Measurement of the modulus and phase of the linear coupling coefficient by analysis of the transverse beam profile

Abstract

We study the dynamics of transverse oscillations near the linear coupling resonance excited by a pair of skew quadrupoles at the Laboratório Nacional de Luz Síncrotron UVX electron storage ring through the analysis of the beam profile. Transverse coherent oscillations were excited with a fast kicker and the profile of the oscillating beam was observed by focusing visible synchrotron radiation from a bending magnet onto a fast charge-coupled device camera. Using a single resonance approximation, we calculated the border of the time-averaged transverse beam profile as a function of the complex coupling coefficient k, which characterizes the distribution of coupling fields along the storage ring. A leastsquares fit of the calculated beam profile border to the experimentally obtained isointensity contours provided a new method to determine both the modulus and the phase of k. The values obtained for the modulus are in good agreement with those from the conventional normal mode tune separation technique, and the values obtained for the phase of k agree with calculations based on the model lattice and the known skew quadrupole distribution. [S1098-4402(98)

Fast and robust global decoupling with coupling angle modulation

“…The blue line represents the rotating coupling C ÿ rot given by Eq. (6). The red line represents the residual coupling C ÿ res in the coupled optics.…”

“…Coupling angle modulation is a fast and robust decoupling scheme, compared to other coupling measurement or correction schemes [5][6][7][8]. According to the beam experiments in the Relativistic Heavy Ion Collider (RHIC), the modulation frequency for RHIC is 0.5 Hz at injection and store, 0.2 Hz on the ramp.…”