• A.Y. Molodozhentsev, T. Koseki, M.J. Shirakata, M. Tomizawa
  KEK, Ibaraki
• A. Ando, J. Takano
  J-PARC, KEK & JAEA, Ibaraki-ken

Dur­ing the early J-PARC Main Ring com­mis­sion­ing and the ma­chine op­er­a­tion with the mod­er­ate beam power the 'fast ex­trac­tion' bare work­ing point has been cho­sen to pro­vide the ma­chine op­er­a­tion in the safe regime. We dis­cuss main ex­per­i­men­tal re­sults ob­tained so far and com­pare with the re­sults of the com­pu­ta­tion­al model of the ma­chine, in­clud­ing the first ex­per­i­men­tal ap­proach to min­i­mize the ef­fect of the 'sum' lin­ear cou­pling res­o­nance. The strat­e­gy to in­crease the beam power with­out chang­ing the op­er­a­tional work­ing point is pre­sent­ed by keep­ing the mod­er­ate space-charge de­tun­ing. The ad­van­tage of the sec­ond har­mon­ic MR RF cav­i­ty, in­clud­ing the es­ti­ma­tion of the beam loss­es dur­ing the in­jec­tion and ac­cel­er­a­tion pro­cess­es, is dis­cussed.

• A.Y. Molodozhentsev, T. Koseki, M. Tomizawa
  KEK, Ibaraki
• A. Ando
  J-PARC, KEK & JAEA, Ibaraki-ken

Dur­ing the early J-PARC Main Ring com­mis­sion­ing the emit­tance growth at the in­jec­tion en­er­gy, caused by the field leak­age of the slow ex­trac­tion sep­tums, has been ob­served. By using the mea­sured field data in the J-PARC Main Ring com­pu­ta­tion­al model we per­form the anal­y­sis of the res­o­nance ex­ci­ta­tion for the 'bare' work­ing points around the 3rd order hor­i­zon­tal res­o­nance, used for the slow ex­trac­tion of the ac­cel­er­at­ed beam. The space charge ef­fects of the low en­er­gy beam with the mod­er­ate beam power are taken into this anal­y­sis. Some pos­si­ble ways to re­duce the trans­verse emit­tance di­lu­tion and the par­ti­cle loss­es dur­ing the ma­chine op­er­a­tion for the 'hadron' ex­per­i­ments are dis­cussed.