[en] A method for the systematic derivation of the Multiplicity Spectrum (MS) of leakage neutrons from ⁹Be assemblies, starting from the forward Kolmogorov equation (familiar from stochastic neutron kinetics) is proposed. An exact solution to the multigroup Kolmogorov equation has been obtained using the method of Probability Generating Function (PGF). The effect of correlation between the two secondary neutrons in the (n, 2n) process on neutron multiplication has been investigated using this formalism. While the average multiplicity is not sensitive to correlation between the secondary neutrons in the (n, 2n) process, the MS for multiplicities ≥ is found to be highly sensitive. When correlation is accounted for the probability P(ν) of leakage of ν neutrons from a ⁹Be assembly differs by orders of magnitude from that without correlation for the higher multiplicities. As the correlation between the two neutrons contains valuable information, experimental study of the MS (especially the higher multiplicity events) can serve as a very powerful tool for the investigation of the (n, 2n) multiplicative process and can help resolve some of the observed discrepancies regarding the multiplication of 14 MeV neutrons in ⁹Be. (author)

[en] The article recalls the historical conditions and circumstances of the discovery of the neutron by J. Chadwick and the first experiments with neutron radiation. (author)

[en] Measurements were made of the neutron spectrum produced by bombarding a thick beryllium target with 30-MeV deuterons at the University of California, Davis cyclotron. This spectrum is of interest in studying the effect of neutrons on materials to be used in future fusion reactors. The spectrum was inferred from the activation of two sets of detector foils placed at 0⁰ to the deuteron beam, one immediately behind the beryllium target block, and one 40 mm to the rear. A least-squares program was used to analyze the foil activation data to obtain the fluence in each of seven energy groups. The neutron spectrum (fluence/MeV) close to the target decreases continuously with energy in the range 5-32 MeV, while the spectrum 40 mm back has a peak at about 13 MeV. The contribution from neutrons of energies less than 10 MeV is much greater than that found in previous spectral measurements made at large distances from the target. This difference is attributed to the neutrons which are emitted at large angles from the deuteron beam. These observations show the importance of evaluating the neutron spectrum near the target if samples of materials are to be irradiated in this location

[en] A fast neutron therapy facility has been established utilizing the classical solid-pole cyclotron of the National Accelerator Centre (CSIR) in Pretoria. The neutron field is generated from the ⁹Be(d,n)¹⁰B reaction using 16 MeV deuterons on a thick target, yielding 0.51 cGy · min^-1 · μA^-1 at an SSD of 135 cm. Essentially the beam characteristics concur with those measured at other centres with comparable energies. 16 refs.; 1 figure; 3 tabs

[en] Low-dimensional moderators were designed for the European Spallation Source (ESS), and the same concepts can be applied to compact sources. At ESS, quasi two-dimensional (2D) high-brightness moderators will serve all the instruments of the initial suite. The design of the moderators is influenced by several factors, such as the layout of the facility, the requirements for beam extraction, and the number of instruments; these constraints led to the choice of the 2D 'butterfly' moderator for ESS. In an accelerator-based compact source, such moderators can be designed in an even more efficient way than for high-power sources, taking advantage of the lower heat loads and of the more compact arrangement of the target-moderator system, which gives more freedom in the optimization of the geometrical setup. Some promising design options such as the presence of a pre-moderator or a 2-target configuration have been explored

[en] In a high statistics study of the reaction γ + Be → π⁺π^-, the authors have observed the Drell process and the ρ - ω interference effects. Based on more than 3x10⁶ photoproduced ρ events collected at the Fermilab E-687, it is shown that these interference effects previously observed at low energy can be accurately studied at higher energy (7.5 < √(s) < 16.). The observed relative branching ratio (ω→ π⁺π^-)/(ρ → π⁺π^-) is 1.3 ^±0.1^±0.2%

[en] The applicability of the Lane-Lynn channel-capture formula is discussed with regard to radiative neutron capture in Be 9

[en] The various cross sections and distributions are presented for a search for charmed particles in proton reactions with beryllium

[en] Recently, the possibility to use compact accelerators coupled to high current ion sources for the production of intense low energy proton or deuteron beams has motivated many research laboratories to develop accelerator based neutrons sources for several purposes, including Neutron Capture Therapy (NCT). The NCT needs a high flux, about 10⁹ n.cm^-2.s^-1, of thermal neutrons (E<10 keV) at the tumour site. Up to now, the NCT required neutron flux was mainly delivered by nuclear reactors. However, the production of such neutron flux is now possible using proton or deuteron beams on specific targets able to stand a high power (∼ 15-30 kW) on a small area (∼10 cm^-2). This specific target design, materials and supports, has to cope with extreme physical constraints. The LPSC team has conceived an original solution formed by a thin (8 μm) rotating beryllium target deposited on a graphite wheel and coupled with a beryllium sputtering device for periodic ⁹Be layer restoration. By means of ⁹Be(d,n)¹⁰B nuclear reaction, this target irradiated by a 10-20 mA deuteron beam (1.45 MeV) should produce the required neutron flux. In order to validate the target design of the neutron flux production and the beryllium target thermal capabilities, we built a 30 cm diameter rotating beryllium target prototype and a compact electron beam line able to deliver a power density of 3 kW/cm². (authors)

[en] The Be abundance in low-metallicity stars is an important probe of cosmic-ray and Big-Bang nucleosynthesis, as well it, stellar evolution models. In particular, significant Be depletion via the (p,d) and (p,α) reactions is observed in some stars. A previous measurerneritt found the low-energy cross section in both reaction channels to be dominated by an s-wave 1^- resonance at E_p= 330 keV. At lower energies a significant but very uncertain contribution was attributed to an opposite-parity subthreshold state. We naive measured A_y(0) and σ(0) for both channels for 80 < E^p< 330 keV. The analyzing power data are sensitive to the interference between states of opposite parity, and will be compared to predictions calculated from previously reported R-matrix parameters. The uncertainty in the extrapolation to lower energies will be discussed