The RHIC tune measurement system

Each of the four fractional betatron tunes of RHIC (two planes, two rings) is measured with a transverse beam kicker and dedicated beam position monitor (BPM). A 1-5 kV pulse is generated by a fast FET switch, passed through a stripline kicker, attenuated, and returned to the instrumentation control room (ICR) for monitoring. When pulsed at 3 kV, the four-meter long kicker gives a gold beam at injection (/spl gamma/=12.6) an angular kick of 11 /spl mu/rad resulting in a betatron amplitude of 0.8 mm at the BPM (/spl sigma//sub beam/=4.3 mm). A single bunch is kicked a few times and then measured for several hundred turns. A fast Fourier transform (FFT) of the position data gives the tune.