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fast ion effects. compare three rings: OTW (3.2 km), OCS (6.1 km), TESLA (17 km) assume partial CO pressure of 0.01 nTorr. analytical estimates of trapping condition exponential FBII rise time incoherent tune shift at end of train. use excel file provided by Tor Raubenheimer;
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fast ion effects compare three rings: OTW (3.2 km), OCS (6.1 km), TESLA (17 km) assume partial CO pressure of 0.01 nTorr analytical estimates of trapping condition exponential FBII rise time incoherent tune shift at end of train use excel file provided by Tor Raubenheimer; add beam sizes from A. Wolski, & parameters for OCS Frank Zimmermann, ILC DR teleconference 04.10.2005
parameters TESLA ring w/o (w) coupling bumps Frank Zimmermann, ILC DR teleconference 04.10.2005
parameters OCS (assume single train, and 5 GeV) Frank Zimmermann, ILC DR teleconference 04.10.2005
parameters OTW Frank Zimmermann, ILC DR teleconference 04.10.2005
results for TESLA damping ring w/o (w) coupling bumps net rise time ty,exp~83 ms (162 ms) total tune shiftDQy~0.188 (0.025) rise-time & tune-shift estimate assumes trapping of CO, 0.01 nTorr CO pressure all around the ring, and 0.3 relative ion-frequency spread; even if ions not trapped for final conditions, certainly they are trapped during the damping process Frank Zimmermann, ILC DR teleconference 04.10.2005
results for OCS damping ring net rise time ty,exp~210 ms total tune shiftDQy~0.04 rise-time & tune-shift estimate assumes trapping of CO, single train, 0.01 nTorr CO pressure all around the ring, and 0.3 relative ion-frequency spread; even if ions not trapped for final conditions, certainly they are trapped during the damping process rise time larger & tune shift smaller than for 17-km ring Frank Zimmermann, ILC DR teleconference 04.10.2005
results for OTW damping ring net rise time ty,exp~199 ms total tune shiftDQy~0.022 rise-time & tune-shift estimate assumes trapping of CO, single train, 0.01 nTorr CO pressure all around the ring, and 0.3 relative ion-frequency spread; even if ions not trapped for final conditions, certainly they are trapped during the damping process rise time similar to & tune shift smaller than for 6.1-km ring Frank Zimmermann, ILC DR teleconference 04.10.2005
conclusion from comparison: • ions like CO are trapped over most of the circumference for all three designs • the 3.2-km ring (OTW) yields smallest tune shifts (~0.022) • smallest growth rates are obtained for both 3.2-km (OTW) and 6.1-km ring (OCS) • exponential rise time is about 200 ms for an average CO pressure of 0.01 nTorr • with coupling bumps the tune shift and rise time for the TESLA ring assume comparable values, but in this case even H ions may be trapped Frank Zimmermann, ILC DR teleconference 04.10.2005