Paper 
Title 
Page 
TUPME011 
Simulated Beambeam Limit for Circular Higgs Factories 
1586 

 K. Ohmi
KEK, Ibaraki, Japan
 F. Zimmermann
CERN, Geneva, Switzerland



We report simulation studies of the beambeam limit for two proposed circular e^{+}e^{−} Higgs factories with circumference of 27 and 80 km, respectively, called LEP3 and TLEP. In particular we investigate the dependence of the steadystate luminosity and transverse beam sizes on the synchrotron tune (or momentum compaction factor) and on the betatron tunes, as well as the consequences of the strong radiation damping and the implications of the large hourglass effect.



TUPME012 
Space Charge Simulation based on a Measured Optics in JPARC MR 
1589 

 K. Ohmi, S. Igarashi, Y. Sato, J. Takano
KEK, Ibaraki, Japan
 S. Hatakeyama
JAEA/JPARC, Tokaimura, Japan



Linear optics parameters, beta, alpha, phase, xy coupling and dispersion are measured by phase space monitor and/or other tools. Nonlinear effects due to the space charge and magnets are dominantly determined by linear optics. For example, the beam distribution is mainly determined by linear optics, and error of beta function at a sextuple magnet is larger than error of magnet strength generally. This means space charge simulation based on the measured optics takes into account of the major part of errors. We discuss how beam loss degrade and which resonances are induced by the errors in the simulations.



TUPME013 
Coherent Thomson Scattering using Beam Echo 
1592 

 K. Ohmi, S. Kamada
KEK, Ibaraki, Japan
 H. Fares
Kanazawa University, Kanazawa, Japan



Longitudinal phase space of the beam is modulated by laser interacting in undulators. The beam can have higher frequency component using the beam echo than than the laser as dicussed by G. Stupakov et al. The modulated beam has a potential to emit coherent radiation with the wave length. We evaluate coherent short wave length (~nm) and/or short pulse (attosec) light source using the beam echo in a low energy accelerator ~100MeV.



TUPME014 
Coherent Synchrotron Radiation Predicted at the SuperKEKB Damping Ring 
1595 

 H. Ikeda, M. Kikuchi, K. Ohmi, K. Oide, D. Zhou
KEK, Ibaraki, Japan



The damping ring of SuperKEKB is under construction in order to inject low emittance positron beam into the main ring. We calculated the bunch lengthening and the energy spread caused by the longitudinal wake, which is dominated by the CSR wake field. The result was within the tolerance level.



TUPME016 
Crosstalk Between Beambeam Interaction and Lattice Nonlinearities in the SuperKEKB 
1601 

 D. Zhou, K. Ohmi, Y. Ohnishi, K. Oide, H. Sugimoto
KEK, Ibaraki, Japan



Momentumdependent lattice nonlinearities have been proven to be important for the luminosity performance in the KEKB Bfactory. As an upgrade of KEKB, the SuperKEKB adopts nanobeam scheme, in which the colliding beams are squeezed to extremely small sizes at the interaction point. Consequently, the lattice nonlinearities in SuperKEKB become more stronger than in KEKB. Using two codes, SAD and BBWS, we did various simulations to study the crosstalk between beambeam interaction and lattice nonlinearities. It is found that lattice nonlinearities can cause remarkable luminosity loss in the SuperKEKB.



TUPME017 
Validation of the Microwave Instability in the Damping Ring of SuperKEKB using VFP Solver 
1604 

 L. Wang
SLAC, Menlo Park, California, USA
 H. Ikeda, K. Ohmi, K. Oide, D. Zhou
KEK, Ibaraki, Japan



Microwave instability driven by CSR impedance in the damping ring of SuperKEKB is a concern due to its high bunch current. To understand the beam dynamics, we simulate the microwave instability using VlasovFokkerPlanck (VFP) solver. The longitudinal wake potential is calculated as a sum of the contributions due to vacuum chamber components distributed around the ring, including geometry wake field and CSR wake. To improve the accuracy of the simulation of microwave instability, the coherent synchrotron radiation impedance is calculated to very high frequency to get more accurate wake field with a short bunch. The CSR wake is much larger than the geometry wake. The threshold is just above the design current and sawtooth type of instability is found above the threshold.


