Development of carbon thin film for Laser‐driven heavy ion acceleration using a XeCl excimer laser

The carbon thin film as a target for laser‐driven heavy ion acceleration has been developed using the carbonization of polyimide induced by the irradiation of a XeCl excimer laser. The relationship between the depth of the crater produced by the laser irradiation and the laser fluence were measured in order to clear the carbonization mechanisms of polyimide. The melting threshold of polyimide was estimated to 0.058 J/cm2. It is found that the carbonization is induced by the irradiation with the laser fluence around or under the threshold