Hannen, V. M.

Ortjohann, H.-W.

Vollbrecht, J.

Weinheimer, C.

Winters, D. F. A.

GSI Repository

In vacuo detection of XUV photons at the ESR using a movable cathodesystem∗V.M. Hannen†1, H.-W. Ortjohann1, J. Vollbrecht1, D.F.A. Winters2, and C. Weinheimer11WWU Mu¨nster, Institut fu¨r Kernphysik, Wilhelm-Klemm-Str. 9, 48161 Mu¨nster; 2GSI Helmholtzzentrum fu¨rSchwerionenforschung GmbH, Planckstr. 1, 64291 DarmstadtThe Institut fu¨r Kernphysik in Mu¨nster is currently de-veloping a system for in-vacuum detection of XUV pho-tons in the wavelength range from < 10 nm up to about250 nm. The system will be installed at the ESR and con-sists of a movable cathode plate with a central slit that canbe positioned around the ion beam axis to catch photonsemitted in the forward direction during the de-excitationof stored highly-charged ions. Secondary electrons emit-ted from the cathode will be guided by a system of ringelectrodes to a multi-channelplate (MCP) detector placedinside the vacuum. A similar detection system for opticalphotons making use of a movable parabolic copper mir-ror and a photomultiplier outside the vacuum, has success-fully been applied in the detection of the HFS transition inlithium-like bismuth in the LIBELLE experiment two yearsago [1, 2]. There it was demonstrated, that the introductionof a suitable optical system at the beam position does notdisturb the stored ions apart from a small loss in beam cur-rent during the movement of the system.Figure 1 displays the result of a tracking simulation pro-duced with the SIMION [3] package. Five ring electrodesare placed between the cathode plate and the MCP, withthe first electrode parallel to the cathode. The CF200 portFigure 1: Electrode representation and simulated electrontracks calculated with the SIMION package.∗Supported by BMBF under contract number 06MS7191† hannen@uni-muenster.deinto which the system can be retracted during injection ofions into the ESR actually acts as an additional sixth elec-trode on ground potential, but has been omitted from thefigure for clarity. In the simulation, more than 75% of thesecondary electrons emitted from the cathode plate are col-lected by the MCP.The new detection system will be used for a measurementof the 3P0−3P1 splitting in beryllium-like krypton in ananti-collinear laser spectroscopy experiment at the ESR [4].The meta-stable state (1s22s2p)3P0 (see figure 2) is popu-Figure 2: Excerpt of the level-scheme of beryllium-likekrypton.lated during the production of the 84Kr32+ ions. For the ex-citation to the (1s22s2p)3P1 state, a laser-beam is injectedanti-collinear to the ions which are stored at a velocity ofβ = 0.69. Due to the Doppler shift, the required wave-length is red-shifted from 118 nm to 276 nm. The pho-tons emitted during de-excitation to the ground state in theforward direction are in turn blue shifted to energies up to170 eV.References[1] M. Lochmann et al., GSI Scientific Report 2011, PNI-AP-01[2] J. Mader et al., GSI Scientific Report 2011, PNI-AP-24[3] SIMION package, Scientific Instrument Services, Inc.,http://simion.com[4] D.F.A. Winters et al., Laser spectroscopy of the(1s22s2p)3P0−3P1 level splitting in Be-like krypton,GSI Experiment E104GSI SCIENTIFIC REPORT 2012 PNI-IONS-EXP-07315

In vacuo detection of XUV photons at the ESR using a movable cathode system

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In vacuo detection of XUV photons at the ESR using a movable cathode system

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