperature should be 120C to completely degass water, 160C to degass most of common hydrocarbons, and 400C to completely clean the system. If you are aiming for UHV in the area of low 10E-9 to low 10E-10 Torr and if system is "UHV clean," then 120C chamber temperature is sufficient, deeper targeted vacuum level would require higher temperature.
2. Ion pump must be heated! Ideally temperature of the ion pump body should be the same, or 10C - 20C lower then the chamber. If chamber is heated to 120C then ideal temp for ion pump body is 100C - 110C. Heating below 100C is ineffective, as bakeout times become unreasonably long.
3. Make sure that there are no "cold spots" on chamber or flanges, some flanges could need local heating.
4. Bake with both chamber and ion pump heated and ion pump "off" while pumping with turbo through bypass valve for at least 12 hours. Note vacuum level at the end of 12 Hrs of the bakeout.
5. Switch ion pump "ON" while everything is *hot* with bypass valve still open to continue pumping with turbo pump. You would see decrease in the vacuum level because of ion pump outgassing, this is normal. Continue heating and pumping with both ion pump "on" and turbo pump through open bypass valve until vacuum improves to the same level as you had at the end of the initial 12Hrs period. At that point close bypass valve and continue pumping with ion pump, while still heating both ion pump and the chamber.
6. Pump for at least another 6 hours, or longer if needed - until vacuum stops improving, i.e. until there is no improvement in vacuum reading on ion pump controller over the period of an hour or so. Note that at this point vacuum reading will fluctuate because of multiple reasons, so "filter" the readings.
7. Switch off heater of the ion pump body, while continue heating the chamber. Let ion pump cool while pumping the hot chamber (gases tend to "condense" into ion pump) for at least three, better 6 hours.
8. Switch off heaters on the chamber and let whole system cool down. It should be possible to reach low 10E-10 Torr range with this procedure, if there are no leaks and no hydrocarbon contamination in your system.

If you decide to bakeout temperatures higher then 140C would require removal of magnets from ion pump. If needed, then do high-temp bakeout over first 12 Hrs, then reduce temperature to 120C, re-assemble the magnets (heat-resistant gloves!) and then continue with the above procedure.