Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory Title AN IMPROVED TIME-OF-FLIGHT ION CHARGE STATE DIAGNOSTIC Permalink

Content Provider	Semantic Scholar
Author	Garvin, James Gill, Robert A. Mac
Copyright Year	2009
Abstract	A time-of-flight diagnostic for analysis of relatively low energy ion beams is described. The system incorporates several novel features which improve its performance in a number of ways. The technique is simple and can . provide an alternative to magnetic analysis of ion beams for the determination of ion charge state and beam composition. INTRODUCTION Analysis of ion beams by time-of-f1ight (TOF) systems is a diagnostic method used in a variety of fields [1 3]. It provides a particularly simple alternative to magnetic analysis for the determination of the charge state distribution of the beam produced by an ion source. We have made extensive use of this kind of system in our work developing the MEVVA (metal vapor vacuum arc) high current metal ion source [4-6]. In our application we need to monitor the charge state distribution of beams of metal ions, from lithium up to uranium, extracted from the ion source at a voltage of from 10 kV to 100 kV and injected into a high vacuum test chamber. We describe here the system we've developed and the improvements we've made. DESCRIPTION OF THE METHOD Ions of mass number A and charge state 0 are extracted from the ion source through a voltage drop V and thus acquire a velocity where e is the electronic charge and m the nucleon mass. In the time-of-flight method, a short pulse is gated out of the main ion beam pulse for analysis. The short sampled pulse is caused to drift through a distance L adequate to allow separation of the various Q/A components in the beam, and the flight time of these components is measured by a detector located at the end of the drift region. In this application the method is a Q/A diagnostic, and since in our case the beam is composed almost entirely of a single mass ion, it provides a charge state analysis. The time in the main beam pulse at .vhich the short time-of-flight pulse is gated out can of course be varied electronically, so allowing the charge state spectrum to be sampled a'., a function of time throughout the beam pulse.
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Language	English
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Resource Type	Article