How to change the Laser gas tube

You may have a low He pressure in your tube - Remember that as far as the He is concerned, is is surrounded be a "He vacuum", so the gas slowly diffuses out.This can be reversed by putting the laser in a plastic bag with a slow trickle of He into it and running the laser several hours. This heats the tube and increases the gas diffusion rate in the tube walls. It's a good idea to monitor the power and voltage so you can stop before the tube accumulates too much He, as that's much more difficult to fix.

I have successfully rejuvenated several He Ne laser tubes. Apparently the He is implanted into the cathode and the remaining gas mixture may not be correct for the tube to continue lasing. I heated the laser tube electrodes by placing the tube in an RF induction furnace coil, which degassd the electrodes.

I am unfamiliar with He Cd lasers, but it is possible that Helium implanted into the electrodes holds the key to the problem, and the same treatment my do the trick

Dear Friend, Thank U for your answer.