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Pixie-4 (obsolete)

We recommend the Pixie-4 Express for new customers

75MHz Multichannel Digital Gamma Finder in PXI format

DGF Pixie-4 - Datasheet
(PDF format, 959KB, April 2015)

The DGF Pixie-4 is a multichannel data acquisition system for 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-4 is based on the CompactPCI/PXI standard which allows data transfer rates from Pixie-4 memory to the host computer of up to 109MB/s. Commercial CompactPCI 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-4 module accepts signals directly from a detector preamplifier or photomultiplier tube. After a digitally controlled gain and offset stage, signals are digitized in a 14-bit ADC at a rate of 75MHz. 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 128K of spectrum memory and 128K of list mode memory.

The Pixie-4 module(s) can be controlled either by an in-crate single board computer or through a fiber optic link 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.

The Pixie-4 Software page contains information about Pixie Viewer software.

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

Click here for details about purchasing the Pixie-4.


Pixie-4 Software

Host software and drivers for the Pixie-4.

Pixie-4 Downloads

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

PXI Support Products

PXI crates, interface modules, power supplies.

Pixie-4 Express

125-500 MHz Multichannel DGF in PXIe format


  • 75MHz, 14-bit digitizing of input signal
  • 32bit/33MHz PCI interface with module-to-host transfer rates up to 109MB/s
  • 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 13.7µs for each channel, in 13.3ns intervals
  • 32K x 32bit on-board spectrum memory for each channel
  • 128K x 32bit additional on-board 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 PXI backplane
  • 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/PXI processor, power, and computer modules


The Pixie-4 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 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 220µs, thus spanning an overall range from 434µs 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.

Pixie-4 Data Acquisition Systems

A basic data acquisition system can consist of a 6-slot PXI 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. This is a very compact standalone solution, for example for clover detectors.

Instead of a single board computer residing in the PXI crate, a regular desktop or laptop computer can act as a remote crate controller using a set of adapter cards with a high speed copper or fiber optic data link. Data readout speeds are somewhat lower (80 MByte/s) for remote controllers. For bigger detector arrays, a larger PXI crate (up to 18 slots) can be used.

The preamplifier power supply developed by XIA also includes an external trigger option. This allows the distribution of clocks and triggers between the PXI backplane and external electronics. Besides the system clock, distributed signals can include an external veto, run start synchronization, event triggers and timing signals.


Inputs Analog Four preamplifier inputs, jumper-selectable input impedance:
50 Ohms or 10 kOhm. Not to exceed +/-3.5V if terminated with 50 Ohms and attenuation is not used. Works with common resistive feedback preamplifiers of either signal polarity.
  Digital (TTL 3.3V) Each module has a single MMCX connector which can be programmed to be used for any of the following functions:

Veto: Logic input for externally timed data collection. Suppresses collection when actively held low.

External Trigger: Logic input for a digital trigger matching the delays in the module.

Status: Logic input adding to the recorded status bit pattern in list mode.

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

A second MMCX connector can be used as output directly from the DSP in custom applications.
Data I/O Interface Compact PCI standard, 33 MHz, 32-bit

Data Transfer Rate Memory readout to host: 109 MB/sec
Digital Controls Gain Coarse gain from 0.97 to 11.3 in 64 steps
+/-10% digital gain adjustment for channel matching
Pulse amplitudes up to 2V (after termination) at gain=1
Proportionally lower at higher gain
  Offset DC offset adjustment: -2.5V to +2.5V
  Trigger Adjustable trigger filter to suppress noise
Filter length: 0.053 to 0.838 us
Threshold range: 4 to 2000 ADC steps (after filter)
  Filtering Trapezoidal filter with peaking times 0.08 to 106 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: 50 ns to 871 us
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
  List Mode Time stamp, energy, optional waveforms for each event stored in 128K (32-bit) word buffer.
  Timing Events are time stamped with 75MHz 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-4.html, last updated November 30, 2017
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