Correction of transverse coupling in a storage ring

Betatron phase and coupling measurements at the Cornell Electron/Positron Storage Ring

“…In actuality, because of solenoids, skew quadrupoles, etc., oscillations of the horizontal and vertical modes will not be strictly in the x and y planes, respectively. This coupling can be parametrized using the C matrix [6,7]. Assuming weak coupling, the motion of the horizontal normal mode at a detector is given by…”

CESR luminosity dependence on magnetic alignment

“…A performance benefit that can be attributed to leveling the quadrupoles in CESR is the reduction of transverse coupling. To measure coupling in CESR a normal mode of the beam is coherently excited by a shaker and the relative phase and amplitude of the two normal transverse (vertical and horizontal) modes is measured [5]. From this measurement the coupling transfer matrix C can be determined.…”

Detection of coupling elements in CESR

“…At CESR, C is measured by observing the horizontal and vertical oscillation of the beam at the detectors in the ring while shaking the beam at a betatron resonance [2]. In order to be able to extract the strength and location of coupling elements from the data, it is necessary to know how C changes across a coupler, and how C propagates in a region where there are no coupling elements.…”

“…In order to be able to keep the coupling under control, a technique for measuring the coupling has been developed at the Cornell Electron/positron Storage Ring CESR [2]. This involves shaking the beam at the betatron resonant frequencies and measuring the response at the 100 or so detectors in the ring.…”