Direct measurement of the neutron neutron scattering cross section at the reactor YAGUAR

Abstract

We propose to perform the first measurement of the neutron–neutron scattering cross section in the through-channel of the pulsed aperiodic reactor YAGUAR (Snezhinsk, Russia). Such a measurement directly determines the neutron–neutron scattering length, and by comparison with the proton–proton scattering length bears upon the issue of charge symmetry of the nuclear force. The proposed experimental set-up, as well as modelling of the neutron density and of the frequency of neutron–neutron collisions is described. Experimental results are reported on the formation and optimization of the thermal neutron field inside the through-channel of the reactor YAGUAR. The instantaneous value of 1.1 × 1018 cm−2 s−1 obtained for the thermal neutron flux density is large enough to perform the first direct neutron–neutron scattering length measurement.

Mirror nuclei 3H and 3He binding energies difference and low energy parameters of neutron-neutron scattering

“…The idea of setting up an experiment for the direct measurement of neutron-neutron scattering length has been developed recently by the DIANNA collabo ration; it is proposed to use the Yaguar pulsed nuclear reactor (Snezhinsk, Russia) for obtaining colliding dense neutron fluxes [13][14][15]. High intensity neutron beams obtained in this way would make it possible to measure a neutron-neutron scattering cross section at zero energy σ nn (0) = and, therefore, the scatter ing length a nn .…”

Constraining the neutron-neutron scattering length using the effective field theory without explicit pions

“…[7]. Direct measurements are on the horizon [8], but until now constraints on a nn come from final-state interactions. However, conflicting values for a nn have resulted from attempts to follow this avenue in different few-nucleon reactions-indeed, conflicting values have resulted from different experiments investigating final-state interactions in n + d → n + n + p.…”

Fundamental Neutron Physics

“…No direct measurements exist. An experiment to determine b nn by viewing a high-density neutron gas near the core of a pulsed reactor that produces an extremely high instantaneous neutron density and measuring a quadratic dependence of the neutron fluence on source power is currently being designed [354,355]. An experiment to let the neutrons in an extracted beam scatter from each other has been considered [356].…”