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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Optimisation of Slow Extraction for SIS-18 and SIS-100 M. Kirk Synchrotrons Group, GSI Spill intensity 78 Kr MeV/u 12 C MeV/u Available at

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Overview Principles of resonant extraction Extraction schemes SIS-18 Spill-ripple feedback Spill intensity control Spill measurement and analysis Hardt condition SIS-100 Not so Hardt condition Power converter ripple (main quadrupoles) RF Knock-Out specification Conclusion & Outlook

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Resonance Theory – Sextupole Perturbation Change variables … B-field of a sextupole # over circumference: Tune Equation of motion

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Resonance Theory – Sextupole Perturbation …to normalized coordinates (u, p) as function of s = point of interest Close to just one resonance (n)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Resonance Theory – Sextupole Perturbation Change variables (u,p) (r, ) to find unstable fixed points (A,B,C) eventually obtaining at the unstable fixed points A,B,C Which yield the conditions on r and … = Separatrix

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Resonance Theory – Sextupole Perturbation … > effective septum width! Area of separatrix Spiral step along the extraction arm Third order/integer resonance Normalised sextupole strength

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Extraction Methods (M. Pullia) Dashed line GSI RF acceleration, Longitudinal noise, Betatron core. Move machine tune towards resonance. Transverse RF excitation. (Q=0)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 RF Knock-Out Extraction Power density Frequency mf 0 Qf*f 0 Transverse Schottky Spectrum PAM spectrum ~5 MHz ~300MHz Pick-Up BW … KO Exc. (m=0, USB) (m+1/3)f 0

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 RF Knock-Out Extraction X X Intensity Dual FM (HIMAC) BPSK (GSI) Separate Function not shown.

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Block Functions of the SIS-18 RF Knock-Out P. Moritz, GSI bel.gsi.de/mk/fg/ko_extr.pdf

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Theory Time variation in tune of a bunched beam subject to ripple from the power supplies to the quadrupoles Therefore area of separatrix will also oscillate: Thus, to minimize sensitivity to ripple in the quadrupoles, extract with as high S as possible without distortion to the separatrix. where,

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Effect of tune ripple on separatrix (a)Beam before powering resonance (b) First Extraction Septum Edge (a) (b) Septum change due to tune ripple Unstable resonant particle at N th turn N …Spill intensity is modulated.

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Ripple Injection Active ripple excitation (Moritz 2003) …spill ripple reduced. Analyzer + generator replaced with feedback amplifier… Extraction delay determined. Sets limit for spill intensity control. F/B off F/B on 300 Hz Traces offset.

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Spill Analysis DAQ Systems at GSI ABLASS / ABLAX Pulse Counting NIM modules (discriminator: analog digital pulse) 4 x 32-bit Multi-Scalers (time slice: bin size) Multi purpose VME module (event decoder) Particles counted: primary beam or secondaries Detectors: Numerous types Detectors at: SIS, HEBT, CAVES Spill intensity versus time Countrate histogram TRigger LOgic Pulse Counting Detector: Scintillator Pile-up ns CFD Firmware (counting etc.) Particles counted: products Detectors at: LAND, FRS ~ particles per Prim. (FRS) Time interval (pulse-pulse) hist. ABLASS/X Detectors Plastic Scintillator Pulse (ELR) ~20 ns Pulse Counting 1 Pulse per Prim. Mean 10 6 Prim./s Bin size min. 10 s Ionisation Chamber Pulse (Gas-ions) ~10 s Current-to-Frequency f max =1 MHz Pulse per Prim. depend on beam Mean Prim./s Bin size >10 s Secondary e - Monitor Pulse (sec. e - ) < 10 ns Current-to-Frequency depend on beam Mean >10 8 Prim./s Bin size >> 10 s

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Spill detection (P. Forck)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-100 Synchrotron Doublet lattice 6 super periods RF-KO

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Hardt Condition Dispersion zero for illustration. Hardt condition. 3 separatrices each with a different momentum (Á. Saá-Hernández)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Several Sextupoles Virtual Sextupole Normalised strength: Betatron phase: 1st Extr. Sept. Virtual Sextupole Driving term (Guignard 1978):

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Chromaticity Correction Chromaticity correction in SIS-18: Adjusted chromaticity (sextupoles on): Natural chromaticity (sextupoles off): N = # 1C-Sextupoles = # 3C-Sextupoles

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-100 Extraction - Powering Scheme Chomaticities: (h), (v). Normalised to tune. Lattice version: TDR, Dec 2008 ! RF-KO Exciter

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Momentum Sensitivity of Separatrix

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Optimising the RF Knock-Out Bandwidth SIS-100: 238 U 28+ B =100Tm BW

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 Quadrupoles - Power Converters 0°0° 120° 240° 0°0° 120° 240° Active filter (50-70 kHz) R (magnets + cable) L (magnets) (-15 ) (+15 ) 12 pulse SCR power converter (50 Hz in)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 Quadrupoles - Power Converters 12-pulse SCR supply. Grid 50 Hz, 3-phase. Main component 600 Hz. Smaller 300 Hz also present ° 30° Active filter reduces U/U 0 to <2%

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 Power Converter Ripple Measurements taken on the flattop of three machine cycles. Circuit Rigidity B [Tm] I n [A] Freq. [Hz] I [mA] I n [A] Freq. [Hz] I [mA] I n [A] Freq. [Hz] I [mA] S01QS1F S12QS1F S01QS2D S12QS2D S01QS3T S11MU Dipoles F-Quadrupoles 2 Series Circuits D-Quadrupoles 2 Series Circuits T-Quadrupoles 1 Series Circuit (H. Welker, H. Ramakers, M. Kirk)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 Power Converter Ripple Measurements taken at constant maximum current in the main quadrupoles. CircuitI n [A] I at 300 Hz [mA] I at 600 Hz [mA] S01QS1F S12QS1F S01QS2D S12QS2D S01QS3T [1] [1] S01QS3T [2] [2] [1] [1] Measured in computer mode. [2] [2] Measured by hand. (H. Welker, H. Ramakers, M. Kirk)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-100 Quadrupoles - Power Converter 600 Hz also in SIS-100 quadrupole power converters: 12 pulse line commutated converter (SCR.) Switching Mode (SM) structure: Hard switching. Supplies current to the main quadrupoles. All main quadrupoles but 2 are superconducting. U max = 640 V at 100 Tm U/U max = 1% Strongest ripple at f = 600 Hz L = 29 mH (series load) R from connecting cable only. Z 2 fL I= U/Z = 59 mA I max = 7.8 kA (100 Tm) I/I = 7.5x10 -6 Closed-loop control has N=18-bit ADC for current measurement. 2 N -1 levels from zero to I max (Unipolar current, Bipolar voltage.) Therefore, minimum possible accuracy is 30 mA 300 Hz component: U/U max = 0.5% would yield same I During flattop: Magnets are not ramped!

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Main Quadrupoles – Power Converter Ripple Spill Quality Factor (I max /I mean ) SIS-100: 100Tm 238 U 28+ ions 0.26 (B = Tm)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Bunched Beam Extraction F and D quadrupoles: I/I=±10 -4 SIS-100: 238 U 28+ at 100 Tm

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Spill Quality - Sensitivity to Momentum Spread Spill Quality Factor (I max /I mean ) RMS Extracted Emittance [mm.mrad] SIS-100: U (A=238, q=28+) at 100Tm DC beam.

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-100 RF Knock-Out System Specification P. Moritz, Detailed Specification on the SIS100 RF KO, EDMS, GSI-B-RF Systems, 31 Jan 2011

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Beam Intensity Control Open-Loop control. SIS U Tm: KO-Amplitude Spill Currents Heavyside b=0 b>0 t4t4 (a=0)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-100: U28+ at 100Tm (V P = 0) Simulation Proportional plus Integral (PI) control: Beam Intensity Control - Spill Feedback

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 Synchrotron SX1,FQ,DQ,SX2,QT Doublet lattice Super periodicity 12 Sextupoles in odd periods SX1 = Res. + Hor. Chro. SX2 = Ver. Chro. FQ = Foc. Quad. DQ = Defoc. Quad. QT = Triplet Quad. ES = Electrostatic Extr. Sept. MS1 = First Extr. Mag. Sept. MS2 = Second Extr Mag. Sept. RF-K.O. = RF Knock-Out Exciter Injection ES MS1,MS2 RF-K.O. Reinjection FQ,DQ,QT

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Beam Intensity Control – Feedforward Measurement Beam: 12 C 6+ Energy: ~300 MeV/u C. Bert, A. Constantinescu, D. Ondreka, M. Kirk et al.

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 RF Knock-Out Simulation - Hardt Condition DC beam: p/p ( ) = 7.7x10 -5 RF Knock-Out: Amplitude (peak) = 2 kV Bandwidth = 6.2 mQ (FW) Bin size 10 s ~1% of ions lost at extr. septum MAX/AVG: ~14 RMS/AVG: ~230% 181 Ta 61+ at 300 MeV/u (B =7.97 Tm) Tunes: (h), 3.27(v) Resonance (1C) + Chromaticity Sextupoles (1C): Amplitude K 2L =0.1 m -2 Phase = -161 Offset K 2L = m -2 Remaining Chrom (3C) Sextupoles: K 2L = m-2

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 SIS-18 RF Knock-Out Simulation - Hardt Condition Animation: Horizontal beam phase space with first extraction septum edge (left)

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Conclusion No real success so far in uniting a good: Extraction efficiency, Beamsize, Transmission to target, AND microstructure! Macrostructure at least could be a success story, even for SIS-100.

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M. Kirk, Beschleuniger Palaver, GSI, 19 th Jan 2012 Preliminary Outlook Code benchmarking Other dynamical effects Other extraction techniques, e.g. stochastic extraction P. Spiller, N. Pyka, P. Moritz, U. Scheeler, G. Franchetti, D. Ondreka, P. Forck, T. Hoffmann, H. Reeg, H. Klingbeil, S. Sorge, E. Feldmeier, A. Dolinskii, H. Eickhoff, T. Furukawa (NIRS), H. Ramakers, H. Welker, Á. Saá Hernández, S. Pietri (FRS), C. Bert, A. Constantinescu, HKR operations crew. Acknowledgements

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