Digital synthesis of pulse shapes in real time for high resolution radiation spectroscopy

Techniques have been developed for the synthesis of pulse shapes using fast digital schemes in place of the traditional analog methods of pulse shaping. Efficient recursive algorithms have been developed that allow real time implementation of a shaper that can produce either trapezoidal or triangular pulse shapes. Other recursive techniques are presented which allow a synthesis of finite cusp-like shapes. Preliminary experimental tests show potential advantages of using these techniques in high resolution, high count rate pulse spectroscopy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31506/1/0000428.pd

Charge calibration of CsI(Tl)/photodiode spectroscopy systems

A charge calibration method for spectroscopy systems that use inorganic scintillators, photodiodes, and charge-sensitive preamplifiers is presented. The shaped square wave (SSW) method accounts for ballistic deficit when long decay time constants are present. The SSW method is demonstrated for CsI(T1) and compared to other calibration methods.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30115/1/0000491.pd

Digital techniques for real-time pulse shaping in radiation measurements

Recursive algorithms for real-time digital pulse shaping in pulse height measurements have been developed. The differentiated signal from the preamplifier (exponential pulse) is amplified and then digitized. Digital data are deconvolved so that the response of the high-pass network is eliminated. The deconvolved pulse is processed by a time-invariant digital filter which allows trapezoidal/triangular or cusp-like shapes to be synthesized. A prototype of a digital trapezoidal processor was built which is capable of sampling and processing digital data in real time at clock rates up to 50 MHz.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31113/1/0000009.pd

Probability Density Function Transformation Using Seeded Localized Averaging

IEEE Transactions on Nuclear Science, January 2012The article of record as published may be located at http://dx.doi.org/10.1109/TNS.2011.2177861Seeded Localized Averaging (SLA) is a spectrum acquisition method that averages pulse-heights in dynamic windows. SLA sharpens peaks in the acquired spectra. This work investigates the transformation of the original probability density function (PDF) in the process of applying the SLA procedure. We derive an analytical expression for the resulting probability density function after an application of SLA. In addition, we prove the following properties: 1) for symmetric distributions, SLA preserves both the mean and symmetry. 2) for unimodal symmetric distributions, SLA reduces variance, sharpening the distributions peak. Our results are the first to prove these properties, reinforcing past experimental observations. Specifically, our results imply that in the typical case of a spectral peak with Gaussian PDF the full width at half maximum (FWHM) of the transformed peak becomes narrower even with averaging of only two pulse-heights. While the Gaussian shape is no longer preserved, our results include an analytical expression for the resulting distribution. Examples of the transformation of other PDFs are presented

Some digital techniques for real-time processing of pulses from radiation detectors.

Digital methods for processing pulses from radiation detectors have been investigated. A processor with improved differential linearity, which implements a moving average technique has been designed. A threshold free approach for peak-detection has been developed. The circuit also provides a timing signal with uncertainty of one sampling period. Techniques have been developed for the synthesis of pulse shapes using fast digital schemes in place of the traditional analog methods of pulse shaping. Efficient recursive algorithms have been developed that allow real time implementation of a shaper that can produce either trapezoidal or triangular pulse shapes. Other recursive techniques are presented which allow a synthesis of finite cusp-like shapes. Experimental tests show potential advantages of using these techniques in high-resolution, high counting rate pulse-height spectroscopy. A digital method for pulse-shape analysis has been developed. Near-optimum weighting function is used for processing digital samples of the signal from a gated integrator. A figure of merit for neutron-gamma pulse-shape discrimination was found to be: 0.78 for 25 keV (electron equivalent) and 3.5 for 500 keV.Ph.D.Applied SciencesElectrical engineeringNuclear engineeringNuclear physics and radiationPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/129275/2/9423223.pd