issues for formation of meic ion beam
DESCRIPTION
Issues for Formation of MEIC Ion Beam. Ya. Derbenev. MEIC Ion Complex Design Mini-Workshop JLab, January 27-28, 2011. O u t l I n e. Concept of high luminosity Required parameters, concepts and problems of : - High energy EC for EIC - Synchronization for EC- - PowerPoint PPT PresentationTRANSCRIPT
Thomas Jefferson National Accelerator Facility
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Issues for Formation of MEIC Ion Beam
MEIC Ion Complex Design Mini-Workshop
JLab, January 27-28, 2011
Ya. Derbenev
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 2
O u t l I n e
• Concept of high luminosity• Required parameters, concepts and problems of :
- High energy EC for EIC
-Synchronization for EC-
- Beam emittance injected in collider ring (required)
- Luminosity lifetime (due to IBS and other) - Crab Crossing
- Acceleration/rebunching in collider ring
- Synchronization for collisions-
- Emittance vs space charge at stacking
- Beam loss at re-bunching
- Microwave beam stability (wakes in SRF cavities and other)
- Electron cloud
- Gaps
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 3
Luminosity in colliders with Electron Cooling
Decrease the bunch length design low beta-star
Decrease transverse emittances design low beta-star
Raise the beam-beam tune shift limit: large Qs (exceeding bb tune shift)
Raise repetition rate by arrangement for crab crossing to eliminate the parasitic bb
-Crab crossing is effective at HF- matches short bunches !
Decrease charge/bunch- receive MW stability, reduce IBS
Diminish the IBS using flat beams (non-coupled optics)
EC in cooperation with strong HF SC field allows one to obtain:
•Very short ion bunches (1cm or even shorter)
•Small transverse emittances
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 4
Forming the ion beamMain issues: •Initial cooling time•Bunch charge & spacing
General recommendations:•Prevent the emittance increase at beam transport (introducing a fast feedback)•Use staged cooling •Start cooling at possibly lowest energy•Use the continuous cooling during acceleration in collider ring, if necessary
Beam bunching, cooling and ramp agenda:•After stacking in collider ring, the beam under cooling can be re-bunched by high frequency SC resonators, then re-injected for coalescence (if needed), more cooling and final acceleration & cooling •The final focus could be switched on during the energy ramp, keeping the Q-values constant
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 5
Lifetime due to Intrabeam Scattering
IBS heating mechanism: Energy exchange at intra-beam collisions leads to x-emittance increase due to energy-orbit coupling, and y-emittance increase due to x-y coupling
Electron cooling is introduced to suppress beam blow up due to IBS, and maintain emittances near limits determined by beam-beam interaction.
Since L 1/ xy , reduction of transverse coupling while conserving beam area, would result in decrease of impact of IBS on luminosity
Electron cooling then leads to a flat equilibrium with aspect ratio of 100:1.
Touschek effect: IBS at large momentum transfer (single scattering) drives particles out of the core, limiting luminosity lifetime.
A phenomenological model which includes single scattering and cooling time of the scattered particles has been used to estimate an optimum set of parameters for maximum luminosity, at a given luminosity lifetime.
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 6
High Energy Electron Cooling
ion bunch
electron bunch
Electron circulator
ring
Cooling section
solenoid
Fast beam kicker
Fast beam kicker
SRF Linac
dumpelectron injector
energy recovery path
Circulator ring by-pass
Path length adjustment
ERL based circulator electron cooler
Initial cooling
After bunching
Colliding mode
Momentum GeV/MeV 12/6.6 60/33 60/33
Beam current A 0.6/3 0.6/3 0.6/3
Particle/bunch 1010 0.7/3.8 0.7/3.8 0.7/3.8
Bunch length mm200/20
010/30 5/15
Energy spread 10-4 5/1 5/1 3/1Hori. Emit.
norm.mm 4 1 0.56
Vert. emtt. norm. mm 4 1 0.11
Laslett tune shift 0.002 0.006 0.1
Cooling length m 15 15 15
Cooling time s 92 162 0.2
IBS growth time (longitudinal)
s 0.9
ERL/CR based staged EC in collider ring
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 7
Feasibility of High Energy Electron Cooling
Beam adapters•Allows one to flatten the e-beam area in order to reach the optimum cooling effect
Advances on electron beam
SRF energy recovering linac (ERL)•Removes the linac power show-stopper•Allows for two stages cooling or even cooling while accelerating•Allows for fast varying the e-beam parameters and optics when optimizing the cooling in real time•Delivers a low longitudinal emittance of e-beam
Electron circulator-cooling ring•Eases drastically the high current and energy exposition issues of electron source and ERL
Beam transport with discontinuous solenoid•Solves the problem of combining the magnetized beam transport (necessary for efficient EC) with effective acceleration
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 8
Beam-beam kicker for EC
Kicker beam is not accelerated after the DC gun
Both beams are flat in the kick section
Flat beams can be obtained from magnetized sources (grid operated).
•Kicker beam is maintained in solenoid. It can be flatten by imposing constant quadrupole field
•Flat cooling beam is obtained applying round-to- flat beam adapters
Circulating beam energy MeV 33
Kicking beam energy MeV ~0.3
Kicking frequency MHz 5 – 15
Kicking angle mrad 0.2
Kicking bunch length cm 15 – 50
Kicking bunch width Cm 0.5
Kicking bunch charge nC 2
Design parameters for beam-beam kicker
A schematic of beam-beam fast kicker
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 9
Synchronization for EC
Injector 5 MeVx25 mA
ERL 75 MeV
Fast kicker
arcarc
Fast kicker
Cooling section
Dumper 125 KWt
ii
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 10
Short bunches make feasible the Crab Crossing
SRF deflectors 1.5 GHz can be used to create a proper bunch tilt
SRF dipole
Final lens FF
Crab Crossing
Parasitic collisions are avoided without loss of luminosity
R. Palmer 1988, general idea
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 11
Crab Crossing for EIC• Short bunches also make feasible the Crab Crossing:• SRF deflectors 1.5 GHz can be used to create a proper bunch tilt
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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
Page 12
Preliminary IP layout for ion beam
CCB with inserted SRF for bunching and dispersive crabbing
• Dipoles bending the beam in addition to arcs• Inserted SRF resonators are sufficient for required
bunching and dispersive crabbing