An impact of Jacques Raynal on nuclear data evaluation

Abstract

Jacques Raynal seminal contributions to the optical model development and numerical implementation of the solution of coupled-channel equations have been key to generate nuclear data for applications in the last three decades. We recall some of the interactions we had with Jacques from late nineties up until his death. His ECIS code was for a long time, since his collaboration with Peter Moldauer in early eighties, the only optical model and compound decay code where Engelbrecht-Weidenmüller transformation was implemented to consider the impact of strongly coupled channels with large direct inelastic cross sections on the decay of the compound channel. Such physical effect, which was neglected for a long time, proved very important to describe the observed enhancement (Relative to the bare Hauser-Feschbach calculation) of the inelastic scattering cross section on 238 U nucleus, which is a major fuel component in nuclear power reactors. Jacques also proposed an unique and very clever method to calculate dispersive integrals analytically in 1996. His excellent mathematical background and programming skills set a very high bar for future generations. This contribution represents a small homage to our dear colleague and friend.

Jacques Raynal

“…The next versions were ECIS86 [13], elaborated to include the treatment of vibration excitation modes and ECIS94 [14], to improve the computing time of the Coulomb scattering problems. New versions of the code were elaborated to solve physical problems submitted by his colleagues, nuclear physicists working in the experimental analysis [15] or in field of the nuclear data evaluation [16]. Jacques Raynal also developed other codes to perform calculations with optical model potentials in the Distorted Wave Born Approximation (DWBA): there was the DWBA91 code used for the analysis of nucleon-nucleus scattering, followed by new versions in 2005 [17] and 2007 [18], in particular to improve the computing operations for specific problems of elastic and inelastic scattering with nucleon-nucleon potentials.…”

“…To analyze the nucleon-nucleus scattering at high energies (several hundreds of MeV), in particular for inelastic scattering with polarized protons, Jacques Raynal developed codes including the Dirac relativistic formalism in coupledchannel (CC) calculations. The OMP parameters were carefully checked in this formalism [30,31,34] and the applications of the Dirac and Schrödinger formalisms were compared on several experimental results of proton scattering on stable targets, like 16 O, 24 Mg and 26 Mg [33] 40 Ca [34], sd shell nuclei [35]. During a conference held at Cuba in 1997, Jacques presented his results on the microscopic description of elastic and inelastic nucleon scattering investigated using the Dirac and Schrödinger formalisms [36].…”

“…-Studies of (p,n) reactions [49]; -Theory works for partial waves in nuclear scattering [50]; -Calculated nuclear data generated for reaction evaluation, using OMP and CC equations [16]; -Calculations of Wigner 3 j coefficients [51]; -Non-locality in OMPs for nucleon-nucleus scattering [52]; -CC analysis of the elastic scattering with exotic nuclei within OMP approach [53]; -Applications to proton-nucleus inelastic scattering [54]; -Developments of Raynal's DWBA code [55] and beyond ECIS and DWBA [56]; -Theory for low energy neutron incident reactions [57] and nucleon-induced inelastic scattering [58]; -CC analysis of elastic and inelastic scattering for the studies of giant resonance excitations; calculations of the sub-Coulomb fusion cross sections [15]; -CC effects in nucleus-nucleus inelastic scattering [59] and in heavy ion reactions [60].…”