[Ground-station] Radiation Susceptibility

Phil Karn karn at ka9q.net
Mon Jun 4 02:28:21 EDT 2018


On 6/3/18 18:41, Tom Clark via Ground-Station wrote:

> I learned from Jan King (W3GEY) way back in the Microsat (i.e. AO-16)
> era some 30 years ago that 74AC logic was intrinsically good for ~200+
> kRad total dosage and 74HC parts were good to around 100 kRad.

Yes, an important lesson was that you can't make any flat assumptions
like "older is better" or "larger feature sizes are better". Every
technology has its own quirks and the only way to really know is to test.

This is true for a lot of extreme environments. One of the regulars at
the local ham lunch used to work on down-hole electronics for oil
drilling. They maintained a catalog of regular off the shelf parts that
had survived their own in-house tests. One absolute requirement: no
solder, as the operating temperature was well above its melting point...

> We (AMSAT) also did a lot of testing on radiation susceptibility using
> medical x-ray machines cranked up to levels associated with "the patient
> is already dead so lets make certain that the remains are sterile";

When I got my stem cell transplant I received several transfusions of
blood products. I asked how they avoided inadvertently transplanting me
with the donor's white blood cells (which wouldn't be matched to me, and
would therefore probably kill me). The answer was very simple: irradiate
everything, thus killing mammalian cells with DNA, which excludes red
cells and platelets. I seem to recall the dose was 12 grays (~1200 rad),
and a special label on the bag turned black to confirm that the full
dose had been absorbed. (I found that reassuring.)

I could always try to find out how this was done. I think the trend in
medical irradiation equipment is toward charged particle (e.g., electron
beam) generators and away from radioactive isotopes like Co-60 or Cs-137
that you can't turn off.

--Phil



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