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#3141 22-Sep-12

#3141 22-Sep-12. Varying Linac Energy, Effect on Ripple. Normal LC2 gain is ~ 10 MeV (@ LC2GS  35)  total energy 26 MeV We reduced LC2 gain to ~ 5 MeV (@ LC2GS  10)  total energy 21 MeV. AR1-BPM-01. frequency (MHz). Dispersion Measurements.

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#3141 22-Sep-12

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  1. #3141 22-Sep-12

  2. Varying Linac Energy, Effect on Ripple • Normal LC2 gain is ~ 10 MeV (@ LC2GS  35)  total energy 26 MeV • We reduced LC2 gain to ~ 5 MeV (@ LC2GS  10)  total energy 21 MeV AR1-BPM-01 frequency (MHz)

  3. Dispersion Measurements • Measured dispersion on AR1-BPM-01, AR1-BPM-02 (after swapping cables from BPM-01, AR1-BPM-03, AR1-BPM-04, AR1-BPM-05, ST2-BPM-03 • AR1Q1/Q4 = 2.18 A and AR1Q2/Q3 = 1.10 A, why? • With these quads, dispersion (m) on BPM1,2,3,4,5,6 from Elegant {-0.000380058,0.330138,-0.0964672,-0.0850524,0.338045,-0.0339197}

  4. Train to Train Bunch Position Jitter. • Took many shots=trains (100) at AR1-BPM-01. • The x-variation within a train is about 60 um RMS, and it’s gaussian, and it doesn’t vary much train-to-train • I wouldn’t call this variation ‘jitter’ as this implies some randomness to the variation. There are random variations but there are also quite well defined ripples that contribute to the variation. • How do we define train-to-train position jitter? • How do we define “the position of a train” ? there are several ways … • Mean bunch position over a train, median bunch position over a train, max bunch position over a train, min bunch position over a train • However we define it, the RMS variation in “the position of a train” is about 60 um and gaussian • The main point (for me) is that the train does not jitter more than the bunches within it. • Also looked atAR1-BPM-05 but energy droop and dispersion here makes conclusions difficult to draw.

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