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Pixie-4 Express
125-500MHz Multichannel Digital Gamma Finder in PXI Express format

DGF Pixie-4e - Datasheet
(PDF format, 271kB, October 2015)

The DGF Pixie-4 Express (Pixie-4e) is a multichannel data acquisition system for fast radiation detectors in nuclear physics and other applications requiring coincident radiation detection. It provides digital spectrometry and waveform acquisition for four input signals per module; several modules can be combined into a larger system. The DGF Pixie-4e is based on the CompactPCI/PXI Express standard which allows data transfer rates from Pixie-4e memory to the host computer of several hundred MB/s. In a suitable PXI Express chassis, multiple modules can be read out in parallel. Commercial CompactPCI or CompactPCI Express modules - DSP processor boards, HV supplies, embedded host computers - can be added to build a flexible standalone data acquisition and analysis system.

Each of the four channels of a Pixie-4e module accepts signals directly from a detector preamplifier or photomultiplier tube. After a digitally controlled gain and offset stage, signals are digitized in a 12-16 bit ADC at a rate of 125-500MHz. Triggering, pile-up inspection and filtering of the data stream is performed in real time; pulse heights and other event data is calculated on an event-by event basis. Results are stored in 32K of spectrum memory per channel and 256MB of list mode memory organized as a FIFO.

The Pixie-4e module(s) can be controlled either by an in-crate single board computer or through a remote PCIe bridge by a desktop computer. XIA provides a set of C driver functions as well as a graphical user interface, the Pixie-Viewer, based on Wavemetric's IGOR PRO. Linux, LabVIEW and ROOT demo code is available.

The Pixie-4e Software page contains information about Pixie Viewer software, which is used to operate the Pixie-4e.

The Pixie-4e Download page contains links to Datasheets, Manuals, Application Notes and Articles.

Click here for details about purchasing the Pixie-4e.


Pixie-4e Software

Host software and drivers for the Pixie-4 and Pixie-500.

Pixie-4e Downloads

Datasheets, Manuals, Application Notes and Articles, as well as downloadable software and firmware.

Pulse Shape Analysis with the Pixie-4e

PXI Support Products

PXI crates, interface modules, power supplies.


16 integrated DGF channels on a single-width 6U PXI card


  • 125-500MHz, 12-16 bit digitizing of input signal
    Standard configurations: 125MHz/16-bit, 500MHz/14-bit, 125MHz/12-bit
  • x4 PCI Express interface with module-to-host transfer rates of several hundred MB/s (interrupt driven DMA)
  • Simultaneous amplitude measurement and pulse shape analysis for each channel
  • Pulse heights measured with up to 16 bits accuracy on each of the four channels
  • Waveform acquisition up to 4K samples for each channel (8-32 us)
  • 32K x 32bit on-board spectrum memory for each channel
  • 256 MB on-board FIFO memory for list mode data
  • Programmable gain, input offset, trigger and energy filter parameters
  • Coincident data acquisition across channels and modules
  • Triggers, run synchronization and clocks distributed over PXIe backplane
  • Online pulse shape analysis reporting sums over characteristic pulse regions (user defined)
  • Graphical user interface and C-based driver libraries
  • Operated through in-crate single board PC or through fiber optic link from desktop
  • Can be combined with commercial CompactPCI/PXIe processor, power, and computer modules
  • Customizable in hardware, firmware and software


The Pixie-4e is best operated through XIAs host control software, the Pixie Viewer. In the Viewer, users can set all parameters relevant to the data acquisition, store them in settings files, and run the modules. Results can be displayed from data files or the module's memory to provide instant feedback on the state of the experiment.
The Pixie Viewer has several diagnostic tools for setting up a new system. There is a display of untriggered waveforms as they are seen by the Pixie module. The time between subsequent samples can be chosen between 53ns and 220Ás, thus spanning an overall range from 434Ás to 1.8 seconds. The waveforms can also be subjected to a fast Fourier transformation (FFT). These displays are useful to investigate if there is any electromagnetic interference in the system, from 50/60Hz to radio-frequency pickup. For system setup, users can employ automated tools to determine the decay time of the preamplifier and to set the offset to a specified fraction of the dynamic range.

The Pixie Viewer is based on IGOR PRO, distributed by WaveMetrics. IGOR PRO is a program package for data display, analysis, and experiment control. It has a rich graphical interface, is documented well and easy to program. Users can easily add their own data analysis to the data acquisition software that XIA supplies.
Experiments that run their own data acquisition software can use XIA's driver (written in C) to integrate Pixie modules into their system. Module setup, start and stop of runs, and data readout can be performed using a small number of functions. The Pixie Viewer is based on the same driver and can be used as a programming example. Other examples are provided for LabView, ROOT, and command line C programs. The C driver is compatible with Linux.

Pixie-4 Express Data Acquisition Systems

A basic data acquisition system can consist of a 8-slot PXIe crate, one Pixie module, a single board host computer, a preamplifier power supply and a high voltage module. The host computer is used to download software and settings to the Pixie module, start and stop runs, read out the data and write it to disk.

Instead of a single board computer residing in the PXIe crate, a regular desktop or laptop computer can act as a remote crate controller using a set of PCIe bridge cards with a high speed copper or fiber optic data link. Data readout speeds are somewhat lower for remote controllers. For bigger detector arrays, a larger PXIe crate (up to 18 slots) can be used.


Inputs Analog Four preamplifier inputs, switch-selectable input impedance:
50 Ohm or 2 kOhm. Not to exceed +/-3.5V if terminated with 50 Ohms and attenuation is not used. Optional 1/8 attenuation. Works with common resistive feedback preamplifiers of either signal polarity.
  Digital (TTL 3.3V) Each module has a front panel MMCX connector which can be used to suppress data collection (Veto).

The Pixie-4e connects to the PXI and PXIe backplane lines, including bussed, nearest neighbor, star and differential star trigger lines. All clock, trigger and synchronization signals are distributed over these lines.

A high density front panel 10-pin connector can be used for I/O in custom applications
Data I/O Interface PCIe standard, x4
  Data Transfer Rate Memory readout to host: several hundred MB/s
  Transfer Type Interrupt driven PCIe DMA transfers from Pixie-4e FIFO memory to host PC memory. FIFO buffer ensures uninterrupted acquisition of detector pulses up to the maximum transfer rate.
Digital Controls Gain

Coarse gain: 8 gain settings from 1.6 to 22.6
+/-10% digital gain adjustment for channel matching
(Gain steps and ranges may vary for digitization rates > 125 MHz)
Pulse amplitudes up to 1.25V (after termination) at gain=1.6
Proportionally lower at higher gain

  Offset DC offset adjustment: -3V to +3V
  Trigger Adjustable trigger filter to suppress noise
Filter length: 0.016 to 0.504 us
Threshold range: 4 to 2000 ADC steps (after filter)
  Filtering Trapezoidal filter with peaking times 0.048 to 63.4 us
Adjustable flat top to eliminate ballistic deficit effects
  Pileup Options to reject (default), ignore, exclusively accept piled up pulses which follow too closely to measure pulse heights individually
  Coincidence Programmable coincidence window: 40 to 1016 ns
Reject unwanted hit patterns of the 4 channels
  Data collection MCA limits and number of bins
Waveform lengths and pre-trigger delay
Data Outputs MCA 1024 to 32,768 channels (32 bits deep) per Pixie channel
Additional memory for sum or 2D spectra
  List Mode Time stamp, energy, optional waveforms for each event buffered in 256MB FIFO.
  Timing Events are time stamped with ADC clock in list mode.
  Statistics Livetime, runtime, input rate, output rate, filter dead time
  Diagnostics ADC trace, baseline distribution, baseline history, FFT noise spectrum

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http://www.xia.com/DGF_Pixie-4e.html, last updated February 9, 2017
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