ffag accelerators for radio-isotopes production
DESCRIPTION
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 Mode1 - 10 Mwatt - PowerPoint PPT PresentationTRANSCRIPT
FFAG Accelerators for Radio-Isotopes Production
Alessandro G. Ruggiero
Brookhaven National Laboratory
FFAG 2007, Grenoble, France
April 12-17, 2007
4/16/2007 FFAG 2007 -- Alessandro G. Ruggiero 2/18
FFAG for Hadron (proton and HI) Applications
Non-Relativistic Velocity < 1 (forget µ and e !)High Power Mode 1 - 10 MwattMedium Energy range 1 - 10 GeV/uHigh Repetition Rate 50 Hz
1 - 10 kHzCW
Narrow Width 10-30 cmLong Drifts > 1 mStrong Focusing (d) FDF (d)
Non Isochronous << T
RI and EN productionEnergy ProductionPulsed and Continuous Neutron ProductionNuclear Waste TransmutationTritium ProductionNuclear Physics (K, π, … mesons)Proton Drivers for Neutrino Factory, -SuperBeams, µ-CollidersNo Medical or Lower Energy or Lower Intensity Applications
RCS
SCL expensive
Cyclotron
FFAG
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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 2006Abstract
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 TUPLS027Abstract
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
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Goals of RIA (SCL) Uranium 238
ECR 12 keV/u Charge State 30RFQ 168 keV/uLow- SCL 9.3 MeV/u 57.5 and 115 MHz
Stripper 1 (Lithium Film) Charge State 69-73Medium- SCL 80.3 MeV/u 172.5 and 345 MHz
Stripper 2 (Carbon Wheel) Charge State 87-90High- SCL 400 MeV/u 805 MHz
CW Mode of Operation 4.2µA-particle 400 kWatt
Reliable but Expensive Project 360 SC Cavities
ECR RFQ
Low- Medium-
High- Section
G = 0.81 G = 0.61 G = 0.49
Stripper 2Stripper 1
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FFAG-Scenarios
Three possible modes of operation;
A. Acceleration with Broadband RF Cavity frep = 1 kHz
B. Pulsed Mode with Harmonic Number Jump frep = 10 kHz
C. CW Mode with Harmonic Number Jump frep = CW
Final Energy 400 MeV/uAverage Power 400 kWattAverage Current 4.2 µA-particle
I.S. Inj. Linac
RFQ
15 MeV/u 80 MeV/u 400 MeV/u
FFAG-1 FFAG-2
4.2 µA-particle
Charge State 30+
Charge State 90+
Charge State 70+
±40.3% ±41.4%
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A. Acceleration with Broadband RF Cavity
FFAG-1 (+70) FFAG-2 (+90)
Injection Extraction Injection Extraction
Circumference m 204 204
Kinetic Energy MeV/u 15 80 80 400
0.1767 0.3885 0.3885 0.7131
Revol. Freq. MHz 0.2597 0.5689 0.5710 1.0438
Revol.Period µs 3.851 1.758 1.751 0.958
h 6 6
RF Frequency MHz 1.558 3.423 3.423 6.273
RF Peak Voltage MVolt 0.8 1.6
RF Phase degrees 60 60
Bunch Area eV/u-s 0.02 0.02
Emittance, norm. π mm-mrad
110 110
sp. ch. 0.018 0.0077 0.016 0.0063
Nions / pulse x 1010 2.63 2.63
Accel. Period ms 0.758 0.726
No. of Revol. 319 611
Rep. Rate kHz 1 1
Ave. Current µA-particle 1093 2397 2403 4400
RF Beam Power kWatt 53.0 116.3 300.0 548.6
60 turns
18 µA-p IonSource
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A. Acceleration with Broadband RF Cavity
Revol. Freq. 3.851 µsI.S. 4 µA-particleStored Current 1093 µA-particleInjected Turns 275Filling Period 1 ms
Long Drift 1.089 mShort Drift 0.130 mF-Length 0.301 mD-Length 0.602 m
No. of Periods 80
I.S. Inj. Linac
RFQ
15 MeV/u 80 MeV/u 400 MeV/u
FFAG-1 FFAG-2Accumulator
F F D
Extraction Trajectory
Injection Trajectory
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Lattice Function along one period
Injection
Ejection
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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 pA (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+; Bmax = 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+; Bmax = 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?
10 MeV/n
To target station and fast fragment spectrometer
67 MeV/n 400 MeV/nECR EBIS RFQ Linac StripperU28+ U56+
Ring 1 Ring 2
Thomas Roser
4/16/2007 FFAG 2007 -- Alessandro G. Ruggiero 10/18
B. Acceleration with Harmonic Number Jump
FFAG-1 (+70) FFAG-2 (+90)
Injection Extraction Injection Extraction
Circumference m 204 204
Kinetic Energy MeV/u 15 80 80 400
0.1767 0.3885 0.3885 0.7131
Revol. Freq. MHz 0.2597 0.5689 0.5710 1.0438
Revol.Period µs 3.851 1.758 1.751 0.958
h 388 x 8 176 x 8 352 x 4 192 x 4
RF Frequency MHz 806.0 803.9
RF Peak Voltage MVolt 2 x (8 x 4) cavities 1 x (4 x 8) cavities
RF Phase degrees 30 60
Bunch Area eV/u-µs 10 10
Emittance, norm. π mm-mrad
100 100
sp. ch. 0.017 0.011 0.010 0.005
Nions / pulse x 109 2.63 2.63
Accel. Period µs 74.0 54.0
No. of Revol. 26 +4/8 40
Rep. Rate kHz 10 10
Ave. Current µA-particle 437 964 961 1762
RF Beam Power kWatt 8.3 238 119 3036
6 turns
75 µA-p Ion Src
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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-2FFAG-1
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CW Mode of Operation ( < 1)
Uranium Mass Number, A = 238Charge State, Q = +90
Rest Energy, E0 = 931.?? MeV/uKinetic Energy, E = 400 keV/uAverage Power, P = 400 kWattAverage 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
Tn
Tn + 1
Tn - 1
Vn
Vn + 1
Vn - 1ECR
Cyclotron, Muons Protons, < 1
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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 n
3 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 – i
2 / f2) / 2 M2 i
2 c2 h
Vn = g n TTF (0 / n) Cavity gap g = RF 0 / 2
Physical Review ST A&B 9, 100101 (2006)
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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
4/16/2007 FFAG 2007 -- Alessandro G. Ruggiero 15/18
Beam-Bunch Time Structure
FFAG-1 FFAG-2
Cavity Groups 8 4Cavities per Group 4 8
0 0.22 0.50Cavity Gap, cm 4.1 9.3RF Phase 30o 60o
RF Voltage / Cavity 2 MVolt 1 MVoltOrbit Separation, mm 2 - 20 2 - 11Beam rms Width, mm 5 - 4 3 - 2.5Beam 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)
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C. CW Mode of Acceleration by HNJ
FFAG-1 (+70) FFAG-2 (+90)
Injection Extraction Injection Extraction
Circumference m 204 204
Kinetic Energy MeV/u 15 80 80 400
0.1767 0.3885 0.3885 0.7131
Revol. Freq. MHz 0.2597 0.5689 0.5710 1.0438
Revol.Period µs 3.851 1.758 1.751 0.958
h 388 x 8 176 x 8 352 x 4 192 x 4
h -1 -1
RF Frequency MHz 806.0 803.9
RF Peak Voltage MVolt 2 x (8 x 4) cavities 1 x (4 x 8) cavities
RF Phase degrees 30 60
Bunch Area eV/u-µs 10 10
Emittance, norm. π mm-mrad
10 10
Nions / turn x 107 2.51 2.51
Accel. Period µs 74.0 54.0
No. of Revol. 26 +4/8 40
Rep. Rate CW CW
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Energy Gain Profile
FFAG-1 FFAG-2
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RF Voltage Cavity Profile for HNJ
cm cm
TM11 TM01 TM11
805 MHz
Gap =4-9 cm
8 MV/m ± 3 MV/m
20 cm
1 m