Transcript Assessment of Present MEIC Ion Complex Design

Ion Accelerator Complex for MEIC
January 28, 2010
Ion Sources
 Main parameters
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Emittance
Pulse current
Pulse length
Repetition rate
 Polarized H¯ and D¯
– Improve degree of polarization
 Light ion polarized sources –
– Demonstrate peak pulse current
 Heavy Ion Sources (ECR)
– Demonstrate ~2 mA over 250 sec
– New generation of ECR sources (56 GHz) in afterglow mode
 Heavy Ion Sources (EBIS)
– Charge per pulse is low – longer accumulation time in the pre-booster
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Multi-beam Ion Linac
 Linac layout
Ion Sources
RFQ
IH
MEBT
Normal conducting
QWR
QWR
HWR
DSR
Stripper
Superconducting
 200 MeV for protons and 70 MeV/u for heavy ions seems close to
optimal for accumulation of required current with specified beam
quality in the pre-booster
 SRF technology for ion beam acceleration is well established
 Further cost reduction is expected due to many new projects
 However, it is unlikely that the cost of the linac drops below $100M
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Pre-Booster
 Current pre-conceptual design satisfies all specifications
required for the collider
– Low emittance
– High current
– Excellent properties of the polarized beams
 Demonstrated technology
– Multi-turn injection of heavy-ion beams
– Electron cooling with DC beams
– 2-harmonic acceleration at low frequency
 Further R&D due to more challenging beam parameters
(low emittance, high current, higher energy,…)
– 3D simulation of the injection
– 3D simulation of acceleartion
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Large Booster
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Longer circumference (factor of 4 longer then pre-booster)
Conceptually similar to the pre-booster
Protons from 3 to 12 GeV
Lead Ions from 1.18 GeV/u to ~4.5 GeV/u
– Fully stripped before the injection into the L-Booster
 Acceleration
– Use low frequencies harmonics 4 or 5
– Higher harmonics may not be necessary (to suppress space charge)
 Lattice – no issues
 Maintain polarization – no significant issues
 Emittance, space charge can be controlled well
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Forming High Frequency (750 MHz) ion bunches
 Concept:
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Accelerate ions to high energies with low frequency RF
Create coasting beam – L-Booster or Main Ring
Adiabatically bunch and accelerate – efficiency ~99% is required
Minimize losses
Momentum collimation
 Develop 750 MHz cavities with variable frequency in the range of
~10 MHz.
– Normal conducting
– Can be a mechanical tuner to vary frequency in timescale of a second
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Main ring
– Protons from 12 to 60 GeV – f ~2MHz for 750 MHz
– Lead ions ~4.5 GeV/u to 23 GeV/u - f ~10MHz for 750 MHz
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Issues with forming of 750 MHz bunches
 Acceleration time – defined by the tuner system in the RF cavities
– Mechanical – seconds
– Ferrites ? The frequency is high
 Acceleration time can be reduced if two RF systems are used: low
frequency (~10 MHz) and high frequency with very low f
 Main Ring is crowded, is there enough space in the MR for
collimation?
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Main Ring
 Transition energy must be lower ~4 GeV/u
 IBS
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