• F. Tamura, M. Nomura, A. Schnase, T. Shimada, H. Suzuki, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Hara, C. Ohmori, M. Tada, M. Yoshii
  KEK/JAEA, Ibaraki-Ken
• K. Hasegawa
  KEK, Ibaraki

The wide-band RF cav­i­ties in the J-PARC RCS are op­er­at­ed in the du­al-har­mon­ic op­er­a­tion, in which each sin­gle cav­i­ty is driv­en by a su­per­po­si­tion of the fun­da­men­tal and the sec­ond har­mon­ic RF sig­nals. By the du­al-har­mon­ic op­er­a­tion large am­pli­tude sec­ond har­mon­ic sig­nals for the bunch shape ma­nip­u­la­tion are gen­er­at­ed with­out extra cav­i­ties. The phase con­trol of the sec­ond har­mon­ic RF is a key for the bunch shape ma­nip­u­la­tion. The fun­da­men­tal RF sig­nal is con­trolled by the phase feed­back loop to damp the dipole os­cil­la­tion. The sec­ond har­mon­ic is locked to the phase of the vec­tor-sum phase of the fun­da­men­tal RF sig­nals. We pre­sent the sys­tem de­tail and the per­for­mance in the beam op­er­a­tion of the RCS.

• A. Schnase, K. Hasegawa, M. Nomura, T. Shimada, H. Suzuki, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Hara, C. Ohmori, M. Tada, M. Yoshii
  KEK/JAEA, Ibaraki-Ken
• T. Koseki, T. Toyama
  J-PARC, KEK & JAEA, Ibaraki-ken
• M. Tomizawa
  KEK, Ibaraki

Ap­ply­ing nar­row band lon­gi­tu­di­nal noise to the beam in J-PARC Main Ring in flat­top, while the ac­cel­er­a­tion volt­age is off might help to coun­ter­act the ef­fect of rip­ple on the slow ex­trac­tion. For this pur­pose, a com­plex noise se­quence out­put by DSP mod­u­lates a cus­tom made DDS syn­the­siz­er to cre­ate sin­gle side spec­tra with­out car­ri­er. The noise is cal­cu­lat­ed start­ing from a de­scrip­tion in fre­quen­cy do­main. Then an al­go­rithm cre­ates nar­row band spec­tra with op­ti­mized be­hav­ior in time do­main. Fre­quen­cy do­main data is trans­formed to time do­main, and the am­pli­tude is smoothed. The smoothed data is trans­formed back to fre­quen­cy do­main, and the spec­tral shape is re­stored. This pro­cess re­peats until the am­pli­tude in time do­main has con­verged, while the de­sired spec­trum shape is pre­served. Noise gen­er­at­ed in this way can be tai­lored for dif­fer­ent re­quire­ments. We show the sig­nal prop­er­ties, the hard­ware, and pre­lim­i­nary beam test re­sults, when the noise is ap­plied to the MR RF sys­tem.

• M. Yamamoto, M. Nomura, A. Schnase, T. Shimada, H. Suzuki, F. Tamura
  JAEA/J-PARC, Tokai-mura
• E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, M. Tada, A. Takagi, K. Takata, M. Yoshii
  KEK, Ibaraki

The Lon­gi­tu­di­nal emit­tance in J-PARC RCS should be con­trolled to ac­cel­er­ate a high in­ten­si­ty pro­ton beam with min­i­mal beam loss. In order to study and min­i­mize the beam loss dur­ing ac­cel­er­a­tion, the op­ti­mized way to add the 2nd high­er har­mon­ic rf has been cal­cu­lat­ed by a par­ti­cle track­ing code. Fur­ther­more, the bunch shape at RCS ex­trac­tion should be con­trolled and op­ti­mized for the MR in­jec­tion. For this pur­pose, the op­ti­mum RCS ac­cel­er­a­tion pat­tern has been cal­cu­lat­ed. We de­scribe the sim­u­la­tion re­sults and the com­par­i­son with the beam test.

• M. Nomura, A. Schnase, T. Shimada, H. Suzuki, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• E. Ezura, K. Hara, C. Ohmori, M. Tada, M. Yoshii
  KEK/JAEA, Ibaraki-Ken
• K. Hasegawa, K. Takata
  KEK, Ibaraki

We have been op­er­at­ing the RF cav­i­ties load­ed with MA cores with a high field gra­di­ent of more than 20 kV/m since Oc­to­ber 2007. We have been mea­sur­ing the RF cav­i­ty impedance at the shut­down pe­ri­ods, and we de­tect­ed the impedance re­duc­tions of RCS RF cav­i­ties on Jan­uary and June 2009. Tak­ing out the RF cav­i­ties from the beam line and open­ing them, we found that many of cores showed a buck­ling at the inner ra­dius. Also de­tach­ment of the epoxy coat­ing in­tend­ed to pre­vent rust­ing was ob­served. We re­port the de­tail of con­di­tion of MA cores and the re­la­tion be­tween the impedance re­duc­tion and core con­di­tion.

• M. Yoshii, K. Hara, C. Ohmori, T. Shimada, H. Suzuki, M. Tada
  KEK/JAEA, Ibaraki-Ken
• E. Ezura, K. Hasegawa, A. Takagi, K. Takata
  KEK, Ibaraki
• M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

The Japan Pro­ton Ac­cel­er­a­tor Com­plex in­cludes the 3GeV rapid cy­cling syn­chrotron (RCS) and the 50GeV main ring syn­chrotron (MR). Both syn­chrotrons use the high field gra­di­ent mag­net­ic alloy (MA) load­ed cav­i­ties. In RCS, 11 RF sys­tems have been fully op­er­a­tional since De­cem­ber 2008. The RCS RF sys­tems are op­er­at­ed with du­al-har­mon­ic ac­cel­er­a­tion volt­ages. Beam ac­cel­er­a­tion and bunch shape ma­nip­u­la­tion are ef­fi­cient­ly tak­ing place. 120kW of the neu­tron user op­er­a­tion was start­ed at the Ma­te­ri­al and Life sci­ence fa­cil­i­ties in Novem­ber 2009. In MR syn­chrotron, the 5th RF sys­tem were in­stalled in Au­gust 2009, and there­fore 5 RF sys­tems are now in op­er­a­tion. Beam com­mis­sion­ing for de­liv­er­ing pro­tons to the hadron fa­cil­i­ty and neu­tri­no beam ex­per­i­men­tal fa­cil­i­ty are under way. The neu­tri­no user ex­per­i­ment is in­tend­ed to start Jan­uary 2010. Pro­ton beam op­er­a­tion with more than 100kW is re­quired. The ap­proach­es to re­al­iz­ing high in­ten­si­ty op­er­a­tion and the MR up­grade plan will be pre­sent­ed.

• C. Ohmori, K. Hasegawa, A. Takagi
  KEK, Ibaraki
• K. Hara, T. Shimada, H. Suzuki, M. Tada, M. Yoshii
  KEK/JAEA, Ibaraki-Ken
• M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Mag­net­ic alloy cav­i­ties are suc­cess­ful­ly used for J-PARC syn­chrotrons. These cav­i­ties gen­er­ate much high­er RF volt­age than or­di­nary fer­rite cav­i­ties. For fu­ture up­grades of J-PARC fa­cil­i­ties, a high­er field gra­di­ent is nec­es­sary. It was found that the char­ac­ter­is­tics of mag­net­ic alloy is im­proved by a new an­neal­ing scheme under mag­net­ic field. A large pro­duc­tion sys­tem using an old cy­clotron mag­net is under con­struc­tion for the J-PARC up­grade. The sta­tus of core de­vel­op­ment will be re­port­ed.

• T. Shimada
  KEK/JAEA, Ibaraki-Ken
• K. Hara, K. Hasegawa, C. Ohmori, M. Tada, M. Yoshii
  KEK, Ibaraki
• M. Nomura, A. Schnase, H. Suzuki, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Sev­er­al mag­net­ic alloy cores of the RF cav­i­ties, which are in­stalled in the 3 GeV rapid cy­cling syn­chrotron (RCS) of J-PARC have shown buck­ling after about two years op­er­a­tion. To find the rea­son, why the local de­for­ma­tion hap­pened, we made a test setup. There we heat up MA cores in air by 500 kHz RF and mea­sure the ther­mal de­for­ma­tion in order to col­lect in­for­ma­tion about the buck­ling pro­cess. The re­sults ob­tained by com­par­ing the ex­pan­sion of cores made by dif­fer­ent pro­duc­tion meth­ods are re­port­ed.