> A bit later:  "An interesting exception exists for very energetic X rays
> and gamma rasy, which can readily penetrate the select gate and then be
> absorbed throughout the gate oxides, the floating gate, or the
> substrate.  However, a broadband flux on the order of 10**13 photons per
> cm [should be cm**2, I imagine] from an X-ray tube operated at 100 KV
> with a tungsten target is necessary to fully erase an EPROM; hence X-rays
> are not regarded as a special reliability concern for EPROMs."

I think the above hits it on the head, somewhat: a UV lamp is designed to
put out LOTS AND LOTS of rather energetic photons.  A medical X-ray will
put out photons that are more energetic, but not nearly as many (the
purpose, remember, is to disrupt molecules of film that are designed to be
easily disrupted, not to knock charge from structures designed to hold it).
I expect any X-ray source powerful enough to significantly erase chips would
also be powerful enough to degrade tissue fairly rapidly; not what you want
in your medical equipment.

On the other hand, my impression is that certain types of fault analysis
require much more powerful X-rays.  For example, a dental X-ray isn't going
to do much good if you're trying to X-ray a 1/4" steel plate (to identify
any internal flaws, for example).  I expect industrial X-rays probably would
be powerful enough to erase OTP's, though with some risk of damage to the
rest of the device.