From frankz@mail.cern.ch Fri Mar 15 21:45:37 2002 Status: RO X-Status: Return-Path: Received: via tmail-2000(13) (invoked by user frankz) for frankz; Fri, 15 Mar 2002 21:45:37 +0100 (MET) Return-Path: Received: from smtp3.cern.ch (smtp3.cern.ch [137.138.131.164]) by mail8.cern.ch (8.12.1/8.12.1) with ESMTP id g2FKja0h000067; Fri, 15 Mar 2002 21:45:37 +0100 (MET) Received: from lxplus031.cern.ch (IDENT:root@lxplus031.cern.ch [137.138.161.104]) by smtp3.cern.ch (8.12.1/8.12.1) with ESMTP id g2FKjZ03010049; Fri, 15 Mar 2002 21:45:35 +0100 (MET) Received: from localhost (frankz@localhost) by lxplus031.cern.ch (8.9.3/8.9.3) with SMTP id VAA06888; Fri, 15 Mar 2002 21:45:47 +0100 X-Authentication-Warning: lxplus031.cern.ch: frankz owned process doing -bs Date: Fri, 15 Mar 2002 21:45:47 +0100 (CET) From: Frank Zimmermann X-Sender: frankz@lxplus031.cern.ch To: sl clic studies , francesco.ruggiero@cern.ch, frank.zimmermann@cern.ch, Grahame Blair , helmut.burkhardt@cern.ch, jacques.gareyte@cern.ch, john.jowett@cern.ch, juliette.thomashausen@cern.ch, maxim.korostelev@cern.ch, ralph.assmann@cern.ch, stefano.redaelli@cern.ch, thys.risselada@cern.ch Subject: Summary of FAT/CLIC meeting 15 March Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Minutes of the FAT CLIC meeting on 15.03.2002 Present: R.A., H.B., M.K., S.R., T.R., D.S., F.Z. (1) CLIC Damping Ring Study (Maxim Korostelev) Maxim solved the three coupled differential equations describing the time evolution of the emittance under the influence of synchrotron radiation and intrabeam scattering (Piwinski theory), using mathematica and assuming a smooth approximation for the arcs made from TME cells and for the wiggler sections. He made a grid scan of the final equilibrium emittances as a function of both the horizontal emittance without intrabeam scattering and of the horizontal damping time, and from this he derived the optimum parameters for arcs and wigglers. The low-current normalized emittance for this optimum case would be 465 nm, the horizontal damping time 4.2 ms; the beam energy is 2.424 GeV, the ring circumference 268.8 m. Assuming an emittance coupling ratio of 3.8% he obtained a final horizontal normalized emittance of about 830 nm, and a rather large vertical emittance. The longitudinal emittance value meets the CLIC specification. Maxim showed the time evolution of emittances and IBS growth times during the store, for the same parameters. The final horizontal IBS growth time is about 8 ms. He now plans to create a MAD model corresponding to this parameter set, and then to compute IBS growth rates with MAD. A study of the dynamic aperture and its optimization is also foreseen. (2) Pantaleo's Damping Ring (Maxim Korostelev and Frank Zimmermann) The parameters of Pantaleo's lattice are beam energy = 2.42 GeV, U0=0.57 MeV, Vrf=1 MV, C=180.15 m (this can fit 4-5 trains). The SR damping times are tau_x = 2.3 ms, tau_y = 5.1 ms, tau_z=6.5 ms. The store time would be much longer, about 50 ms. The equilibrium emittances w/o IBS are 0.83 micron (x), 0.008 micron (y, 1% coupling), and sigma_z0=1.8 mm, sigma_delta0 = 1.2e-3. The longitudinal norm. emittance is about 5000 eVm, exactly the CLIC requirement. The IBS (emittance) growth times computed by MAD are tau_x = 0.96 ms, tau_y=200 ms, tau_z=11.5 ms, indicating that the horizontal blow up due to IBS will be quite substantial. (3) 500-GeV Collimation System (Thys Risselada) Thys reported that an attempt to scale the 3-TeV lattice to 500 GeV, increasing the bending angles by a factor of 4 and keeping all lengths constant, was not successful. The chromatic properties of the beam line degraded substantially (in particular the energy dependence of the beta function), exactly the opposite effect of what was expected. On the positive side, it appeared that the unscaled 3-TeV collimation system might still work satisfactorily even at 500 GeV. (4) Muon Studies and Visit of H.-J. Schreiber (Helmut Burkhardt) Heinz-Juergen Schreiber (DESY/Zeuthen) visited CERN for two days at the beginning of the week. He fully supports the GEANT4 programming effort of Helmut and collaborators. Heinz-Juergen and Helmut discussed the EPAC paper on the CLIC muon studies. Concerning GEANT4, the new cross sections derived by the Russian collaborators and implemented by Helmut in the code are still confidential, until the collaborators have published their results. Grahame Blair's program development should also be kept in mind and integrated with the muon simulations. Grahame's programme has the great advantage that it can read optics files produced by MAD. Heinz-Juergen is interested in the energy calibration for linear colliders, and he might attend the Nanobeam 2002 workshop. (4) Comparison of Simulation Codes (Stefano Redaelli, Daniel Schulte) Stefano showed a table comparing the simulation results for a CLIC final focus, as obtained by DIMAD, MAD and Merlin. He considered two different vertical emittances, beams with and without nonzero energy spread, and with synchrotron radiation switched on or off. He used the same initial particle distribution for all tracking programmes. The agreement between the three codes is impressive. Discrepancies are mainly seen if synchrotron radiation is on, and here, the fluctuation for DIMAD seems to be higher than in the other two codes. For off-energy particles (no SR), MAD appears to be more different from DIMAD and Merlin. Stefano is presently trying to also get a result from PTC, with the help of Frank Schmidt. Without SR, PTC gives the same result as the other codes, but there is still a problem running the latest version of PTC including radiation. Ralph pointed out that Grahame's simulations should also be included in the code comparison. Daniel presented results from an independent simulation with PLACET (to which he has recently added bending magnets etc.). His results were in excellent agreement with the other three codes, and extremely close to those of Merlin. He pointed out that the generator of the synchrotron radiation energy spectrum is the same in both Merlin and PLACET. It is a generator written by Helmut Burkhardt. Daniel also mentioned that most of the blow up from the Oide effect arises in the second-to-last quadrupole. (5) AOB A discussion started on our strategy for integrated simulations, the tools to be used, and the interfaces. There was no final conclusion, and this question will be a topic of the next meeting. The Oide effect on the luminosity will be studied by Stefano with help from Ralph. The next chairman will be Ralph Assmann. ************************************************************ Email: Frank.Zimmermann@cern.ch Address: CERN, SL Division, AP Group CH-1211 Geneva 23, Switzerland Telephone: +41 (22) 767 9054 TeleFax: +41 (22) 783 0552