[en] The first chapter presents the installation of the source at the MAMI accelerator and explains the conditions under which it became possible to transport practically all electrons produced in the source to the experiment and thereby although aim excellent emittance values and beam stability. The notoric problematics of the finite lifetime of the photocathode could be not only removed but the contributing processes clarified, so that at the today further development potentials are sketched. In the following chapter studies are presented, which concern the depolarization of the electron ensemble in the photoemission from the III/V heterostructures used at MAMI. The third chapter describes the control of the symmetry of the beam parameters at the helicity change of the electron beam

[en] The operation of an rf gun with a GaAs crystal installed as the cathode has been tested in anticipation of eventually producing a polarized electron beam for a future e⁺/e^- collider using an rf photoinjector

[en] NEA-GaAs based photocathodes allow the production of spin-polarized electron beams for fundamental research. We demonstrate how semiconductor properties influence salient parameters such as polarization and beam brightness. We present techniques that provide remedies for the extreme sensitivity to environmental factors. These are discussed for the specific installation that has provided spin-polarized beam at the MAMI facility during the last decade. (author)

[en] False asymmetries in electron scattering experiments utilizing photoelectron sources are generated by imperfections of the light polarization optics. The false asymmetries are amplified by an analyzing power of the photocathodes. We have demonstrated compensation techniques which allow to approach zero intensity asymmetry with good stability. Even in the absence of analyzing powers fluctuations may be generated by more subtle effects like varying interference patterns of the exciting laser beam. (orig.)

[en] The Electron Nucleon Collider, proposed as an extension to the High Energy Storage Ring (HESR), is currently investigated and a first layout of the Interaction Region (IR) proposed. The limited size of the machine, the low beam energy and the Lorentz force vector pointing in the same direction for both beams make the IR design demanding. In this paper we present the parameters of the IR magnets, show the boundary conditions given by the beam dynamics and the experiments. We present first 2D designs for the electron and proton triplet magnets along with the separating dipole next to the collision point. Different methods to shield the beam in the spectrometer dipoles are investigated and presented.

[en] Möller and Mott polarimeters have been compared concerning their measurement accuracy in a dedicated 'spin dance' experiment. The results obtained with the different polarimeters at vastly different energy ranges were in agreement with each other within the given systematic uncertainties of a few percent. We discuss investigations of background conditions which may allow to reduce this important contribution to the uncertainties in the Mott polarimeter to a value below 1.0%

[en] The assumption of a constant charge per lifetime of NEA photocathodes was tested at polarized electron currents of several mA. Polarized electrons were produced from bulk GaAs photocathodes by laser illumination with a photon energy close to the band gap. We demonstrate that cathode heating, ion trapping and increased relative beam loss due to space charge effects may lead to reduction of charge lifetime. We also find that cathode lifetime increases by a factor four when we increase the photon energy to 2.3 eV

[en] Electron/photon tensor-correlation coefficients may allow to design a polarimeter that can measure all components of beam polarization simultaneously-a so-called vector polarimeter. Besides its purpose as a beam diagnostic device this vector polarimeter would also allow to test theoretical predictions for the electron-photon polarization correlations at energies between 1 MeV and 3.5 MeV. As a first step we have set up a measurement of the helicity transfer to the photon as a function of energy which is based on the Compton absorption method.

[en] The Small Thermalized Electron Source at Mainz (STEAM) is a dc photoemission source. It is designed to operate at up to 200 kV bias voltage with an accelerating field of up to 5MV m⁻¹ at the cathode surface. In several experiments, the properties of GaAs operating under the conditions of spin-polarized photoemission were investigated. Its performance, quantum efficiency lifetime and surface charge limit observations for bulk-GaAs will be discussed. (paper)

[en] An important part of the new accelerator MESA (Mainz Energy-recovering Superconducting Accelerator) is the low-energy beam transport system connecting the 100 keV electron source with the injector. The present setup includes the chopper and bunching system. The devices are of highest importance in order to achieve sufficient bunch compression, particularly at higher bunch charges and currents. With the circularly deflecting cavity of the chopper system it is possible to measure the longitudinal profile of the bunches upstream of the buncher, whereas downstream the longitudinal size will be measured by Smith-Purcell radiation. Based on experimental results obtained from this setup, we will discuss the beam parameters and compare them with simulations of the beamline. (paper)