R. Barday

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.

Target-thickness effects in electron–atom bremsstrahlung

We report on a study of target-thickness effects on the degree of the linear polarization as well as on the emission probability of bremsstrahlung arising in the collision of 100 keV electrons with thin gold targets. For this purpose an experiment at the electron source SPIN at the TU Darmstadt as well as Monte Carlo simulations have been performed. The results indicate that for high-Z targets the degree of linear polarization is significantly altered by straggling of the electrons inside the target.

Status and recent developments at the polarized-electron injector of the superconducting Darmstadt electron linear accelerator S-DALINAC

At the superconducting Darmstadt electron linac a 100 keV source of polarized electrons has been installed. Major components had been tested prior to installation at an offline teststand. Commissioning of the new source at the S-DALINAC will take place early in 2011. We report on the performance of the teststand, simulations, developments on the laser systems, new radio-frequency components for the S-DALINAC injector, and the status of the implementation of the source.

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.

Polarized Electrons in Darmstadt: Recent Developments

The injector of the superconducting Darmstadt electron linear accelerator S‐DALINAC will soon be extended by a source of polarized electrons. A test set‐up of the future source consists of a 100 keV GaAs polarized gun and associated beamline including an assembly for polarization manipulation and determination. We give a short overview of the existing and planned polarimeters at the different accelerator sites, introduce briefly the future implementation of the polarized source at the S‐DALINAC and list experiments that are planned with polarized electron and photon beams.

Electron polarimetry with bremsstrahlung

Due to the spin-orbit interaction, the electron scattering from the nucleus is sensitive to the spin orientation of that electron. This is used for polarimetry of electron beams in the Mott method. The spin-orbit interaction was also observed in bremsstrahlung. In this article we analyze its potential for polarimetry as an alternative to the Mott method. It can simultaneously measure all three electron polarization components. It should work in the energy range of 50 keV up to several MeV and can be applied at beam intensities higher than 100 nA. It needs a thin heavy element target, two or four x-ray detectors and one x-ray linear polarimeter.

Polarization Of The High‐Energy End Of The Electron‐Nucleus Bremsstrahlung In Electron‐Atom Collisions

The linear polarization of bremsstrahlung radiation emitted in collisions of spin‐polarized and unpolarized electrons with carbon and gold targets has been measured for an incident kinetic energy of 100 keV. We present preliminary results for the degree of linear polarization for incident unpolarized electrons as a function of bremsstrahlung photon energy.

Status Report of the New Darmstadt Polarized Electron Injector

We present the status of the polarized injector for the superconducting Darmstadt electron linear accelerator S‐DALINAC. An offline teststand of the source was built to test all components of the S‐DALINAC polarized injector SPIN. The new electron source will deliver a 100 keV polarized beam and complement the present thermionic source operating at 250 kV. Results of the beam properties measurements will be introduced and an outlook on the upcoming installation of the new injector at the S‐DALINAC will be given.

Observation of the spin–orbit interaction in bremsstrahlung

The effects of the spin?orbit interaction are pronounced for an electron scattered in a Coulomb field of the nucleus. They cause the electron scattering plane to turn or precess as the electron moves. This precession is visible through linear polarization of bremsstrahlung. The first experiment to observe it is described in this contribution.

Linear Polarization of the High-Energy End of Bremsstrahlung in Electron-Atom Collisions

We report on the effects of electron spin polarization on the bremsstrahlung polarization properties occuring in collisions of polarized electrons with thin target foils.