Presentation on theme: "Optimisation of Slow Extraction for SIS-18 and SIS-100"— Presentation transcript:
1 Optimisation of Slow Extraction for SIS-18 and SIS-100 M. KirkSynchrotrons Group, GSISpill intensity78Kr MeV/u12C MeV/uAvailable at
2 Overview Principles of resonant extraction Extraction schemes SIS-18 Spill-ripple feedbackSpill intensity controlSpill measurement and analysisHardt conditionSIS-100“Not so Hardt” conditionPower converter ripple (main quadrupoles)RF Knock-Out specificationConclusion & Outlook
3 Resonance Theory – Sextupole Perturbation B-field of a sextupoleEquation of motion# over circumference: „Tune“Change variables …
4 Resonance Theory – Sextupole Perturbation …to normalized coordinates (u, p) as function of s = point of interestClose to just oneresonance (n)
5 Resonance Theory – Sextupole Perturbation Change variables (u,p) (r,) to find unstable fixed points (A,B,C) = Separatrixeventually obtainingat the unstable fixed points A,B,CWhich yield the conditions on r and …
6 Resonance Theory – Sextupole Perturbation …Area of separatrix„Third order/integer“ resonanceNormalised sextupole strengthSpiral step along the extraction arm> effective septum width!
9 RF Knock-Out Extraction BPSK (GSI)XX‘Dual FM (HIMAC)IntensitySeparateFunctionnot shown.
10 Block Functions of the SIS-18 RF Knock-Out P. Moritz, GSIbel.gsi.de/mk/fg/ko_extr.pdf
11 TheoryTime variation in tune of a bunched beam subject to ripple from the power supplies to the quadrupoleswhere,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.
12 Effect of tune ripple on separatrix Beam before powering resonance(b) First Extraction Septum EdgeSeptum change due to tune rippleNUnstable resonant particle at Nth turn(b)(a)14710…Spill intensity is modulated.
13 Ripple Injection Active ripple excitation (Moritz 2003) …spill ripple reduced.Analyzer + generatorreplaced with feedback amplifier…300 HzTraces offset.F/B onExtraction delay determined.Sets limit for spill intensity control.F/B off
14 Spill Analysis DAQ Systems at GSI ABLASS / ABLAXTRigger LOgicPulse CountingNIM modules (discriminator: analogdigital pulse)4 x 32-bit Multi-Scalers (time slice: bin size)Multi purpose VME module (event decoder)Particles counted: primary beam or secondariesDetectors: Numerous typesDetectors at: SIS, HEBT, CAVESSpill intensity versus timeCountrate histogramPulse CountingDetector: ScintillatorPile-up nsCFDFirmware (counting etc.)Particles counted: productsDetectors at: LAND, FRS~ particles per Prim. (FRS)Time interval (pulse-pulse) hist.ABLASS/X DetectorsPlastic ScintillatorPulse (ELR) ~20 nsPulse Counting1 Pulse per Prim.Mean 106 Prim./sBin size min. 10 sIonisation ChamberPulse (Gas-ions) ~10 sCurrent-to-Frequency fmax=1 MHzPulse per Prim. depend on beamMean Prim./sBin size >10 sSecondary e- MonitorPulse (sec. e-) < 10 nsCurrent-to-Frequencydepend on beamMean >108 Prim./sBin size >> 10 s
22 Optimising the RF Knock-Out Bandwidth BWSIS-100:238U28+B=100Tm
23 SIS-18 Quadrupoles - Power Converters 12 pulse SCR power converter0°(-15)120°240°R (magnets + cable)(50 Hz in)Active filter(50-70 kHz)L (magnets)0°(+15)120°240°
24 SIS-18 Quadrupoles - Power Converters 12-pulse SCR supply.Grid 50 Hz, 3-phase.Main component 600 Hz.Smaller 300 Hz also present.-15120°+1530°120°Active filter reduces U/U0 to <2%
25 SIS-18 Power Converter Ripple Measurements taken on the flattop of three machine cycles.CircuitRigidity B [Tm]61018In[A]Freq.[Hz]I[mA]S01QS1F4203000.270012706000.70.5S12QS1F0.1S01QS2D4000.366512030.6S12QS2D0.410.8S01QS3T81137248S11MU21092218204334010508900F-Quadrupoles2 Series CircuitsD-Quadrupoles2 Series CircuitsT-Quadrupoles1 Series CircuitDipoles(H. Welker, H. Ramakers, M. Kirk)
26 SIS-18 Power Converter Ripple Measurements taken at constant maximum current in the main quadrupoles.CircuitIn [A]I at 300 Hz [mA]I at 600 Hz [mA]S01QS1F17640.50.8S12QS1F17600.20.4S01QS2D1750S12QS2DS01QS3TS01QS3T8078200.3 Measured in „computer“ mode. Measured by „hand“.(H. Welker, H. Ramakers, M. Kirk)
27 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.Umax = 640 V at 100 TmU/Umax = 1%Strongest ripple at f = 600 HzL = 29 mH (series load)R from connecting cable only.Z 2fLI=U/Z = 59 mAImax = 7.8 kA (100 Tm)I/I = 7.5x10-6Closed-loop control has N=18-bit ADC for current measurement.2N-1 levels from zero to Imax (Unipolar current, Bipolar voltage.)Therefore, minimum possible accuracy is 30 mADuring flattop: Magnets are not ramped!300 Hz component: U/Umax = 0.5% would yield same I
28 Main Quadrupoles – Power Converter Ripple SIS-100: 100Tm 238U28+ ionsSpill Quality Factor (Imax/Imean)0.26 (B= Tm)
29 Bunched Beam Extraction SIS-100: 238U28+ at 100 TmF and D quadrupoles: I/I=±10-4
30 Spill Quality - Sensitivity to Momentum Spread SIS-100:U (A=238, q=28+) at 100TmDC beam.Spill Quality Factor (Imax/Imean)RMS Extracted Emittance [mm.mrad]
31 SIS-100 RF Knock-Out System Specification P. Moritz, “Detailed Specification on the SIS100 RF KO”, EDMS, GSI-B-RF Systems, 31 Jan 2011
32 Beam Intensity Control Open-Loop control. SIS U Tm:Spill CurrentsKO-Amplitudeb>0b=0(a=0)t4Heavyside
33 Beam Intensity Control - Spill Feedback SimulationProportional plus Integral (PI) control:SIS-100: U28+ at 100Tm(VP = 0)
37 SIS-18 RF Knock-Out Simulation - Hardt Condition Animation: Horizontal beam phase space with first extraction septum edge (left)
38 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.
39 Preliminary Outlook Acknowledgements Code benchmarking Other dynamical effectsOther extraction techniques, e.g. stochastic extractionAcknowledgementsP. 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.
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