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          Institute: MPI für Kernphysik     Collection: Spectroscopy and Dynamics of Trapped and Stored Ions     Display Documents

ID: 439335.0, MPI für Kernphysik / Spectroscopy and Dynamics of Trapped and Stored Ions
Intense electron beams from GaAs photocathodes as a tool for molecular and atomic physics
Authors:Krantz, Claude
Referees:Wolf, Andreas; Stöhlker, Thomas
Date of Approval (YYYY-MM-DD):2009-10-28
Name of University:Ruprecht-Karls-Universität
Place of University:Heidelberg
Physical Description
(e.g. Total Number of Pages):
V, 130 S. : graph. Darst.
Audience:Experts Only
Abstract / Description:We present cesium-coated GaAs photocathodes as reliable sources of intense, quasi-monoenergetic electron beams in atomic and molecular physics experiments. In long-time operation of the Electron Target of the ion storage ring TSR in Heidelberg, cold electron beams could be realised at steadily improving intensity and reliability. Minimisation of processes degrading the quantum efficiency allowed to increase the extractable current to more than 1mA at stable cathode lifetimes of 24 h or more. The benefits of the cold electron beam with respect to its application to electron cooling and electron-ion recombination experiments are discussed. Benchmark experiments demonstrate the superior cooling force and energy resolution of the photoelectron beam compared to its thermionic counterparts. The long period of operation allowed to study the long-time behaviour of the GaAs samples during multiple usage cycles at the Electron Target and repeated in-vacuum surface cleaning by atomic hydrogen exposure. An electron emission spectroscopy setup has been implemented at the photocathode preparation chamber of the Electron Target. Among others, this new facility opened the way to a novel application of GaAs (Cs) photocathodes as robust, ultraviolet-driven electron emitters. Based on this principle, a prototype of an electron gun, designed for implementation at the HITRAP setup at GSI, has been built and taken into operation successfully.
Document Type:PhD-Thesis
Affiliations:MPI für Kernphysik/Group of K. Blaum
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