Table of Contents
Advertisement
PSI System Controls and Diagnostics
10 Principle of Operation
10.1 Wideband digital pulse processing
Traditional photomultiplier pulse-processing energy analysis systems generally feature a Pre-
amplifier close to, or in, the photomultiplier base. Depending on signal to noise considerations,
the preamplifier may be a fast current amplifier or a charge integrator. The preamplifier signal is
transmitted to a shaping amplifier which produces an output whose height reflects the amount of
charge delivered by the photomultiplier. For energy spectrometry the pulse height is measured
by an analog to digital converter, for example in a multi-channel analyzer. For simple pulse
counting, the pulse is compared with low and possibly high limits in a single channel analyzer
and scaled.
The D100 uses a different approach. The basic pulse shape from the multiplier anode is
preserved and digitized at high rate. All pulse size and shape analysis then occurs in a FPGA
(field-programmable gate array) device using numerical processing algorithms. The algorithms
are executed in real time on a pulse by pulse basis, and can include various characterizations in
addition to the traditional pulse size analysis. These can include pulse width analysis and pulse
shape analysis for pileup rejection, and dynamic background correction.
PMT
PMT
Figure 11. Comparison of traditional pulse processing (above) and D100 pulse processing
(below).
D100 User Manual
Integrating
amplifier
D100
Fast
amplifier
D100_UM_081027
Shaping
amplifier
ADC
FPGA
Pulse
height
analyzer
Page 26 of 46
Advertisement
Table of Contents
