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Status of the Collider Ring Design

Status of the Collider Ring Design. Y. Alexahin (FNAL APC). 3TeV Lattice design Arc Cell with Combined-Function Magnet for 1.5TeV Fringe Field and Multipole Errors in 1.5TeV IR Strong-Strong Beam-Beam Simulations Plans. MAP 2012 Winter Meeting, SLAC, March 4-8 2012.

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Status of the Collider Ring Design

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  1. Status of the Collider Ring Design Y. Alexahin (FNAL APC) • 3TeV Lattice design • Arc Cell with Combined-Function Magnet for 1.5TeV • Fringe Field and Multipole Errors in 1.5TeV IR • Strong-Strong Beam-Beam Simulations • Plans MAP 2012 Winter Meeting, SLAC, March 4-8 2012

  2. 2 *=5mm 3 TeV c.o.m. MC IR Optics (Preliminary!) chromaticity correction sextupoles M1 M2 From Telluride y (m) x (m) 20*Dx (m) s (m) Wx Wy s (m) 10*DDx (m) MC Design Status- Y. Alexahin MC workshop 06/30/2011

  3. 3 *=5mm 3 TeV MC Lattice Performance (w/o Arcs) Large Qx= -1.65105  octupole (and decapole) correctors at M2  DA < 4   compensating octupole at M1  DA > 5   CSIy [m] *(cm) x* From Telluride y* 5 p Qy Qx p  CSIx [m] Fractional parts of the tunes 1024 turns DA Static momentum acceptance 0.5% and Dynamic Aperture ~ 5 seem feasible – the arc sextupoles are too weak to have any effect MC Design Status- Y. Alexahin MC workshop 06/30/2011

  4. 4 3 TeV MC Arc Cell Dx (m) SY SA SY SX SX DDx(m)/2 y (m) x (m) From Telluride  Central quad and sextupole SA control the momentum compaction factor and its derivative (via Dx and DDx) w/o significant effect on chromaticity  Large  -functions ratios at SX and SY sextupole locations simplify chromaticity correction  Phase advance 300/ cell  spherical aberrations cancelled in groups of 6 cells  Large dipole packing factor  small circumference (C~4.5 km with 10T dipole field) MC Design Status- Y. Alexahin MC workshop 06/30/2011

  5. 5 3TeV Lattice Design Issues  Equalize chromatic functions Wx=Wy to increase DA (requires larger y)  Add bending field in quads (wherever possible)  Design IR-to-Arc matching / RF section which: a) allows for * variation in wide range (3mm – 3cm) b) has enough space with low ’s and Dx for RF c) has no long straights w/o bending field to spread ’s d) has a place with high x and low Dx for halo extraction (we can put special insertions in the arcs but this will increase C – higher costs, lower Lumi) Conditions a) and c) are difficult to reconcile: – if x changes at a bend then Dx will change all over the ring. – if we try to adjust the bending angles we will change the orbit. Possible solution: a chicane with variable B-field – no net bending angle, negligible variation in C (hopefully) Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  6. 6 3TeV IR update a(cm) Q8 Q9 B1 Q7 Q4 Q5 Q6 Q3 Q2 5y Q1 5x s(m) • Aperture requirement  >10 max +30 mm as in 1.5 TeV case • The number of different apertures increased to 6 to follow more closely the beam sizes • No horizontal displacement in Q1-Q7 due to large horizontal beam size Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  7. 7 3TeV *=5mm Lattice Design (Intermediate) CCS Arccell Matching Section IR Optics and chromatic functions in IR, horizontal Chromatic Correction Section (CCS), Matching Section and the first arc cell (out of 6 per arc) Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  8. 8 Matching Section Generic Design *=5mm IR & CCS arc chicane *=3mm *=3cm Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  9. 9 Chicane Parameters & Ring Performance B(T) in chicane  The required B-field in chicane is quite low – magnets can be shorter to free space for RF cavities or pulsed halo deflectors.  Chicane length is 84.5m, depth at *=3cm is 19.6cm – small effect on the total circumference  The quad strength is high (up to 300T/m for *=3mm) – can be reduced by horizontal phase advance redistribution between the matching section and the arc – no big effect on DA is expected.  With such redistribution the required B-field in chicane gets higher – optimization needed  After quick (and sloppy) chromatic correction the momentum acceptance is 0.45% for *=5mm and 0.4% for *=3mm.  The on-momentum dynamic aperture is O.K. *(cm)  CSIy [m] 5.5  CSIx [m] 1024 turns DA for *=5mm (MAD8 LIE4) Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  10. 10 1.5 and 3TeV Design Parameters s (TeV) 1.5 3 * (cm) (bare lattice) 1 (0.5-2) 0.5 (0.3-3) _max (km) 48 118 Av. Luminosity / IP (1034/cm2/s) 1.25 4.4 Max. bending field (T) 10 10 Av. bending field in arcs (T) 8.3 8.4 Circumference (km) 2.5 (2.7) 4.45 No. of IPs 2 2 Repetition Rate (Hz) 15 12 Beam-beam parameter / IP 0.087 0.087 Beam size @ IP (m) 6 3 Bunch length (cm) 1 0.5 No. bunches / beam 1 1 No. muons/bunch (1012) 2 2 Norm. Trans. Emit. (m) 25 25 Energy spread (%) 0.1 0.1 Norm. long. Emit. (m) 0.07 0.07 Total RF voltage (MV) at 800MHz 20 250 Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  11. 11 1.5TeV Arc Cell with Combined Function Magnets Motivation:  spread neutrino radiation from decays in quads (a must for 3TeV and higher)  contain decay electrons close to midplane (may be open midplane magnets can work?) Cell length is ~ 10% smaller. Combined-function magnet parameters (2nd iteration) name L(m) B(T) G(T/m) "QDA1" 3. 9. -33.1616 "QFA2" 3.7 8. 79.3608 "QDA3" 5. 9. -42.5 "QDA3" 5. 9. -42.5 "QFA4" 3.7 8. 71.3405 Pure dipoles (orange) are 10T Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  12. 12 Fringe Fields in 1.5TeV IR magnets (V.Kapin) Dynamic Aperture in the plane of initial coordinates at IP for p/p=0 (MADX) DA area as function of p/p  Effect of quad FF on DA is significant, but not disastrous – should be easily correctable  Effect of dipole FF is negligible  Good agreement between maps from COSY (with dipole FF included) and MADX PTC (allegedly w/o dipole FF) Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  13. 13 Rref=40mm b1=10000 b3=-5.875 b5=-18.320 b7=-17.105 IR Open-Midplane Dipole Nonlinearities (V.Kapin) IR dipole coil cross-section and good field region (Vadim Kashikhin) Calculated multipole components in the magnet body Effect of multipole components on DA in 1.5TeV case: decapole is most detrimental Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  14. 14 IR Open-Midplane Dipole Nonlinearities (cont’d) Correction of the vertical nonlinear chromaticity does not help Decapole effect on off-momentum DA  The exact mechanism of the off-momentum DA reduction is not determined yet  The observed strong effect of the decapole error is an argument against open-midplane design  If an open-midplane design will be eventually chosen (for IR dipoles), some space should be reserved for multipole correctors. Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  15. 15 Strong-Strong BB Simulations (K.Ohmi) Very low synchrotron tune (0.0006 for 1.5TeV)  single bunch breakup instability. Will the beam-beam tunespread help? Kazuhito performed simulations with narrow-band impedance (while I asked him for a wide-band) Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  16. 16 Strong-Strong BB Simulations (K.Ohmi) No hint of instability with beam-beam on. Should repeat the simulations with a wide-band impedance Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

  17. 17 Plans • Lattice design: - complete 1.5TeV design with new tuning & collimation sections - finish the 3TeV design • Fringe fields & Multipoles: - include realistic long. profile (Enge function) in MAD-X (F.Schmidt, CERN) or borrow from COSY-Infinity (V.Kapin) - nonlinear corrector arrangement for fringe field and multipole error correction (V.Kapin, F.Schmidt) • Strong-Strong Beam-Beam Simulations: - K.Ohmi (KEK) will come at Fermilab in October - A.Valishev and E.Stern (FNAL) also promised to look • Self-Consistent Longitudinal Dynamics: - V.Balbekov & L.Vorobiev (FNAL GS) can address it (using ORBIT?) + From Telluride + + – MC Design Status- Y. Alexahin MC workshop 06/30/2011

  18. 18 Summary & Outlook  3TeV IR optics upgraded to equalize chromatic perturbations in horizontal and vertical planes resulting in a larger dynamic aperture  A promising general solution for IR-to-Arc matching section is found which allows for * variation in wide range (3mm-3cm) with minor effect on dispersion and the orbit.  On its basis particular designs with RF or halo extraction will be developed  1.5TeV arc cell designed basing on combined-function magnets. Waiting for MARS simulation results to start work on 3TeV design.  A strong effect of the decapole error in open-midplane IR dipoles on the off-momentum dynamic aperture is observed making the open-midplane design less attractive  Strong-strong beam-beam simulations were performed which show that the beam-beam tunespread suppresses impedance-driven single bunch breakup instability. Collider Ring Design – Y.Alexahin, MAP Collaboration Meeting, SLAC, March 5, 2012

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