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Fundamental limit of nonscaling fixed-field alternating-gradient accelerators
1Department of Physics, Indiana University, Bloomington, Indiana 47405, USA and GSI, Darmstadt, D64291, Germany.
Physical Review Letters
|October 10, 2006
Summary
Systematic nonlinear space-charge resonances can increase emittance in nonscaling fixed-field alternating-gradient (FFAG) accelerators. Avoiding specific phase advances and controlling tune ramp rates are key to mitigating this emittance growth.
Area of Science:
- Particle accelerator physics
- Beam dynamics
Background:
- Nonscaling fixed-field alternating-gradient (FFAG) accelerators are susceptible to emittance growth.
- Systematic nonlinear space-charge resonances are a primary cause of this emittance increase.
Purpose of the Study:
- To investigate methods for avoiding systematic nonlinear space-charge resonances in nonscaling FFAG accelerators.
- To determine the relationship between tune ramp rate and resonance strength.
- To analyze emittance growth scaling properties near linear resonances.
Main Methods:
- Multiparticle numerical simulations were employed.
- Phase advances were analyzed to identify problematic values (pi/2 and pi/3).
- Tune ramp rates were empirically correlated with the 4th order space-charge resonance strength.
Main Results:
- Emittance growth is substantial due to systematic nonlinear space-charge resonances.
- Avoiding phase advances of pi/2 and pi/3 in FFAG cells is crucial.
- A minimum tune ramp rate was empirically determined against the 4th order resonance strength.
- Emittance growth exhibits simple scaling when crossing linear half-integer and sum resonances.
Conclusions:
- Careful selection of phase advance and tune ramp rate is essential for managing emittance in nonscaling FFAGs.
- Understanding resonance behavior is key to designing stable and efficient FFAG accelerators.
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