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impedance

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CT04 Bunch Length Measurements in LEP pick-up, synchrotron, photon, monitoring 59
 
  • A.J. Burns, H. Schmickler
    CERN, Geneva, Switzerland
  For many years a streak camera has been used for observing the longitudinal distribution of the particles in any LEP e+ or e- bunch (5-50 ps r.m.s. length) on a turn by turn basis, using synchrotron light. In 1996, a comparison made with the longitudinal vertex distributions of 3 LEP experiments allowed the identification and elimination of certain systematic errors in the streak camera measurements. In 1997, a new bunch length measurement technique was commissioned that uses the high frequency slope of the bunch power spectrum from a button pickup. In 1998, this new method was confronted with measurements from the streak camera and the LEP experiments. The measurements made in 1996 and 1998 are presented, with emphasis on the calibration of the two instrumental methods and their respective precision and limitations.  
 
PS16 The fast head-tail instability suppression in multibunch mode at VEPP-4M feedback, injection, kicker, dipole 138
 
  • G. Karpov, V. Kiselev, V. Smaluk, N. Zinvich
    BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
  In this paper the bunch-by-bunch transverse feedback system for suppression fast head-tail as well as coupled bunch instabilities is described. The experimental results of the feedback affecting on the current threshold are presented. The effects of reactive and resistive feedback on the current threshold are discussed. Two times as large the bunch current than the threshold current was obtained.  
 
PT19 A method for measurement of transverse impedance distribution along storage ring pick-up, betatron, vacuum, storage-ring 202
 
  • V. Kiselev, V. Smaluk
    BINP, Budker Institute of Nuclear Physics, Novosibirsk, Russia
  A new method for measurement of transverse couple impedance distribution along storage ring is described. The method is based on measuring of a closed orbit deviation caused by local impedance. Transverse impedance acts on the beam as a defocusing quadrupole, strength of which depends on the beam current. If a local bump of closed orbit has been created at the impedance location, then the orbit deviation occurs while varying the beam current. The local impedance can be evaluated using the orbit deviation measured. Measurement technique is described, the method accuracy is evaluated. The method described was successfully used for measurement of the impedance distribution along the VEPP-4M storage ring.