SIS-18 RF KNOCK-OUT OPTIMISATION STUDIES Contact Information Dr. Markus Kirk, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstr. 1, D-64291 Darmstadt Phone: +49 (0)6159 71-1542 m.kirk@gsi.de Design and Layout by P. Schwab May 2013 SIS-18 RF KNOCK-OUT OPTIMISATION STUDIES Markus Kirk, David Ondreka, Peter Spiller (GSI Darmstadt, Planckstraße 1, D-64291 Darmstadt) IPAC 2013 Shanghai, PRC ABSTRACT The extraction efficiency of the SIS-18 heavy ion synchrotron and temporal structure of its spill are part of the upgrades to the GSI accelerator complex. Losses to the extraction septum can be minimised through implementation of the Hardt condition resulting however in a poorer quality of the spill microstructure at resolutions of a few s due to lowering of the horizontal chromaticity from its ‘natural’ value. Ways to improve the extraction efficiency and spill microstructure are investigated with a tracking code. One possibility for improvement may be to use an alternative modulation applied to the RF knock-out exciter. SX1,FQ,DQ,SX2,QT Doublet Lattice Super periodicity 12 Sextupoles (SX) in odd periods SX1 Resonance + Horizontal Chromaticity SX2 Vertical Chromaticity FQ Focusing Quadrupole (horizontally) DQ Defocusing Quadrupole QT Triplet Quadrupole ES Electrostatic Extraction Septum MS1 First Extraction Magnetic Septum MS2 Second Extraction Magnetic Septum RF-K.O. RF Knock-Out Exciter: 750 mm x 200 mm. Max. 350 Vp  Max. Effective Voltage ~1.3 kVp Injection ES MS1,MS2 RF-K.O. Reinjection FQ,DQ,QT SIS-18 Hardt condition for optimum extraction efficiency Dual FM BPSK with PRN RF Knock-Out Modulations: Simulation Parameters DC circulating beam: 12C6+ at 400 MeV/u (6.35 Tm) with  = 0.04% (2) Tunes (4.3296, 3.27) Third integer resonance Qh=13/3 Sextupole amplitude K2L=0.03 m-2 SPILL-RIPPLE ONLY FROM EXCITER Present Operation: / = -6.9 Moving peak-to-average of spill (1ms window) BPSK: Max. Ueff = 1.3 kV (0.965 rad deflection) Dual FM: Max. Ueff = 4.5 kV Centre Frequency 301 kHz Span 27 kHz Repetition Rate 1 kHz Carrier at 328 kHz: Dn(s) = 0 (illustration) Dn(s)  0 (Hardt condition) Septum 3 Separatrices each with a different momentum Chromaticity changed from -6.9 to -0.3 At Septum Entrance: Hardt Condition: / = -0.3 BPSK: Max. Ueff = 1.1 kV (White Noise: Max. Ueff = 5.5 kV) Dual FM: Max. Ueff = 5.3 kV Hardt condition