Hello Alan,

my next preoccupation would be that during such long exposure or the
very very high levels encountered in particles in space applications
would not only transport the gate charge, but also "shoot holes" in the
semiconductor structure as well. Shielding the entire semiconductor will
reduce this risk also, but do you have any knowledge of the
semiconductor being altered in dotation or structure due to radiation
effects?

Greets
Jochen Feldhaar DH6FAZ

"Alan B. Pearce" schrieb:
>
> >I had a girlfriend who is a doctor in a vet clinic. So I made up a test
> >card of EPROMs and EEPROMs, in two batches.
> >She then exposed them to the X-rays, the first batch for about 10 secs,
> >the second four times that.
> >I wanted to get maybe a second life out of the big number of OTP parts
> >that are around...
> >
> >But sorry, no go, the intensity was WAY too low, and as it was in a
> >clinic I am inlcined to say that YES, it would have stained a film...
>
> X-rays will eventually erase EPROM's.
> I remember a story related by someone presenting a paper at a conference. He
> worked in a university that had a medical section, and was asked to build a
> dummy patient that could be used by students when training on a x-ray
> machine so they could see the motion of organs. This machine must have been
> capable of continuous display.
>
> Everything worked well for a while, but then intermittently the dummy body
> would give an involuntary twitch, with intervals between twitches getting
> shorter until the dummy body went into total spasm. The x-ray machine had
> erased the EPROM's used. In this situation the solution was to move to
> bipolar fusible link proms that were pin compatible.
>
> As a side issue to this, in the space electronics environment where I now
> work, we use small pieces of tantalum sheet glued and tied over the top and
> bottom of components that do not have sufficient radiation capability for
> earth orbit flight. One of my colleagues recently did this for some EEPROMS
> used on a low earth orbit instrument he was working on. Tantalum is
> apparently one of the highest density metals when it comes to stopping
> radiation, presumably on a weight/radiation stopping trade-offs, but that is
> not my area of expertise.
>
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