Hamburg 2009 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 3: Präzisionsmassenspektrometrie, Ionenfallen, FT-IZR-MS, Moleküle, Cluster III

MS 3.7: Talk

Monday, March 2, 2009, 17:45–18:00, VMP 8 R05

Intense electron pulses for HITRAP from a robust GaAs photocathode using UV pulse irradiation — •Claude Krantz¹, Dmitry A. Orlov¹, Andreas Wolf¹, Giancarlo Maero², Frank Herfurth², and Wolfgang Quint² — ¹Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg — ²Gesellschaft für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt

The HITRAP facility includes a multiring Penning trap to store decelerated highly charged ions (HCI) from the GSI accelerator complex at temperatures of 4 K. The trap will simultaneously store 10⁵ HCI of initial kinetic energies of 6 keV/u and 10⁹ cold electrons of temperature k_BT = 10 eV, achieving electron cooling of the ions through Coulomb scattering with the electrons and subsequent synchrotron radiation of the latter. Electrons need to be produced in pulses of around 100 ns in order to efficiently fill the cooler trap. For this purpose a photoelectron gun has been developed at the Max-Planck-Institute of Nuclear Physics (MPIK) based on a GaAs-photocathode. Following experience gathered at the MPIK in the operation of such photocathodes, the electron gun will be operated in reflection mode using a pulsed UV light source. Test measurements performed at the MPIK show that in this regime the quantum efficiency of the photocathode can be expected to be stable and robust against many vacuum degradations at a value > 10⁻³, which, by itself, would permit single-shot filling of the cooler trap. Commissionning will allow to determine an optimal trap-filling procedure.