Dresden 2011 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 6: Ion Storage Rings
MS 6.2: Vortrag
Mittwoch, 16. März 2011, 14:30–14:45, GÖR 229
Study of the Rate Acceptance of a Time-of-Flight detector for IMS at FRS-ESR — •Natalia Kuzminchuk1,2, Samuel Ayet1,2, Marcel Diwisch1, Benjamin Fabian1, Hans Geissel1,2, Ronja Knoebel2, Yuri Litvinov3, Wolfgang Plass1,2, Christoph Scheidenberger1,2, Baohua Sun1,2, and Helmut Weick2 — 1Justus-Liebig-Universität Gießen — 2GSI, Darmstadt — 3MPI-K, Heidelberg
For Isochronous Mass Spectrometry at the FRS-ESR facility a TOF detector is used for the measurement of the revolution times of stored ions. In the detector, ions passing a thin carbon foil release secondary electrons, which are transported to microchannel plates (MCPs) by electric and magnetic fields. Because of the high revolution frequencies in the ESR, a high rate acceptance is required as well as good timing characteristics. Offline studies show that MCPs with 5 µm pore size can accept a higher count rate than MCPs with the same active diameter but with a commonly used pore size of 10 µm. To show the advantages of MCPs with 5 µm pore size, the saturation effects were investigated online in the ESR with Ne and Ni primary beam as well as with U fission fragments. Comparison of the experimental results with Monte Carlo simulations prove that MCPs with 5 µm channel diameter are at least 3 times more resistant to the higher rates than MCPs with 10 µm pore size. In addition, the number of revolutions of the stored ions could be increased significantly by using thinner carbon foils.