PIXIE-4 User’s Manual
V2.69
©
XIA
2015. All rights reserved.
iii
1 Overview
The Digital Gamma Finder (DGF) family of digital pulse processors features unique
capabilities for measuring both the amplitude and shape of pulses in nuclear spectroscopy
applications. The DGF architecture was originally developed for use with arrays of multi-
segmented HPGe gamma-ray detectors, but has since been applied to an ever broadening range
of applications.
The DGF Pixie-4 is a 4-channel all-digital waveform acquisition and spectrometer card based
on the CompactPCI/PXI standard for fast data readout to the host. It combines spectroscopy
with waveform capture and on-line pulse shape analysis. The Pixie-4 accepts signals from
virtually any radiation detector. Incoming signals are digitized by 14-bit 75 MSPS ADCs.
Waveforms of up to 13.6 μs in length for each event can be stored in a FIFO. The waveforms
are available for onboard pulse shape analysis, which can be customized by adding user
functions to the core processing software. Waveforms, timestamps, and the results of the pulse
shape analysis can be read out by the host system for further off-line processing. Pulse heights
are calculated to 16-bit precision and can be binned into spectra with up to 32K channels. The
Pixie-4 supports coincidence spectroscopy and can recognize complex hit patterns.
Data readout rates through the CompactPCI/PXI backplane to the host computer can be over
100Mbytes/s. The PXI backplane is also used to distribute clocks and trigger signals between
several Pixie-4 modules for group operation. With a large variety of CompactPCI/PXI
processor, controller or I/O modules being commercially available, complete data acquisition
and processing systems can be built in a small form factor.
1.1 Features
•
Designed for high precision γ-ray spectroscopy with HPGe detectors.
•
Directly compatible with scintillator/PMT combinations: NaI, CsI, BGO, and many
others.
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Simultaneous amplitude measurement and pulse shape analysis for each channel.
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Input signal decay time: as fast as 150ns and up to 10ms, exponentially decaying.
•
Wide range of filter rise times: from 53ns to 109μs, equivalent to 27ns to 50μs
shaping times.
•
Programmable gain and input offset.
•
Excellent pileup inspection: double pulse resolution of 50 ns. Programmable pileup
inspection criteria include trigger filter parameters, threshold, and rejection criteria.
•
Digital oscilloscope and FFT for health-of-system analysis.
•
Triggered synchronous waveform acquisition across channels, modules and crates.
•
Dead times as low as 1
s per event are achievable (limited by DSP algorithm
complexity). Events at even shorter time intervals can be extracted via off-line ADC
waveform analysis.
•
Digital constant fraction algorithm measures event arrival times down to a few ns
accuracy.
•
Supports 32-bit 33 MHz PCI data transfers (>100 Mbytes/second).