现代加速器技术的发展，如FEL、直线对撞机等机器，对束团长度测量提出了在ps、sub-ps束团长度情况下，分辨率１０fs左右的无阻、快速测量的技术要求。目前发展的束团长度测量技术难以同时满足以上技术要求或者代价高昂。本课题基于圆柱形腔体TM010模的R/Q值远大于腔式BPM利用的TM110模R/Q值的特性，提出了基于腔体TM010模的束团长度频域测量方法并开展相关研究。首先从理论上解决了束团纵向分布偏离高斯分布情况下的束团长度频域测量方法的适用性问题；其次，在参考腔式BPM相关成熟技术，解决了高次模的激发与耦合、束团offset修正等问题；最后，提出了一种信号处理算法以解决信噪比高达120dB的信号处理困难。最终，本课题提出的束团长度电子学频域测试系统，信噪比可望达到１１２ｄＢ，在ｐｓ、sub-ps束长情况下，可以实现分辨率高达１０fs左右的无阻、快速束长测量。

With the development of accelerator technology, such as FEL, linac collider, beam length measurement should be done when beam length is only ps, even sub-ps case, and the resolution should be about 10fs with fast measurement and un-interrupting beam technology. It is difficult to satisfy all the requirement using the common beam length measurement technology. The study is based on the fact that the TM010 mode of cylindrical cavity has the higher R/Q than the other beam instrument monitor, such as the TM110 mode using in the cavity BPM. Then the beam length can be measured using the TM010 signals in frequency domain with electronic method.First,it is proved that beam length measurement in frequency domain can be used when the beam longitudinal distribution is not Gaussian distribution. After resolving some important technologies referring to CBPM system, such as high order mode's couple, system gain calibration in locale site and beam offset modification with Bessel function, the original system signal noise ration(SNR) is expected to up to 112dB.An efficient algorithm is also provided to achieve the signal measurement with SNR up to 120dB.Then the beam length measurement in frequency domain with electronic method can achieve ps and sub-ps range with resolution up to 10fs. At the same time this measurement is no stopping to beam and even achieves the bunch-by-bunch measurement.