Study on strip spiral Blumlein line for the pulsed forming line OF INTENSE ELECTRON-BEAM ACCELERA.pdf

Study on strip spiral Blumlein line for the pulsed forming line of intense electron-beam accelerators J.L. LIU,1,2 X.B. CHENG,1 B.L. QIAN,1 B. GE,1 J.D. ZHANG,1 AND X.X. WANG2 1College of Photoelectical Engineering and Science, National University of Defense Technology, Changsha, China 2Department of Electrical Engineering, Tsinghua University, Beijing, China (RECEIVED 1 August 2008; ACCEPTED 21 November 2008) Abstract The pulse forming line (PFL) is the key part of the intense electron-beam accelerators (IEBA), which determines the quality and characteristic of the output beam current of the IEBA. Compared with the accelerator with traditional Blumlein line, an IEBA based on strip spiral Blumlein line (SSBL) can increase the duration of the output pulse in the same geometrical dimension. But the disadvantage of the SSBL is that the output voltage waveform at the matched load may be distorted, which influences the electron beam quality. In this paper, according to the electromagnetic theory, formulas for calculating the main electric parameters of SSBL (inductance, capacitance, transmission time, and characteristic impedance) are deduced. The effect of the geometric parameters of SSBL on the slowing coefficient is analyzed. The designed condition of SSBL for the output ideal voltage pulse in the matched load is obtained by theoretical analysis. Furthermore, the Karat code is used to simulate the output voltage waveform of SSBL on the matched load for different spiral angels. At last, a couple of contrastive experiments are performed on an electron-beam accelerator based on the SSBL with water dielectric. The experimental results agree with the theoretical and simulated results. Keywords: Intense electron-beam accelerator; Strip spiral Blumlein line; Voltage waveform 1. INTRODUCTION Intense electron beam generation from laser plasma accelera- tors and conventional accelerators is a very active research topic due to numerous applications (Chen et al., 2008; Kulagin et