| 摘要 |
PROBLEM TO BE SOLVED: To provide a hollow plasma pillar in which the density is lower in the position near the axis than in the peripheral part to prevent the divergence with the refraction of light by letting interfere two laser breams having the same wave length from horizontal and vertical directions and forming a plasma accelerating tube. SOLUTION: Laser beams 9, 10 are divided into two with a translucent mirror 2 and a total reflection mirror 3, then let interfere with electron beams 8 to generate an interference fringe, and plasma slabs 12 are formed at optional intervals. By passing aslant electron beams through a number of plasma slab rows formed, an alternating electric field perpendicular to the proceeding direction of the electron beam, or an undulating electric field component is obtained. By letting interfere laser beams from horizontal and vertical directions, an optical guide 11 having the density lower in the position near the axis than the peripheral plasma part 12 is formed. For example, a hollow plasma pillar in which the plasma density is 1×10<10> /cm<3> in the peripheral part, and 1×10<14> /cm<3> in the central part, and the inner dimensions of a square pillar are about 10μm in length and width and height is 10mm is obtained.
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