Ohkawa, T.

Paper	Title	Page
TUP21	Beam Dynamics Design of J-PARC Linac High Energy Section	339
	M. Ikegami, T. Kato, S. Noguchi KEK, Ibaraki H. Ao, Y. Yamazaki JAERI/LINAC, Ibaraki-ken K. Hasegawa, T. Ohkawa, A. Ueno JAERI, Ibaraki-ken N. Hayashizaki TIT, Tokyo V.V. Paramonov RAS/INR, Moscow
	J-PARC linac consists of a 3 MeV RFQ linac, a 50 MeV DTL (Drift Tube Linac), a 190 MeV SDTL (Separate-type DTL), and a 400 MeV ACS (Annular-Coupled Structure) linac. Recently, the beam dynamics design of the ACS part has been slightly modified to reduce construction cost. Namely, the number of klystron modules are reduced from 23 to 21, and the number of accelerating cells in one klystron module is increased from 30 to 34 to maintain the total energy gain. This design change curtails the margin for RF power by around 5 %, and the total length of the ACS section is nearly unchanged. The beam matching section between SDTL and ACS is also revised correspondingly. These modifications of the design are described in this paper together with 3D particle simulation results for the new design.
TUP22	A Simulation Study on Chopper Transient Effects in J-PARC Linac	342
	M. Ikegami KEK, Ibaraki Y. Kondo, T. Ohkawa, A. Ueno JAERI, Ibaraki-ken
	J-PARC linac has an RF chopper system to reduce uncontrolled beam loss in the succeeding ring injection. The chopper system is located in MEBT (Medium Energy Beam Transport line) between a 3 MeV RFQ and a 50 MeV DTL, and consists of two RFD (Radio-Frequency Deflection) cavities and a beam collector. During the rising- and falling-times of the RFD cavities, the beams are half-kicked and cause excess beam loss downstream. In this paper, the behavior of these half-kicked beams is examined with 3D PARMILA simulations, and resulting beam loss is estimated.
	Transparencies
TUP23	A Simulation Study on Error Effects in J-PARC Linac	345
	M. Ikegami KEK, Ibaraki Y. Kondo, T. Ohkawa, A. Ueno JAERI, Ibaraki-ken
	In high-current proton linacs, prevention of excess beam loss is essentially important to enable hands-on maintenance. In addition, requirements on the momentum spread and transverse emittance are quite severe for J-PARC linac to realize effective injection to the succeeding RCS (Rapid Cycling Synchrotron). As losses and beam-quality deterioration are believed to be mainly caused by various errors, such as misalignment, RF mistuning, etc, it is essentially important to perform particle simulations for J-PARC linac with as realistic errors as possible to estimate their effects. In this paper, effects of realistic errors on beam loss and beam-quality deterioration in J-PARC linac are examined with a systematic 3D simulations with PARMILA. Necessity of transverse collimation is also discussed.