higher-order-mode

Paper	Title	Other Keywords	Page
MOPCH159	Coupler Design Considerations for the ILC Crab Cavity	coupling, dipole, luminosity, damping	430
	P. Goudket, C.D. Beard CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire G. Burt Microwave Research Group, Lancaster University, Lancaster
	Transverse deflecting cavities, such as the ILC crab cavity, commonly operate in the TM110 dipole mode. This means that in addition to the higher order modes (HOMs), that need to be controlled for every cavity, the fundamental TM010 mode and the other polarisation of the dipole mode also need to be damped. As the resonant frequency of the fundamental mode is much lower than the cut-off frequency of the beampipe, this mode becomes trapped in the cavity and difficult to extract using conventional HOM couplers, hence a dedicated coupler is likely to be required. The ILC crab cavities will require excellent damping of all undesirable modes in order to maintain maximum luminosity at the IP.
TUPCH133	Comparison of Measured and Calculated Coupling between a Waveguide and an RF Cavity Using CST Microwave Studio	coupling, simulation, linac, damping	1328
	J. Shi, H. Chen, S. Zheng TUB, Beijing D. Li LBNL, Berkeley, California R.A. Rimmer, H. Wang Jefferson Lab, Newport News, Virginia
	Accurate predications of RF coupling between an RF cavity and ports attached to it have been an important study subject for years for RF coupler and higher order modes (HOM) damping design. We report recent progress and a method on the RF coupling simulations between waveguide ports and RF cavities using CST Microwave Studio in time domain (Transit Solver). Comparisons of the measured and calculated couplings are presented. The simulated couplings and frequencies agree within ~ 10% and ~ 0.1% with the measurements, respectively. We have simulated couplings with external Qs ranging from ~ 100 to ~ 100, 000, and confirmed with measurements. The method should also work well for higher Qs, and can be easily applied in RF power coupler designs and HOM damping for normal-conducting and superconducting cavities.
WEXPA01	Latest Developments in Superconducting RF Structures for Beta=1 Particle Acceleration	TESLA, XFEL, KEK, damping	1837
	P. Kneisel Jefferson Lab, Newport News, Virginia
	Superconducting RF technology is since nearly a decade routinely applied to different kinds of accelerating devices: linear accelerators, storage rings, synchrotron light sources and FEL's. With the technology recommendation for the International Linear Collider (ILC) a year ago, new emphasis has been placed on improving the performance of accelerating cavities both in Q-value and in accelerating gradients with the goal to achieve performance levels close to the fundamental limits given by the material parameters of the choice material, niobium. This paper will summarize the challenges to SRF technology and will review the latest developments in superconducting structure design. Additionally, it will give an overview of the newest results and will report on the developments in alternative materials and technologies.
	Transparencies
WEPCH123	Large Simulation of High Order Short Range Wakefields	simulation, dipole, SLAC, DESY	2209
	A. Bungau Cockcroft Institute, Warrington, Cheshire R.J. Barlow UMAN, Manchester
	We present a formalism for incorporating intra-bunch wake fields into particle-by-particle tracking codes, such as MERLIN and BDSIM. Higher order wake field effects are incorporated in a manner which is computationally efficient. Standard formulae for geometric, resistive and dielectric wake fields are included for various apertures, particularly those relevant for ILC collimators. Numerous examples are given.
THPCH031	Impedance and Beam Stability Study at the Australian Synchrotron	impedance, synchrotron, storage-ring, resonance	2844
	R.T. Dowd, M.J. Boland, G. LeBlanc, M.J. Spencer, Y.E. Tan ASP, Clayton, Victoria
	We present the preliminary results of an impedance study of the Australian Synchrotron storage ring. Beam stability thresholds have been determined and an overall impedance budget set. Broad-band impedance has been evaluted for various components of the vacuum chamber, using both analytical formulae and results from MAFIA simulations. Narrow band resonances have also been investigated, with particular attention paid to higher order modes in the RF cavities and their effect on multi-bunch instabilities.