Measurement of input beam emittance to obtain MeV, mA-class heavy ion beams in a VERFQ linac

To obtain mA-class beams which can assure high throughput in an MeV ion implantation process, a high current ion beam injection system and a variable energy radio frequency quadrupole (VERFQ) linac driven by an external LC-resonance electric circuit were constructed. A newly designed computer controlled emittance monitor was installed, and the horizontal and vertical normalized emittances of the input beam were simultaneously measured. The normalized emittances of P ⁺ ion beams were comparable to the designed RFQ acceptance (0.05 π cm · mrad). However, the P ²⁺ ion beams had a horizontal emittance that was about twice as large as the acceptance. By adjusting the emittance diagram so that the beam current fit the acceptance was maximized, the P ⁺ and P ²⁺ currents of 1 emA (electric mA) were obtained at energies of 1 MeV and 2 MeV under the cw operation condition, respectively.