Stuttgart 2012 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 4: Ion Storage Rings
MS 4.2: Vortrag
Dienstag, 13. März 2012, 11:00–11:15, V57.06
Isochronous mass spectrometry with longer observation of ions and improved timing performances of a time-of-flight detector at ESR — •Natalia Kuzminchuk1,2, Marcel Diwisch1, Samuel Ayet2, Timo Dickel1,2, Hans Geissel1,2, Ronja Knöbel1,2, Wolfgang Plaß1,2, Christoph Scheidenberger1,2, Baohua Sun1,2, and Helmut Weick2 — 1Justus-Liebig-Universität Gießen — 2GSI, Darmstadt
Using Isochronous Mass Spectrometry at the FRS-ESR the mass of the exotic nuclei can be deduced from precise revolution time measurements by a time-of-flight detector. In the detector, the ion impinge on a thin carbon foil and the emitted secondary electrons are deflected by 180∘ with an applied electric and magnetic fields to two MCP detectors. Due to the high revolution frequencies of the ions in the ESR (∼2 MHz), a high rate acceptance is required as well as good timing characteristics. The rate capability improvements developed in offline work using MCPs with smaller pore size and employing thinner carbon foils were studied online with 238U fragments for the first time at the FRS-ESR facility. As a result, up to 10 times more revolutions of the stored ions in the ring were observed. To improve the timing accuracy the TOF detector was modified for higher kinetic transport energies of the secondary electrons from the foil to the MCPs. Offline measurements with a radioactive alpha source showed that the time accuracy of the detector was improved by up to 50 %.