电磁铁摇摆器磁场的二维数值计算

TWO DIMENSIONAL NUMERICAL CALCULATIONS OF MAGNETIC FIELD OF ELECTROMAGNETIC WIGGLER

本文根据泊松方程用数值计算给出了电磁铁摇摆器的二维磁场分布,定量地讨论了磁极形状、磁隙大小、周期长短和电流大小等因素对峰值磁场强度的影响,重点讨论了如何根据二维磁场分布选择磁极形状才能提高峰值磁场强度和抑制磁饱和的问题。将计算的二维磁场分布和摇摆器磁场的理想波形相比较,可以帮助我们确定进入摇摆器的束流半径应该控制的范围。在对电磁铁摇摆器磁场二维数值计算的基础上,还探讨了适用ATA电子束的PALADIN摇摆器用于ETA电子束带来的结构设计和材料选择等问题。

A 2-D magnetic field distribution of a electromagnetic wiggler has been given numerically by solving Poisons's equation. The parameters affecting the peak magnetic field 0. are discussed quantitatively, including the configuration of magnet poles. the size of gap, the wavelength and the current exciting the magnet poles. In comparison with an ideal wiggler. the 2-D field region can be divided into three parts. They are called good, medialand bad region.respectively.This can help us determine the controlled extent of radius of the beam entering the wiggler. The 2-D magnetic field calculation results show that a good configuration of magnet poles can increase the value of B. and suppress saturation in the poles. This conclusion is in agreement with the analysis result given by K. Halbach. According to the nonunifor -mity of 2-D magnetic field distribution and the comparison of the field with the satura-tion magnetic induction B. a further basis for selecting magnet pole configuration can be. provided. On the basis of 2-D numerical calculation of the magnetic field of electromagnetic wiggler. the question of adapting PALADIN wiggler (PW) to the electron beam of 3-5 MeV is discussed. For the electron beam, it is desired that the peak magnetic field can reach 0.4T and the magnetic gap is large enough to install the waveguide. For attaining above specifications, a substantial modification of PW is necessary. The noteworthy respects have been investigated preliminarily in this paper, including adopting the high B, material to make the magnet poles, increasing wavelength decreasing the gap using a elliptical waveguide of instead the rectangular and selecting the pole configuration.