Assignment:
1. What thickness of concrete (density 2200 kg m -3) is needed to attenuate a collimated beam of 1-MeV y rays, by la factor of 106? The mass attenuation coefficient of concrete µm = 0.064 cm2 g-1 .
2. A thin (1 mg/cm2) target of 48Ca is bombarded with a 10-nA beam of a particles. A detector, subtending a solid angle of 2 x 10-3 steradians, records 15 protons per second. If the angular distribution is measured to be isotropic, determine the total cross section (in mb) for the 48Ca (a,p) reaction. Take the atomic mass of 48Ca to be 48 u.
3. What is the half-life of the resonance in 113Cd, shown in Figure 1.16, if it has a total width of 0.133 eV? Compare this with the collision time for a 0.17-eV neutron, which is approximately the time it takes for the neutron to pass the nucleus. Take the nuclear radius to be R = 1.2A1/3 fm.
4. Calculate the maximum energy a 5-MeV a particle can transfer to an electron initially at rest. Assume the a particle is infinitely massive compared with the electron.