BEAM TEST OF INITIAL BEAM LOADING COMPENSATION FOR ELECTRON LINACS

For the high-intensity electron linacs, one of the noble schemes to get a sufficient intensity is to accelerate the multi-bunch beam in an RF pulse generated by the klystron. It is very useful technique for FEL linacs and/or to increase the injection rate for the storage rings. Furthermore, it can realize the high energy transfer efficiency of the RF power to the beam. In the multi- bunch operations, however, it has also a troublesome defect called "Initial-Beam-Loading" effect, which causes the large energy spread along the bunch train within the beam pulse. The initial-beam-loading effect can be considered as a sum of the single-bunch beam loadings. Since it may cause serious beam loss in the linacs and the beam lines to follow, it should be corrected to the tolerable level by using the some suitable method. We have developed the initial-beam-loading compensation system, which can modulate the phase and amplitude of the low level RF signal (1,2). Beam test using this system was carried out at the 125-MeV electron linac of Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. Its result shows that our system well corrects the energy spread due to initial beam loading effect. In this paper, we report the results of beam test.