386 7 Nuclear Physics – I
7.36 If the mean range of 10 MeV protons in lead is 0.316 mm, calculate the mean
range of 20 MeV deuterons and 40 MeVα-particles.
[University of Manchester]
7.37 Show that the range ofα-particles and protons of energy 1–10 MeV in alu-
minium is 1/1,600 of the range in air at 15◦C, 760 mm of Hg.
7.38 Show that except for small ranges, the straggling of a beam of^3 He particles is
greater than that of a beam of^4 He particles of equal range.
[University of Cambridge]
7.39 The range of a 15 MeV proton is 1,100μm in nuclear emulsions. A second
particle whose initial ionization is the same as the initial ionization of proton
has a range of 165μm. What is the mass of the particle? (The rate at which a
singly ionized particle loses energyE, by ionization along its range is given
by dE/dR=K/(βc)^2 MeVμm whereβcis the velocity of the particle, and
Kis a constant depending only on emulsion; the mass of proton is 1,837 mass
of electron)
[University of Durham]
7.40α-particles and deuterons are accelerated in a cyclotron under identical con-
ditions. The extracted beam of particles is passed through an absorber. Show
that the range of deuteron will be approximately twice that ofα-particles.
7.41 Theα-particle fromTh C′have an initial energy of 8.8 MeV and a range in
standard air of 8.6 cm. Find their energy loss per cm in standard air at a point
4 cm distance from a thin source.
[University of Liverpool]
7.42 Compare the stopping power of a 4 MeV proton and a 8 MeV deuteron in the
same medium.
7.43 (a) Show that the specific ionization of 480 MeVα-particle is approximately
equal to that of 30 MeV proton
(b) Show that the rate of change of ionization with distance is different for the
two particles and indicate how this might be used to identify one particle,
assuming the identity of the other is known.
[University of Bristol]
7.44 Calculate the thickness of aluminum in g cm−^2 that is equivalent in stop-
ping power of 2 cm of air. Given the relative stopping power for aluminum
S= 1 ,700 and its density= 2 .7gcm−^3.
7.45 Calculate the minimum energy of anα-particle that can be counted with a
GM counter if the counter window is made of stainless steel (A≈56) with
2 .5mgcm−^2 thickness. Take the density of air as 1.226 g cm−^3 , and atomic
weight as 14.6.
7.46 Calculate the range in aluminum of a 5 MeVα-particle if the relative stopping
power of aluminum is 1,700.