J.F.J. van den Brand

Measurement of spin correlation parameters in the Δ region for the 1H⃗(e⃗,e′) reaction

Sensitivity to the quadrupole transition form factors (C2 and E2) of the N-Δ excitation can be obtained by measuring double-polarization electromagnetic observables in the Δ-region. Such measurements have been carried out with the internal target facility at NIKHEF. Radiative corrections are an important ingredient of the data interpretation. They need to be evaluated carefully, taking into account their spin-dependence, in order to compare the data to theoretical models of pion electroproduction. From these comparisons the E2/M1 and C2/M1 ratios can be extracted.

Polarized deuterium internal target at AmPS (NIKHEF)

We describe the polarized deuterium target internal to the NIKHEF medium-energy electron storage ring. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used to monitor the injected atomic beam intensity and polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas in the storage cell. This device was supplemented with a tensor polarization analyzer using the neutron anisotropy of the 3H(d,n)α reaction at 60 keV. This method allows determining the density-averaged nuclear polarization of the target gas, independent of spatial and temporal variations. We address issues important for polarized hydrogen/deuterium internal targets, such as the effects of spin-exchange collisions and resonant transitions induced by the RF fields of the charged particle beam.

Quasi-elastic electron scattering from polarixed 3He

Quasi-elastic electron scattering may provide precise information on the S′ and the D-wave parts of the 3He ground-state wave function, the neutron form factors, and the role of spin-dependent reaction mechanism effects. An experiment is being performed at the AmPS storage ring at NIKHEF (Amsterdam, the Netherlands), where polarized electrons (up to 900 MeV) are used in combination with large acceptance electron and hadron detectors. Preliminary results from data at four-momentum transfer squared Q2=0.15 GeV2 are presented.

A Compton backscattering polarimeter for measuring longitudinal electron polarization

Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is nondestructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF a Compton polarimeter has been constructed to measure the polarization of the longitudinally polarized electrons stored in the AmPS ring. First results obtained with the polarimeter, the first Compton polarimeter to measure the polarization of a stored longitudinally polarized electron beam, are presented in this paper.

Proton knock‐out from tensor polarized deuterium

A status report is given on experiment 91‐12, which is the first internal target experiment performed at the internal target facility of NIKHEF. The aim of this experiment is to measure the asymmetry in the (e,e′p) reaction from a tensor polarized deuterium target with unpolarized electrons. An update on the experimental setup and results of an extensive set of test measurements are presented.