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FFAG Accelerators for Radio-Isotopes Production

FFAG Accelerators for Radio-Isotopes Production. Alessandro G. Ruggiero Brookhaven National Laboratory FFAG 2007, Grenoble, France April 12-17, 2007. FFAG for Hadron (proton and HI) Applications. Non-Relativistic Velocity  < 1 (forget µ and e !) High Power Mode 1 - 10 Mwatt

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FFAG Accelerators for Radio-Isotopes Production

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  1. FFAG Accelerators for Radio-Isotopes Production Alessandro G. Ruggiero Brookhaven National Laboratory FFAG 2007, Grenoble, France April 12-17, 2007

  2. FFAG for Hadron (proton and HI) Applications • Non-Relativistic Velocity  < 1 (forget µ and e !) • High Power Mode 1 - 10 Mwatt • Medium Energy range 1 - 10 GeV/u • High Repetition Rate 50 Hz • 1 - 10 kHz • CW • Narrow Width 10-30 cm • Long Drifts > 1 m • Strong Focusing (d) FDF (d) • Non Isochronous  << T • RI and EN production • Energy Production • Pulsed and Continuous Neutron Production • Nuclear Waste Transmutation • Tritium Production • Nuclear Physics (K, π, … mesons) • Proton Drivers for Neutrino Factory, -SuperBeams, µ-Colliders • No Medical or Lower Energy or Lower Intensity Applications RCS SCL expensive Cyclotron FFAG FFAG 2007 -- Alessandro G. Ruggiero

  3. Previous Studies • AGS-based Facility for RIP following FAIR (T. Roser, Februray 2006) • too complicate RCS • needed accumulator ring(s) and e-cooling A.G. Ruggiero “AGS-less RIA with FFAG Accelerators”, BNL Internal Report, C-A/AP 238, May 2006 • Abstract • We have studied the use of Non-Scaling Fixed-Field Alternating-Gradient (FFAG) accelerators for the acceleration of heavy ions to produce radioisotopes and exotic nuclear fragments. We have taken as reference a beam of nuclei of Uranium 238 partially stripped to +28 charge state. • A.G. Ruggiero, T. Roser, D. Trbjevic, “A Non-Scaling FFAG for Rare Isotopes Production”, Proceedings of EPAC, Edinburgh, Scotland TUPLS027 • Abstract • This is a report to demonstrate the use of Non-Scaling Fixed-Field Alternating-Gradient (FFAG) accelerators [1] in acceleration of partially stripped ions of Uranium-238 for Rare Isotopes Production. The following example assumes a beam final energy of 500 MeV/u with an average beam output current of 1 µA-particle and a beam average power of 120 kWatt. • P.N. Ostroumov, Phys. Rev. Spec. Topics Acc. and Beams, 5(2002) 030101 FFAG 2007 -- Alessandro G. Ruggiero

  4. Goals of RIA (SCL) Uranium 238 Low- Medium-  • ECR 12 keV/u Charge State 30 • RFQ 168 keV/u • Low- SCL 9.3 MeV/u 57.5 and 115 MHz • Stripper 1 (Lithium Film) Charge State 69-73 • Medium- SCL 80.3 MeV/u 172.5 and 345 MHz • Stripper 2 (Carbon Wheel) Charge State 87-90 • High- SCL 400 MeV/u 805 MHz • CW Mode of Operation 4.2µA-particle 400 kWatt • Reliable but Expensive Project 360 SC Cavities ECR RFQ Stripper 1 Stripper 2 G = 0.81 G = 0.61 G = 0.49 High- Section FFAG 2007 -- Alessandro G. Ruggiero

  5. Charge State 90+ 15 MeV/u 80 MeV/u 400 MeV/u Charge State 30+ 4.2 µA-particle I.S. Inj. Linac RFQ FFAG-1 FFAG-2 Charge State 70+ FFAG-Scenarios • Three possible modes of operation; • Acceleration with Broadband RF Cavity frep = 1 kHz • Pulsed Mode with Harmonic Number Jump frep = 10 kHz • CW Mode with Harmonic Number Jump frep = CW Final Energy 400 MeV/u Average Power 400 kWatt Average Current 4.2 µA-particle ±40.3% ±41.4% FFAG 2007 -- Alessandro G. Ruggiero

  6. A. Acceleration with Broadband RF Cavity 60 turns 18 µA-p IonSource FFAG 2007 -- Alessandro G. Ruggiero

  7. 15 MeV/u 80 MeV/u 400 MeV/u I.S. Inj. Linac RFQ Accumulator FFAG-1 FFAG-2 A. Acceleration with Broadband RF Cavity • Revol. Freq. 3.851 µs • I.S. 4 µA-particle • Stored Current 1093 µA-particle • Injected Turns 275 • Filling Period 1 ms • Long Drift 1.089 m • Short Drift 0.130 m • F-Length 0.301 m • D-Length 0.602 m • No. of Periods 80 FFAG 2007 -- Alessandro G. Ruggiero

  8. Lattice Function along one period Injection Ejection FFAG 2007 -- Alessandro G. Ruggiero

  9. Thomas Roser FFAG heavy ion driver 400 MeV/u, 400 kW, 1 kHz  6.3 x 1012 nucleon/pulse = 2.6 x 1010 U/pulse = 4.2 pmA (OK for ECR) Use EBIS as space charge neutralized accumulator. Extract pulses for single turn injection. Accelerate multiple charge states. Energy choices: Kinetic E Momentum Beta Rev. Frequency (C=153m) Injection Ring 1 10 MeV/u 137 MeV/c/u 0.145 0.28 MHz Injection Ring 2 67 MeV/u 381 MeV/c/u 0.359 0.70 MHz Extraction 400 MeV/u 954 MeV/c/u 0.713 1.39 MHz Ring 1: U28+; Brmax = 9.2 Tm  B ~ 0.8 T for 50% filling factor; 1ms acc. time  500 turn acceleration  2 MeV/turn  40 keV/m for 50 m rf  broadband Finemet cavities? Ring 2: U56+; Brmax = 12.2 Tm  B ~ 1.0 T for 50% filling factor; 1ms acc. time  1000 turn acceleration  3 MeV/turn  60 keV/m for 50 m rf  broadband Finemet cavities? Ring 1 Ring 2 To target station and fast fragment spectrometer ECR EBIS RFQ Linac 10 MeV/n U28+ 67 MeV/n Stripper U56+ 400 MeV/n FFAG 2007 -- Alessandro G. Ruggiero

  10. B. Acceleration with Harmonic Number Jump 6 turns 75 µA-p Ion Src FFAG 2007 -- Alessandro G. Ruggiero

  11. Constant-RF Voltage Profile (805 MHz) • Using these RF Voltage Profiles it is possible to operate in CW mode provided that the Ion Source delivers continuously 4.2 µA-particles. • Ratio of Initial to Final Harmonic Number = f / i = 4.04 FFAG-1 FFAG-2 FFAG 2007 -- Alessandro G. Ruggiero

  12. Vn - 1 Tn Tn - 1 Vn Tn + 1 Vn + 1 CW Mode of Operation ( < 1) • Uranium Mass Number, A = 238 • Charge State, Q = +90 • Rest Energy, E0 = 931.?? MeV/u • Kinetic Energy, E = 400 keV/u • Average Power, P = 400 kWatt • Average Current, I = P/AE = 4.2 µA-ion • M equally-spaced cavities around ring at constant frequency fRF and phase RF • Energy Gain En = (Q/A) eVn sin RF • fRF = constant = n hn f∞ --> n+1 hn+1 = n hn • f∞ = C / c T / T = C / C –  /  C / C <<  /  • = 0, Isochronous ECR Cyclotron, Muons Protons,  < 1 FFAG 2007 -- Alessandro G. Ruggiero

  13. Harmonic Number Jump (HNJ) • The variation of h with  can be calculated precisely on a computer, but here we use a linear approximation ( a very good one indeed!) • En+1 = E0n2n3h / (1 – pn2) hn h = hn+1 – hn • = (Q/A) eVn sin RF •  • hn is local value between cavity crossings • h is harmonic number jump between cavity crossings = –1 • pn2 << 1 • By integration • Max. energy gain per crossing Emax = Efff2h M c / fRF Ctot • Number of Crossings nf = fRF Ctot (1 – i / f) / Mi c h • Acceleration Period tf = fRF Ctot2 (1 – i2 / f2) / 2 M2i2 c2h • Vn = g n TTF (0 / n) Cavity gap g = RF0 / 2 Physical Review ST A&B 9, 100101 (2006) FFAG 2007 -- Alessandro G. Ruggiero

  14. Consequences of Harmonic-Number Jump • To avoid beam losses, the number of bunches ought to be less than the harmonic number at all time. On the other end, because of the change of the revolution period, the number of RF buckets will vary. There is a difference between the case of acceleration below and above transition energy. Below transition energy the beam extension at injection ought to be shorter than the revolution period. That is, the number of injected bunches cannot be larger than the RF harmonic number at extraction. The situation is different when the beam is injected above the transition energy. In this case the revolution period decreases and the harmonic number increases during acceleration. • Below Transition Above Transition hf / hi = f / i FFAG 2007 -- Alessandro G. Ruggiero

  15. Beam-Bunch Time Structure • FFAG-1 FFAG-2 • Cavity Groups 8 4 • Cavities per Group 4 8 • 0 0.22 0.50 • Cavity Gap, cm 4.1 9.3 • RF Phase 30o 60o • RF Voltage / Cavity 2 MVolt 1 MVolt • Orbit Separation, mm 2 - 20 2 - 11 • Beam rms Width, mm 5 - 4 3 - 2.5 • Beam rms Height, mm 7.5 5.0 ECR Ion Source 4.2 µA-ion Tfinal Tinitial Bunching Freq. = 57 MHz (1 bunch / 14 rf buckets) FFAG 2007 -- Alessandro G. Ruggiero

  16. C. CW Mode of Acceleration by HNJ FFAG 2007 -- Alessandro G. Ruggiero

  17. Energy Gain Profile FFAG-1 FFAG-2 FFAG 2007 -- Alessandro G. Ruggiero

  18. RF Voltage Cavity Profile for HNJ cm cm 8 MV/m ± 3 MV/m 805 MHz Gap =4-9 cm 20 cm TM11 TM01 TM11 1 m FFAG 2007 -- Alessandro G. Ruggiero

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