短語詞組短語beam spreading radius 擴束半徑beam waist radius 光腰半徑beam spot radius 光斑半徑beam spread radius 束擴散半徑effective beam radius 電子束等效尺寸optimized beam radius 最佳電子束半徑entrance beam radius 入射光束半徑initial beam radius 初始束流半徑initial amplitude beam radius 初始束流半徑 返回 beam radius