W. Dreves

Polarization monitors for polarized heavy ion beams

Abstract Reactions of various spin type are discussed in respect to their use as calibrator and monitor for polarized heavy ion beams.

Elastic scattering of vector polarized 7Li on 58Ni

The elastic scattering of 6Li from 4He has been subject of recent investigations1,2). In all cases the observed angular distributions of the differential cross section show pronounced structures at intermediate and backward angles. These structures have been interpreted1,2) as due to the elastic transfer of a deuteron between the two 4He-cores. In order to obtain a more detailed information on the reaction mechanism a study of the vector analyzing power for this reaction had been started using the polarized 6Li beam of the Heidelberg EN-tandem3). The experiment has been performed at 22.8 MeV beam energy and scattering angles of 35 < θcm < 150°. As 4He target a gas cell was used which was specifically constructed to allow for measurements of the left-right asymmetry. The entrance and exit windows consisted of Havar-foils of 2.1 mg/cm2. The target has been operated at pressures around 500 torr 4He corresponding to an effective target thickness between 30 and 80 μg/cm2. Taking into account the energy loss in the entrance foil and in the gas target the beam energy at the active volume of the gas cell is Elab ≈ 21.3 MeV. The scattered 6Li- and the rescattered 4He-nuclei have been detected with ΔE-E telescopes. Relative and absolute normalization of the data has been obtained by measuring the Rutherford scattering of 6Li from a 3.6% Kr-admixture to the 4He-gas.

Dependence of deformed heavy ion (7Li) scattering on the orientation of the alignment axis

Abstract The scattering of aligned 7 Li on 58 Ni at E Li = 14.22 MeV was investigated for different spin alignment axes of the mass quadrupole moment of 7 Li. For a fixed scattering angle the change in cross section due to the alignment of the quadrupole moment turns out to be proportional to the change in distance between the 7 Li and 58 Ni surfaces at the distance of closest approach.

Investigation of the 58Ni(7Li, 6Li)59Ni reaction with vector polarized 7Li

Abstract Angular distributions of the cross section and of the vector analyzing power for the 58Ni(7 Li , 6Li)59Ni reaction leading to several groups of levels in the final nucleus have been measured at ELi = 20.3 MeV. The observed Q-value dependence of the vector analyzing power can to a large extent be attributed to a kinematical effect caused by the polarization of the orbital angular momentum of the transferred neutron in 7Li.

Production of a polarized23Na beam

A vector-polarized23Na+ beam has been produced using an atomic beam source and a surface ionizer. A nuclear polarization t10 ≥ 0.47 was deduced from the circular polarization of the light emitted after beam-foil excitation.

Determination of the alignment of a 7Li beam by means of the Doppler-shift method

Abstract It is demonstrated that an analysis of the shape of the Doppler-broadened 0.478 Mev γ-line from 7Li Coulomb excitation allows the determination of the alignment of a 7Li beam, provided the alignment of the beam can be switched on and off.

Determination of the electric quadrupole moment of 7Li by Coulomb scattering of an aligned 7Li beam

A new experimental method to determine nuclear electric quadrupole moments using aligned heavy ion beams is presented. From the Coulomb scattering of an aligned 7Li beam the electric quadrupole moment of 7Li was determined to be Q=(−34±6)emb.

Elastic scattering of aligned lithium ions from nickel

Aligned lithium 6 and 7 beams were elastically scattered from nickel-58 at 12.7 MeV. The measured tensor analyzing power was converted into a defined cross section ratio for the fully aligned and the upolarized beams. The angular distributions for the two beams coincide within experimental errors. 3 references. (JFP)