Production of an extended plasma column in vacuum by irradiating a target by a quasi-Bessel beam

A technique of focusing the heating radiation was investigated, which makes it possible to produce an extended (under laboratory conditions, up to 1 m and over) plasma column and enables an easy output of VUV radiation. A pla ne solid-state target in vacuum was arranged along the caustic of a conic l ens (axicon), which focused the laser beam. An analytic dependence, which d escribes the spatial intensity distribution of the heating radiation in the case of a nontransparent, partially reflecting target, was derived and exp erimentally verified. Experiments on the irradiation of an aluminium target in vacuum with a 5-J, 5-ns pulse of a neodymium-glass laser were performed . A plasma column up to 30 mm in length and no greater than 10 mum in diame ter was formed. A rather intense plasma radiation was recorded in the VUV r ange.