Simulation of the d + 3 H →3 He + 2 n; 2 n → n + n Reaction

Results of a simulation of setups intended to search for excited states of few-nucleon systems decaying into two clusters are presented.     

Construction of a Lyapunov functional for a class of controlled population balance models

In this paper, we consider a class of controlled population balance equations describing granulation processes in chemical engineering. Such a control system admits an equilibrium which is not asymptotically stable in general. In order to stabilize this equilibrium, we consider the perturbed system and introduce a Lyapunov functional candidate as a weighted L²-norm. It is shown that the weight function for this construction may be defined in terms of solutions to a certain differential inequality. We present a solution of this differential inequality in a particular case and discuss possible extensions of this approach for multidimensional hyperbolic systems. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Estimates for distributions of the Voronoi polygon's geometric characteristics

An exponential upper bound on the distribution of the Voronoi polygon having n hyperfaces is proved. Using a new integral formula for the Poisson process, the conditional distribution of volume of the fundamental region given n is found to be gamma distribution. This yields an upper bound on distribution of the polygon's volume.     

Setup for studying quasi-free neutron-neutron scattering in the energy range of 20–60 MeV

A setup installed on the RADEX neutron beam channel (Institute for Nuclear Research, Russian Academy of Sciences) and designed to study quasi-free nn scattering in the n + d → p + n + n reaction is described. The setup is a two-arm time-of-flight spectrometer composed of scintillation neutron hodoscope (in the left arm), a scintillation neutron detector (in the right arm), and an active scintillation deuterated target for detecting protons. Secondary neutrons are detected at angles corresponding to the kinematic conditions of quasi-free nn scattering. Events are selected at low energies of the outgoing proton spectator. It is shown that data on neutron-neutron quasi-free scattering can be obtained in a wide range of primary-neutron energies.     

Aggregate and fractal tessellations

Consider a sequence of stationary tessellations {Θ ⁿ }, n=0,1,…, of ℝ ^d consisting of cells {C ⁿ (x _i ⁿ )}with the nuclei {x _i ⁿ }. An aggregate cell of level one, C ₀ ¹(x _i ⁰), is the result of merging the cells of Θ¹ whose nuclei lie in C ⁰(x _i ⁰). An aggregate tessellation Θ₀ ⁿ consists of the aggregate cells of level n, C ₀ ⁿ (x _i ⁰), defined recursively by merging those cells of Θ ⁿ whose nuclei lie in C ^{n −1}(x _i ⁰). We find an expression for the probability for a point to belong to atypical aggregate cell, and obtain bounds for the rate of itsexpansion. We give necessary conditions for the limittessellation to exist as n→∞ and provide upperbounds for the Hausdorff dimension of its fractal boundary and forthe spherical contact distribution function in the case ofPoisson-Voronoi tessellations {Θ ⁿ }. Received: 3 June 1999 / Revised version: 22 November 2000 / Published online: 24 July 2001     

Study of the structure of neutron halo using neutron transfer reaction

To estimate the probability of two-neutron configurations in halo nuclei, we propose an experimental method of studying neutron-neutron correlations at periphery of such nuclei by measuring two-neutron transfer reaction. The experimental study of ⁶He + A ↦ ⁴He + B for various targets is performed using ⁶He beam of Flerov Laboratory of Nuclear Reactions (JINR, Dubna) at energy of about 15 MeV/u and technique of nuclear photoemulsions. Searching for events of two-nucleon transfer reaction and their processing is performed using the PAVICOM-setup at P.N. Lebedev Physical Institute.     

Data on Neutron–Neutron Scattering Length from the Reaction $$\boldsymbol{n+^{2}\textrm{H}\to n+n+p}$$ at $$\boldsymbol{E_{n}=60}$$ MeV

Physics of Atomic Nuclei - The $${}^{1}S_{0}$$ neutron–neutron ( $$nn$$ ) scattering length was measured in the neutron–deuteron ( $$nd$$ ) breakup reaction at an energy of 60 MeV. The...     

Investigating neutron-neutron and proton-proton correlations in few-nucleon systems in reactions with two nucleons in the final state

The great disagreement between theory and experiment observed in nd and pd interactions indicates that investigations of mechanisms for various processes in few-nucleon systems should be continued. It is planned to investigate the reactions d + ³H → ³He + (nn) and ³He + d → ³H + (pp) in order to study nn and pp correlations in ³He and ³H nuclei. Test measurements of the d + ²H → ²He + (nn) reaction, performed with the deuteron beam at the Institute of Nuclear Physics, confirm that it is methodologically possible to perform the planned experiments.     

Reaction <Emphasis Type="Italic">d</Emphasis> + <Superscript>2</Superscript>H → <Superscript>3</Superscript>He + <Emphasis Type="Italic">n</Emphasis> as a source of quasi-monoenergetic neutrons for studying the properties of neutron detectors

The responses of two liquid scintillators to neutron irradiation are investigated. Monoenergetic neutrons are obtained in the reaction d + ²H → ³He + n in different configurations of a coincidence experiment involving the detection of both neutrons and the ³He nucleus. In the experiment, the 15 MeV deuteron beam from the U-120 accelerator at the Skobeltsyn Institute of Nuclear Physics, Moscow State University, hits a target of deuterated polyethylene, and the secondary neutrons obtained in the reaction irradiate the EJ-301 and EJ-315 liquid scintillators under study.     

Low-Energy Parameters of Neutron–Neutron Interaction: Analysis of Data Obtained in <Emphasis Type="Italic">nd</Emphasis> and <Emphasis Type="Italic">dd</Emphasis> Breakup Reactions

Data obtained in recent years for the neutron–neutron scattering length in nd and dd breakup reactions are analyzed. Serious discrepancies between experimental data from different studies may be explained by the effect of three-nucleon forces depending on the velocity of separation of a neutron–neutron pair and a charged fragment. It is shown that the data under analysis can be approximated by a smooth curve representing the dependence of the scattering length on the parameter R, which determines the fragment-separation distance after a fixed time. This dependence makes it possible to obtain the scatteringlength value for R→∞—that is, in the absence of the effect of three-nucleon forces.