Y Ohnishi KEKB LER for ILC Damping Ring
Y. Ohnishi / KEKB LER for ILC Damping Ring Study Lattice simulation of lattice errors and optics corrections. November 1, 2007 Y. Ohnishi / KEK
Y. Ohnishi / KEK Emittance and Lattice Errors l The purpose of this study is to check a feasibility of the low emittance with optics corrections for the KEKB LER. l Simulation study: KEKB LER lattice includes machine errors. The machine errors are magnet alignment errors, field gradient errors, and BPM accuracy. l l BPM error means an alignment error. These errors are generated by Gaussian distributions with random seed numbers. 2
Y. Ohnishi / KEKB LER Lattice for ILC Damping Ring Study bx* = 90 cm by* = 3 cm injection point nx/ny = 47. 53/42. 59 l ex = 1. 5 nm l ns = -0. 013 sz = 4. 3 mm ap = 2. 5 x 10 -4 3
Y. Ohnishi / KEK Lattice Errors Multipole components and fringe field have been included in the design lattice. Following errors are produced with random numbers according to Gaussian. The values are one standard deviation(s). alignment error Dx (mm) alignment error Dy (mm) rotation error Dq (mrad) gradient error Dk/k Bending magnet 100 0. 1 1 x 10 -4 Quadrupole magnet 100 0. 2 3 x 10 -4 Sextupole magnet 100 0. 2 5 x 10 -4 4
Y. Ohnishi / KEK Optics Corrections l Correction of closed orbit distortion l XY coupling correction l measurement: l l corrector: l l symmetric vertical local bumps at sextupole pairs(-I' connection) Dispersion correction l measurement: l l orbit response changing rf frequency. corrector: l l vertical orbit response induced by a horizontal single kick due to a steering magnet. asymmetric local bumps at sextupole pairs(-I' connection) Beta correction l measurement: l l orbit response induced by a single kick due to a steering magnet. corrector: l fudge factors to quadrupole magnet power supplies(families) 5
Y. Ohnishi / KEK Optics Corrections by using sextupoles (1) l Sextupoles are located at arc sections and LCC(LER only). vertical bump (+) @sextupole -I' vertical bump (-) @sextupole xy coupling (+) vertical dispersion (-) induced by horizontal dispersion xy coupling corrector cancel xy coupling (+) vertical dispersion (+) induced by horizontal dispersion cancel xy coupling (-) vertical dispersion corrector vertical dispersion (+) induced by horizontal dispersion 6
Y. Ohnishi / KEK Optics Corrections by using sextupoles (2) l Sextupoles are located at arc sections and LCC(LER only). Not used horizontal bump (+) @sextuple quadrupole element (+) -I' beta corrector horizontal bump (+) @sextuple -I' horizontal bump (-) @sextuple quadrupole element (+) cancel quadrupole element (-) horizontal dispersion (-) cancel horizontal dispersion (+) horizontal dispersion corrector horizontal dispersion (+) 7
Y. Ohnishi / KEK Optics Corrections and Vertical Emittance (pm) #samples : 100 (error bar: standard deviation) ey/ex = 1% open circle: COD correction only closed circle: COD+XY+Dispersion+Beta correction ey/ex = 0. 2% Errors of BPMs (s) target emittance ratio 8
Y. Ohnishi / KEK Optics Corrections and Vertical Emittance s(Dby/by@BPM) (%) #samples : 100 Error of BPMs: s = 10 mm Each point means a different seed number to give machine errors. COD correction only COD+XY+Dispersion+Beta correction 0. 2% ey (pm) Optics corrections can achieve ey/ex=0. 2 %, where ex=1. 5 nm. l BPM accuracy should be less than 10 mm. l 9
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