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Update on MEIC Nonlinear Dynamics Work
V.S. Morozov Teleconference on Nonlinear Dynamics August 4, 2015 F. Lin
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Nonlinear Parameter Study Continued
Phase advance between the h and v sextupoles adjusted to exactly /2 in both planes Phase advance from IP to sextupoles adjusted to exactly (n+1/2) in appropriate planes W minimized at IP using “non-linear” sextupoles x,y = 1 using “linear” sextuples Betatron tunes: x = 25.22, y = 23.16 No significant improvement IP
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Some Non-Linear Parameters
Chromaticities dnux/dp = e-01; dnux/dp2 = e+03; dnux/dp3 = e+06 dnuy/dp = e-01; dnuy/dp2 = e+03; dnuy/dp3 = e+06 Chromatic function dependence dbetax/dp (m) = e-02; dbetay/dp (m) = e-02 Non-linear dispersion etax2 (m) = e+00; etax3 (m) = e+02 etay2 (m) = e+00; etay3 (m) = e+00 Tune dependence on amplitudes dnux/dJx (1/m) = e+02; dnux/dJy (1/m) = e+04; dnuy/dJy (1/m) = e+02 1st-order driving terms h11001 = e+01; h00111 = e+01; h10100 = e+00; h10010 = e+00; h21000 (1/m1/2) = e-02; h30000 (1/m1/2) = e-03; h10110 (1/m1/2) = e+01; h10020 (1/m1/2) = e+01; h10200 (1/m) = e+00; h20001 = e+00; h00201 = e+01; h10002 (1/m1/2) = e+00; 2nd-order driving terms h22000 (1/m) = e+02; h11110 (1/m) = e+04; h00220 (1/m) = e+02; h31000 (1/m) = e+01; h40000 (1/m) = e+02; h20110 (1/m) = e+03; h11200 (1/m) = e+04; h20020 (1/m) = e+03; h20200 (1/m) = e+03; h00310 (1/m) = e+02; h00400 (1/m) = e+01
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What Is the Issue? Second order amplitude dependent tune shift
Consider a single CCB (the downstream one) with N = 3 h/v sextuple cross-talk within a single CCB explains the large x/Jy value: (x/Jy)21 and (x/Jy)23 independent of tune and add up x/Jy j Total 1 2 3 k 223.0 -223.0 -20.0
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Conclusions & Outlook There seems to be a fundamental problem with the CCB scheme There appear to be no phase advance combination that would cancel sextupole contributions to x/Jy Additional sextupole(s) needed, this then starts resembling –I sext pair scheme x/Jy is the hardest to compensate with octupoles, would require three of them Important lesson: phase advance between sextupole pairs matters Further work Present a side by side comparison to the collaboration and make a down selection Get non-interleaved –I sextupole pair optics from SLAC for further studies Continue optimization Continue error studies Start thinking about the electron ring
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