• P. Tan, M. Fan, B. Qin, Y.Q. Xiong
  HUST, Wuhan

A primary design of a compact THz FEL oscillator is presented, which is consisted of an independently tunable cell thermionic rf gun (ITC-RF Gun), a rf linac, a planar undulator and an near concentric optical cavity composed of symmetrical spherical mirrors with an on-axis outcouple hole. Without α-magnet and other bunch compressor, the size of this machine is decreased sharply. The effect of the electron beam parameters on THz radiation is discussed. It is found that the influence of energy spread is pronounced and the influence of emittance is neglectable. Large current is required to got saturation in several us. Then the optimized beam parameters and basic design parameters are summarized.

• J. Xiong, K.F. Liu, B. Qin, P. Tan, Y.Q. Xiong, J. Yang
  HUST, Wuhan

The design of compact terahertz (THz) radiation source based on free electron laser (FEL) has been implemented, whose concept machine is consisting of a thermionic RF gun (ITC-RF Gun), a LINAC, a hybrid undulator combined with an optical resonance cavity of hole-coupling mode. The aim of the project is to provide a stable coherent THz (1~3THz) source. The hybrid undulator system is the critical component for compact terahertz FEL. Emission wavelength is related to the period and the peak magnetic field of the hybrid undulator. In particular, the magnetic structure by adding side magnet blocks to each pole will increase the field strength, avoid too small gap, and make the system more compact. Simulations using RADIA are presented. The feature of designs, optimization of the magnetic parameters and field analysis will be discussed.