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| TUA1I02 |
Theoretical Study of Emittance Transfer
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82 |
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- H. Okamoto
Hiroshima University, Higashi-Hiroshima
- K. Kaneta
HU/AdSM, Higashi-Hiroshima
- A. Sessler
LBNL, Berkeley, California
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Funding: Work supported in part by the U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-05CH11231.
Liouville's theorem implies that the six-dimensional phase-space volume occupied by a charged-particle beam is an approximate invariant unless the beam is subjected to dissipative interactions (such as in cooling). Symplectic conditions, in a Hamiltonian system (once again, no dissipation), put constraints upon emittance transfer between the various degrees of freedom. [1] We can, however, even in non-dissipative Hamiltonian systems arrange for partial emittance transfers. This process results in phase space correlations and change in the emittance projections on to various phase planes; namely, the projected emittances in three degrees of freedom are controllable while the direction and amount of a possible emittance flow are not very flexible because of the symplectic nature of Hamiltonian system. In some applications, it is clearly advantageous to optimize the ratios of projected emittances despite the effect of correlations. Since the three emittances are not always equally important, we may consider reducing the emittance of one direction at the sacrifice of the other emittance(s). As a possible scheme to achieve such emittance control, we study a compact storage ring operating near resonance. The basic features of linear and nonlinear emittance flow are briefly discussed with numerical examples. A general discussion touching on some of these matters has been previously presented. [2]
[1] E. D. Courant, Perspectives in Modern Physics, edit R. E. Marshak (1966).[2] H. Okamoto, K. Kaneta and A. M. Sessler, to be published in J. Phys. Soc. Jpn.
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Slides
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| TUA2C06 |
A Split-Function Lattice for Stochastic Cooling
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99 |
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- J. Wei
BNL, Upton, Long Island, New York
- S. Wang
IHEP Beijing, Beijing
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Funding: * Work performed under the auspices of the US Department of Energy.
During the EPAC 2006 we reported the lattice design for rapid-cycling synchrotrons used to accelerate high-intensity proton beams to energy of tens of GeV for secondary beam production. After primary beam collision with a target, the secondary beam can be collected, cooled, accelerated or decelerated by ancillary synchrotrons for various applications. For the main synchrotron, the lattice has: - flexible momentum compaction to avoid transition and to facilitate RF gymnastics
- long straight sections for low-loss injection, extraction, and high-efficiency collimation
- dispersion-free straights to avoid longitudinal-transverse coupling, and
- momentum cleaning at locations of large dispersion with missing dipoles.
Then, we present a lattice for a cooler ring for the secondary beam. The momentum compaction across half of this ring is near zero, while for the other half it is normal. Thus, bad mixing is minimized while good mixing is maintained for stochastic beam cooling.
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Slides
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| TUA2C07 |
Advanced HESR Lattice with Non-Similar Arcs for Improved Stochastic Cooling
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102 |
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Optimized stochastic cooling requires special ion optical conditions in a storage ring. The frequency slip factor strongly influences the mixing factor, and strong requirements have to be fulfilled by the unwanted mixing of the path from pickup to kicker and the wanted mixing on the way from kicker to pickup. Several ideas for a lattice with "irregular" momentum compaction factor have been investigated. The influence of possible lattice modifications to the stochastic cooling performance for COSY will be discussed. Investigations of a lattice optimized for the stochastic cooling in HESR will be summarized.
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Slides
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| THAP02 |
Implementation of Synchrotron Motion in Barrier Buckets in the BETACOOL Program
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163 |
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- A. V. Smirnov, A. O. Sidorin, G. V. Trubnikov
JINR, Dubna, Moscow Region
- O. Boine-Frankenheim
GSI, Darmstadt
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In the case of the internal pellet target the electron cooling and the stochastic cooling systems cannot compensate the mean energy losses of the ion beam. In bunched ion beams the space charge limit is reduced and the influence of intrabeam scattering is enhanced, which causes a decrease of the luminosity in comparison with a coasting beam. To resolve these problems barrier buckets are proposed for experiments with the pellet target. In the barrier bucket the long ion bunch fills nearly the whole circumference of the storage ring and a rf pulse is applied at the head and at the tail of the bunch. The general goal of the BETACOOL program is to simulate long term processes (in comparison with the ion revolution period) leading to the variation of the ion distribution function in six dimensional phase space. The investigation of the beam dynamics for arbitrary distribution functions is performed using multi particle simulation in the frame of the Model Beam algorithm. In this algorithm the ion beam is represented by an array of macro particles. The heating and cooling processes involved in the simulations lead to a change of the particle momentum components and particle number, which are calculated each time step. The barrier bucket model was developed in the Model Beam algorithm of the BETACOOL program. The trajectory of each model particle is solved analytically for a given barrier bucket voltage amplitude. An invariant of motion is calculated from the current position of the model particle and from the barrier bucket voltage amplitude. Then the phase of the invariant is calculated in accordance with the integration step and the particle gets a new coordinates. The heating and cooling effects are applied in usual procedure of the Model Beam algorithm. First simulation results for the FAIR storage rings are presented.
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| THAP19 |
Influences of Space Charge Effect during Ion Accumulation Using Moving Barrier Bucket Cooperated with Beam Cooling
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206 |
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- T. Kikuchi, S. Kawata
Utsunomiya University, Utsunomiya
- T. Katayama
GSI, Darmstadt
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Space charge effect is important role for stacking of antiprotons and ions in an accumulation ring. The Coulomb force displaces the beam orbits from the designed correct motion. The beam particles kicked out from the ring acceptance by the space charge force are lost. The space charge effect interfere the beam stacking, and the number of the accumulated beam decreases and the emittance is increased. The longitudinal ion storage method by using a moving barrier bucket system with a beam cooling can accumulate the large number of secondary generated beams*. After the multicycle injections of the beam bunch, the stored particles are kicked by the space charge effect of the accumulated beam. Using numerical simulations, we employ the longitudinal particle tracking, which takes into account the barrier bucket voltage, the beam cooling and the space charge effect, for the study of the beam dynamics during the accumulation operations.
*T. Katayama, P. Beller, B. Franzke, I. Nesmiyan, F. Nolden, M. Steck, D. Mohl and T. Kikuchi, AIP Conference Proc. 821 (2005) 196.
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| THAP20 |
Internal Target Effects in the ESR Storage Ring with Cooling
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210 |
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- V. Gostishchev, C. Dimopoulou, A. Dolinskii, F. Nolden, M. Steck
GSI, Darmstadt
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The accurate description of the internal target effects is important for the prediction of operation conditions which are required for the performance of experiments in the storage rings of the FAIR facility at GSI. A number of codes such as PTARGET, MOCAC, PETAG01 and BETACOOL have been developed to evaluate the beam dynamics in the storage ring, where an internal target in the combination with an electron cooling is applied. The systematic benchmarking experiments were carried out at the ESR storage ring at GSI. The ‘zero’ dispersion mode (dispersion at target position is about 0 m) was applied to evaluate the influence of the dispersion function on the beam parameters when the internal target is ON. The influence of the internal target on the beam parameters is demonstrated. Comparison of the experimental results with the Bethe-Bloch formula describing the energy loss of the beam particles in the target as well as with simulations with the BETACOOL code will be given.
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| FRM2C05 |
Simulation Study of Beam Accumulation with Moving Barrier Buckets and Electron Cooling
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238 |
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- T. Katayama, C. Dimopoulou, B. Franzke, M. Steck
GSI, Darmstadt
- T. Kikuchi
Utsunomiya University, Utsunomiya
- D. Möhl
CERN, Geneva
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An effective ion beam accumulation method in NESR at FAIR project, is investigated with numerical way. The princile of accumulation method is as follows: Ion beam bunch from the collector ring or synchrotron is injected in the longitudinal gap space prepared by moving barrier voltage in NESR. Injected beam becomes instantly coasting beam after switching off the barrier voltage and is migrated with the previously stacked beam. After the momentum spread is well cooled by electron cooling, the barrier voltage is switched on and moved to prepare the empty gap space for the next injection. This process is repeated say 20 times to attain the required intensity. We have investigated this stacking process numerically, including the Intra Beam Scattering effect which might limit the stacking current in the ring. Detailed simulated results will be presented for the NESR case as well as the ESR experimental parameters.
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Slides
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