Development of a laser ion source for a four-beam Interdigital-H type Radio Frequency Quadrupole Linac

The multi-beam acceleration method is an acceleration technique for low-energy, high-intensity, heavy ion beams, which involves accelerating multiple beams to decrease space charge effects, and then integrating these beams by a beam funneling system. At the Tokyo Institute of Teclmology, in order to demonstrate that a four-beam interdigital-H type radio frequency quadruple (IH-RFQ) linear accelerator is suitable for high-intensity heavy ion beam acceleration, we have been developing a four-beam III-RFQ linac prototype. As an injection system for the four-beam III-RFQ linac, we are developing a laser ion source. The laser ion source is directly connected to the RFQ cavity without a low energy beam transport system, and generates four-ablation plasmas by irradiating a graphite target with four split laser. The plasmas expand through plasma transport pipes and go directly into each RFQ channel. We have measured the carbon ion beam properties of the laser ion source such as the output beam current and the charge state spectrum.