Alf Göök

Reactions with polarized electrons and photons at low momentum transfers at the superconducting Darmstadt electron linear accelerator S-DALINAC

A source of polarized electrons has been installed at the superconducting Darmstadt electron linear accelerator S-DALINAC. Experiments with polarized electrons from 100 keV to about 80 MeV are expected to commence in early 2011. This contribution summarizes the status of the polarized source as well as ongoing preparations for the experimental program with polarized beams. In particular, we present results on unpolarized test experiments of the 234,238 U(γ,f) reactions and considerations for the 2 D(� e,ep) and 3 He(� e,ep) reactions.

Compton transmission polarimeter for a very precise polarization measurement within a wide range of electron currents

For new experiments with polarized electron and positron beams the precise and quick measurement of the beam polarization is required. The relative electron polarization has been monitored on-line using a compact transmission Compton polarimeter for a wide range of average electron currents up to 100/μA and electron beam energy of 3.5 MeV. The asymmetry induced by the beam polarization can be monitored precisely with ΔA/A < 0.2 %. Even small relative variations of the beam polarization during a beam time may be detected using this polarimeter, such as an increase ~ 1 % and subsequent decrease of the beam polarization.

RECENT RESULTS FROM PHOTON-INDUCED FISSION EXPERIMENTS AT THE S-DALINAC

Bremsstrahlung with endpoint energies slightly above the fission barrier is produced from stopping an electron beam in a thick copper target. Mass, total kinetic energy (TKE) and angular distribution of the fission fragments were determined by means of the double kinetic energy technique, using a twin Frisch-grid ionization chamber. First results on angular distributions and their correlations with mass and TKE of the fragments as well as an analysis within the fission-mode concept of the multi-modal random neck-rupture model by Brosa et al.[2], are presented [3]. It is shown that the emission angle of the fission fragments can be extracted from an electron drift-time measurement [4] and that the target thickness influences the experimental results [5].

ELECTRON BEAM POLARIMETRY AT LOW ENERGIES AND ITS APPLICATIONS

Low energy (E-k similar to 100 keV) Mott scattering polarimetry is a widely established technique to measure the polarization of an electron beam. We analyze the feasibility of Mott scattering at e ...

Photo‐fission at the S‐DALINAC

Experiments on photo-induced fission of 238U and 234U using bremsstrahlung with endpoint energies between 6 MeV and 9 MeV have been carried out at the superconducting Darmstadt electron linear acce ...