Biomedical Engineering Reference
In-Depth Information
23.
Use the nonrelativistic stopping-power formula and show that
Eq. (10.7) holds.
24.
What are the relative magnitudes of the responses of an
E
(-d
E
/d
x
)
particle identifier to a proton, an alpha particle, and a
stripped carbon nucleus?
The
W
value for silicon is 3.6 eV ip
-1
. Calculate the mean
number of ion pairs produced by a 300-keV beta particle
absorbed in Si.
25.
26.
Calculate the number of ion pairs produced by a 4-MeV alpha
particle in
(a)
36
eV ip
-1
)
an ionization chamber filled with air (
W
=
3.6
eV ip
-1
).
(b)
a silicon surface-barrier detector (
W
=
27.
At a temperature of absolute zero, some electrons occupy states
at the donor impurity levels of an n-type semiconductor
(Fig. 10.18). True or false?
28.
Why is reverse, rather than forward, bias used for
semiconductor junctions in radiation measurements?
29.
A 1.27-MeV photon loses 540 keV and 210 keV in successive
Compton scattering events in the sensitive volume of a Ge
detector before escaping.
(a)
Estimate the total number of secondary electrons produced
by the events.
(b)
Would the device register the passage of the photon as a
single event or as two events?
30.
A silicon semiconductor detector has a dead layer of 1
µ
m
followed by a depletion region 250
µ
m in depth.
(a)
Are these detector dimensions suitable for alpha-particle
spectroscopy up to 4 MeV?
(b)
For beta-particle spectroscopy up to 500 keV?
31.
If 2.1 MeV of absorbed alpha-particle energy produces 41,100
scintillation photons of average wavelength 4800 Å in a
scintillator, calculate its efficiency.
32.
A 600-keV photon is absorbed in a NaI(Tl) crystal having an
efficiency of 11.2%. The average wavelength of the scintillation
photons produced is 5340 Å, and 11% of them produce a signal
at the cathode of the photomultiplier tube. Calculate the
average energy from the incident radiation that produces one
photoelectron at the cathode (the “
W
value”).
33.
Figure 10.30 was obtained for a 4
4 in. NaI(Tl) crystal
scintillator. Sketch the observed spectrum if measurements
were made with the same source, but with a NaI crystal that
was
(a)
×
very large
(b)
very small.
