RVFL-Based Optical Fiber Intrusion Signal Recognition With Multi-Level Wavelet Decomposition as Feature

The optical fiber pre-waming system （OFPS） has been gradually considered as one of the important means for pipeline safety monitoring. Intrusion signal types are correctly identified which could reduce the cost of troubleshooting and maintenance of the pipeline. Most of the previous feature extraction methods in OFPS are usually quested from the view of time domain. However, in some cases, there is no distinguishing feature in the time domain. In the paper, firstly, the intrusion signal features of the running, digging, and pick mattock are extracted in the frequency domain by multi-level wavelet decomposition, that is, the intrusion signals are decomposed into five bands. Secondly, the average energy ratio of different frequency bands is obtained, which is considered as the feature of each intrusion type. Finally, the feature samples are sent into the random vector functional-link （RVFL） network for training to complete the classification and identification of the signals. Experimental results show that the algorithm can correctly distinguish the different intrusion signals and achieve higher recognition rate.

Cavity fundamental mode and beam interaction in CEPC main ring

Background CEPC is a 100-kilometer-long electron-position collider,aiming to produce Higgs,W and Z-pole.Double ring(DR)is the baseline design of its main ring,and advanced partial double ring(APDR)is the alternative one.Purpose The purpose of this paper is to study the beam loading effects and the corresponding longitudinal beam dynamics of CEPC DR and APDR.Methods The phase shift of the bunches modulated by the bunch gap is calculated with the approximation formulas and simulated with the program.All these methods are compared,and the application conditions of them are also elaborated.In addition,the longitudinal coupled-bunch instability in CEPC main ring is calculated by analytical formulas.Results In CEPC DR high-lumi Z,the phase shift can be reduced to 0.51 deg(°).Besides,the total number of unstable longitudinal modes is 15 in CEPC DR high-lumi Z when no feedback system is added.Conclusion The phase shift of the bunches in CEPC can be reduced to an acceptable value if the optimal filling pattern is chosen.For CEPC APDR,the RF parameters are calculated and the beam loading effects are tolerable.

Beam-induced HOM power in CEPC collider ring cavity

Background The power loss of cavity high-order modes(HOMs)is a key issue in Circular Electron and Positron Collider(CEPC)RF system design.A large HOM power may cause a quench of SC cavity.Purpose The purpose of this article is to study the beam-induced HOM power for CEPC collider ring.The factors influencing the cavity HOM power are also investigated.Methods Starting with the beam filling patterns,the beam spectrums of different beam time structures are deduced.Then,the longitudinal impedance is simulated for CEPC 2-cell 650 MHz cavity.Finally,the cavity HOM power is calculated for CEPC CDR design.Results The cavity HOM power is 459 W for Higgs,506 W for W and 1026 W for Z-pole.These values are smaller than the average values.There is no overlap between beam spectral lines and cavity HOM frequency.Conclusion The filling patterns of CEPC CDR Higgs,W and Z are safe.The dangerous filling patterns can be identified for CEPC Z-pole by scanning different parameters.