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N number of delta rays

  1. Jun 25, 2009 #1
    Im trying to find the number of delta rays though a material and am having some trouble with the units, can anyone help?

    The number of delta rays through a material is given by N=epsilon(1/E1 - 1/Emax), where epsilon=[2*Pi*A^2*e^4*ne*x]/[m*c^2], where A is unitless, [ne]=cm^-3, and the denominator is in MeV's. I think I want epsilon in MeV's because N should be unitless, so it would cancel out the MeV from the rest of the equation.

    My problem is the factor of e. I know it can't be in coulombs, so I need to somehow convert it to the right units. From what Im seeing it needs to be in cm*MeV to have epsilon end up in MeV's.

    I know Coulombs/(4*Pi*epsilon not) is Joules*Meters, but Im not sure how to use that correctly without introducing a factor of (4*Pi*epsilon not) that isnt part of the equation.
  2. jcsd
  3. Jun 25, 2009 #2
    I don't recognize what you are talking about. Are you talking about the Bethe Bloch energy loss equation dE/dx for charged particles in matter, and the ionization constant I ? I think that if you have dE/dx for a thickness dx, and the average energy loss per delta ray, the ratio would give the number of delta rays. There is an N that appears in dE/dx, which is atoms per cm3.
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