• S. Igarashi, T. Oogoe, H. Someya, S. Yamada
  KEK, Ibaraki
• Y. Kuniyasu
  MELCO SC, Tsukuba
• S. Nakamura
  J-PARC, KEK & JAEA, Ibaraki-ken

Ef­forts have been made to re­duce the mag­net­ic field rip­ple of the bend­ing, quadrupole and sex­tupole mag­nets of the J-PARC main ring using the trim coils of the mag­nets. The quadrupole mag­net has 24 turn main coil and 11 turn trim coil per pole those can be con­sid­ered as a pri­ma­ry wind­ing and a sec­ondary wind­ing of a trans­former. When the trim coil is short­ed, the in­duced trim coil cur­rent can­cels the field rip­ple. The field rip­ple of the quadrupole mag­net was re­duced by a fac­tor of 6 by short­ing trim coil. The trim coil cur­rent, how­ev­er, de­forms the ac­cel­er­a­tion field pat­tern if the coil is short­ed all the time of the cur­rent pat­tern of flat bot­tom, ac­cel­er­a­tion, flat top and re­cov­ery. The MOS­FET relay was used to short the coil and to re­duce the field rip­ple dur­ing the flat bot­tom and flat top. The cir­cuits were built for the quadrupole and sex­tupole mag­nets. The plan has been made to wind op­ti­mized trim coils for the bend­ing mag­nets.

• T. Toyama, D.A. Arakawa, S. Hiramatsu, S. Igarashi, S. Lee, H. Matsumoto, J.-I. Odagiri, M. Okada, M. Tejima, M. Tobiyama
  KEK, Ibaraki
• K. Hanamura, S. Hatakeyama
  MELCO SC, Tsukuba
• Y. Hashimoto, K. Satou, J. Takano
  J-PARC, KEK & JAEA, Ibaraki-ken
• N. Hayashi
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Ex­pe­ri­ences of op­er­at­ing BPM's dur­ing beam com­mis­sion­ing at the J-PARC MR are re­port­ed. The sub­jects are: (1) bug re­port, statis­tics and es­pe­cial­ly the ef­fect of a beam duct step, (2) po­si­tion res­o­lu­tion es­ti­ma­tion (<30 mi­crom­e­ters with 1 sec av­er­ag­ing), (3) beam based align­ment.

• H. Someya, S. Igarashi
  KEK, Ibaraki
• S. Nakamura
  J-PARC, KEK & JAEA, Ibaraki-ken

The power sup­ply cur­rent rip­ple of the quadrupole mag­nets of the J-PARC main ring has been mea­sured to be the order of 10^-4. The mag­net­ic field of the quadrupole mag­nets has been mea­sured and the rip­ple fre­quen­cy dis­tri­bu­tion of each mag­net was ob­served to be de­pend­ing on where the mag­net is in the mag­net chain. A trans­mis­sion line model for the cable and mag­nets was able to ex­plain the dis­tri­bu­tion. The field rip­ple made by the com­mon mode cur­rent rip­ple was re­duced by chang­ing the mag­net ca­bling to be sym­met­ri­cal with re­spect to the N and S poles of the quadrupole mag­nets. The com­mon mode rip­ple was dras­ti­cal­ly re­duced. The nor­mal mode rip­ple of 600, 1200 and 1800 Hz how­ev­er re­mained. The field rip­ple was fur­ther re­duced using re­sis­tors those are con­nect­ed in par­al­lel to the mag­net coils and by­pass the cur­rent rip­ple. It was ef­fec­tive to the high­er fre­quen­cy rip­ple of 1200 and 1800 Hz and the ef­fect was in a good agree­ment with an elec­tric cir­cuit sim­u­la­tion pro­gram LT­spice.

• G.H. Wei
  KEK/JAEA, Ibaraki-Ken
• A. Ando, Y. Hashimoto, T. Koseki, J. Takano
  J-PARC, KEK & JAEA, Ibaraki-ken
• S. Igarashi, K. Ishii, M. Tomizawa, M. Uota
  KEK, Ibaraki
• P.K. Saha, K. Satou, M.J. Shirakata
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

The beam com­mis­sion­ing of J-PARC (Japan Pro­ton Ac­cel­er­a­tor Re­search Com­plex) MR (Main Ring) was start­ed from May 2008 and is in progress. As usual, in­jec­tion tun­ing is in the first stage and strong­ly re­lat­ed to other tun­ing items. Start­ing with de­sign schemes, mak­ing ad­just­ment due to leak­age field in­flu­ence from in­jec­tion sep­tum, doing en­ve­lope match­ing con­sid­er­ing di­lu­tion of beam pro­file in Main Ring are re­port­ed in this paper. The 'With­out bump' scheme was got on June 15th 2008, while 'With bump' scheme on Febru­ary 15th 2009. Beam orbit be­ta­tron os­cil­la­tion to the MR close orbit which cause by in­jec­tion error is less than 1 mm both in hor­i­zon­tal and ver­ti­cal di­rec­tion. Mean­while, Beam Op­tics match­ing for 3 GeV beam from 350BT to MR has been well done too, which is also very im­por­tant.

* T. Koseki, Challenges and Solutions for J-PARC Commissioning and Early Operation, in these proceedings

• G.H. Wei
  KEK/JAEA, Ibaraki-Ken
• A. Ando, T. Koseki, J. Takano
  J-PARC, KEK & JAEA, Ibaraki-ken
• K. Fan, S. Igarashi, K. Ishii, T. Nakadaira, M. Tomizawa, M. Uota
  KEK, Ibaraki
• H. Harada, P.K. Saha
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

The beam com­mis­sion­ing of J-PARC/MR has been start­ed from May 2008 and is in progress*. One key pur­pose of MR com­mis­sion­ing is the 30 GeV beam fast ex­trac­tion to Neu­tri­no beam line, which re­flect the over­all com­mis­sion­ing re­sult. In the MR, the third straight sec­tion is as­signed for the fast ex­trac­tion. 5 kick­ers and 8 septa were in­stalled there, which can give beam a bipo­lar kick to in­side or out­side of MR. In­side kick means beam to Neu­tri­no Os­cil­la­tion Ex­per­i­ment, while out­side kick means beam dumped to abort line. How­ev­er be­fore com­mis­sion­ing, the mea­sured mag­net­ic field dis­tri­bu­tion of each septa shows non-lin­ear pro­file along the hor­i­zon­tal di­rec­tion. In order to find the in­flu­ence, a sim­u­la­tion with these mea­sured field has been per­formed. De­pends on this study and some OPI (Op­er­a­tion In­ter­face) made by code SAD for orbit mod­i­fi­ca­tion on­line, fast ex­trac­tion of 30 GeV beam to Neu­tri­no line has been achieved on April 23rd 2009. Beam orbit have been tuned to less than 0.5 mm and 0.1 mrad in both hor­i­zon­tal and ver­ti­cal at the be­gin­ning of Neu­tri­no line, which is also the end of MR fast ex­trac­tion. And so far, 100 kW con­tin­u­al op­er­a­tion to neu­tri­no line have been achieved, too.

* T. Koseki, "Challenges and Solutions for J-PARC Commissioning and Early Operation", in these proceedings

• K. Ohmi, K. Fan, S. Igarashi, Y. Sato
  KEK, Ibaraki
• H. Hotchi, Y. Shobuda
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Non­lin­ear space charge in­ter­ac­tion in high in­ten­si­ty pro­ton rings caus­es beam loss, which lim­its the per­for­mance. Sim­u­la­tions based on par­ti­cle in cell method has been per­formed for JPARC-Rapid Cycle Syn­chrotron and Main Ring. Beam loss es­ti­ma­tion dur­ing ac­cel­er­a­tion and res­o­nances anal­y­sis are dis­cussed with var­i­ous sim­u­la­tions using dy­nam­ic and frozen mod­els.