H.D. Choi

The polarized heavy ion source at the NSF in daresbury

A source producing beams of polarized 6Li, 7Li and 23Na ions has been constructed and installed at the Nuclear Structure Facility in Daresbury Laboratory. The design and performance characteristics of individual components are described together with results of a commissioning run performed with a 175 MeV tensor-polarized 23Na beam. An on-target intensity of up to 20 pnA was observed with a tensor polarization of t20 = 0.20 measured in a zero-degree polarimeter based on the 1H(23Na, α)20Neg.s. reaction.

Quantum-mechanical analysis of analysing powers of the 54Fe(7Li, 6Li)55Fe reaction at 70 MeV

Abstract The differential cross sections, first- and second-rank analysing powers were measured for several states in 55 Fe using the 54 Fe( 7 Li, 6 Li) reaction with a 70 MeV polarised 7 Li beam. Only the T T 20 exhibits a clear j -dependence while most of the T kq s are sensitive to the l -values of the final states. The results were successfully described by complex CCBA calculations involving channel coupling in the entrance partition and spectroscopic properties of the projectile. The quantum-mechanical analysis confirms the reaction dynamics assumed in the semiclassical approach to the nucleon transfer process in heavy-ion collisions.

Analysing powers of the 6Li continuum from the 7Li + 54Fe interaction at 70MeV

Abstract The vector analysing power T T 10 and a full set of second-rank analysing powers were measured for the 6 Li continuum from the 7 Li + 54 Fe interaction at 70 MeV corresponding to a Q -value interval between −23 and −4 MeV and an angular range 12.5° ⩽ θ c.m. ⩽ 35.3°. Main features of the data are well reproduced by a semiclassical model of the analysing powers in transfer reactions considering 6 Li as a spectator. The behaviour of analysing powers determined the choice of the average trajectory as a smooth function of the reaction Q -value.

Tidal symmetry in scattering of polarized 23Na from 208Pb

Abstract The data for differential cross sections and transverse tensor analysing powers in scattering of polarized 23 Na from 208 Pb at 170 MeV were obtained for the ground, first and second excited states of 23 Na. The measurements were performed with the QMG/2 magnetic spectrometer at Daresbury Laboratory. The extracted data were analysed on the basis of the tidal symmetry model and the adiabatic approximation. The ground-state reorientation coupling together with two-channel and three-channel coupling schemes for 23 Na states have been attempted. Both nuclear and Coulomb terms were used in the reorientation and coupling potentials. The differential cross section and the transverse tensor analysing powers in the elastic channel are successfully described in the tidal symmetry model. However, the data in the inelastic channels are only approximately described by this model. Comparison of these results with exact coupled-channel calculations shows the implications of tidal symmetry breaking in the inelastic channels.

Tidal symmetry in the scattering of polarised 23Na

The differential cross section, vector analysing power and three components of the second-rank tensor analysing power were measured for quasi-elastic scattering of 170 MeV 23Na from 208Pb. The data have been successfully interpreted in terms of the tidal symmetry model and the sign and magnitude of the observed polarisation effects are in good agreement with the known quadrupole moment of 23Na.

Mechanism of the elastic and inelastic scattering of polarised 7Li by 54Fe at 70 and 50 MeV

Abstract Differential cross sections and the analysing powers iT11, TT20, T20 and T21 were measured for both the elastic scattering of 70 and 50 MeV polarised 7Li from 54Fe and the inelastic scattering to the first excited states of the projectile and target. In both the elastic scattering and target excitation, the second-rank analysing powers follow the shape effect relations while the analogous projectile excitation data do not. Two-channel adiabatic tidal symmetry calculations reproduce only the elastic scattering data, A coupled-channels analysis including unbound states of 7Li and a cluster folding-model spin-orbit potential accounts for the main features of all the observables.

Fusion-fission of aligned 23Na with 138Ba

Fusion/fission cross sections and T20(fis) analysing powers together with angular distributions of quasi-elastic cross sections and T20(qel) are reported for the interaction of an aligned 23Na beam with a 138Ba target at 143, 152, 164, and 174 MeV incident beam energies. The alignment dependent partial wave distributions for fusion, obtained from the analysis of the quasi-elastic data, were used as input for a statistical model calculation of the fission cross section and analysing power.

Analysing powers of the 54Fe(7Li, 6He)55Co reaction at 50 MeV

Measurements of TT10, TT20, T20 and T21 analysing powers are reported for the 54Fe(7Li, 6He) reaction using a 50 MeV polarized 7Li beam. The vector analysing powers exhibit a strong dependence on the j=l+or-1/2 value of the 55Co final-state proton orbital which can be applied in nuclear spectroscopy. CCBA calculations, including reorientation and channel coupling in the projectile, reproduce correctly all the experimental data.

The alpha -continuum from the interaction of 70 MeV polarized 7Li with 54Fe

The first- and second-rank analysing powers were measured for the alpha -particle continuum from the interaction of 70 MeV polarized 7Li with 54Fe. The data are consistent with a partial fusion reaction mechanism as the dominant process and can be described by a semiclassical model of analysing powers in transfer reactions.

The Li+n clustering of Li from the H(Li, d)Li reaction

The T20 analysing power has been measured at 0 degrees for the 1H(7Li,d)6Li reaction leading to the ground and first excited states in 6Li. The data have been analysed in terms of a simple cluster model of 7Li. The T20 value for the ground-state transition is well described assuming a 6Li+n cluster structure for 7Li where the 6Li core acts as a spectator and no nucleon spin flip takes place.