52 research outputs found
Two-point theory for the differential self-interrogation Feynman-alpha method
A Feynman-alpha formula has been derived in a two region domain pertaining
the stochastic differential self-interrogation (DDSI) method and the
differential die-away method (DDAA). Monte Carlo simulations have been used to
assess the applicability of the variance to mean through determination of the
physical reaction intensities of the physical processes in the two domains.
More specifically, the branching processes of the neutrons in the two regions
are described by the Chapman - Kolmogorov equation, including all reaction
intensities for the various processes, that is used to derive a variance to
mean relation for the process. The applicability of the Feynman-alpha or
variance to mean formulae are assessed in DDSI and DDAA of spent fuel
configurations.Comment: 15 pages, 5 figures. Submitted to EPJ Plu
Discrete Feynman-Kac formulas for branching random walks
Branching random walks are key to the description of several physical and
biological systems, such as neutron multiplication, genetics and population
dynamics. For a broad class of such processes, in this Letter we derive the
discrete Feynman-Kac equations for the probability and the moments of the
number of visits of the walker to a given region in the phase space.
Feynman-Kac formulas for the residence times of Markovian processes are
recovered in the diffusion limit.Comment: 4 pages, 3 figure
Energy Correlation of Prompt Fission Neutrons
In all cases where neutron fluctuations in a branching process (such as in multiplicity measurements) are treated in an energy dependent description, the energy correlations of the branching itself (energy correlations of the fission neutrons) need to be known. To date, these are not known from experiments. Such correlations can be theoretically and numerically derived by modelling the details of the fission process. It was suggested earlier that the fact that the prompt neutrons are emitted from the moving fission targets, will influence their energy and angular distributions in the lab system, which possibly induces correlations. In this paper the influence of the neutron emission process from the moving targets on the energy correlations is investigated analytically and via numerical simulations. It is shown that the correlations are generated by the random energy and direction distributions of the fission fragments. Analytical formulas are derived for the two-point energy distributions, and quantitative results are obtained by Monte-Carlo simulations. The results lend insight into the character of the two-point distributions, and give quantitative estimates of the energy correlations, which are generally small
BOOK REVIEW: "Neutron Noise: A Treatise on the Physics of Branching Processes," I. PÁZSIT and L. PÁL
Theory of particle detection and multiplicity counting with dead time effects
The subject of this paper is the investigation of the effect of the dead time on the statistics of the particle detection process. A theoretical treatment is provided with the application of the methods of renewal theory. The detector efficiency and various types of the dead time are accounted for. Exact analytical results are derived for the probability distribution functions, the expectations and the variances of the number of detected particles. Explicit solutions are given for a few representative cases. The results should serve for the evaluation of the measurements in view of the dead time correction effects for the higher moments of the detector counts
- …