Ohnishi, Y.

Paper	Title	Page
WEOFI01	Beam Dynamics Measurements in the Vicinity of a Half-integer Resonance	1902
	T. Ieiri, J.W. Flanagan, H. Fukuma, H. Ikeda, Y. Ohnishi, K. Oide, M. Tobiyama KEK, Ibaraki
	The operating point of the betatron tune set near a half-integer is a crucial parameter to make high luminosity in electron/positron ring colliders. Dynamic beam-beam effects would change the optics parameters of the colliders, depending on the betatron tune and the beam-beam parameter. On the other hand, existence of the half-integer stopband makes the beam unstable. Therefore, beam behavior near a half-integer might provide interesting issues from the viewpoint of beam dynamics. We measured a frequency response of the beam across a half-integer for measuring the betatron tune at KEKB. A sharp spike just at a half-integer was observed in the tune spectrum. We believe that the spectrum would be a nonlinear resonance caused by some off-momentum particles in a bunch, not by a coherent motion of a whole bunch. The horizontal beam size measured using a synchrotron radiation monitor indicated a slight increase when the tune approached a half-integer. The variations in the beam size are discussed, considering both dynamic beam-beam effects and a beta beat due to the half-integer stopband.
	Transparencies
WEPCH026	Recent Progress of Optics Measurement and Correction at KEKB	1981
	A. Morita, H. Koiso, Y. Ohnishi, K. Oide KEK, Ibaraki
	We present the progress of the optics measurement and the correction scheme of the KEKB operation for example off-momentum beta correction.
WEPCH078	Measurement of Wake Effects by Means of Tune Shift in the KEKB Low-Energy Ring	2101
	T. Ieiri, H. Fukuma, Y. Ohnishi, M. Tobiyama KEK, Ibaraki
	The electron cloud produced by the positron beam induces single-bunch and coupled-bunch wakes, in addition to a tune shift. Effects of the dipole wake-field including the electron cloud were tried to measure in the KEKB Low Energy Ring. A test bunch was placed behind a bunch-train of the positron beam, even though a test bunch itself might interact with the remaining electron cloud. We measured a current-dependent tune-shift of a test bunch under constant train-current, while changing the bucket position of a test bunch. The tune shift indicated a strong defocusing field, however, tended to a focusing field when a test bunch approached a train with high train-current. The results are discussed, considering variations of the electron cloud density.
THPCH116	Continuous Circumference Control and Timing System for Simultaneous Electron-positron Injection at the KEKB	3074
	M. Suetake, H. Koiso, Y. Ohnishi, K. Oide KEK, Ibaraki
	We have continuously controlled ring circumference with a new method of synthesizer control at the KEKB. The new method stands for continuous controlling of reference frequency of synthesizers. Due to the new circumference control, we stabilized the KEKB circumference within about 6 micrometers. In Fall 2006, KEKB will introduce simultaneous electron-positron injection scheme. We have to change the timing system of KEKB to control the injection phase with pulse-to-pulse injection. We show the plan of the new timing system due to the simultaneous injection scheme.