RHIC AC dipole design and construction

Abstract

Two ac dipoles with vertical and horizontal magnetic field have been proposed at RHIC for applications in linear and non-linear beam dynamics and spin manipulations. A magnetic field amplitude of 380 Gm is required to produce a coherent oscillation of 5 times the rms beam size at the top energy. We take the ac dipole frequency to be 1.0% of the revolution frequency away from the betatron frequency. To achieve the strong magnetic field with minimum power loss, an air-core magnet with two seven turn winding of low loss Litz wire resonating at 64 kHz is designed. The system is also designed to allow one to connect the two magnet winding in series to resonate at 37 kHz for the spin manipulation. Measurements of a half length prototype magnet are also presented.

Parametrization of the driven betatron oscillation

“…This property makes it a useful diagnostic tool of a synchrotron. AC dipoles have been employed in the BNL AGS and RHIC [3][4][5], CERN SPS [6,7], and FNAL Tevatron [8][9][10]. There is an ongoing project to develop AC dipoles for LHC as well [11].…”

“…Although this difference has typically been ignored in previous analyses [5,12], it could affect interpretation of the function more than 12% in a typical operational condition of the Tevatron. This paper proceeds as follows.…”

Diagnostics of the Fermilab Tevatron using an AC dipole

“…Synchrotron diagnostics using the AC dipole was first tested in BNL AGS [4]. The AC dipole has been also employed in the BNL RHIC [14,15], the CERN SPS [16,17], and the FNAL [18,19,20,21] and will be used in CERN LHC [22]. The AC dipole, located at one point on the synchrotron, has a weak sinusoidallyvarying dipole field which deflects the beam particles slightly.…”

“…These properties of the AC dipole makes it a useful diagnostic tool of a synchrotron. AC dipoles have been employed in the AGS and RHIC in BNL [4,14,15], CERN SPS [16,17], and FNAL Tevatron [18,19,20].…”

Initial Tests of an AC Dipole for the Tevatron

“…Therefore, besides the typical roll-off of the audio amplifier over 20 kHz, the system can maintain 80 % of output within the range of ±2 kHz which corresponds to ±0.04 of ν m . In contrast to the AC dipole system for the RHIC which has a high Q magnet and spoiler [8], our system naturally has low Q. …”