The production of high brightness electron beams is a key technology that allows many of today's advanced beam applications, such as free-electron lasers, linear colliders, Compton scattering sources, and energy-recovering linear accelerators. Therefore, the Deutsches Elektronen-Synchrotron (DESY), the member of the Helmholtz-Gemeinschaft runs a development program for rf electron sources with the goal of:

• design of rf electron sources;
• characterization and optimization of beam quality;
• optimization of operational parameters.

In order to reach these goals it is indispensable that, besides further development of simulations and theoretical approaches, high quality measurements of the beam emittance are carried out. For this purpose a dedicated test facility for rf guns and complete photo injectors - Photo Injector Test Facility at DESY in Zeuthen (PITZ) - was built and went into operation in January 2002.
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