Minutes of the ABP-LCE team meeting on 16.01.04 present: EB, WH, AK, EM, FR, DS, EV, FZ ---------------------------------------------------------------------- (1) Minutes & Pending Actions ----------------------------- OLD ACTION -> Fr will contact OB regarding ZBASE tutorial. OK. It is scheduled for today 16:00. OLD ACTION -> CB head-tail growth rates for updated LHC impedance (FR) Pending. Requires response to JPK. OLD ACTION -> AK will check CB rise time for Roman-Pot impedance. AK sees no effect. He will increase the impedance in order to scale. OLD ACTION -> AK will check if the effect of Schottky monitor is important in simulations. Again there is no discernible effect. OLD ACTION -> Organize ABP-RF-BDI meeting on beam-beam diagnostics with feedback (EV). No decision yet on who should be invited. ACTION -> WH will plan this meeting. OLD ACTION -> FZ will contact M.Zobov on shallow-taper impedance. Done. According to M. Zobov, the formula of the 1994 report may not be applicable in this regime. FR pointed out that M. Dyachkov had a web site with an online program for computing this type of impedances. OLD ACTION -> FZ find web site. CERN site is not operational as suspected. And M. D'yachkov resigned from TRIUMF about a year ago. R. Baartman and D. Kaltchev are trying to track him down. OLD ACTION -> Collimator Impedance Calculation with Gdfidl (DS). Only 4 out of 7 nodes are running. Negotiations are underway with CLIC for additional computing power. FR points out that this study has high priority and should be finalized within 2-3 weeks, in view of the prototype needed for the SPS collimator test. Accurate hardware description is required. Gaps could be made invisible by proper design. (2) Some Plans for 2004 ----------------------- WH - PhD student will start in June. Work will be on coherent beam-beam interaction. Tracking with beam-beam is now available in MAD and will be further pursued. FZ - Assumed responsibility for SPS BBLR project. Should devote 4 weeks in January-March for Tevatron wire-compensation study. E-cloud simulations ongoing for SPS benchmarking and LHC extrapolation. ESGARD activities coming up (should amount to 10-20% of working time). Supervision for WW, MK and EB. Help for JR Lopez. Contributions to CLIC studies on damping rings and final focus (30%?). Contributions to LHC impedance and ZBASE. EV - Apply Transient-Ripple Study to LHC. Examine bandwidth-limit problems. Use of modal filters; correction for bandwidth limit. (3) Tune Shift and Tune Spread due to Electron Cloud (EB) ---------------------------------------------------------- EB presented the results of an analytical calculation for the position-dependent tune shift due to the electron pinch. she considered a linear transverse force and various longitudinal beam profiles. She first solved the equations of motion for an electron, then used Liouville's theorem to find the electron density at an arbitrary time starting from an initial Gaussian. Finally, from the electron distribution the tune shift follows. Results were compared with a simulation model. In the simulation the nonlinear force makes a large difference, lading to a nearly constant electron density after a quarter oscillation. The electron-centroid oscillation frequency varies with the size of the cloud. (4) Using Feedback to Damp Transient Ripple Effects at SPS Extraction to CNGS (EV) --------------------------------------------------- EV presented encouraging preliminary results on the damping of kicker ripple affecting the second CNGS batch in the SPS. The figure of merit is the bunch offset and emittance at the moment the second batch is extracted. A realistic model of the ripple is used, which amounts to 12% of the full kick strength at the start of the second batch. The damping time provided by the damper greatly varies along the bunch train due to bandwidth limitations and change in ripple amplitude. The main requirements for CNGS arise from the tight aperture and from the request to maintain a stable beam on target. (5) E-cloud Simulation Results (FZ). ------------------------------------ New results for WAMPAC 1&3. WAMPAC1 simulations agree with measurements if the maximum emission yield is about 1.5 for 25 ns spacing and less than 1.75 for 75 ns spacing. For WAMPAC3 and 25 ns spacing agreement is reasonable if the secondary yield is around 1.2-1.3. For 75-ns the measured heat load is higher than simulated. JMJimenez suggested that WAMPAC3 results should be discarded, since the apparatus is not understood. Simulation results for LHC at injection confirm a strong dependence on the number of batches, especially for the lower values of delta_max. (6) AOB ------- Manpower for the BBLR project would be highly welcome, perhaps in the framework of ESGARD or US-LARP? FR suggests that FZ provides a written estimate of the required resources, including project milestones and optional delays in the data analysis in case of reduced resources. Td'Amico will help with some outstanding ZBASE modifications. Enclosed: slides by EB, EV, and FZ.