Author: Heiliger, D.
Paper Title Page
MOPFI006 A New Load Lock System for the Source of Polarised Electrons at ELSA 294
  • D. Heiliger, W. Hillert, B. Neff
    ELSA, Bonn, Germany
  Funding: supported by DFG (SFB/TR16)
The inverted source of polarized electrons at the electron stretcher accelerator ELSA routinely provides a pulsed beam with a current of 100 mA and a polarization degree of about 80%. One micro-second long pulses with 100 nC charge are produced by irradiating a GaAs strained-layer superlattice photocathode (8 mm in diameter) with laser light. Future accelerator operation requires a significantly higher beam intensity, which can be achieved by using photocathodes with sufficiently high quantum efficiency. Therefore, and in order to enhance the reliability and uptime of the source, a new extreme high-vacuum (XHV) load lock system was installed and commissioned. It consists of a loading chamber in which an atomic hydrogen source is used to remove any remaining surface oxidation, an activation chamber for heat cleaning of the photocathodes and activation with cesium and oxygen and a storage chamber in which up to five different types of photocathodes with various diameters of the emitting surface can be stored under XHV conditions. Additionally, tests of the photocathodes' properties can be performed during accelerator operation.