# Calculating Activity of proton beam

1. Mar 19, 2013

### wormhole228

1. The problem statement, all variables and given/known data
A natural lithium target 3.8 mg cm-2
thick is bombarded with a
125 µA beam of 3.5 MeV protons initiating a 7Li(p,n) reaction.
Assuming a reaction cross section of 300 mb, calculate the
activity produced by a 15 minute bombardment.

2. Relevant equations
λN=$\phi$$\sigma$NT(1-e-λt)
I=I0e-μx

3. The attempt at a solution
125μA=125μC/s(1 proton/1.602*10-19C)(15*60s)=7.022*1017 protons. I'm not really sure where I would go from here. I got μ/$\rho$=0.0258 cm2/g. Yet, I can't find the actual linear attenuation coefficent. I figured we would use the activation equation, but I'm not sure on the flux, and the other units.

2. Mar 21, 2013

### Staff: Mentor

You can convert the given area density to an atomic density - ideally in the units atoms/barn. Together with the given cross-section, ...

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