From: "Emmanuel Tsesmelis" Date: 28. July 2006 6:09:08 PM GMT+02:00 To: "lhc-upgrade-interface" Subject: Meeting on Machine-Experiment Interface Issues for the LHC Luminosity Upgrade 28 July 2006 Dear Colleagues, Further to the request for a discussion between representatives from the machine and experiments on aspects of possible LHC upgrade scenarios, we would like to propose the meeting to be held on Friday, 1 September 2006 at 14:00 in Conference Room Bldg. 160-1-009 Provisional Agenda: =================== 1) Introduction E. Tsesmelis 2) Overview of LHC Upgrade Scenarios W. Scandale 3) Parameters for an Early Beam Separation Scheme J.-P. Koutchouk 4) Statements from the Experiments 5) A.O.B. The discussion will aid to advance the development of critical issues of the LHC upgrade scenarios in view of reaching concrete conclusions at the upcoming LUMI'06 Workshop (http://care-hhh.web.cern.ch/CARE-HHH/LUMI-06). Particular issues which require input from the experiments at the above-mentioned meeting are the following: ======================================================================== ========================================= (1) DO THE EXPERIMENTS RULE OUT THE "LONG-BUNCH SCENARIO" WITH ABOUT 500 EVENTS PER CROSSING? [see the last column in: http://care-hhh.web.cern.ch/CARE-HHH/LHC%20Upgrade%20Paths/LumiUpgrade-p arameters-and-heat-loads.pdf ] Or are there physics scenarios and detector upgrade options where this scenario could be of interest? Specifically, our baseline scenario for the evolution of beam parameters calls for "shorter bunches" where we increase the number of bunches and go from 25 ns to 12.5 ns (or 10 or 15 ns) bunch spacing. However, according to our simulations this shorter bunch spacing could imply an intolerable heat load from the electron cloud (c.f. the second page of the table in above pdf file). In this regard, the long-bunch scenario represents a valuable back-up option. Namely, if we reduce the number of bunches and increase the charge per bunch, heat load no longer is a problem. In addition the total beam current is reduced, easing collimation and machine protection. On the other hand the number of pile up events increases significantly, namely to about 500 events per crossing, which has to be compared with about 90 events per crossing in the shorter-bunch upgrade. Only the first few years of LHC operation can tell us whether the baseline option is feasible or not. We kindly request your input to understand whether it is worth spending any time on developing a "long-bunch upgrade" or whether the experiments dismiss such scenario ab initio. (2) CAN "SLIM" S.C. MAGNETS BE INSTALLED DEEP INSIDE THE UPGRADED ATLAS AND CMS DETECTORS AND UNDER WHICH BOUNDARY CONDITIONS, SUCH AS ENVELOPE, VOLUME, MATERIAL, OR FRINGE FIELD? Specifically, there are numerous scenarios for the upgrade of the detector regions. Most effective are the schemes where iron-less superconducing dipoles or quadrupoles (D0 or Q0) are installed inside the detectors. We would like to get an answer from the experiments as to whether such options are excluded or feasible, and, in the latter case, which space would be available, and which requirements on magnet material, volume etc. must be met. In the Q0 option, the front-face of the first `slim' quadrupole will be located at 13 m. either side of the IP with a possibility to shift it to 15 m. We note that if the electron cloud is a problem and the scenario with longer bunch spacing is ruled out in view of the increased pile up, the D0 or Q0 options may be our only chance to recover part of the luminosity increase expected from an upgrade. If we can neither increase the pile up events nor install magnets inside the detectors, and if electron cloud heat turns out to be a problem as predicted, it may be difficult to find any alternative and more acceptable approach for boosting the luminosity. ======================================================================== ========================================= For your information and in preparation of the discussion, we would like to point you to a number of recent links and documents: LHC Upgrade Machine-Experiment Interface site http://rhallwil.web.cern.ch/rhallwil/LHC_UPGRADE/ CARE-HHH web site http://care-hhh.web.cern.ch/CARE%2DHHH/ W. Scandale, LHC Luminosity and Energy Upgrades, EPAC'06, Edinburgh, 2006 http://care-hhh.web.cern.ch/CARE%2DHHH/Literature/TUXPA03.pdf E. Laface, R. Ostojic, W. Scandale, D. Tommasini, C. Santoni, Interaction Region with Slim Quadrupoles, EPAC'06, Edinburgh, 2006 http://care-hhh.web.cern.ch/CARE%2DHHH/Literature/WEPCH044.pdf J.-P. Koutchouk, G. Sterbini, An Early Beam Separation Scheme for the LHC, EPAC'06, Edinburgh, 2006 http://care-hhh.web.cern.ch/CARE%2DHHH/Literature/MOPLS011.pdf Proceedings of LHC LUMI 2005 Workshop "Scenarios for the LHC Luminosity Upgrade" http://care-hhh.web.cern.ch/CARE%2DHHH/LUMI-05/Proceedings/proceedings_l umi05.htm Best regards, W. Scandale E. Tsesmelis F. Zimmermann