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Features

• Complete spectrometer with digital trigger, filter, pileup rejection, MCA and waveform capture at 80 MHz.
  
• Designed for high precision gamma-ray coincidence spectroscopy with HPGe detectors.
  
• Directly compatible with scintillator/PMT combinations: NaI, CsI, LaBr3, and many others.
  
• Synchronous waveform acquisition across channels and modules.
  
• Acquisition conditional to on-board coincidence tests between channels.
  
• Pulse heights computed to 16bit precision for each of the four channels (binned on-board into 32K spectra).
  
• Addback spectrum for clover detectors.
  
• Level-1 FAST CAMAC and USB 2.0 data I/O.
  
• Fast block reads from on-board list mode memory .
  
• Front panel I/O for external vetoing (global or channel specific) and for trigger and multiplicity information.
  
• Clock and trigger distribution between modules via auxiliary connector on rear.
  
• Programmable gain, offset, trigger filter and threshold, energy filter rise and flattop times.
  
• User programmable DSP for pulse shape analysis.
  
• Compatible with earlier 40 MHz models (Revision D and E).
  

Specifications

• Preamp Signal Inputs (4 Analog)
  Impedance: 50 or 5k Ohms, jumper selectable
  Voltage range: -2.5V to +2.5 V DC, accepts input from most common resistor feedback preamps of either polarity. Other input impedances and voltage ranges by special order.
  DC offset: between -2.5V and +2.5V, with 16 bit precision .
  Gain: Factor of 1-10 gain range, in 64 steps <10%. Digital gain adjustment for channel matching.
  
• Multiplicity Unit and I/O
  Input: 50 Ohm terminated analog input, from output of previous module or open.
  Output: Sum of input plus 50mV per fast trigger from enabled channels (into 50 Ohms).
  Delay: Input to output delay is 10 ns.
  
• Digital Front Panel I/O
  Busy Output / Sync Input: used to get synchronized timer and run start/stop operation, by externally OR'ing Busy outputs from many DGF modules and returning the result to their Sync inputs
  GFLT (gate) Input: Its presence (logic 1) can be required for event triggering on a channel-by-channel basis. To be valid, it must arrive within a peaking time after pulse detection.
  Trig Output: Trigger outputs from many DGFs may be externally OR'ed and used to veto the external GFLT generating logic to enforce common dead times whenever at least one module incurs dead time.
  GSLT (validation) Input: Optional digital input
  Channel GATE Inputs: Used to inhibit acquisition in individual channels with dedicated GATE signal. User can specify GATE window and rejection polarity. If rejection is disabled, GATE status for each channel is reported in the list mode data stream.
  
• Software Controls (stored on file)
  Filtering: Triangular/Trapezoidal. Filer rise time and flat top set independently between 0.025 - 100 microseconds in small steps. Alternaive integration methods for very fast pulses or rectangular pulses.
  Pileup: Independently set trigger filter parameters, pulse detection threshold, and pileup inspection criteria may be tuned to achieve best results in every situation and gamma-ray energy regime.
  Data acquisition: Choose waveform record lengths from 0 - 12.7 microseconds for local processing, or export to host.
  Coincidence: Coincidence window and combination of acceptable hit patterns.
  Analog signal conditioning: Gain, offset, pulse polarity, preamplifier decay time.
  Trigger: Channel trigger enable, trigger distribution across channels and modules.
  
• Data outputs
  List mode: Configurable output stream buffered in local memory, 8K words deep, may span many events. Local 8K buffer is transferred to 128K external memory from which it can be read out in a fast USB 2.0 block read. Each event may contain a time stamp, pulse height information, timing information for each channel, results from requested pulse shape analyses, and digitized waveforms. Time stamps are in units of 12.5 ns. The run start time is 48-bits long. The event time is 32 bits, derived from a digital leading edge discriminator. Pulse shape analysis with a software constant fraction discriminator can yield sub-bin timing to a few ns in the best cases.
  Spectra: 32K words of spectrum memory per channel. Can set lower limits for spectrum entries and can combine bins to create smaller spectra (16K, 8K, ...) .
  Statistics: Records run duration, event rate and both live time and input rate per channel.
  

Performance

• Dead time:
  Filter dead time: (2 * peaking time + flat top time)
  Additional dead time for raw data transfer to DSP: approximately 3x length of waveform.
  
• Event processing time:
  Pulse height reconstruction: About 1.5 microseconds per pulse. Performed after storing of raw data while acquisition continues.
  Pulse shape analysis for CFD timing: adds about 800ns plus length of waveform to analyze.
  
• Data transfer:
  CAMAC: The DGF-4C will perform according to the fast CAMAC level-1 protocol and supports 400ns read cycles in block transfer mode.
  USB 2.0: The DGF-4C currently achieves data transfer rates of about 20Mbyte/s from on-board memory.
  
• Energy resolution:
  Comparable to best analog units. Degradation at high count rates is typically dominated by imperfect pole/zero cancellation in the preamplifier.
  

Ordering Information

• Power Requirements:
  +6 volts @ 4.1A, -6 volts @ 0.3A, no current on +12 volts or -12 volts.
  
• Dimensions:
  Single width CAMAC module.
  
• Weight (shipping):
  3.0 lbs.
  
• Manual: Hardware and software manuals provided with each oerder.
  
• Accessories: 4 BNC-SMA adapter cables and 1 backplane clock/trigger cable provided with each instrument.
  
• Software: The DGF-4C uses downloadable files for its internal digital signal processing electronics. Host control software including these files is provided by XIA. C driver libraries for integration in user systems and/or user software are provided upon request. Customized firmware and software can be developed for nominal NRE fees.

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http://www.xia.com/DGF-4C.html, last updated November 19, 2008
© XIA LLC 2008