CO2 Laser: What changes since the beginning?

CO2 Laser: What changes since the beginning?

Since the beginning of the project, this winter, a few things change.

Here a quick summary:

    The first version was maybe the simple one, few copper tubing, a glass tube and two alignment plate. Initially the two connectors were meant to pump down the system and and the gas mixture into the tube. But this design is silly because the mixture added is directly suck up by the pump and didn't go on the whole tube. Actually to fill the tube, you need first to stop the pump, fill the tube and then pump down again the system. The easiest system found to hold the tube are three curtain holder, they are isolating and strong enough to hold it.

Note: On this drawing the glass tube appear quite short but it is to facilitate the representation. On the real tube the tube length is about 80cm. 

   The second version is like the first one, except for the water-cooling system and the support system. The water cooling system is just an acrylic tube with two small tube connect to it. I use a small aquarium pump to circulate the water. The support is two pieces of wood, stronger than the curtain holder, because the curtain holder wasn't rigid enough, precise adjustment was therefor impossible. The connection between the copper tubing and the glass tube also evolved, before the tightness was insure by tape, but there were tiny leak between each tape layer. So it was replaced by silicon join, witch extremely reliable and tight. Unfortunately, the plasma start exactly on the junction between copper and glass near the silicon and burn the silicon. I think silicone vapor are at the origin of the plasma conductivity and color changes. Moreover when I start the plasma the pressure rise dramatically.

   The third version should solve the previous issue, but pushing away the silicon the plasma start line, as you can see it on the image. The mirror alignment system has been installed. Unfortunately, the plasma cover the whole copper part and continue to burn the silicon.