Irie, Y.

Paper	Title	Page
TUYLH03	Challenges facing the Generation of MW Proton Beams using Rapid Cycling Synchrotrons	113
	Y. Irie KEK, Ibaraki
	The MW proton source using rapid cycling synchrotron (RCS) has many challenging aspects, such as (1) large aperture magnets and much higher RF voltages per turn due to a low energy injection and a large and rapid swing of the magnetic field, (2) field tracking between many magnet-families under slightly saturated conditions, (3) RF trapping with fundamental and higher harmonic cavities, (4) H- charge stripping foil, (5) large acceptance injection and extraction straights, (6) beam loss collection, and (7) beam instabilities. These are discussed in details mainly on the basis of the J-PARC 3GeV RCS, which is under construction in Japan. Issues (3) to (7) are common with another scheme of MW spallation neutron source, i.e. full-energy linac + accumulator ring. Comparisons with the SNS design in the US are then made. Reliability/availability of these machines is very important theme which finally determines the successful operations. From the experiences in the existing machines, we will discuss the factors necessary toward the better performance.
	Video of talk
	Transparencies
TUPKF034	Low Output-Impedance RF System for 2nd Harmonic Cavity in the ISIS Synchrotron	1036
	T. Oki, S. Fukumoto, Y. Irie, M. Muto, S. Takano, I. Yamane KEK, Ibaraki R.G. Bendall, I.S.K. Gardner, M.G. Glover, J. Hirst, D. Jenkins, A. Morris, S. Stoneham, J.W.G. Thomason, T. Western CCLRC/RAL/ISIS, Chilton, Didcot, Oxon J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf, G. Pile ANL, Argonne, Illinois
	In the ISIS facility based at Rutherford Appleton Laboratory (RAL) in the UK, second target station project was funded, which requires to increase the current intensity by 1.5-times (300 micro-A). Four 2nd harmonic RF cavities will be installed in the ISIS synchrotron in order to increase the trapping efficiency, and to mitigate the space charge detuning. A very low output-impedance RF system for the 2nd harmonic cavity has been developed by the collaboration between RAL, Argonne National Laboratory (US) and KEK (Japan). The system comprises the 240 kW triode as a final amplifier with plate-to-grid feedback path. The measured output-impedance was less than 30 ohms over the frequency range of 2.7 - 6.2 MHz, which agreed well with calculations. High power test was also performed under frequency swept mode at 50 Hz repetition. The operation was almost stable, and more than 12 kVpp was obtained as maximum. The voltage gain of the final amplifier was 25 - 30, which decreased gradually with frequency due to decreasing input-impedance of triode. The beam test is planned at ISIS in near future.
THPLT071	Upgraded Symplectic 3D Beam Tracking of the J-PARC 3 GeV RCS	2655
	M.J. Shirakata, H. Fujimori, Y. Irie KEK, Ibaraki
	The J-PARC 3 GeV ring is a rapid cycling synchrotron which consists of the large bore size magnets. The beam tracking with the 3D distributed magnetic fields is kept developing in order to investigate the beam injection process. In the case of the high intensity hadron accelerator, an accurate beam simulation is important for the designing because a very small amount of beam loss can be critical from the maintenance point of view. In order to improve the tracking accuracy and to save the calculation time, the symplectic integration with the fractal decomposition method has been introduced. The updated simulation results of the beam injection on the J-PARC 3 GeV RCS and the improved performance of ‘GenericSolver' are presented in this paper. The quadrupole fields are also treated as the 3D distributed magnetic fields because they interfered with the bump magnet fields. The remarkable features on the large bore magnet system in the ring accelerator are also discussed.