KEK, Ibaraki
Recent progress of KEKB and nano beam scheme adopted in KEKB upgrade are discussed. For the present KEKB, chromatic x-y coupling, which was the key parameter to improve luminosity, is focussed. Beam-beam simulations with weak-strong and strong-strong models for nano beam scheme are presented. A weak-strong simulation was done in the presencee of the longitudinal micro-wave instability. Finally status of beam simulations in KEK supercomputers is presented.
HU/AdSM, Higashi-Hiroshima
JAEA/Kansai, Kyoto
TUB, Beijing
JAEA/TARRI, Gunma-ken
An ultimate goal in accelerator physics is to produce a "zero-emittance" beam, which is equivalent to making the beam temperature the absolute zero in the center-of-mass frame. At this limit, if somehow reached, the beam is Coulomb crystallized. Schiffer and co-workers first applied the molecular dynamics (MD) technique to study the fundamental features of various Coulomb crystals. Their pioneering work was later generalized by Wei et al. who explicitly incorporated discrete alternating-gradient lattice structures into MD simulations. This talk summarizes recent numerical efforts made to clarify the dynamic behavior of ultra-cold and crystalline ion beams. The MD modeling of beam crystallization in a storage ring is outlined, including how one can approach the ultra-low emittance limit. Several possible methods are described of cooling an ion beam three-dimensionally with radiation pressure (the Doppler laser cooling).
KU Leuven, Kortrijk
TEMF, TU Darmstadt, Darmstadt
The modeling of eddy-current phenomena in superconductive accelerator magnets is challenging because the large differences in geometrical dimensions (skin depth vs. magnet size) and time constants (ramping time vs. relaxation time). The paper addresses modeling issues as e.g. the ferromagnetic saturation of the iron yoke, the eddy-current losses in the yoke end parts, the eddy-current losses in the beam tube and possible eddy-current losses in the windings. Heavy saturation, small skin depths and small time constants render simulations of this kind to be challenging. The simulation approach is used in combination with an optimization procedure involving both continuous and integer-valued parameters.
ANL, Argonne
BNL, Upton, Long Island, New York
Optimization of dynamic and momentum apertures is one of the most challenging problems in storage ring design. For storage-ring-based x-ray sources, large dynamic aperture is important in obtaining high injection efficiency, which leads to efficient operation and protects components from radiation damage. X-ray sources require large momentum aperture to obtain sufficiently long Touschek lifetimes with low-emittance beams. We have developed effective methods of optimizing dynamic and momentum apertures that rely directly on tracking using a moderately sized Linux cluster. After reviewing the method, we present examples of its application to APS operations, upgrades, and next-generation storage rings.
PSI, Villigen
For the 250 MeV test injector, it is planned to use a 2.6 cell RF gun originally developed for high current and charge operation in the CLIC test facility CTF-2. First start-to-end simulations assuming perfect field symmetries show, that this gun should be able to generate bunches at 200 pC with an emittance of below 400 nm rad, which would be compatible with the requirements for the SwissFEL. This gun uses double side coupled RF feeds in the last cell as well as tuners in the last two cells, which give transverse multipole effects in the field and phase space distribution and may lead to a deteriorated emittance. Since the beam in the last cell is already relativistic at energies between 4 and 6.4 MeV, this effect can be computed in a clean way by looking at the distributions of the integrated beam voltage at the cavity iris and deriving any transverse kicks via the Panovsky-Wenzel theorem. Doing this approach for the various operation modi planned for the PSI injector shows an emittance dilution well below the critical thresholds.