Moslem Amiri

Quick algorithms for real-time discrimination of neutrons and gamma rays

Several new methods for the digital discrimination of neutrons and gamma-rays in a mixed radiation field are presented. The methods introduced discriminate neutrons and gamma rays successfully in the digital domain. They are mathematically simple and exploit samples during the life time of the pulse, hence appropriate for field measurements. All these methods are applied to a set of mixed neutron and photon signals from a stilbene scintillator and their discrimination qualities are compared.

Optimum filter-based discrimination of neutrons and gamma rays

An optimum filter-based method for discrimination of neutrons and gamma-rays in a mixed radiation field is presented. The existing filter-based implementations of discriminators require sample pulse responses in advance of the experiment run to build the filter coefficients, which makes them less practical. Our novel technique creates the coefficients during the experiment and improves their quality gradually. Applied to several sets of mixed neutron and photon signals obtained through different digitizers using stilbene scintillator, this approach is analyzed and its discrimination quality is measured.

General solutions for MTTF and steady-state availability of NMR systems

Voting redundancy is a well-known technique to improve the fault tolerance of digital systems. Calculation of reliability and availability is a necessary part of every fault tolerant system design. Conventional techniques, including block diagram method, are unsuccessful when there is dependent failure, repair, or standby operation in the system. Use of Markov models also almost fails when system is composed of many elements or is repairable. However, the alternatives to reliability and availability, i.e. mean time to failure and steady state availability, respectively, are easily measurable using Markov graphs. In this paper, novel general form solutions for calculation of mean time to failure and steady-state availability of N-modular redundancy systems are presented.

Digital data processing of stilbene

Stilbene is a proven spectrometric detector for mixed fields of neutrons and gamma rays. By digital processing of shape output pulses from the detector it is possible to obtain information about the energy of the interacting neutron / photon and distinguish which of these two particles interacts in the detector. Another numerical processing of digital data can finalize the energy spectrum of both components of the mixed field. The quality of the digitized data is highly dependent on the parameters of the hardware used for digitization and on the quality of software processing. Our results also show how the quality of the particle type identification depends on the sampling rate and as well as the method of processing of the sampled data.

Application of digital signal processing in discrimination of neutrons and gamma rays

Two new methods for the digital discrimination of neutrons and gamma-rays in a mixed radiation field using digital signal processing techniques are presented. While almost all of the pulse-shape discrimination methods use time-domain features of signals, the proposed procedures successfully separate these radiations using their frequency-domain data. These methods are computationally simple, hence appropriate for field measurements. Applied to several sets of mixed neutron and photon signals obtained through different digitizers using stilbene scintillator, these approaches are analyzed and their discrimination qualities are measured.

Significant reliability improvement of NMR systems

Majority voted redundancy is increasingly implemented in fault-tolerant design today. In this technique, a voter receives parallel bits from an odd number of digital components and votes for the majority. Reliability improvement is the main focus of every fault tolerant system design. In this paper, we first present a viable alternative to the voting redundancy concept in order to significantly increase the reliability of conventional voting systems for five parallel components or higher. Then, an implementation of this novel concept is described.

Neutron/gamma-ray discrimination through measures of fit

Statistical tests and their underlying measures of fit can be utilized to separate neutron/gamma-ray pulses in a mixed radiation field. In this article, first the application of a sample statistical test is explained. Fit measurement-based methods require true pulse shapes to be used as reference for discrimination. This requirement makes practical implementation of these methods difficult; typically another discrimination approach should be employed to capture samples of neutrons and gamma-rays before running the fit-based technique. In this article, we also propose a technique to eliminate this requirement. These approaches are applied to several sets of mixed neutron and gamma-ray pulses obtained through different digitizers using stilbene scintillator in order to analyze them and measure their discrimination quality.