How Good a Vacuum System is Really Needed?
None of the gas lasers we will be discussing requires a vacuum better than about 0.1 Torr when operating. However, in order to clear them of contaminants in a timely and economical manner (without a semi-inifinite number of purge and back-fill cycles), it is desirable to be able to pump down to a much lower pressure than this. The better your vacuum capability – to a point – the easier it will be to obtain a pure gas fill. Less gas will be needed (due to fewer pump-down and back-fill cycles) and time will be saved. However, there is no need to go overboard. My rule-of-thumb (read: wild guess) is that a vacuum system capable of reliably pumping down to 1/100th of the lowest operating pressure is adequate for dealing with a laser tube that has a single vacuum/gas fill port. Pumping to 1/10th the desired final pressure may even be good enough if the laser tube is fabricated to have a gas-fill port at one end and a vacuum port at the other. For a flowing gas design (e.g., CO2 laser), the r
None of the gas lasers we will be discussing requires a vacuum better than about .5 Torr when operating. However, in order to clear them of contaminants in a timely and economical manner (without a semi-inifinite number of purge and back-fill cycles), it is desirable to be able to pump down to a much lower pressure than this. The better your vacuum capability – to a point – the easier it will be to obtain a pure gas fill. Less gas will be needed (due to fewer pump-down and back-fill cycles) and time will be saved. However, there is no need to go overboard. My rule-of-thumb (read: wild guess) is that a vacuum system capable of reliably pumping down to 1/100th of the lowest operating pressure is adequate for dealing with a laser tube that has a single vacuum/gas fill port. Pumping to 1/10th the desired final pressure may even be good enough if the laser tube is fabricated to have a gas-fill port at one end and a vacuum port at the other. For a flowing gas design (e.g., CO2 laser), the re
