I'm running out of places to look (lots of Googling, SE, [articles and books are too specific and never give a good overview]), and yet I am still unsure about how exactly radiation can degrade mechanical parts and electronic devices. Could someone summarise the mechanisms involved, for either of those or both?
I'm working as a mechanical+electrical designer in the Space industry, that is why I am particularly interested in that. This is purely out of curiosity though.
Here is a start, please correct and improve:
We call radiation high energy photons (X-rays & gamma rays) or high energy particles (i.e. travelling in a straight line through space):
- Alpha particles, which are Helium atoms
- Beta particles, which are electrons
- Ions (I'm surprised they don't capture/release electrons rapidly)
Galactic cosmic rays can apparently be any atom, though usually protons (after all, that's what space is mostly made of).
- High energy photons can give sufficient energy to electrons to make them leave their orbits, ionising the atom. I assume the cristal lattices of metals try to rearrange for example, making it swell and embrittle, but I don't know what the resulting ions become (I've always thought ions were only temporary, except dissolved in e.g. water)
- High energy particles certainly have the same effect by ejecting atoms on impact.
- It seems like transmutation, where high energy particles break nucleii so that the atom is transformed into an another element, is very rare.
- I assume ionisation is the main failure mechanism in electronic devices, mainly in transistors because it can create currents where there is supposed to be none and perhaps trigger a runaway (affecting doping of the junctions, thanks dmckee).
- High energy rays can be effectively absorbed by dense materials with high atomic numbers such as lead because their many electrons increase the probability of absorbtion of the photons
- Alpha particles don't go very far; even though they carry lots of energy they are big and any material can stop them. beta particles are lighter, faster and penetrate further but still are stopped relatively easily because they are charged. Neutrons are somtething else, stopped by nucleii and therefore smaller lighter elements with small atom diameters can be packed in the same volume to stop them more effectively.
Edit: Wikipedia has a nice page covering effects on electronics here (keywords are key...): http://en.wikipedia.org/wiki/Radiation_hardening