Abstract
Measurements of the beam's bunch length in the Cornell Electron-Positron Storage Ring (CESR) have been made using a streak camera. The streak camera uses visible synchrotron radiation produced by the beam to measure its longitudinal distribution. A description of CESR, the experimental setup, the streak camera used, and systematic errors and analysis techniques of the streak camera are described in this paper. The dependence of the bunch distribution on the current and accelerating rf voltage for a single bunch CESR was measured and compared with a theoretical model of CESR. The CESR vacuum chamber impedance is determined from the measured bunch distributions and is presented in this paper.
Highlights
In the Cornell Electron-Positron Storage Ring (CESR), electrons collide with positrons at center-of-mass energies between 9.4 and 11.2 GeV
The main components of the accelerator complex are (i) the electron gun which produces the electrons, (ii) the linac which accelerates the electrons to 300 MeV to be injected into the synchrotron or is used to make positrons, (iii) the synchrotron which accelerates the electrons and positrons to their final energy where they are injected by the transfer lines into CESR, and (iv) CESR
In CESR, four five-cell rf cavities are used to replace the energy lost due to synchrotron radiation
Summary
In the Cornell Electron-Positron Storage Ring (CESR), electrons collide with positrons at center-of-mass energies between 9.4 and 11.2 GeV. Under normal colliding beam conditions at the time of the measurements there were nearly nine evenly spaced bunch trains with two bunches in each train for a total of 18 electron and 18 positron bunches. CESR has two wiggler magnets, located near the interaction region, which produce synchrotron radiation for the Cornell High Energy Synchrotron Source (CHESS). The measurements presented in this paper were taken when only one electron or positron bunch was present in the CESR. The measurements were performed on both the electron and positron bunches when the opportunity for beam time was available. Earlier measurements of the CESR bunch length, using an x-ray sensitive photoconducting detector and the beam spectrum, as a function of current have shown no bunch. Energy (on/off resonance) Circumference Revolution period rf frequency Horizontal tune (Qx) Vertical tuneQy Longitudinal tuneQs Harmonic number. The resolutions of these previous measurements were not capable of measuring the effects presented in this paper
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