New:

Our contributions at ICPA-18 conference

Software for digital Doppler broadening spectroscopy developed in our group is now available for free download.

Digital CDB spectrometer



Detector part of digital CDB spectrometer

  • first digital CDB spectrometer in the world (built in 2010)
  • detectors: Canberra coaxial HPGe detectors, relative efficiency 30, 35 %.
  • digitizer: Detector signals are sampled in the real time using two channel digitizer Acqiris DC440 (12-bit, maximum sampling frequency 420 MHz)


Two-channel 12-bit digitizer used for sampling of detector signals

  • operation: Digital CDB spectrometer can work in two modes:
    • semi-digital setup - detector pulses are firstly shaped by pseudo-Gaussian filter in spectroscopy amplifier in order to improve the signal-to noise ration. Output signals from spectroscopy amplifier with pseudo-Gaussian shape are sampled by digitizer. Acquired waveforms are analyzed by our software cmfit
      • the maximum of sampled waveforms is determined by parabolic fitting;
      • digital filters are engaged to examine shape of each waveform and reject pulses distorted by pile-up or by ballistic deficit.
    • pure-digital setup - detector pulses (i.e. output of the charge sensitive preamplifier) are digitized directly. Sampled waveforms are fitted by a model function consisting of exponential decay function convoluted with a Gaussian.
  • software: Analysis of sampled waveforms is performed by software developed in our group.
  • resolution:
    semi-digital setup: 0.99 KeV (at 511 keV)
    pure-digital setup: 0.88 KeV (at 511 keV)

Full description of the digital spectrometer can be found in the following paper:

Our digital CDB spectrometer was succesfully employed for a precise low background measurement of positron annihlation-in-flight.


Two-dimensional CDB spectrum measured on Mg target using 68Ge/68Ga positron generator and showing the contribution from positron annihilation-in-flight