Order the following in terms of typical penetration depth in materials, lowest to highest, when the particles initially have an energy in the MeV range. Answer with a string, e.g. ABCD (this is not the correct answer) A. Electrons B. Ions C. Gamma particles D. Neutrons Answer: BADC Whas the atom mass 183.85u and the electron the mass 0.00054858u. The minimum atomic recoil energy needed to create damage in W is 42 eV [F. Maury et al, Radiat. Eff. 38, 53 (1978)]. What is the energy of electrons needed to start creating damage in W in the classical ap- proximation? Answer in units of keV, points are given if answer is within 5% of the correct value. Answer: 7033.1 x W has the atom mass 183.85u and the electron the mass 0.00054858u. Assume that the minimum atomic recoil energy needed to create damage in W is 42 eV. What is the energy of electrons need to start creating damage in W in the relativistic, exact calculation? Answer in units of keV, points are given if answer is within 10% of the correct value. Answer: 83.93 x What are the units of stopping power equivalent to? Select one: a. Power b. Force c. Energy x d. Pressure An energetic carbon ion (mass = 12 amu) with initial energy 30 MeV is penetrating a typical solid, say Si. Which of the following describes best its slowing down before it stops? Select one: 1. It first slows down by collisions with electrons, then speeds up by nuclear collisions. 2. It first slows down mainly by nuclear collisions, then by collisions with electrons which are stronger than those with nuclei 3. It first slows down by collisions with electrons which first strengthen and then weaken, then starts slowing down by nuclear colli- sions which first get stronger and then weaken 4. It first slows down by collisions with electrons which first strengthen and then weaken, then starts slowing down by nuclear x collisions which first weaken and then get stronger. 5. It first slows down by collisions with electrons which continuously weaken, then starts slowing down by nuclear collisions which first get stronger and then weaken 6. It first slows down by collisions with electrons which first weaken and then strengthen, then starts slowing down by nuclear colli- sions which first get stronger and then weaken A gold ion (mass 197 amu) with initial energy of 500 MeV is penetrating a pure elemental metal. Which of the following describes best the mechanism by which it produces damage in the material? Select one or more: 1. It first produces damage by electronic stopping power in an ion track, then starts x producing damage also by nuclear collisions 2. It produces damage only by nuclear collisions 3. It does not produce any damage lon tracks have not been observed in pure elemental metals. It first produces damage by nuclear collisions, then starts producing damage also by electronic stopping power in an ion track. 5. It first produces damage by electronic stopping power in an ion track, then stops down A hydrogen ion (mass 1 amu) with initial energy of 100 eV is penetrating W, which has the threshold displacement energy 40 eV. Which of the following describes best the mechanism by which it produces damage in the material? Select one or more: 1. It produces damage by electronic excitations 2. It kicks a W atom into the vacuum 3. It does not produce any damage 4. It first penetrates the material and then in the end kicks a W atom off its lattice site. *

What is the difference between (rays and characteristic x rays? Is either necessarily more energetic than the other? Which can be the most energetic?

(a) Find the velocity of a neutron that has a 6.00-fm wavelength (about the size of a nucleus). Assume the neutron is nonrelativistic. (b) What is the neutron's kinetic energy in MeV?

(a) If the average molecular mass of compounds in food is 50.0 g, how many molecules are mere in 1.00 kg at food? (b) How many ion pairs are created in 1.00 kg of food, if it is exposed to 1000 Sv and it takes 32.0 eV to create an ion pair? (c) Find the ratio of ion pairs to molecules. (d) If these ion pairs recombine into a distribution of 2000 new compounds, how many parts per billion is each?

Experiments are performed with ultra-cold neutrons having velocities as small as 1.00 m/s. (a) What is the wavelength of such a neutron? (b) What is its kinetic energy in eV?

Unreasonable Results A physicist scatters (rays from a substance and sees evidence of a nucleus 7.51013m in radius. (a) Find the atomic mass of such a nucleus. (b) What is unreasonable about this result? (c) What is unreasonable about the assumption?

What is the ratio of the velocity of a (particle to that of an (particle, if they have the same nonrelativistic kinetic energy?

(a) What is the uncertainty in the energy released in the decay of a due to its short lifetime? (b) What traction of the decay energy is this, noting that the decay mode is (so that all the mass is destroyed)?

(a) The lifetime of a highly unstable nucleus is 10-20. What is the smallest uncertainty in its decay energy? (b) Compare this with the rest energy of an electron.

A neutron generator uses an (source, such as radium, to bombard beryllium, inducing the reaction 4He+9Be12C+n. Such neutron sources are called RaBe sources, 0r PuBe sources if they use plutonium to get the (s. Calculate the energy output of the reaction in MeV.