1. CAT-KEK-Sokendai School on Spallation Neutron Sources 1 Rapid Cycling Synchrotron (I) CAT-KEK-Sokendai School on Spallation Neutron Sources K. Endo (KEK) Feb. 2-7, 2004

2. CAT-KEK-Sokendai School on Spallation Neutron Sources 2 Contents 1)Rapid Cycling Synchrotron 2)Accelerator-Based Pulsed Neutron Sources – Existing Facilities 3)Next Generation Spallation Neutron Sources 4)Advantage/Disadvantage of RCS 5)Combined or Separated function RCS 6)Proton Driver for Neutrino Factory

3. CAT-KEK-Sokendai School on Spallation Neutron Sources 3 Rapid Cycling Synchrotron (RCS) (1) Increasing the repetition rate to 10~60Hz, it is possible to obtain much higher proton intensity. This type is called as a “rapid cycling synchrotron,” but it requires special design consideration including its power supply. Magnet: AC magnet made of laminated steel plates and requires design study using 2D or 3D field simulation code. Power supply: Resonant circuit to provide with sinusoidal current under the operation of the basing DC power supply. Operation: Combined function is easy. Separated function requires a precise tracking between Bending and Focusing fields.

4. CAT-KEK-Sokendai School on Spallation Neutron Sources 4 Rapid Cycling Synchrotron (2) Resonance Condition: Loads including magnets, capacitor and choke transformer are in resonance condition. Energy exchanged between magnets and capacitors, while the pulse power supply provides the losses. Utilize Full AC Field Swing: superpose DC field to AC field to have Injection at bottom AC field. Choke Transformer is introduced to decouple the pulse power supply. Reduce magnet voltage: adopt multi-mesh circuit.

5. CAT-KEK-Sokendai School on Spallation Neutron Sources 5 Rapid Cycling Synchrotron (3) – White circuit

6. CAT-KEK-Sokendai School on Spallation Neutron Sources 6 Rapid Cycling Synchrotron (4) Example of magnet, coil and pole end profile for rapid cycling synchrotron. Effect of magnet end pole profile (a) Rogowsky profile, and (b) Distribution of flux lines.

7. CAT-KEK-Sokendai School on Spallation Neutron Sources 7 Rapid Cycling Synchrotron (5)

8. CAT-KEK-Sokendai School on Spallation Neutron Sources 8 Rapid Cycling Synchrotron (6) Multi-mesh circuit NINA electron synchrotron combined function magnet Max. energy = 4GeV Mean orbit rad. = 35.1m Bending rad. = 20.8m Injection energy = 40MeV Field @4GeV = 0.64T Repetition = 50Hz

9. CAT-KEK-Sokendai School on Spallation Neutron Sources 9 Accelerator-Based Pulsed Neutron Sources Existing Facilities Acc. typeBeam Energy (MeV) Rep. Rate (Hz) Av. Beam Current (  A) Pulse Width (ms) Beam Power (kW) IPNS (ANL)Linac/RCS (CF, 13.6m dia.) 50  450 30 15 0.1 7 KENS (KEK)Linac/RCS (CF, 12m dia.) 40  500 20 6 0.1 3 ISIS (RAL)Linac/RCS (SF, 52m dia.) 70  800 50 200 0.1 160 LANSCE_PSR (LANL)Linac/AR (SF, 30m dia.) 800 20 125 750  0.25 100 SINQ (PSI)Cyclotron 72  590 continuous 1500900

10. CAT-KEK-Sokendai School on Spallation Neutron Sources 10 Layout of Proton Sources

11. CAT-KEK-Sokendai School on Spallation Neutron Sources 11

12. CAT-KEK-Sokendai School on Spallation Neutron Sources 12 Next Generation Spallation Neutron Sources SchemeMax. beam power (MW) Bunch compression (  sec) Magnet system NSNS (USA) 1GeV Linac +60Hz-AR 1 2 (upgrade) 1000 to 0.5SF (FODO) ESS (EU) 1.334GeV Linac + 50Hz- AR x 2 5600 to 0.4SF (Triplet) J-PARC (Japan) 0.4GeV Linac +25Hz-3GeV RCS 1500 to 0.1SF (FODO)

13. CAT-KEK-Sokendai School on Spallation Neutron Sources 13 NSNS (1) – ORNL 1,2,3,4) H - ion source+2.5MeV RFQ: LBNL 50mA-H - Linac NC-DTL+CCL: LANL (2.5  200MeV). SC-Linac: JLab. (200  1000MeV). Accumulation Ring: BNL Charge exchange injection (H -  p) 1200 turn injection, Short (1  sec) and intense proton pulses are extracted at 60Hz. Mercury target: ORNL Exp. Facilities: ANL+ORNL Extraction is a single turn with full aperture at a pulse repetition rate of 60Hz. Extraction system consists of a full-aperture kicker and a Lambertson magnet septum. Vertically kicked and horizontally extracted.

14. CAT-KEK-Sokendai School on Spallation Neutron Sources 14 NSNS (2)

15. CAT-KEK-Sokendai School on Spallation Neutron Sources 15 NSNS (3)

16. CAT-KEK-Sokendai School on Spallation Neutron Sources 16 ESS (European Spallation Source) (1)

17. CAT-KEK-Sokendai School on Spallation Neutron Sources 17 ESS (2) 5) - Options for 5MW proton beam @50Hz in pulse of time duration 1  s or less 1.0.8GeV H - linac + 3 ARs 2.1.334GeV H - linac + 2 ARs 3.0.8GeV H - linac + 2 RCSs of 3GeV and 25Hz 4.2.4GeV H - linac + 1 AR 5.0.8GeV H - linac + 1.6 or 3GeV superconducting FFAG, 30GeV KAON Factory type accelerator, or 1GeV proton induction linac Expensive 2 nd option: highest operational reliability 3 rd option: secondary consideration for a long pulse (2ms) facility Low energy injection: severe space charge limit but less severe heat problem for H - stripping foil

18. CAT-KEK-Sokendai School on Spallation Neutron Sources 18 ESS (3) – AR option Two 50Hz, 1.334GeV AR (Accumulation Ring). AR’s act to compress the time duration of the Linac Pulse by a multi-turn (1000 turns/ring) charge exchange injection.

19. CAT-KEK-Sokendai School on Spallation Neutron Sources 19 ESS (4) – RCS option Two 25Hz RCS operate out of phase at 3GeV, 50Hz. Very high power RF system occupies more straight sections than 1.334GeV AR, leading to 4 superperiods. Mean radius: 45.9m Injection: 0.8GeV Space charge tune shift: 0.2, twice of AR. Injection flat bottom: 2.5ms Dual harmonics: 20Hz sinusoidal rise and 40Hz fall.

20. CAT-KEK-Sokendai School on Spallation Neutron Sources 20 J-PARC (1) 6)

21. CAT-KEK-Sokendai School on Spallation Neutron Sources 21 J-PARC (2)

22. CAT-KEK-Sokendai School on Spallation Neutron Sources 22 J-PARC (3) - Future upgrade

23. CAT-KEK-Sokendai School on Spallation Neutron Sources 23 Advantage/Disadvantage of RCS 7) 1)Neutron yield is proportional to beam power (E b x I b ). Trade off between repetition rate, beam current and beam energy. RCS achieves high power at low repetition rate at reasonable cost compared to linac/compressor scenario. 2)RCS requires high power RF cavity 3)Care for Eddy current due to rapid change of Magnetic field 4)Space charge limit at low energy injection, so the peak current in RCS is several times smaller 5)Longer beam-in-ring time (10 to 20ms) compared to linac/compressor ring (1 to 2  s) will have a greater risk of instabilities associated with large number of cavities.

24. CAT-KEK-Sokendai School on Spallation Neutron Sources 24 Comparison of Linac- and RCS-based concepts Linac-basedRCS-based Beam energylowhigh Beam currenthighlow Beam loss controlseveremitigated H - ion sourcehigh current high duty moderate Construction costexpensiveless costly Required RF power for AR or RCS lowhigh

25. CAT-KEK-Sokendai School on Spallation Neutron Sources 25 Reducing RCS-RF power by Dual-frequency mode Excitation

26. CAT-KEK-Sokendai School on Spallation Neutron Sources 26 Combined or Separated function RCS Tracking between dipole and quadrupole fields Combined Separated Tracking maintained but limited tunability. NINA, Fermilab, KEK-PS Dipoles and quads are serially connected, but requires trim quad windings or dependent correction quad. SSC, SSRL Serial resonance circuit for quad. J-PARC Independent excitation of B, QF and QD, each phase adjusted within ±1  sec. No magnet saturation. BESSY II Booster (10Hz)

27. CAT-KEK-Sokendai School on Spallation Neutron Sources 27 Tuning of QF and QD for Separated-function RCS

28. CAT-KEK-Sokendai School on Spallation Neutron Sources 28 Proton Driver for Neutrino Factory (1) 8) - RCS based Proton driver for neutrino factory, fitting into CERN-ISR beam power: 4MW final bunch duration: 1ns RAL: Synchrotron-based two RCS options 1) 1.2GeV @50Hz + 5GeV @25Hz 2) 3GeV @25Hz + 15GeV @12.5Hz CERN: Linac-based proton driver 2.2GeV @75Hz linac + Accumulator and Compressor rings

29. CAT-KEK-Sokendai School on Spallation Neutron Sources 29 Proton Driver for Neutrino Factory (2) - Linac-based

30. CAT-KEK-Sokendai School on Spallation Neutron Sources 30 References 1)W.T. Weng et al, “Accumulator Ring Design for the NSNS Project,” PAC97, pp.970. 2)D. Raparia et al, “The NSNS Ring to Target Beam Transport Line,” BNL/NSNS Technical Note No.006. 3)J. Wei et al, “Low-Loss Design for the High-Intensity Accumulator Ring of the Spallation Neutron Source,” PRST-AB, 3, 080101 (2000) 4)“Final Design Review: SNS Super Conducting Linac RF Control System,” 2000. 5)G. Bauer et al (ed.), “The ESS Feasibility Study Vol. III Technical Study,” ESS-96-53-M, 1996. 6)Draft of “Accelerator Technical Report for High-Intensity Proton Accelerator Facility Project,” JEARI/KEK Joint Team, http://hadron.kek.jp/member/onishi/tdr/index.htmlhttp://hadron.kek.jp/member/onishi/tdr/index.html 7)Y. Cho, “Synchrotron-Based Spallation N eutron Source Concept,” APAC98, Tsukuba, 1998. 8)C,.R. Prior et al, “Synchrotron-Based Proton Drivers for a Neutrino Factory,” EPAC2000, Vienna, 2000, pp.963-965.