应用被动式高次谐波腔改善合肥光源的束流寿命(英文)

Lifetime increase using a passive higher harmonic cavity for Hefei Light SourceⅡ

高次谐波腔被用于同步辐射光源中拉长束团,降低束团密度,从而提高束流寿命,并且对光源亮度影响很小。理论推导了加入高次谐波腔之后的有关纵向束流动力学方程,计算了改造后的合肥光源(HLS-II)在加入三次谐波腔时最优条件下的寿命改善因子为2.9,束团长度为45.65 mm;计算还表明束团在均匀填充模式下谐波腔中的束流负载效应对束团拉伸的影响可以忽略。经过大量数值模拟计算,优化设计了一个带有高次模阻尼的三次谐波腔。

Higher harmonic cavities are used in light sources to lengthen the bunch and increase the beam lifetime without effects on beam brightness. Some longitudinal beam dynamic equations with higher harmonic cavity are derived.. Calculations for Hefei Light Source II （HLS-II） with a third harmonic cavity under the optimum conditions are presented. The results show that the factor of lifetime improvement is 2.9 and the bunch length is 45.65 mm. The transient beam loading effect on the bunch length in harmonic cavity may be neglected for uniform fill of all rf buckets. Meanwhile, a third harmonic cavity with higher order modes damping was optimized through a large number of simulations .