阐述了利用倍频腔束团长度监测器测量北京正负电子对撞机二期工程电子直线加速器束团长度的原理,通过两个月的测试和数据采集,测得的束团长度集中在1.4～2.0mm之间,与理论值1.5mm基本相符.根据不同时刻的记录,基频腔峰值电压与束流流强探测器BCT3所测流强值近似成正比关系;当大幅改变预聚束器和聚束器参数而束流流强不变时,反映聚束质量的五倍频腔信号也随之大幅改变,而反映流强信号的基频腔信号则变化不大,这些试验结果与理论分析完全一致.

The principle of measuring the bunch length of the Beijing electron positron collider upgrade(BEPCⅡ) linac by harmonic bunch length monitor is presented.The measured bunch length ranging between 1.4 mm and 2.0 mm agrees well with the theoretic calculation of 1.5 mm.The electron beam current measured by the beam current monitor(BCT3) is almost in direct proportion to the induced voltage of the fundamental harmonic.When the parameters of the pre-buncher and buncher are adjusted greatly while the beam current being unchanged,the fifth harmonic signal has a great change,but the fundamental signal changes gently.The test results are all in good agreement with the theoretic analysis.