Space-charge compensation using coupled magnet in J-PARC linac

Chimura, Motoki ; Harada, Hiroyuki  ; Takayanagi, Tomohiro   ; Kinsho, Michikazu  

In low-energy regions where space-charge fields become pronounced, such as in high-intensity proton accelerators, beam quality deteriorates rapidly over short distances of a few meters. Simulations in the 3 MeV beam transport line of the J-PARC linac show that the emittance increases by more than 50% at a short distance of 3 m. Therefore, we proposed a method to compensate a space charge force by using an octupole magnetic field and showed that the emittance increase can be suppressed from the simulation. We have developed a new coupled magnet to realize a higher quality and intensity beam by applying this method to an actual accelerator. In this talk, we will report the design and beam simulation results of the new coupled magnets that can generate quadrupole and octupole magnetic fields simultaneously.