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US-LARP Progress on IR Upgrades

US-LARP Progress on IR Upgrades. Tanaji Sen FNAL. Topics. IR optics designs Energy deposition calculations Magnet designs Beam-beam experiment at RHIC Strong-strong beam-beam simulations Future plans. US-LARP effort on IR designs.

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US-LARP Progress on IR Upgrades

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  1. US-LARP Progress on IR Upgrades Tanaji Sen FNAL

  2. Topics • IR optics designs • Energy deposition calculations • Magnet designs • Beam-beam experiment at RHIC • Strong-strong beam-beam simulations • Future plans US-LARP: IR Upgrades

  3. US-LARP effort on IR designs • Main motivation is to provide guidance for magnet designers • Example: aperture and gradient are no longer determined by beam optics alone. Energy deposition in the IR magnets is a key component in determining these parameters • Use as an example for field quality requirements • Examine alternative scenarios • Not intended to propose optimized optics designs US-LARP: IR Upgrades

  4. IR designs • Quadrupoles first – extension of baseline • Dipoles first – triplet focusing • Dipoles first – doublet focusing US-LARP: IR Upgrades

  5. Triplet first optics Lattice Vers. 6.2 Nominal β* = 0.5 β* = 0.25 J. Johnstone US-LARP: IR Upgrades

  6. Gradients, beta max – quads first optics US-LARP: IR Upgrades

  7. Dipole first optics Additional TAS absorber in the present layout – per N. Mokhov IP D1a TAS2 D1b TAN US-LARP: IR Upgrades

  8. Dipoles First - Matching • Beams in separate focusing channels • Matching done from QT13(left) to QT13(right) • Lattice Version 6.2 • Triplet quads Q1 – Q3 at fixed gradient = 200 T/m, exactly anti-symmetric • Positions and lengths of magnets Q4-QT13 kept the same • Strengths of quads Q4 to Q9 < 200 T/m Q10 on the left has 230 T/m. Could be changed if positions and lengths of Q4-Q7 are changed. • Trim quad strengths QT11 to QT13 < 160T/m US-LARP: IR Upgrades

  9. Dipole first – collision optics, triplets • TAS1 absorber (1.8m) before D1a • Dipole D1a starts 23 m from IP • TAS2 absorber (1.5m) after D1a • 0.5m space between D1a-TAS2 and TAS2-D1b • L(D1b) = 8.5m • D1, D2 – each 10m long, ~14T • 5m long space after D2 for a TAN absorber • Q1 starts 55.5 m from the IP • L(Q1) = L(Q3) = 4.99 m, • L(Q2a) = L(Q2b) = 4.61m Collision optics β*= 0.25m US-LARP: IR Upgrades

  10. Gradients, beta max – dipoles first, triplets US-LARP: IR Upgrades

  11. Dipoles first and doublet focusing • Features • Requires beams to be in • separate focusing channels • Fewer magnets • Beams are not round at the IP • Polarity of Q1 determined by • crossing plane – larger beam • size in the crossing plane to • increase overlap • Opposite polarity focusing at other • IR to equalize beam-beam tune shifts • Significant changes to outer triplet • magnets in matching section. Q1 D2 Q2 IP D1 D2 Focusing symmetric about IP US-LARP: IR Upgrades

  12. Doublet Optics – Beta functions J. Johnstone US-LARP: IR Upgrades

  13. Gradients, beta max – dipoles first, doublets US-LARP: IR Upgrades

  14. Features of this doublet optics • Symmetric about IP from Q1 to Q3, anti-symmetric from Q4 onwards • Q1, Q2 are identical quads, Q1T is a trim quad (125 T/m). L(Q1) = L(Q2) = 6.6 m • Q3 to Q6 are at positions different from baseline optics • All gradients under 205 T/m • Phase advance preserved from injection to collision • At collision, β*x= 0.462m, β*y = 0.135m, β*eff= 0.25m • Same separation in units of beam size with a smaller crossing angle ΦE = √(β*R/ β*E) ΦR = 0.74 ΦR • Luminosity gain compared to round beam Including the hourglass factor, US-LARP: IR Upgrades

  15. Chromaticity comparison Including IR1 and IR5 • Chromaticity of dipoles first with triplets is 99 units larger per plane than quads first • Chromaticity of dipoles first with doublets is 31 units larger per plane than dipoles first with triplets US-LARP: IR Upgrades

  16. Chromaticity contributions • Inner triplet and inner doublet dominate the chromaticity • Anti-symmetric optics: upstream and downstream quads have opposite chromaticities • Symmetric optics: upstream and downstream quads have the same sign of chromaticities US-LARP: IR Upgrades

  17. Energy Deposition US-LARP: IR Upgrades

  18. Energy Deposition Issues • Quench stability: Peak power density • Dynamic heat loads: Power dissipation and cryogenic implications • Residual dose rates: hands on maintenance • Components lifetime: peak radiation dose and lifetime limits for various materials US-LARP: IR Upgrades

  19. Energy Deposition in Quads First • Energy deposition and radiation are major issues for new IRs. • In quad-first IR, Edep increases with L and decreases with quad aperture. • Emax > 4 mW/g, (P/L)max > 120 W/m, Ptriplet >1.6 kW at L = 1035 cm-2 s-1. • Radiation lifetime for G11CR < 6 months at hottest spots. More radiation hard material required. N, Mokhov A. Zlobin et al, EPAC 2002 US-LARP: IR Upgrades

  20. Energy deposition in dipoles Problem is even more severe for dipole-first IR. Cosine theta dipole On-axis field sprays particles horizontally power deposition is concentrated in the mid-plane L = 1035 cm-2 s-1 Emax on mid-plane (Cu spacers) ~ 50 mW/g; Emax in coils ~ 13 mW/g Quench limit ~ 1.6 mW/g Power deposited ~3.5 kW Power deposition at the non-IP end of D1 N. Mokhov et al, PAC 2003 US-LARP: IR Upgrades

  21. Open mid-plane dipole R. Gupta et al, PAC 2005 Open mid-plane => showers originate outside the coils; peak power density in coils is reasonable. Tungsten rods at LN temperature absorb significant radiation. • Magnet design challenges addressed • Good field quality • Minimizing peak field in coils • Dealing with large Lorentz forces w/o a • structure between coils • Minimizing heat deposition • Designing a support structure US-LARP: IR Upgrades

  22. Energy deposition in open mid-plane dipole TAS TAS2 TAN • Optimized dipole with TAS2 • IP end of D1 is well protected by TAS. • Non-IP end of D1 needs protection. Magnetized TAS is not useful. Estimated field 20 T-m • Instead split D1 into D1A and D1B. Spray from D1A is absorbed by additional absorber TAS2 • Results (N. Mokhov) • Peak power density in SC coils ~0.4mW/g, well below the quench limit • Dynamic heat load to D1 is drastically reduced. • Estimated lifetime based on displacements per atom is ~10 years US-LARP: IR Upgrades

  23. Magnets US-LARP: IR Upgrades

  24. Nb3Sn at 1.8K Nb3Sn at 4.35K NbTi at 1.8K NbTi at 4.35K Gradient vs Bore size Current LHC mm US-LARP: IR Upgrades

  25. Magnet Program Goals • Provide options for future upgrades of the LHC Interaction Regions • Demonstrate by 2009 that Nb3Sn magnets are a viable choice for an LHC IR upgrade (Developed in consultation with CERN and LAPAC) • Focus on major issues: consistency, bore/gradient (field) and length 1. Capability to deliver predictable, reproducible performance: TQ (Technology Quads): D = 90 mm, L = 1 m, Gnom > 200 T/m 2. Capability to scale-up the magnet length: LQ (Long Quads) : D = 90 mm, L = 4 m, Gnom > 200 T/m 3. Capability to reach high gradients in large apertures: HQ (High Gradient Quads): D = 90 mm, L = 1 m, Gnom > 250 T/m 1. • Supporting R&D • Sub-scale dipoles & quads with L=0.3 m, Bcoil = 11-12 T • issues relevant to the whole program(end-preload, training, quench protection, alignment of support structures) • Long coil fabrication and tests with L=4 m, Bcoil = 11-12 T • Radiation hard insulation US-LARP: IR Upgrades

  26. Short Quad Models: FY08-FY09 Goal: increase Quad gradient using 3-layer and/or 4-layer coils Engineering design starts in FY06 and fabrication in FY07 3-layer: G=260-290 T/m 4-layer: G=280-310 T/m US-LARP: IR Upgrades

  27. Magnet R&D challenges • All designs put a premium on achieving very high field: • Maximizes quadrupole aperture for a given gradient. • Separates the beams quickly in the dipole first IR => bring quads as close as possible to the IP. • Push Bop from 8 T -> 13~15 T in dipoles or at pole of quad => Nb3Sn. • All designs put a premium on large apertures: • Decreasing * increases max => quad aperture up to 110 mm? • Large beam offset at non-IP end of first dipole.=> Dipole horizontal aperture >130 mm. • Energy deposition: quench stability, cooling, radiation hard materials. • Nb3Sn is favored for maximum field and temperature • margin, but considerable R&D is required to master this • technology. US-LARP: IR Upgrades

  28. Beam-beam phenomena US-LARP: IR Upgrades

  29. RHIC Beam-beam experiment Question: Do parasitic interactions in RHIC have an impact on the beam ? Experiment – April 2005 Change the vertical separation between the beams at 1 parasitic interaction Observe beam losses, lifetimes, tunes vs separation Beam Conditions • 1 bunch of protons in each ring • Injection Energy 24,3 GeV • Bunch intensities ~ 2 x 1011 • 1 parasitic interaction per bunch Bunches separated by ~10σ at opposite parasitic US-LARP: IR Upgrades

  30. RHIC beam-beam experiment W. Fischer et al (BNL) • Observations • !st set of studies: tunes of blue and yellow beam were asymmetric about diagonal • Blue beam losses increased as separation decreased. No influence on yellow beam. • Next set of studies: tunes symmetric about diagonal • Onset of significant losses in both beams for separations below 7σ • There is something to compensate • Phenomena is tune dependent • Remote participation at FNAL Orbit data – time stamp corresponds to time of measurement, Not to time of orbit change Shift orbit data to the right US-LARP: IR Upgrades

  31. RHIC – Wire compensator New LARP Task for FY06 • RHIC provides unique environment • to study experimentally long-range • beam-beam effects akin to LHC • Proposal: Install wire compensator • In summer of 2006, downstream of • Q3 in IR6 • Proposed Task • Design and construct a wire compensator • Install wire compensator on movable stand in a ring • First study with 1 proton bunch in each ring with 1 parasitic at flat top. Compensate losses for each separation with wire • Test robustness of compensation w.r.t current ripple, non-round beams, alignment errors, … Possible location of wire IP6 Parasitic interaction Phase advance from parasitic to wire = 6o US-LARP: IR Upgrades

  32. Strong-strong beam-beam simulations J. Qiang, LBL • Strong-strong simulations done with PIC style code Beambeam3D (LBNL) • Emphasis on emittance growth due to head-on interactions under different situations • Beam offset at IP • Mismatched emittances and intensities • Numerical noise is an issue – growth rate depends on number of macro-particles M. Continuing studies to extract asymptotic (in M) growth rates. • Continuing additions to code: crossing angles, long-range interactions Nominal case Beams offset by 0.15 sigma Emittancegrowth 50% larger US-LARP: IR Upgrades

  33. IR and Beam-beam tasks – FY06-07 • IR design Quad first – lowest feasible * consistent with gradients and apertures, field quality Dipoles first – Triplet: *, apertures, gradients, field quality Dipoles first – Doublet: explore feasibility • Beam-beam compensation Phase 2: Build wire compensator, machine studies in RHIC and weak-strong simulations with BBSIM • Strong-strong beam-beam simulations: emittance growth with swept beams (luminosity monitor), wire compensation, and halo formation (Beambeam3D) • Energy Deposition IR designs (quadrupole and dipole first), tertiary collimators, and the forward detector regions (CMS, TOTEM, FP420 and ZDC). US-LARP: IR Upgrades

  34. Issues • IR design issues - What are the space constraints from Q4 to Q7? - By how much can L* be reduced, if at all? - Solutions need to be updated for Lattice Version 6.5. MAD8 version of the lattice would be helpful. • Beam-beam experiment at RHIC - How can the RHIC experiments be more useful to the LHC? Is a pulsed wire necessary in the LHC? • Crab cavities - How much space will be needed? - Cornell has expertise and interest in designing these cavities • Energy Deposition - Progress on quadrupole design which can absorb heat load at 10 times higher luminosity US-LARP: IR Upgrades

  35. IR Workshop at FNAL • October 3-4. 2005 at FNAL • Topics - IR designs for the upgrades - Energy deposition, quench levels, TAN/TAS integration - Magnet designs for the IR magnets - Beam-beam compensation: wires, e-lens - Feasibility of large x-angles and crab cavities in hadron colliders US-LARP: IR Upgrades

  36. Backup Slides US-LARP: IR Upgrades

  37. Doublet optics - dispersion US-LARP: IR Upgrades

  38. Design Studies A. Zlobin • IR Magnets • Magnetic design and analysis • Mechanical design and analysis • Thermal analysis • Quench protection analysis • Test data analysis • Integrate with AP and LARP magnet tasks • Cryogenics • IR cryogenics and heat transfer studies • Radiation heat deposition • Cryostat quench protection US-LARP: IR Upgrades

  39. Model Magnet R&D G.L. Sabbi • Main program focus (Technology Quadrupoles) • 2-Layer quads, 90 mm aperture, G > 200 T/m ASAP • Considerations • Design approach – end loading options, preload • Fabrication techniques • Structure options – TQS, TQC Opportunity to arrive at best-of-the-best and increase confidence in modeling Convergence through working groups and internal reviews US-LARP: IR Upgrades

  40. Technology Quads: Features and Goals • Objective: develop the technology base for LQ and HQ: • evaluate conductor and cable performance: stability, stress limits • develop and select coil fabrication procedures • select the mechanical design concept and support structure • demonstrate predictable and reproducible performance • Implementation: two series, same coil design, different structures: • TQSmodels: shell-based structure • TQC models: collar-based structure • Magnet parameters: • 1 m length, 90 mm aperture, 11-13 T coil peak field • Nominal gradient 200 T/m; maximum gradient 215-265 T/m US-LARP: IR Upgrades

  41. FY08-09: Long Quads (LQ) • R&D issues: • long cable fabrication and insulation • stress control during coil reaction, cable treatment, pole design • coil impregnation procedure, handling of reacted coils • support structures, assembly issues • reliability of design and fabrication Plan: scale-up the TQ design to 4 meter length (LQ) • FY06: fundamental scale-up issues addressed by Supporting R&D: • general infrastructure and tooling • long racetrack coil fabrication and test • scale-up and alignment issues for shell-based structure US-LARP: IR Upgrades

  42. Block-type IRQ coils and mechanical structure (FNAL) US-LARP: IR Upgrades

  43. Larger-aperture separation dipole (LBNL) Shell-type coil design Block-type coil design ~200 mm horizontal aperture thick internal absorber Bmax=15-16 T, good field quality 1.5-2 m iron OD Current Status: Several IR quad designs were generated and compared with 90 mm shell-type quads including magnetic and mechanical parameters. US-LARP: IR Upgrades

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