Vacuum Technology for Home-Built Gas Lasers

Many areas of scientific research and industrial production require vacuum conditions - where most (or as much as possible) of the air has been removed leaving little or nothing behind. While written specifically for the needs of home-built gas lasers, much of what follows is applicable to other medium to high vacuum systems and includes some general testing, maintenance,
Vacuum Technology for Home-Built Gas Lasers - schematic

and repair information not found elsewhere. All but one of the gas lasers described in the chapters on specific home-built lasers require a decent vacuum system to remove air from the laser tube so that it can be back-filled with the required lasing gases at a low pressure. These include the HeNe, Ar/Kr, CO2, HeHg, CuCl/CuBr, and multiple gas (PMG) lasers. The N2 laser requires only a `low` vacuum since it runs at a substantial fraction (e. g. , perhaps 20%) of atmospheric pressure and some versions can run at ambient pressure (1 atm). Remove (nearly) all the air from the apparatus. For almost all the gas lasers we will be describing, air is poison. It must be purged from the tube before the required gases can be admitted. Only with most of the air gone, can proper and efficient lasing action take place. Even a small amount of residual air may result in erratic or weak operation - or no output beam at all! Pump out residual gases resulting from outgassing from the glass, seals, adhesives, finger prints, and other contamination on the surface and in the crevices of the laser tube assembly. Some materials like vacuum grease do not cause problems. However, a single finger print can represent a veritable reservoir of unwanted vaporous contamination! Control the pressure of the gas fill as individual gases or gas mixtures are admitted to the apparatus either prior to or during operation as the electrical discharge buries gas...

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