Biomedical Engineering Reference
In-Depth Information
Fig. 11.12
Problem 69.
deposited in a subslab of thickness 0.25 cm at a certain depth in
the slab is found to be 347 MeV. From these data, determine
what the energy absorbed per unit mass (absorbed dose) would
be at this depth for a uniform, broad beam of normally incident
neutrons with unit fluence.
71.
The total linear attenuation coefficient for 10-keV electrons in
water is 77.6
µ
m
-1
, partitioned as follows:
Elastic scattering
38.2
µ
m
-1
lonization
37.4
Excitation
2.0
77.6
µ
m
-1
Total
(a)
What is the probability that a 10-keV electron will travel
100 Å without having an interaction?
(b)
What is the probability that it will travel 200 Å without
interacting and then experience its first collision as an
ionization within the next 10 Å?
(c)
What is the probability that the first collision will be an
excitation at a distance between 60 Å and 80 Å?
72.
Attenuation coefficients for 10-keV electrons in water are given
in the last problem. Using the sequence of random numbers
R
i
, in Table 11.6, find the flight distance and type of collision
for three electrons. Take the event types in the order given as
the last problem.
73.
In a certain radiation-transport problem, the probability density
P
(
Q
)
for energy loss
Q
decreases linearly with
Q
from
Q
= 0
to
the maximum possible value of
Q
,
Q
= 800
eV, where
P
(800) = 0
.
(a)
Write an analytic function for the normalized distribution
P(Q)
with
Q
expressed in eV.
(b)
What are the units of
P
(
Q
)
?
