CERN-ACC-SLIDES-2016-0002 EuCARD-2 Enhanced European Coordination for Accelerator Research & Development Presentation Present Achievements of Induction Synchrotron and its Possibility for Super-Bunch Yoshimoto, Takashi (KEK) 14 November 2016 The EuCARD-2 Enhanced European Coordination for Accelerator Research & Development project is co-funded by the partners and the European Commission under Capacities 7th Framework Programme, Grant Agreement 312453. This work is part of EuCARD-2 Work Package 5: Extreme Beams (XBEAM) . The electronic version of this EuCARD-2 Publication is available via the EuCARD-2 web site <http://eucard2.web.cern.ch/> or on the CERN Document Server at the following URL: <http://cds.cern.ch/search?p=CERN-ACC-SLIDES-2016-0002> CERN-ACC-SLIDES-2016-0002
Present achievements of induction synchrotron and its possibility for super-bunch acceleration 2014/11/14 Takashi Yoshimoto** **KEK digital accelerator group/Tokyo institute of technology
Su Super-bu bun Contents What is induction synchrotron ? System of KEK digital accelerator Three induction acceleration technique • wide-band acceleration • novel beam handling • (super-bunch acceleration) Upgrade plan for super-bunch acceleration Problem of super-bunch acceleration in high intensity synchrotron Conclusion 2
What is Induction synchrotron ? KEK digital accelerator (Wide-band fast cycling induction synchrotron) 1) Induction cells, not RF cavities !! 200 keV beam is directly injected. Beam Induction cell Circumference C 0 37.7 m Rep-rate f 10 Hz Injec. Energy E inj 200 keV 3 1) T. Iwashita, et al. , “KEK digital accelerator”, Phys. Rev. ST-AB 14, 071301(2011) 2) K. Takayama, et al. ,"Experimental Demonstration of the Induction Synchrotron" , Phys. Rev. Lett. 98, 054801 (2007)
Three distinguished features of Induction synchrotron Super-bunch acceleration 1) Novel beam handling Acceleration Voltage Wide-band acceleration 2) Time Advantages Rev. frequency: 0 ~ a few MHz So many ion species can be provided in a broad energy range. Disadvantages • Space charge limit & residual gas interactions in low energy region • In small ring (~100 m), max. rev. frequency is limited by semiconductor switching of acc. volt.. 4 1) K.Takayama, et al , “ Superbunch Hadron Colliders ”, Phys. Rev. Lett. 88, 144801 (2002) 2) K.Takayama, et al , “All -ion accelerators: An injector-free synchrotron ”, Journal of Applied Physics 101, 063304 (2007)
RF acceleration & Induction synchrotron Conventional RF acceleration Induction acceleration Voltage Voltage Beam Beam Time Time Confinement & Acceleration function are combined. Hamiltonian contour plot Hamiltonian contour plot Phase Phase 5
RF acceleration & Induction synchrotron Induction acceleration Conventional RF acceleration Voltage Voltage Acc. V Beam Time Beam Time Time Conf. V Beam Confinement & Acceleration function are combined. Hamiltonian contour plot Hamiltonian contour plot Phase Phase Separate function can creates a longer bucket ⇒ Diminishing space charge effect. 6
Switching Power Supply for Induction cells S1 S3 Switching power supply DC Acc. cell 1 2 ………. 7 1) S2 S4 2) 1) One arm consists of 7-series MOSFETs. Gate drive power MOSFET(rear side) drive IC (rear side) 2) water Waveform generated by switching power supply copper heat sink (2.5kV, 20A, 1MHz) Next generation of SPS: K.Okamura, et al , MOPME068 in IPAC’14 7 “ SiC-JFET Switching Power Supply toward for Induction Ring Accelerators”
Fully programmed control of KEK digital accelerator In advance, all information for acceleration timings is load to FPGA. Virtual B(t) decides ideal revolution period and acc. timings. Virtual PC FPGA DC (V) B control (t) V Input data (Revolution period, Acc. timings) Switching power supply Acceleration gap Start trigger V Induction cells (1 to 1 pulse transformer) Beam Bending magnet B q Magnetic core 8 Ion source T. Yoshimoto, et al, “ Heavy ion beam acceleration in the KEK digital accelerator: ~”, Nucl. Inst. Meth. A 733 (2014) 141-146
How to generate confinement voltages Ideal magnetic field B[T] 0.84 T (Injection) (Extraction) 0.039 T Reference signals:12 μs→ 1 μs ( which generate every ideal rev. period of beam) 50 t [ms] 0 Reference signals:12 μs→ 1 μs C 1 D 0 T ( t ) c D B(t) determines T(t) uniquely… 2 Q e 2 D B A m c 0 Rev. period T (12 μs~1 μs ) Here, ratio of charge to mass ： Q/A charge element ： e V[kV] T/6 bending radius: r +1.6 kV unit mass: m 0 ideal magnetic field ： B(t) 150 ns Time Beam -1.6 kV Conf. voltages are generated every turn. 9 1 turn 2 turn
How to generate acceleration voltage Reference signals (signals of ideal rev. period) :12 μs→ 1 μs Required acc. voltage per turn V(t): Ideal magnetic field dB ( t ) Pulse density function for acceleration V ( t ) C 0 dt ρ : bending radius C 0 : circumference Rev. period T B(t) : ideal magnetic field (12 μs~1 μs ) Voltage[kV] N 1 N 1 ( V ( n ) V ( n ) V ) +1.8 kV 0 0 n 1 n 1 ( N 1 ) 150 ns N 1 N 0 ( V ( n ) V ( n ) V ) 0 0 Time n 1 n 1 Beam V 0 : constant induction acc. voltage -1.8 kV δ (n) : acc. density table N : turn number Induction acc. voltages are generated discretely Pulse density control in order to give required acc. voltage spuriously. 10
Result of beam acceleration Overview Zoom-up view (End of acceleration) Beam signal Extraction Beam signal Injection B B control (t)=B actual( t) Experimental conditions: Injection timing 0.039 → 0.51 Bending magnetic flux density [T] Time Mass to charge ratio A/Q 4/1 0.05 → 8 Energy [MeV/u] ~100 μA Injection current *K.Takayama, T.Yoshimoto, et al ,“Induction acceleration of heavy ions 11 in the KEK digital accelerator”, Phys. Rev. ST-AB 17, 010101(2014)
Wide-band acceleration (experiment) Acceleration voltage V acc ( ± 1.6 kV, experiment) 50 40 Time[ms] 30 Beam waveform (experiment) 50 20 40 10 Just after acceleration 30 Time[ms] 0 Beam signal 20 0 2 4 6 8 10 12 Time[ μ s] Cofinement voltage V bb ( ± 2 kV, experiment) 10 50 0 40 0 2 4 6 8 10 12 30 Time[ μ s] Time[ms] Rev. period: 12 μs→ 1 μs !! 20 Beam bucket : 2 μs→ 200 ns 10 0 12 Time[ μ s] 0 2 4 6 8 10 12
Beam survival & discussion Beam survival: ~ 10% Reasons • Vacuum ( ～ 10 -6 Pa) Strong interaction with residual gas in low energy (200 keV ~) • Non-zero dispersion optics (D = 1.4 m at Induction cell region ) Unfortunately, present optics was designed for the PS booster ring 40 years ago. • Discrete acceleration In our case, acc. voltages are constant because of DC power supply. Therefore we do not generate acc. voltage every turn. Solution: Time varying DC power supply to meet required voltage demand may be ideal, especially for super-bunch acceleration. 13
Development of FPGA code for novel beam handling ~12,000 ns FPGA signal PC FPGA 120 ns 0 ns Set signal 360 ns Upload Time Reset signal 240 ns … Induction Cell Time Voltage @ Cell#1 … Calculated clock table (1 clock = 5 ns @200MHz) cell#2… cell#1 Turn Period Actual acc. voltages 1,2400,0,24,48,72 ,400,412,424,436,… (cell#1,#2,#3,#4) 2,2399,0,24,48,72,400,412,424,436 … … … … This FPGA code can generate arbitral pulse timings at each cell (Max.5) in each turn (Max.5000). 14 Therefore everyone can program each arbitral pulse easily and flexibly.
Comparison of IS and RF beam handling RF splitting (experiment) 1 @ CERN IS splitting & merging (experiment) @ KEK Merging Beam Splitting RF merging (experiment) 2 @ FERMI IS and RF beam handlings are qualitatively different. 1. It is easy to decide each beam length and quantity. 2. Timing control of acc. voltages is so simple. time 1. R.Garoby: STATUS OF THE NOMINAL PROTON BEAM FOR LHC IN THE PS,CERN/PS 99-013 (RF) 15 2. Philip S. Martin and David W. Wildman: BUNCH COALESCING AND BUNCH ROTATION IN TBE FERNILAB MAIN RING: OPERATIONAL EXPERIENCE AND COMPARISON WITH SMJLATIONS, Proc. EPAC88, Rome , Italy , 1988 (IOP, 1989) p.785
Simulation of novel beam handling Experiment Simulation Beam bucket ( ± 1.5 kV) Beam bucket ( ± 1.5 kV) Expansion Compression Beam The beam motion of the experiment is reproduced in the simulation macroscopically. Therefore it is easy to design the beam length and quantity. 16 20
How to realize super-bunch acceleration in the KEK digital accelerator ? 1. Asymmetric pulse for super bunch acceleration Acc. V Time Time Beam Beam 2. Time varying DC power supply Discrete acceleration Continuous acceleration at every turn 17
1. Asymmetric pulse for super bunch acceleration Acc. V Time Time Beam Super-bunch beam S1 S3 120 ohm S1 120 ohm S3 cable cable DC1 DC1 (300V) 0V) S2 S4 DC1 DC1 S2 S4 DC2 DC2 (300 00V) V) (900V) 0V) Induction Induction cell cell Different voltages are applied to positive and negative pulses. 18
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