A. Georgiev

Publications (4)4.34 Total impact

• Article: Digital signal processing and algorithms for /spl gamma/-ray tracking

  W. Gast, R.M. Lieder, L. Mihailescu, M.J. Rossewij, H. Brands, A. Georgiev, J. Stein, Th. Kroll
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  ABSTRACT: Gamma-ray tracking is a new concept to improve efficiency and sensitivity of the next generation, high resolution /spl gamma/-ray spectrometers. Tracing multiple scattered /spl gamma/-rays inside an array of large volume composite, segmented Ge-detectors, the photo energies of the individual /spl gamma/-rays and their incident directions can be precisely reconstructed. This results in an improved efficiency and peak-to-total ratio, and a reduced Doppler-broadening. The reconstruction efficiency depends on how accurate the positions, where the /spl gamma/-rays interact with the Ge-crystals, can be localized. Novel digital signal processing hardware modules and related software algorithms are described, which allow an online determination of the energies, times, and interaction positions of the /spl gamma/-rays by analyzing the shapes of the charge signals induced on the segments.
  IEEE Transactions on Nuclear Science 01/2002; · 1.45 Impact Factor
• Article: An analog-to-digital conversion based on a moving window deconvolution

  A. Georgiev, W. Gast, R.M. Lieder
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  ABSTRACT: A high-performance analog-to-digital conversion technique for nuclear spectroscopy applications with unconventional architecture is described. This technique is planned to be used in Phase III of the European γ-ray facility project EUROBALL. The conversion is based on the Moving Window Deconvolution (MWD) method for signal processing in nuclear spectroscopy which has been introduced recently. This method allows the conversion to be represented as a sequence of measurements of the total charge of the event and consequently, by applying for example a simple oversampling scheme to achieve a high accuracy. The proposed MWD-type conversion exhibits very low differential and integral nonlinearities over a 14-bit resolution range with an effective conversion dead-time virtually zero. The last feature combined with an inherent pipeline conversion structure is of great importance for applications in large-scale multi-detector arrays like EUROBALL. The key parameters of the development have been theoretically estimated and measured with a prototype consisting of a free running A/D converter and a digital signal processor
  IEEE Transactions on Nuclear Science 09/1994; · 1.45 Impact Factor
• Article: Digital pulse processing in high resolution, high throughput, gamma-ray spectroscopy

  A. Georgiev, W. Gast
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  ABSTRACT: A new method for processing signals produced by high resolution, large volume semiconductor detectors is described. These detectors, to be used in the next generation of spectrometer arrays for nuclear research (i.e., EUROBALL, etc.), present a set of problems, such as resolution degradation due to charge trapping and ballistic deficit effects, poor resolution at a high count rate, long term and temperature instability, etc. To solve these problems, a new approach based on digital moving window deconvolution (MWD) is developed
  IEEE Transactions on Nuclear Science 09/1993; · 1.45 Impact Factor
• Article: X-ray detectors with digitized preamplifiers

  J. Stein, F. Scheuer, W. Gast, A. Georgiev
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  ABSTRACT: With direct digitization of detector pulses, software algorithms are used to calculate the energy of incident photons. Fast high resolution sampling adc's and digital signal processors replace shaping amplifiers and spectroscopy adc's. The difference between the classical analog approach for pulse processing and direct digitization can be summerized as follows. In analog systems, a preamplifier output is filtered by analog means and then digitized to be acquired in a multichannel analyzer, whereas the full digital system will digitize first and then filter by application of algorithms. According to the sampling theorem, both approaches are equivalent. However, using digital signal processing for filtering allows the use of filter functions that cannot be practically realized with analog means. Those digital filter functions promise resolution and throughput close to the theoretical limit. The first commercially available ADSP (Analog to Digital Signal Processor) uses a moving window deconvolution to deconvolve the preamplifier characteristic. All algorithms are calculated in real time, thus there is no dead time added through the computation of an event. A filter function with a trapezoidal impulse response calculates the energy in real time. An adaptive digital trigger allows excellent low energy detection. Another benefit for X-ray applications are very long shaping constants, resulting in 125 eV resolution at 5.9 keV with SiLi detectors. The ADSP consists of an analog linear amplification stage, a 20 MHz sampling adc, circuits for digital signal preprocessing, and four floating point DSPs, performing 240 MFLOP/s. It has been built into a 2-wide NIM module to replace virtually any adc/shaping amplifier combination.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.