Shel wrote: > What I read is that the proposed system will be using electron beams, > so perhaps we're making some headway in finding out if the system > will damage film or not. Any further comments by those in the know > about these things?
I heard this as well on NPR yesterday on the way home from work. They didn't say anything about the typical electron current or electron energy of these electron guns. They ~did~ say, as many on the list have already noted, that the penetration depth isn't very large, so that letters would likely have to be laid flat for this to do any good. One thing energetic electrons are very good at doing is ionizing things, so it may be that at least part of the bactericidal action is due to localized generation of nasty oxidizing agents like ionized molecular and atomic oxygen, ionized nitrogen, etc. Another thing energetic electrons are good at doing is knocking core electrons out of metal atoms, resulting in X-ray emission. In fact, this is exactly how an X-ray tube is constructed -- an electron beam of several kilovolts to a few tens of kilovolts impinges on a metal target, like copper. Could be that the damage to film would arise due to X-ray emission from electron bombardment of the metal cassettes and metal spools used in packaging roll film. I also heard the same NPR commentator make remarks regarding use of gamma irradiation facilities for mail. Current facilities in the US are used for sterilization of foods and medical devices, and they apparently would not accept mail for gamma sterilization. A new gamma irradiation facility might cost somewhere in the neighborhood of several million USD and take up to a year to build. IIRC, the commentator stated that several hundred such facilities would be needed to irradiate all mail in the US. Thus, widespread use of gamma sounds like it will not be feasible. God help the poor SOB who ships a fungus-infected lens. Imagine the consequences if some postal employee -- or FBI agent, Secret Service agent, INS agent, etc., etc. -- recognize the fungus as "some unidentified biological agent". Yikes! Bill Peifer Rochester, NY - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
