---------------------------------------------------------------- Minutes of the ABP-LCE team meeting of 06.06.03 present: TdA, AK, FR, DS, LV, FZ excused: WH, EM ---------------------------------------------------------------- (1) follow up on action items ----------------------------- ACTION ==> LV will send a (positive) reply concerning IR8 DONE ACTION ==> FR will ask Bruno Spataro to perform MAFIA calculations for the following list of items: - recombination chambers at IR2 - tanks for the OTR screens and wire scanners - geometric impedance of LHC collimators STILL TO BE DONE ACTION ==> LV will attend the ATLAS workshop at CERN on 2-3 June and contribute in connection with the impedance of Roman pots. DONE. NOTHING SPECIAL TO REPORT. The roman pots are no problem for the beam, but the beam signal will perturb their electronics. ACTION ==> AK will perform new LHC simulations and discuss with FR concerning future developments of his PhD thesis work. AK performs simulatons for resistive-wall chamber and 20-m long collimator made from graphite at top energy. He simulates 10, 200 and 2808 equidistant bunches with the nominal total LHC charge. Growth time is 460 turns for 10 bunches and 350 turns for 200 bunches. The last case is still executing. FR recommends to compare the result with the classical formula for the res.-wall growth rate. ACTION ==> AK will compare his results with the classical expectation and further discuss future plans for his PhD work with BZ and FR. (2) Z-base mini-team -------------------- Team consists of TdA, LV and EM. TdA provides informatics support and can help solving problems within a day. LV provides impedance knowledge. EM is presently occupied with PS work. LV reports that in the past D. Brandt entered the information into the data base. Deepa Angal Kalinin's results on HOMs still need to be included. Also the LHC beam screen is an important item, with significant impedance contributions both in the transverse (geometry, r.w.) and in the longitudinal plane (holes). LV points out that FR's knowledge and general strategy needs to be transferred either to EM or another young member of the team, possibly to two. According to D. Brandt, via communicaton by LV, H. Tsutsui had already implemented Zbase interpolation routine during his previous visit. If confirmed, he would not need to look into this during his visit now. H. Tsutsui will arrive at midnight on June 15. There is a new proposal by F. Caspers to use oblique copper strips embedded in carbon to reduce the low-frequency impedance, which H. Tsutsui might look at. ACTION: identify and instruct a 'user' for Z-base (FR) P. Sievers has asked how much Cu coating would be required to substantially reduce the impedance of graphite. LV's spontaneous answer was a couple of microns, but he will confirm this later. FR recalled that this might have been 0.5 mm. ACTION: LV will confirm thickness of Cu coating for effective shielding. (3) e-cloud studies ------------------- The scrubbing run is ongoing. LV reports that it was not possible to inject 6 batches due to heating of the ferrite of the extraction kickers (which do have a cooling system based on ceramic posts). LV is in contact with kicker experts. LV also reminded the team that the impedance of the SPS is increasing this year and also the following years. The latest version of the ECLOUD with corrections by D. Schulte should be posted on the web by the middle of next week. There is an overflow problem with the option inel=2 after 45 bunches (inel=2 represents elastic scattering according to I. Collins and R. Cimino). It would be nice if this problem could be resolved before the next version is released.If not, a warning will be listed in the web instructions. Synchrotron radiation simulations for the LHC experimental long straight sections are underway (FZ and A. Rossi). Results should be ready by the time of the Insertion Region Review, on June 19. The PHOTON code was revived. Earlier, simulations were peformed for LHC cersion 6.2 using MAD8. Switching now to LHC version 6.4 and MADX, several problems were encountered: apertures are included in the database only a few percent of the ~12000 MAD elements. The apertures for other elements, in particular all drifts, must be entered by hand, or assigned in the PHOTON code. Orbit correction in MADX does not finish in the default mode, but using some options of W. Herr's example. However, often twiss and plot commands do no longer execute afterwards. This could be a memory problem in the interactive mode. ACTION: ==> send SR results to A. Rossi before Insertion Region Review (FZ) A. Ferrari sent FLUKA results for charged particles down to 1 keV which emerge from a collimator jaw that is hit by protons with impact parameters between 0 and 200 nm. The corresponding number of electrons in his first estimate is of the order of for 4e11 protons lost per second. We will refine this estimate, and perhaps perform multipacting simulations for different collimation gaps. There is an LHC collimation review at the LTC on June 25. We are asked to send R. Assmann a preliminary assessment. The EGS version from KEK can handle low-energy electrons, and FZ and/or others can use it to compute the secondary electrons much more precisely. This is a longer term project (several months time scale). ACTION: ==> send assessment to R. Assmann before the LTC (FZ and/or DS?) ACTION: ==> update collimator impedance using new baseline by the collimation team and prepare short LTC presentation (LV+FR) FZ showed the result of a simple quantum-mechanical calculation that indicates the reflectivity of low-energetic electrons hitting the chamber wall should be 1, consistent with the measurements by Collins and Cimino. (4) group meeting next week --------------------------- FR has to report about activities of all team members. Everybody is asked to send him a few lines a list of activities, collaborators, and expertise, in particular those outside of the LCE core topics (e.g., CLIC). (5) other business ------------------ FR informed the team that JJ has officially been transferred to the LEI team (K.H. Schindl). The attached pdf file contains: (1) list of ongoing activities by FZ, (2) quantum-mechanical estimate of electron reflectivity at low energy (FZ following Mike Blaskiewicz), (3) fluence spectrum of e-/e+ escaping from collimator jaw from A. Ferrari