Nonscaling 10 to 20 muon FFAG with sextupole

Nonscaling 10 to 20 muon FFAG with sextupole Shinji Machida CCLRC/RAL/ASTe. C 6 -10 November, 2006 http: //hadron. kek. jp/~machida/doc/nufact/ ffag/machida_20061110. ppt & pdf 1

Motivation • Chromaticity correction (even small) helps time of flight problem. – Linear nonscaling FFAG has very small (negative at some region) dispersion. – Chromaticity correction is hard because sextupole strength tends to be high. • Scaling FFAG has reasonable size of dispersion. – Nonscaling FFAG with reasonable size of dispersion may have chromaticity correction easily. – We have to give up “isochronous” condition. We will use low (~10 MHz) RF frequency as scaling FFAG. • 10 to 20 Ge. V muon FFAG uses “almost rectangular” magnet. In practice, scaling FFAG scheme may have similar magnet and optics we will talk here. 2

EPAC 06 presentation by Mori 3

Chromaticity correction • With 2 family of sextupole, tune excursion can be reduced within an integer. • Orbit excursion is about 0. 5 m. 4

Dynamic aperture with sextupole • Dynamic aperture becomes comparable with scaling FFAG, but depends strongly on turn number. 5

Summary • For 10 to 20 Ge. V muon ring, pure scaling FFAG and nonlinear (sextupole) nonscaling do not make difference (? ) in terms of tune excursion, orbit excursion, and dynamic aperture. • To make a fair comparison, we should repeat the similar study for scaling FFAG. c. f. Low frequency (31 MHz) bunching scheme has been proposed by S. Brooks. 6