Systematic and precise investigation of beam dynamics in a high-intensity, electron linac for the injector of the B-meson experiment

点击翻译按钮获取中文摘要

For systematic and precise investigation of beam dynamics in a high-intensity, electron linac for the injector of the B-meson experiment, the following research items have been carried out : (1) improvements of the alignment system, (2) beam-based alignment, (3) measurements of wake-field effects, (4) observation and optimization of bunch profiles, (5) tuning of isochronicity in the 180-degree arc section, (6) beam optimization by a downhill simplex method, (7) optics tuning based on the accomplishments of the above items. In the item (1), light-detection circuits were upgraded so that a data acquisition system by computers was constructed, while in the item (2), beam positions and field centers of magnets were adjusted within a precision of 0.1 mm by observing beam position monitor signals. Quadrupole-wake field effects were directly observed for the first time by measuring beam positions when initial offsets were given (item (3)). The results are in good agreement with a calculation based on the measurements of bunch profiles (4). In the item (5), the isochronicity in the arc section were examined by using a bunch-profile measurement system and accomplished by performing optics corrections, while in the item (6), the positron beam intensity was increased by applying a downhill simplex method to several parameters of the primary electron beam. With all above results, we could carry out the following tasks (item (7)) : (A) development of the software programs for realizing a real-time optics correction, (B) its application to the case for abnormal beam states : prompt beam diagnosis and cures, (C) precise investigation of the quadrupole-wake field effects. Especially in the task (C), it was clarified that the quadrupole-wake field effects show non-linearity as well as x-y coupling phenomena in the orbit. This is the first result obtained in the world.