devices that do not need to talk to the beamline computer directly, such as amplifiers,
SCAs, gates, and TACs. The crates, such as CAMAC, FASTBUS, VME, and PXI,
have backplanes that can send data to and receive commands from the beamline
computer. Accordingly, they will contain the devices that convert signals to numbers, such as scalers and ADCs. Good descriptions of all of these electronics are of
course on Wikipedia and also in Knoll.
5.15.11 The Trend toward Digital
Just as the signals for our telephones and televisions have gone digital, so has much
of the electronics for X-ray detection. A key step has been replacement of analogue
shaping amplifiers with numerical processing of digitized detector waveforms, either
directly from NaI(Tl) detectors or following preamplification (Fig. 5.16). The benefits of digital processing include (a) better time and energy resolution, (b) better
pileup rejection, and (c) higher throughput. As ADCs and processing electronics
keep getting faster, this trend is likely to continue for some time.
5.16 Suggested Exercises
1. Calculate the photon flux (I 0 ) at 20 keV if a 10 cm N 2 -filled ion chamber gives a
measured current of 1 pA.
2. Calculate the number of electron-hole pairs produced by a 10 keV photon in Ge.
3. Calculate the theoretical best energy resolution for a Si diode detector at 20 keV.
4. Calculate the theoretical maximum number of Cooper pairs disrupted in a
Nb STJ.
5. Calculate the temperature change in a TES detector when a 6.4 keV photon is
absorbed in a Bi absorber that is 4 μ thick with a cross section that is 320 μ by
305 μ. Assume a heat capacity of 1 pJ K
À1 [202].
6. Calculate the deadtime losses for a random incident flux of 10
5 photons s
À1 for a
paralyzable detector system with a deadtime of 10 μs. Do the same for a
non-paralyzable system.
5.17 Reference Books and Review Articles
1. Radiation Detection and Measurement, Glenn Knoll, fourth Edition, Glenn
F. Knoll, John Wiley & Sons, New York, 2010 ISBN-10: 0470131489. A classic
resource about detectors of ionizing radiation. Updated to include more on
cryogenic devices.
5.17 Reference Books and Review Articles
129
SCAs, gates, and TACs. The crates, such as CAMAC, FASTBUS, VME, and PXI,
have backplanes that can send data to and receive commands from the beamline
computer. Accordingly, they will contain the devices that convert signals to numbers, such as scalers and ADCs. Good descriptions of all of these electronics are of
course on Wikipedia and also in Knoll.
5.15.11 The Trend toward Digital
Just as the signals for our telephones and televisions have gone digital, so has much
of the electronics for X-ray detection. A key step has been replacement of analogue
shaping amplifiers with numerical processing of digitized detector waveforms, either
directly from NaI(Tl) detectors or following preamplification (Fig. 5.16). The benefits of digital processing include (a) better time and energy resolution, (b) better
pileup rejection, and (c) higher throughput. As ADCs and processing electronics
keep getting faster, this trend is likely to continue for some time.
5.16 Suggested Exercises
1. Calculate the photon flux (I 0 ) at 20 keV if a 10 cm N 2 -filled ion chamber gives a
measured current of 1 pA.
2. Calculate the number of electron-hole pairs produced by a 10 keV photon in Ge.
3. Calculate the theoretical best energy resolution for a Si diode detector at 20 keV.
4. Calculate the theoretical maximum number of Cooper pairs disrupted in a
Nb STJ.
5. Calculate the temperature change in a TES detector when a 6.4 keV photon is
absorbed in a Bi absorber that is 4 μ thick with a cross section that is 320 μ by
305 μ. Assume a heat capacity of 1 pJ K
À1 [202].
6. Calculate the deadtime losses for a random incident flux of 10
5 photons s
À1 for a
paralyzable detector system with a deadtime of 10 μs. Do the same for a
non-paralyzable system.
5.17 Reference Books and Review Articles
1. Radiation Detection and Measurement, Glenn Knoll, fourth Edition, Glenn
F. Knoll, John Wiley & Sons, New York, 2010 ISBN-10: 0470131489. A classic
resource about detectors of ionizing radiation. Updated to include more on
cryogenic devices.
5.17 Reference Books and Review Articles
129