Thursday Summary of Working Group I Initial questions I: LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 1

Thursday Summary of Working Group I Initial questions II: LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 2

Thursday Summary of Working Group I main points from Pantaleo Raimondi’s presentation I: -local chromaticity correction via dispersion inside the triplet magnets and two pairs of sextupoles (one inside at the location of dispersion and one with phase advance of p) can correct chromaticity and geometric aberrations  works well for linear collider final focus (cancellation up to forth order)  Frank Zimmermann showed that the concept can be applied to circular collider LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 3

From ILC to LHC (1) Much smaller chromaticity: Wmax=L*/by*=4/0.0001=40000 for ILC Wmax=L*/b*=50/0.025=2000 for LHC Much larger emittance and sizes 300nm/3nm for ILC 4mm/4mm for LHC Much larger D allowed at the Final Quads: D=0.2m for ILC D>2m for LHC (increase in the size at the Quads negligible) Much smaller energy acceptance De=+-2% for ILC De=+-0.1% for LHC Very weak and long bends needed for ILC to reduce blow-up from SR.

From ILC to LHC (2) Much weaker sexupoles Much easier task overall Much weaker sexupoles Much smaller second order geometric aberrations and spurious higher order residual aberrations. A possible strategy for LHC: Look for a solution that can be implemented (and removed) anytime simply rematching betas and Ds and chromaticity by varying quads and sexupoles (Safest approach)

Thursday Summary of Working Group I main points from Riccardo de Marias’s presentation I: -matched optics solution for dipole first layout for Beam1 and Beam2 with squeeze and tunability study:  18 km b-max requires additional Q’ correction  dispersion of 15 cm from D1/D2 arrangement for free  could be increased for D’ = 0 at the IP  dispersion changes sign left and right from IP  SF: kissing scheme could allow equal signs of D but vertical D is quite small LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 6

Thursday Summary of Working Group I main points from Riccardo de Marias’s presentation II: -optics study relies on Nb3Sn technology:  10 m long dipole magnets with B = 15 T  quadrupole magnets with 260 T/m and 80 mm aperture  11 T coil field  IR layout provides magnetic TAS for “free” LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 7

Thursday Summary of Working Group I main points from Oliver Brüning’s presentation I: -proposal of a low gradient solution that could be realized with NbTi technology  18 km b-max requires additional Q’ correction maximum gradient of 70 T/m allows more than 200mm diameter with a peak coil field of 5.5 T Dispersion inside the triplet could be increased for D’ = 0 at the IP  Layout still requires an improved TAS absorber LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 8

Options for a Quadrupole First Layout Layout and optics derived from Combined function solution: D1/D1  3.7 T Q1  47T/m  d = 212mm Q2  70T/m  d = 143mm Q3  47T/m  d = 212mm Q3b  6T/m aperture estimate assumes a peak coil field of 5 T!  dispersion matched to 1.5m in ‘triplet’ for Q’ correction! LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 9

Options for a Quadrupole First Layout Layout and optics derived from Combined function solution: D1/D1  3.7 T Q1  47T/m  d = 212mm Q2  70T/m  d = 143mm Q3  47T/m  d = 212mm Q3b  6T/m aperture estimate assumes a peak coil field of 5 T!  dispersion matched to 1.5m in ‘triplet’ for Q’ correction! LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 10

Thursday Summary of Working Group I main points from Jean-Pierre Koutchouks’s presentation I: -NbTi technology only adequate for L = 1034 cm-2 sec-1 -true luminosity upgrade requires Nb3Sn or equivalent technology (b10 tolerance and chromatic aberrations) discussion showed that NbTi with low gradient might still be an option if the geometric reduction factor can be maximized lower L* is clearly advantageous LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 11

Thursday Summary of Working Group I main points from Joachim Keil’s presentation I: -b-beat in HERA-e and HERA-p of the order of 40% (peak) measurement via the closed orbit response matric measurement in HERA-e takes 2 to 4 hours rewriting the equations of the coefficients provides linear system of equations that can be solved via SVD alternate fitting for b and f values for BPM and corrector parameters with fixed values converges within less than 100 iterations to self consistent solution  method is limited by BPM and corrector scaling errors LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 12

Thursday Summary of Working Group I Main summary I: -two options for dealing with the increased heat load inside the triplet magnets: 1) construct more robust triplet magnets that can tolerate the increased peak heat load  new magnet technology (will it be ready by 2011?) 2) reduce the peak heat load with an upgrade of the TAS absorber (dipole first layout offers this for “free”) LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 13

Thursday Summary of Working Group I Main summary II: -two options for dealing with the increased heat load inside the triplet magnets: 1) beam beam wire compensation 2) bunch shortening (RF power and IBS?) 3) CRAB cavities 4) D0 installation inside the detector All proposals are independent of IR layout and should be studied with high priority as they offer efficient L increase! LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 14

Thursday Summary of Working Group I Main summary III: how confident are we that Nb3Sn will be a mature technology by the time we want to build the triplet upgrade? -is a peak coil field of 11T really realistic?  proposal to follow at least two design approaches: one based on NbTi technology (> 4th generation!) on base on new magnet technology (1st generation design!) LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 15

Thursday Summary of Working Group I Main summary IV: repository with optics solutions is very desirable! (linked to HHH CARE WWW page?)  we should all use the same input format (MADX) -identified three layout options that should be studied in more detail: 1) dipole first based on Nb3Sn technology with L* = 19m 2) quad first layout based on Nb3Sn technology L* = 19m 3) low gradient quad first layout based on NbTi technology LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 16

Thursday Summary of Working Group I Main summary V: we desperately need to fix L* and required length for TAS upgrade (inflation of solutions)!  this point was already raised at HHH workshop in 2004!  Tanaji promised an answer for the TAS after October US-LARP workshop in Fermilab!  Emmanuel will clarify the L* options with the LHC integration team (we agreed to assume L* = 19m for now as a reasonable estimate)  the goal is to have an update of the 3 proposals by end 2005 LHC LUMI 2005; 3.9.2005; Arcidosso Oliver Brüning 17