----------------------------------------------------------- Minutes of the ABP-RLC team meeting of 27.05.2005 present: UD, AG, WH, EM, FR, DS, FZ web site: http://ab-abp-rlc.web.cern.ch/ab-abp-rlc/ ------------------------------------------------------------ (1) Minutes of last meeting, pending actions, announcements ----------------------------------------------------------- FR informed the team of a new CERN-GSI bilateral agreement, which includes the collaborations on space-charge experiments in the PS and on emittance growth due to electron cloud (with Giuliano Franchetti). This agreement comes in addition to GSI participation in CARE-HHH. FR announced that there will be a general ABP group meeting on June 29. FR reported that the team should create a risk list for the DG, listing consequences and mitigation measures. It was felt that risk could include electron cloud and beam-beam effects, and mitigations more staff and more computing power. There are several types of risk, e.g., that our predictions have an error, or that specifications are not followed, or that required parameters are not reached. FR recommended the creation of an RLC pending action web site. FZ created such a web site after the meeting: http://ab-abp-rlc.web.cern.ch/ab-abp-rlc/Actions/actions.htm Follow-up on actions from last meeting: => ACTION => compare the size of the longitudinal geometric wake with RW longitudinal wake from A. Koschik (FR) STATUS: PENDING, FR will talk to A. Koschik => ACTION => attempt to derive a general nonlinear theory including the inductive bypass (EM) STATUS: PLANNED => ACTION (EM+FZ): compare and understand the different predictions of the Burov-Lebedev theory calculated by FZ and EM. STATUS: ONGOING A comparison is being carried out for a typical example parameter set. A difference by a about a factor 1.8 was found between EM's tune shift and FZ's tune shift calculated from the Burov-Lebedev theory. FZ's calculation based on the Piwinski wake field approaches the value of Elias, for a ten times smaller emittance. A direct comparison of the impedance values for the first two theories was suggested by AG. (2) Impedance Studies (FR) ------------------------- FR reported a revision of the impedance for the ALICE RB26 vacuum chambers, which encountered difficulties applying Ni coating on stainless steel. The Ni is required as a substrate for the Cu coating. At the moment Au is being investigated as a possible substrate instead of Ni. ALICE may drop the Cu coating, if no technological solution is found. The object in question has a length of 6 m. FR expressed concern that our specifications are so readily abandoned. On Monday a meeting was held on trapped modes in the injection region. FR and AG participated. J. Koopman sent information, drawings etc. on the LHC wire scanners to FR, including the position of ferrites. Follow-up is required. BDI has also sent a drawing of a fast current transformer BCT for LHC. The impedance needs to be estimated and included into the database. Volunteers were looked for, (3) IBS studies (FZ) -------------------- FZ was asked by FS to review the IBS implementation in MAD-X and possible generalization to non-ultrarelativistic energies, triggered by an observation that the MAD predictions do not agree with the observations in the CERN low-energy machines. FZ discussed with Michel Martini, who confirmed that J.-Y. Hemery found large differences between the three codes MAD-8, MAD-X and BeamOptics, and that MADX did not reproduce experimental results. He suggested to replace the Bjorken-Mtingwa expression in MADX by the non-relativistic Conte-Martini solution, which is also implemented in BeamOptics. FZ re-derived the expression for the IBS growth rate starting from the initial general formula of Bjorken and Mtingwa, and extending it to the case of non-zero vertical dispersion, which is of great importance for the CLIC damping ring, and may be relevant also for the LHC. In the limit of zero vertical dispersion FZ's results should reduce to those of Conte-Martini, which they do in the longitudinal and vertical planes. In the horizontal plane, FZ solutions and C-M's differ by two additional terms in the CM expression. An inspection of MAD-X yielded the surprising result that the C-M expressions are already those used in MAD-X. So the IBS formulae in MAD-X should be exactly the same as those in BeamOptics, and the reported different predictions from these two codes cannot be explained by the neglect of non-relativistic terms in MAD-X. Dropping the two unconfirmed terms from the CM solution in MAD-X only marginally changes the horizontal growth rate at injection into the LHC. Reducing the beam energy in the MAD input to 5 GeV/c the effect is still less than 1%. FZ plans to implement the revised formula, including vertical dispersion, in MAD-X when he finds some spare time. FR recommended a benchmarking of the MAD-X IBS predictions against results from the Tevatron or RHIC, and a follow-up of the differences noticed by J.-Y.H. FZ pointed out that other theories of IBS exist, such as those by Piwinski, Piwinski-Martini, and Kubo-Oide, and which, in principle, could also be included in MAD-X. FZ discussed IBS calculations with Alexander Smirnov, who is presently visiting CERN, and whose program BETACOOL includes a suite of about 7 alternative IBS calculations. EM pointed out that Anton Piwinski gave an overview of IBS calculations in his PAC05 Prize Talk. (4) Highlights from PAC05 (EM, DS) ----------------------------------- DS reported on ILC presentations at PAC05. The new GDE director Barry Barish described the organization. There will be 1 regional director for each of the three regions, and in addition also 1 civil engineer per region. Susanna Guiducci described the status of the damping ring design, Andre Seryi that of the beam delivery system, and Hitoshi Hayano the main linacs. The beam delivery system is in an excellent shape. Also Susanna's talk well captured the damping ring situation. In the linac presentation some decisions were taken based on KEK simulations, about which the other regions apparently had not been informed. Still some better coordination may need to be done. Carlo Rubbia mentioned in his talk that at LHC a light Higgs may not be found, if supersymmetry does not exist. DS discussed parallel tracking with Andreas Adelmann. EM showed a number of slides (posted on the web), describing the winners of the various accelerator prizes and their achievements, a session on Einstein's legacy, as well as discussions of PS benchmarking for the Montague resonance with Ingo Hofmann (octupoles off, on, and faster dynamic crossing). The effect of the Montague resonance depends on the detuning with amplitude. FR expressed some bewilderment that no zeroth order optics model of the PS exists, which would include the detuning with amplitude, and that as a result we do not yet have any reliable simulation. EM recalled that an optics-model prediction has very recently become available (as reported by M. Martini in the APC), and EB could now do a simulation for this value of detuning with amplitude. FZ suggested to also measure the value of this detuning in an experiment as verification. FR pointed out that space charge could limit the performance of a Super-ISR. EM further reported on a PAC05 talk by Mike Blaskiewicz, who drew the positive conclusion that stochastic cooling is feasible for RHIC ion beams. A new facility, RIA, makes use of a s.c. proton linac, and will cost about 1000 M$. It will enter the femtosecond time scale of rare isotopes. Some further information on RIA was asked for by RLC team members. After the meeting, John Jowett added the following information: The Rare Isotope Accelerator (RIA) proposal has been around for several years. You can find out more at http://www.sc.doe.gov/production/henp/np/projects/RIA.html and in the NSAC Long Range Plan at http://www.sc.doe.gov/production/henp/np/nsac/nsac.html (5) Reports from Other Meetings and AOB --------------------------------------- FZ mentioned a presentation on COLDEX results by Vincent Baglin at the APC, where no reduction in heat load was observed though the measured electron current at the wall decreased. This is attributed to the change in the electron energy spectrum during the processing. FZ expressed concern that this does not appear fully consistent with typical ECLOUD results where a decrease in delta_max always reduces both the electron flux and the heat load. FR reported that Hans Braun has revised work packages for CLIC. A staff is still missing for work on damping ring, rf power source, and CTF-3 commissioning. FR reminded the team that there will be a selection board next week Wednesday. Tours of the PS complex by EM and of CTF-3 by RC are planned. If RLC staff happens to meet one or several candidates, friendly discussions are highly encouraged. Posted on the web: Slides by EM, FZ Web site: http://ab-abp-rlc.web.cern.ch/ab-abp-rlc/