Ion beam distributions from a laser ion source with a pair of semicylindrical electrodes measured by a multichannel Faraday cup

The intensity distributions of a neodymium ion beam that was extracted from laser photoionized plasma were measured by scanning a multichannel Faraday cup. The lateral width of ions at the position of the Faraday cup, which was broad without any additional electric field, was reduced by the additional concentric potential with a pair of semicylindrical electrodes set outside of the extraction electrode. The central ion beam intensity increased by about two times with these electrodes. The kinetic energy of the ion beam was derived by comparing the time lag of the ion signal appearance. These results were useful for the application of the laser photoionized ion beam.