I have never heard of argon being a problem. I heard that helium is a no no. Many people I have talked too have said argon has less of a tendency to leak out as it has a larger molecule then nitrogen. I think the main reason its not used is that it costs more then nitrogen.Many people don't know that the air we breath is already over 78% nitrogen. Its about 20% oxygen,argon about 1% and the rest made up of alot of other gases. I have never seen any reports of argon having any effect on the indium seals of the tube.Argon is used alot in high quality optics and scopes.Indium is pretty tuff stuff and is used in many types of seals in all kinds of enviroments. Helium is present in the air we breath and some scopes are not purged at all.From many articles I have read its a very rare occurance for the indium seals to break down in a NV tube.The major cause of tube failure is a breakdown or cracking in the potting material after many years.Abuse of the tube (bright lights, lasers) are another problem.Here is a post from Ed on another forum related to tube failure.
Thin film tubes, such as ITT‘s products, have as much of a lifespan as does any other Gen III tube, which is rated at 10,000 hours. After all, what wears out in the image intensifier? Power supply? Not likely. Potting material? Sometimes but with current manufacturing processes, this is unlikely at least for the first 20 years or so. The Module’s Indium seals? Possible but not likely. The MCP? No. The Screen? No. The PhotoCathode – Yes, if Ion etching is allowed to occur. The purpose of the “film” or Aluminum Oxide ion barrier membrane, is to stop positive ions and neutral gas molecules from reaching the PhotoCathode. Regardless of its thickness, it does its job. Now, Filmless, like NG’s products, have no Aluminum Oxide ion barrier membrane. The filmless technology relies solely on the ability to scrub the inside of the Module so that all gas molecules are gone which is a perfect vacuum. Near impossible to do, so any gas left in the module of a filmless image tube gets hit by electrons traveling in the channels of the MCP. This action produces the positive ions and neutral gas molecules, which etch the PhotoCathode and slowly poison it. This would lead to a much lower life span