pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2020; 70: 686-691

Published online August 31, 2020 https://doi.org/10.3938/NPSM.70.686

## Characteristics of Radiation in a Free-electron Laser with Two-section Wiggler

TaeHoon KIM, Yun Seong PARK, Soon-Kwon NAM*

Department of Physics, Kangwon National University, Chuncheon 24341, Korea

Correspondence to:snam@kangwon.ac.kr

Received: July 6, 2020; Revised: July 16, 2020; Accepted: July 16, 2020

### Abstract

We developed an extended time-dependent free-electron laser by using a two-section wiggler code to analyze the effect of the wiggler wave number ratio ($\alpha$). We studied the intensity of radiation for different ratios of various wiggler wave numbers in a two-section wiggler by using an extended time-dependent simulation code that we developed. For the simulations, we used a 1$^\text{st}$ section wiggler length of 0.4 m -- 0.8 m and 2nd section wiggler length of 1.2 -- 1.6 m. The intensity of radiation was analyzed at various times from -10 $\mu$s to 10 $mu$s and various detuning parameters from -2.5% to 2.5% for the ratio of the wiggler wave number. The radiation intensity was optimized at wiggler wave number ratio ($\alpha$) of 0.25 at time, $t$ = 2.0 $\mu$s for a detuning parameter of 1.0% by using a time-dependent FEL code with two-section wiggler.

Keywords: Free-electron laser, Two-section wiggler, Wave number