Beam Loading Compensation for the Nlc Low Frequency Linacs

The NLC low rf linacs are heavily loaded by a beam of about 130 ns in macropulse length (90 bunches) and a current up to 2.75 Amps. Beam loading voltage generates a large energy spread along the bunch train. This energy spread is critical for lattice design and, if not properly compensated, induces emittance growth and in turn lowers the luminosity of the machine. In this paper, we study the AF and AT beam loading compensation techniques for the NLC low rf linacs. We will apply these methods to the NLC low rf linacs to demonstrate the efficacy of these methods. Finally, we discuss a hybrid AT+ AF method to improve the efficiency of beam loading compensation.