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Subject: Re: X-Radiation / Safety
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Date: 04/28/03 at 11:00 AM
Posted by: Joe Sitter
In Reply to: Re: X-Radiation / Safety posted by Scott Cargill on 12/05/02 at 2:25 AM:
Gosh, even hasty publishing on a web page can have its' pitfalls but I really don't think that the foolish act of cigarette smoking by others should ever give a careless, or uneducated hobbyist or professional a sense of security with sloppy x-ray practice.
I have nearly 40 years as an electronics hobbyist and 25 as a semiconductor professional. I have worked with well-shielded industrial particle (positive ions) accelerators for 24 years with lots of training. In the late 80s I also became interested in radiography so I studied the subject in the nearby university science library (ASU). That place has three, large floors of only science books. I've designed and built many fine HV power supplies and early-on, tied them to large high vacuum rectifier tubes (they have much smaller focal spots if used backwards) to make a cold cathode, field emission x-ray source running @ about 200 uA and 165 KeV. One of the 1st things I did however, was to build an integrating G-M counter so I could easily have an idea or sense of what I was doing. I also obtained several Pb plates to use as shields wherever needed. I usually left the room while holding my G-M meter and stop-watch when making a polaroid exposure. FYI, Polaroid #57 film (iso 1600) needs about 400 mr @150KeV to image through 3/16" of steel and much less if looking at tiny electronic devices. It can produce a sharp image of objects as small as 250 um (maybe smaller) because it has no intensifying screen.
I probably did hundreds of hours of study in university level textbooks on the engineering, technical and safety aspects of radiology, diffraction and x-ray chemical analysis. I always like to learn a subject to a high level of detail. I also like to cook from scratch whenever I do that. So, in 88'-90' I even grew my own ZnS:Ag:Cl and other types of scintillator crystals in my high temp. furnace and used them to make x-ray conversion phosphor paints that I applied to the input fiber-optic faceplate of a military night vision image tube in order to make a LIXI scope (per the 1981 NASA patent description). It was sensitive enough to display the beautiful cascades of cosmic and terrestrial particles we call "background" radiation. With an image receptor like that you need only 100 uA tube current to get a speckle-free image. You can actually see individual x-ray photons with this instrument because its' extremely sensitive.
These days I'm designing a filmless digital image receptor for an NDT customer and working with microflouroscopy systems for electronics manufacturers. When needed, I now just use a prepared rare earth conversion phosphor but the experience gained by teaching myself has become fairly valuable. Thx, Joe.
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