Re: cosmic rays

[john grant <grantjoh@pacbell.net>]

BERNARD L COHEN wrote:



> On Fri, 27 Sep 2002, john grant wrote:

>

> > How does the fact that the cosmic rays go all the way through the body factor into

> > this?

> >

> > BERNARD L COHEN wrote:

> >

> > >         All natural radiation strikes an average person's body about

> > > 15,000 times per second. Cosmic rays account for less than 1/4 of this, or

> > > about 3500 times per second.

>

>         These numbers aree estimated from the doses. For total radiation,

> I use 80 mrem per year = 80 mrad per year. I take the average energy of

> gamma rays in natural radiation deposited in the body to be 0.6 MeV, and

> the average mass of the body to be 70 Kg. Using the definition 1 mrad = 1

> E-5 joules deposited per Kg, it is straightforward to calculate the number

> of gamma rays.

>         I didn't do any deep thinking about the difference between cosmic

> rays and other natural radiation, but just assumed that the number of

> gamma rays was proportional to the dose. My apologies if a more accurate

> treatment was required.



A 0.6 MeV gamma would likely travel one inch or less in the body.

A high energy muon would travel more than 60 inches in a standing person.



Seems like there should be a 60 to 1 factor in there.





************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.

You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/