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Injector Cyclotron for a Medical FFAG
H- compact AIMA cyclotron
concept Design Results
M. Conjat, J. Mandrillon,
P. Mandrillon, J. Pasternak
Tentative Layout (according to J.Pasternak)
AIMA cyclotron (1.75 m diameter)
Septum 0.7 T
6 quads in straights
Preliminary geometry of injection line into RACCAM FFAG
conceptDesign Results
conceptDesign Results
Concepts….Design Choices
Variable energy-extraction from 7 to 15 MeV Suitable: 1 energy step corresponds to a 1cm depth step in tissues.
Fast accelerationParticles reach 15 MeV in 60 turns, well separated.
Simple design H- acceleration Multi strippers extraction system with fast switches.
High energy gain per turn Power is pulsed in order to get a 50 kV peak to peak acceleration voltage,
with 6 gaps/turn.
A single cavity 3 dees galvanically connected, working on the 3rd Harmonic
External High Brightness H- MultiCusp Ion Source10 mA/cm², 5mA dc (to accelerate 350A)
TYPE OF CYCLOTRON: Negative ion
Size 1.75 diameter
Weight 13 tons
Ion source: H- MultiCusp, external
Extracted Current density (dc) 10 mA/cm²
MAGNET: Closed geometry, 3 sectors
Average field 1.55 tesla
Pole radius 38 cm
Amp turns 52580
RF SYSTEM: 1 single cavity
Number of dees 3
RF voltage 50 kV
RF frequency 70.6 MHz
RF power ~2 kW, pulsed (dc: 2%)
Resultsconcept
DesignMain Characteristics
high brightness multicusp ion source
AIMA cyclotron for FDG Production
Extracted beam intensity requirements
Maximum Dose Rate 5 Gray/min
FFAG (100 Hz rep. rate) 2.5 108 proton/cycle,
3 109 proton/cycle needed at injection
With multiturns injection (10t):
3 108 proton/ turn needed at injection
10 turns to fill the FFAG 3 s (injection F: 3 MHz, 10 revolution time)
With the Cyclotron at 70.6 /3rd Harm:
~200 cyclotron bunches
Cyclotron: ~1.5 107 proton/bunch
Cyclotron DC Current equivalent
170 A
Requirement at FFAG injection: Energy Dispersion < 50 keV Cyclotron DC Current goal:350 A
Resultsconcept
Design
About the magnet design
r
r & z versus Radius with ‘EUQUIL’
z
3D calculation CST, Compared with measures
B-field Isochronisms versus Radius with ‘EUQUIL’
Resultsconcept
Design
About the Dynamic design
3D electrostatic calculation& Central region optimization with ‘AGORA’
Energy gain in gaps optimization to accelerate fast.
Median plane acceleration
Trajectories
& Centers of Curvature
Resultsconcept
Design
R (cm)
Energy Gain in gap 6:
90 %
conceptconcept Design
Results
Multiple strippers to find a Cyclotron Energy
FocusVariable Energy ~7 to ~15 MeV
Variable energy extraction
Strippers
Energy Focus
conceptconcept Design
Results
Extraction Energy - 14 Mev
Horizontal Envelop (1 ) mm mrad
Vertical Envelop (1 ) mm mrad
Energy spread 75% < 50 KeV
Normalized Transversal Emittances:
0.5 mm mrad vertical (worst case)
0.3 mm mrad horizontal
+ multiple scattering due to stripper traversal
Bunch length in 1st gap: 15°
4 mm
1 mrad
20 mrad
15 mm
Tracking at Extraction
Envelop at Focus
conceptconcept Design
Results
Extraction Energy - 11 Mev
Horizontal Envelop (1 ) mm mrad
Vertical Envelop (1 ) mm mrad
Energy spread 81% < 50 KeV
Normalized Transversal Emittances:
0.5 mm mrad vertical (worst case)
0.3 mm mrad horizontal
+ multiple scattering due to stripper traversal
Bunch length in 1st gap: 15°
4 mm
0.6 mrad
30 mrad
20 mm
Tracking at Extraction
Envelop at Focus
conceptconcept Design
Results
Extraction Energy - 8 Mev
Horizontal Envelop (1 ) mm mrad
Vertical Envelop (1 ) mm mrad
Energy spread 91% < 50 KeV
Normalized Transversal Emittances:
0.5 mm mrad vertical (worst case)
0.3 mm mrad horizontal
+ multiple scattering due to stripper traversal
Bunch length in 1st gap: 15°
Tracking at Extraction
Envelop at Focus
4 mm
0.4 mrad
40 mrad
30 mm