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MC Lattice Design Status

MC Lattice Design Status. Y. Alexahin, E. Gianfelice-Wendt, A. Netepenko (FNAL APC). Joint MCTF-NFMCC meeting Fermilab, October 16, 2009. Various MC lattice designs studied. 2.  1996 by Carol J., A. Garren  1996 by K.Oide

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MC Lattice Design Status

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  1. MC Lattice Design Status Y. Alexahin, E. Gianfelice-Wendt, A. Netepenko (FNAL APC) Joint MCTF-NFMCC meeting Fermilab, October 16, 2009

  2. Various MC lattice designs studied 2  1996byCarol J., A. Garren  1996 by K.Oide  “Dipole first” (2007) ~ satisfy the requirements  Eliana’s “synthetic” (2009)  Asymmetric dispersion  “Flat top” ________________ 1996 designs (especially by K.Oide) had extremely high sensitivity to field errors MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  3. “Dipole First” IR Design Option - a Quick Fix 3 x y Dx DDx/50 Wx Wy Dipole before the first quad creates larger dispersion in IR -> weaker sextupoles It may also help to protect the detector from backgrounds: decay electrons and Bethe-Heitler muons  Detector backgrounds  Marginal Dynamic Aperture  Sensitivity to beam-beam MC Lattice Update - Y. Alexahin 4th LEMC workshop, Fermilab, June 09, 2009

  4. Eliana’s New Synthetic Design 4  1 IP with  = 1cm  quad first at 6.5m  dipoles fill all available space  no octupoles chromatic correction sextupoles  Good DA but with bad tunes  Momentum compaction  Sensitivity to beam-beam? MC Lattice Update - Y. Alexahin 4th LEMC workshop, Fermilab, June 09, 2009

  5. “Flat top” design (failed attempt) 5 -S1 S1 The idea: bad effects of S1 should be cancelled by -S1 since the betatron phases do not change much: x = d / x ~ 10-2 In reality turned out to be very large (~ 108m-1) Why with Eliana’s design it was small despite large phase advance error x~0.1? The answer: small x =24m ! Moving the sextupole by a few meters to the focal point where x=/2 but x~0.5m improved the DA even more! y x Dx Wy Wx MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  6. New paradigm 6  Chromaticity of the larger -function should be corrected first (before  is allowed to change) – and in one kick to reduce sensitivity to errors!  To avoid spherical aberrations it must be y then small x will kill all detuning coefficients and RDTs (this will not happen if y  x)  Chromaticity of xshould be corrected with a pair of sextupoles separated by -I section to control DDx (smallness of y is welcome but not sufficient)  Placing sextupoles in the focal points of the other -function separated from IP by  = integer reduces sensitivity to the beam-beam interaction. These considerations uniquely determine the IR layout. Eliana came very close to it (feminine intuition!), just minor corrections were needed. Requirements adopted for the new version:  full aperture A = 10sigma_max + 2cm  maximum tip field in quads = 10T (G=200T/m for A=10cm)  bending field 8T in large-aperture open-midplane magnets, 10T in the arcs  IR quad length < 2m (split in parts if necessary!) – no shielding from inside MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  7. “Streamlined” Eliana’s design 7 correctors Dx (m) multipoles for higher order chrom. correction RF quads sextupoles bends y Chrom. Correction Block x Wy Wx MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  8. Arc cell 8 Requirements:  cancel positive contribution to c and dc /dp from IR and CCB (c ~10-3/ IP)  maximum dipole packing factor (to minimize circumference)  does not need to be an achromat – great simplification! Various types of arccells considered: FODO (with reversed bends), KEKB and Carol’s FMCs. A new type of FMC developed: SVC Dx QF1 SDDX SDDX  Dx (and c) is easily controlled by QF1  DDx (and dc /dp ) is controlled by SDDX  Sextupoles are not strong  can be organized in usual interleaved families As it came out from the first attempt, 10 cells are needed per arc  phase advances / cell =7/5, 3/2. I’ve chosen x,y =7/5 With 2 IPs C=2.6km, default tunes 20 For the next iteration we’ll try larger cells (4-6 cells per arc) with x,y =3/2 to reduce the number and strength of quads and sexts DDx/5 SHC SHC x y MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  9. Momentum acceptance 9  Minimum nonlinear detuning at Qx21.5, Qy 20.5  Such tunes are best for orbit stability as well  Octupole and decapole correctors were used to reduce Qy’’ and Qy’’’  No attempt to correct DDx globally (only per arccell)  Certainly we can achieve 1%, but need only 0.3% Qx p Qy c x* y* p p MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  10. Dynamic Aperture (MAD8) 10  CSIy [m]  CSIy [m] beam-beam =0.1/IP 1024 passes (512 turns) no beam-beam, 2048 passes (1024 turns)  CSIx [m]  CSIx [m] DA=  CSI / N= 4.5 for N=25 m  Nonlinear correction has not been done yet (will increase DA)  No synchrotron oscillations  No fringe-fields  No magnet imperfections and misalignments (will decrease DA) MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  11. Basic parameters 11 Eliana’s new “Dipole first” “New-new” Beam energy, GeV 750 750 750 Number of IPs 1 2 2 Circumference, km 3.6 3.1 2.6 *, cm 1 1 1 _max, km 64 32 48 Momentum compaction 7.7e-5 5.5e-5 9.3e-5 Momentum acceptance, % 0.96* 0.63 0.8 Tunes 26.45/24.45 42.1/41.1 21.54/20.54 DA,  for =25m ~7 ~3 ~4.5 ------------------------------------------------------------------------------- *) static acceptance with no RF MC Lattice Update - Y. Alexahin 4th LEMC workshop, Fermilab, June 09, 2009

  12. KEKB arccell (A. Netepenko) 12 Sasha just finished his version of the ring:  cell magnet length=5 m, field=12 T, gaps between them ~ 0.6 m  Just 3 cells/arc  C=2.34km ! c=6.4e-6  Difficulty encountered: independent control of Dx and c. Probably can be solved (there is enough quads)  Additional sextupoles can be installed to control DDx  |Dx|=9m is a bit scary  ax~3cm MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  13. Next steps 13 Ay Qx Qy Ax 2048 turns DA for reference emittance N=10 m (=4.4 for N=25 m) computed with MADX PTC_TRACK Probably the tunes can be lowered to provide room for beam-beam tuneshift MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  14. Summary & Outlook 14  Search for the optimum IR optics finished (Eliana is the winner!)  Tracking studies show that all requirements of the high-emittance option can be satisfied  Luminosity increased by > 10% due to smaller circumference Next steps:  Update IR design in accordance with A.Zlobin and N.Mokhov recommendations concerning realistic magnet design and shielding  Study effects of fringe fields, add nonlinear correctors if necessary  Design orbit correction and tuning circuits  Study effect of misalignments and magnet imperfections  Down-select arc cell configuration MC Lattice Update - Y. Alexahin MCTF-NFMCC meeting, Fermilab, October 16, 2009

  15. IP: marker; DR1: drift, L=6.; QLB1: quadrupole, L=1.5, k1=0.1; ! k1=0.3*G[T/m]/p[GeV/c]=0.1 for G=250T/m in D=7cm aperture (Nb3Sn) DRSH: drift, L=0.3; ! shielding QLB2: quadrupole, L=1.7, k1=0.077; ! k1=0.3*G[T/m]/p[GeV/c]=0.08 for G=200T/m in D=10cm aperture (Nb3Sn) OCT1: octupole, k3l=kO1; DR2: drift, L=0.5; ! shielding & multipole correctors QLB3: quadrupole, L=1.7, k1=-0.052; ! D=15cm aperture (Nb3Sn) DRSH: drift, L=0.3; ! shielding QLB4: quadrupole, L=1.7, k1=-0.052; ! D=15cm aperture (Nb3Sn) OCT2: octupole, k3l=kO2; DR3: drift, L=1.5; ! vertical correctors QLB5: quadrupole, L=1., k1=-0.038; ! D=15cm aperture DRT2: drift, L=0.25; ! technological gap BE1: rbend, L=6, angle=0.0192; !angle= 0.3*L*B[T]/p[GeV/c], B=8T V=15cm aperture (open midplane Nb3Sn) SLB1: sextupole, L=0.5, k2=-0.346; QF4: quadrupole, L=2, k1=0.034;

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