The Physics of eRHIC Introduction Scientific highlights Detectors Summary R. Milner
Scaling VFFAG eRHIC Design
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Transcript of Scaling VFFAG eRHIC Design
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Scaling VFFAG eRHIC Design
Progress Report 4
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 1
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Last time:
• Found FODO lattices rated for 9.4 and 9.5GeV– Extrapolation suggests both allow orbit excursions
of less than 7cm (k=30m^-1) with <10^-6 losses• But this is without alignment errors
– Location relative to resonances understood
• 9.5GeV/80% packing factor lattice became baseline for scaling VFFAG arc magnet design
• Synchrotron radiation ~10MW to first order
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 2
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I. Macroparticle Weighting
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 3
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Greater accuracy for tail losses
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 4
• Generate macroparticles roughly uniformly as a function of normalised radius out to >10
• Weights are w = f(r)/g(r) where:– f(r) is desired real phase space density function– g(r) is density of generated macroparticles
• Details available in the note on distributions: http://stephenbrooks.org/ral/report/2013-9/4ddist.pdf
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Comparison: 9.5GeV FODO lattice
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 5
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Zoom: ‘resonance’ features remain
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 6
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Comparison: 8GeV FODO lattice
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 7
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Comparison: 9.4GeV FODO lattice
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 8
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Comparison: 10GeV FODO lattice
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 9
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II. Error Studies of FODO Lattice
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 10
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Tracking with translational errors
• Random offsets were generated for each magnet in 500 cells (then reused)
• Error in each axis a normal distribution with mean 0 and standard deviation – RMS 3D distance offset = sqrt(3) ~ 1.73– 99% single axis offset ~ 2.58– 99% 3D distance offset ~ 3.37
• Tracked 2 turns at 1.2GeV, disrupted beam
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 11
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Beam loss vs. error sigma
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 12
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Loss vs. k and for 9.5GeV lattice
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 13
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=100um transmission
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 14
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=100um beam centroid
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 15
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=100um norm. RMS emittances
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 16
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=10um transmission
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 17
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=10um beam centroid
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 18
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=10um norm. RMS emittances
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 19
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=2.5um transmission
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 20
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=2.5um beam centroid
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 21
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=2.5um norm. RMS emittances
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 22
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=1um transmission
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 23
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=1um beam centroid
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 24
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=1um norm. RMS emittances
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 25
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=0 transmission
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 26
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=0 beam centroid
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 27
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=0 norm. RMS emittances
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 28
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III. Synchrotron Radiation Losses
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 29
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Compensation-free designs
• FFAG arcs transmit a continuum of energies so don’t strictly speaking need compensation of synchrotron energy losses– All examples given for “9.5GeV” FODO lattice– Assumed FFAG straights radiate same rate as arcs
• Constraints:– My FFAG arcs won’t transmit beam below 1.2GeV– Assumed ring linac won’t transmit below 100MeV
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 30
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Schematic changes
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 31
Before
Source, 10?MeV dump 100MeV
ERL1.1GeV
ERL
Compensation RF
After
~200MeVlinac
1.xGeVERL
100MeVERL?
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9-pass 10GeV (worst)
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 32
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9-pass 9GeV
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 33
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6-pass 10GeV
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 34
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6-pass 9GeV (<10MW)
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 35
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6-pass 9GeV to 13.5GeV, 6.1mA
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 36
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6-pass 9GeV to 14.9GeV, 3.3mA
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 37
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This may or may not be practical?
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 38
Source, dump
Overdrive mode
197MeVlinac
1.474GeVnot quite
ERL
100MeVERL
RF
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4-pass 10GeV (~10MW, long linac)
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 39
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IV. VFFAG Options Comparison
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 40
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FFAG type Synchrotron radiation
Dynamic aperture / error tolerance
Time of flight Energy range / multiple rings
Vertical (nonlinear) scaling** #
10MW at 9-10GeV
Not impossible but difficult
1-beta effect only Infinite / one ring
Vertical linear nonscaling * ##
Potentially to 20GeV 50mA
Better?
Unknown but better than horizontal FFAG
Probably factor 3x / two rings for 10GeV, three rings for 20-30
Vertical nonlinear nonscaling *** ###
Potentially to 20GeV 50mA
Also bad?
At least as good as linear nonscaling VFFAG
At least as good as linear nonscaling VFFAG
Horizontal linear nonscaling * ##
20GeV OK Linear magnets Problematic Two/three rings
Non-FFAG 20GeV OK Presumably good Each ring exact Too many rings
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 41
*, **, *** indicate complexity of magnets and correction#, ##, ### indicate conceptual difficulty
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V. Future Work
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 42
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Next steps (if scaling VFFAG)
• Develop “straight” cell for full ring lattice• Work with magnet and FFAG splitter designers• Decide on RF/linac energies• Open issues:
– Emittance growth from SR photon emission– Coherent synchrotron radation?
• “End-to-end” tracking of full ring– Eventually track with fieldmaps from magnet
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 43
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Next steps (if non-scaling VFFAG)
• Try linear field NS-VFFAG first (“Davidtron”)– Much less synchrotron radiation– Expect better dynamic aperture– Easier to build (correct and understand!) magnets– Will likely need a cascade of rings 1-3, 3-10 etc.
• Develop quadrupole field models for Muon1 and/or VFFAG tracker code
• Try to search and understand lattice space
July 15, 2013 Stephen Brooks, eRHIC FFAG meeting 44