Forck, P

Franczak, B J

Meyer, U

Moritz, P

Peters, A

Strehl, P

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CURRENT MEASUREMENTS OF SLOWLY EXTRACTED IONSFROM A SYNCHROTRONP. Forck, B. Franczak, U. Meyer, P. Moritz, A. Peters, P. StrehlGesellschaft f. Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt, GermanyAbstractThe talk reports on low intensity measurements during slow extraction fromthe heavy ion synchrotron SIS using various detector systems. Due to thevariation in the extraction time (0.1 to 10 s) and the various ions species, thecurrent varies about five orders of magnitude.Until now the standard detectors for the current measurement are scintilla-tors for low, ionization chambers for medium and secondary electron monitorsfor high currents. There performances are briefly discussed. In particular thelinearity and the calibration of ionization chambers provided for medium in-tensities and secondary emission monitors for higher currents are discussed.Results from new developed diamond particle counters, which have 2 ordersof magnitude higher rate capability than scintillators are reported. Due to theshort pulse length of 1 ns (FWHM) an average count rate capability up to10 particles per second is possible. These detectors can be used for fast ions(minimum ionizing particle) as well as for slow ions delivered by the LINAC.For high ion currents above 1 nA a super-conducting SQUID based device isused, which measures the magnetic field (about some fT) of ion currents. Theperformance of it is shown.With the described detectors careful investigations are done concerning thevariation of the current with high time resolution (20 mus binning). High fluc-tuations are seen, which shows the sensitivity of the resonance extraction dueto power supplier ripple. The time structure can be smoothed drastically bybunching the ion beam inside the synchrotron due do a ’smearing’ of the trans-verse phase space region close to the separatrix.As an application of position measurement devices the computer aided beamalignment between the synchrotron and the target places is presented.The synchrotron delivers a large variety of ion kinds and energies. Since thesettings of the extraction elements is mainly determined by extraction effi-ciency rather than beam position, some individual adjustment is needed in or-der to put the beam exactly on the various targets.To accomplish this the ion optics program MIRKO used for the design of ringsand beam lines was extended to an online version, which reads the beam posi-tions and reads/writes the beam line magnets directly. From two positions inboth transverse planes the starting conditions of the beam are calculated andfrom these the settings of two correction elements per plane are determinedand sent directly to the magnets.This is done using a simple dialog box on the control console which in additionallows manual entry of beam positions that cannot be read by computer, e.g.fluorescent screens or halo counters. Normally the beam position is correctedin one or two steps and the time for compuation is negligible.90

Current measurements of slowly extracted ions from a synchrotron

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