Open AccessObservations of bunch lengthening effects in the APS 7-GeV storage ring
Author(s) -
A.H. Lumpkin,
Bingxin Yang,
Yong-Chul Chae
Publication year - 1996
Language(s) - English
Resource type - Reports
DOI - 10.2172/432947
Subject(s) - storage ring , physics , synchrotron radiation , synchrotron , optics , microwave , beam (structure) , dynamic aperture , streak , streak camera , voltage , linear particle accelerator , laser , quantum mechanics
Measurements of the bunch length and horizontal beam size at a dispersive point in the lattice versus single-bunch current have been done on the Advanced Photo Source (APS) 7-GeV storage ring. These data are relevant to issues (limits) of obtaining high peak currents for storage-ring-based FELs. Bunch lengths from {sigma}{sub {tau}} {approx} 25 to 70 ps were measured using a Hamamatsu C5680 dual-sweep streak camera. Additional complementary data on energy spread deduced from horizontal beam size at a dispersive point in the lattice were also tracked versus single-bunch current. Both optical synchrotron radiation (OSR) and x-ray synchrotron radiation (XSR) techniques were used. For the set of data taken at a synchrotron frequency of 1.2 kHz (indicating rf gap voltage {<=} 6 MV), the significant bunch lengthening without a comparable horizontal size change ({Delta}E growth) is consistent with the potential well distortion model rather than the predictions of a microwave instability calculation. With higher rf gap voltage, peak currents up to 400 A were observed. A bunch-lengthening effect in multibunch mode was also observed as the stored-beam current approached the available rf power limit