| 1. |
- Anderson, Johan, 1973, et al.
(författare)
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Derivation and quantitative analysis of the differential self-interrogation Feynman-alpha method
- 2012
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Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 127:2, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- A stochastic theory for a branching process in a neutron population with two energy levels is used to assess the applicability of the differential self-interrogation Feynman-alpha method by numerically estimated reaction intensities from Monte Carlo simulations. More specifically, the variance to mean or Feynman-alpha formula is applied to investigate the appearing exponentials using the numerically obtained reaction intensities.
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| 2. |
- Anderson, Johan, 1973, et al.
(författare)
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Two-point theory for the differential self-interrogation Feynman-alpha method
- 2012
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Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 127:8, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Chernikova, Dina, 1982, et al.
(författare)
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A general analytical solution for the variance-to-mean Feynman-alpha formulas for a two-group two-point, a two-group one-point and a one-group two-point cases
- 2014
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Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 129:11, s. Art. no. 259-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a full derivation of the variance-to-mean or Feynman-alpha formula in a two-energy-group and two-spatial-region treatment. The derivation is based on the Chapman-Kolmogorov equation with the inclusion of all possible neutron reactions and passage intensities between the two regions. In addition, the two-group one-region and the two-region one-group Feynman-alpha formulas, treated earlier in the literature for special cases, are extended for further types and positions of detectors. We focus on the possibility of using these theories for accelerator-driven systems and applications in the safeguards domain, such as the differential self-interrogation method and the differential die-away method. This is due to the fact that the predictions from the models which are currently used do not fully describe all the effects in the heavily reflected fast or thermal systems. Therefore, in conclusion, a comparative study of the two-group two-region, the two-group one-region, the one-group two-region and the one-group one-region Feynman-alpha models is discussed.
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| 4. |
- Di Vecchia, Paolo, et al.
(författare)
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The physics of the θ-angle for composite extensions of the standard model
- 2014
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Ingår i: The European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 129:12
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Tidskriftsartikel (refereegranskat)abstract
- We analyse the θ-angle physics associated to extensions of the standard model of particle interactions featuring new strongly coupled sectors. We start by providing a pedagogical review of the θ-angle physics for Quantum Chromodynamics (QCD) including also the axion properties. We then move to analyse composite extensions of the standard model elucidating the interplay between the new θ-angle with the QCD one. We consider first QCD-like dynamics and then generalise it to consider several kinds of new strongly coupled gauge theories with fermions transforming according to different matter representations. Our analysis is of immediate use for different models of composite Higgs dynamics, composite dark matter and inflation.
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| 5. |
- Pal, L., et al.
(författare)
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A special branching process with two particle types
- 2011
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Ingår i: European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 126:2, s. 1-26
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Tidskriftsartikel (refereegranskat)abstract
- Traditional theories of neutron fluctuations in subcritical stationary multiplying systems with analytical solutions disregard the energy dependence of the neutrons, i.e. they treat only one type of neutrons in the branching process. In several recent applications, such as certain coincidence measurements in nuclear safeguards and Accelerator-Driven reflected fast-reactor Systems (ADS), energy dependence of the neutrons must be included into the description. The simplest of such models, still allowing analytical solutions, is to distinguish between two types of neutrons, fast and thermal, corresponding to the two-group theory of traditional reactor physics. The purpose of the present paper is to extend the traditional theory of neutron fluctuations to two neutron types, fast and thermal. We will consider the special case when branching is only induced by one of the two types, giving rise to the progeny of the other type only (thermal fission generating fast neutrons). Stationary injection of neutrons by an extraneous source, as well as the detection process, are taken into account. The results obtained have applications in current problems of nuclear safeguards and reactivity measurements in ADS.
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| 6. |
- Tennfors, Einar
(författare)
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On the idea of low-energy nuclear reactions in metallic lattices by producing neutrons from protons capturing "heavy" electrons
- 2013
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Ingår i: The European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 128:2, s. 15-
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Tidskriftsartikel (refereegranskat)abstract
- The present article is a critical comment on Widom and Larsens speculations concerning low-energy nuclear reactions (LENR) based on spontaneous collective motion of protons in a room temperature metallic hydride lattice producing oscillating electric fields that renormalize the electron self-energy, adding significantly to the effective electron mass and enabling production of low-energy neutrons. The frequency and mean proton displacement estimated on the basis of neutron scattering from protons in palladium and applied to the Widom and Larsens model of the proton oscillations yield an electron mass enhancement less than one percent, far below the threshold for the proposed neutron production and even farther below the mass enhancement obtained by Widom and Larsen assuming a high charge density. Neutrons are not stopped by the Coulomb barrier, but the energy required for the neutron production is not low.
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