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How can I use the mass attenuation coefficient to find the amount of radiation dosage reduction?
I'm designing a hypothetical space habitat and I need to know how much radiation can be deflected by the materials used in the wall. However, I'm new to understanding attenuation so I don't know what equations, variables, constants, etc. are involved and what I'd make of them.
I was told that the mass attenuation coefficient is important and looking it up, it seems it helps understand how much energy is reduced of the energetic particles. However, I'm not sure how to find out how much radiation in rads is reduced.
Any help would be appreciated.
This is an inflatable habitat so it couldn't use metal or anything stiff. I was planning for polyethylene but once I found out what the material was, it apparently is really stiff the thicker it is and now I'm considering water but that might be really thick and heavy, I don't know. I am aware that all GCR cannot be protected against so I was wondering if there was a way to calculate any materials protection against radiation since some of the materials in the wall other than the radiation protection might protect against it as well.
2 Answers
- bestonnet_00Lv 71 decade agoFavorite Answer
I do hope you're willing to make the walls about 2 metres thick because that's what it'll take to stop space radiation (specifically cosmic rays) well enough to obey the current radiation exposure standards for the general public. With a space station designed for shorter duration stays in low Earth orbit and not built from space materials you'll find that you're best bet is actually to not bother with *any* radiation shielding at all because with the type of radiation you'll have to deal with in space small amounts of shielding can actually increase the dose from cosmic rays (Bremsstrahlung or secondary radiation, low Z materials do help here so avoid Lead and the like and use polyethylene instead).
Solar flares are easier to deal with but come at the expense of increased cosmic ray exposure due to secondary radiation so if you can't shield it properly (which if it has to move around is likely) the best way to do things is to have a storm shelter that everyone goes to during a big solar flare and no shielding.
Your best bet though is probably to read through the 1975 NASA Ames Stanford Summer Study on space settlements.
- ?Lv 71 decade ago
Absorption depends upon the type of radiation (e.g. protons or gamma rays) and their energy, and the type of material used for the shield. There are different methods for calculating the attenuation of each type of radiation.
Mass attenuation coefficient is only used for EM radiation - gamma rays in your case. You have to look up the value for the particular gamma ray energy you are interested in, and the type of material the shield is made from.
If you have a shield of thickness x metres, density d, and the mass absorption coefficient is k, then gamma radiation is reduced by the factor e^-(dkx), compared to not having the shield. ('e' is the base of natual logarithms (2.7 approx)).
If you want a more in-depth analysis, you'll have to do some internet searches I'm afraid.
E.g. if for a certa