RHIC VERTICAL AC DIPOLE COMMISSIONING

the natural betatron tune v, and ac dipole tune v,, The RHIC vertical ac dipole was installed in the sum- mer of 2001. The magnet is located in the interaction re- gion between sector 3 and sector 4 common to both beams. The resonant frequency of the ac dipole was first config- ured to be around half of the beam revolution frequency to act as a spin flipper. At the end of the RHIC 2002 run, the ac dipole frequency was reconfigured for linear optics studies. A 0.35 mm driven betatron oscillation was excited with the vertical ac dipole and the vertical betatron func- tions and phase advances at each beam position monitor (BPM) around the RHIC yellow ring were measured using the excited coherence. We also recorded horizontal turn- by-turn beam positions at each BPM location to investigate coupling effects. Analysis algorithms and measurement re- sults are presented. where fm is the ac dipole oscillation frequency and fr,, is the beam revolution frequency. The desired driven oscillation amplitude for our studies was 0.1 cr, where (T is the rms beam size. To achieve this with a beam emittance of 20n mm-mrad at the storage en- ergy of 100 GeV (magnetic rigidity Bp = 834.0 T-m), the oscillation amplitude of the ac dipole field is 78 Gauss-m, provided that S=O. 1.