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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

IR designs Quadrupoles first – extension of baseline Dipoles first – triplet focusing Dipoles first – doublet focusing Tanaji Sen US-LARP: IR Upgrades

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

Gradients, beta max – quads first optics B’[T/m] Left Right βmax[m] Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 QT11 QT12 QT13 -200 200 82 -67 59 -199 150 -164 184 57 -43 -40 -Q1.L -Q2.L -Q3.L -Q4.L -Q5.L -58 199 -155 166 -193 -56 -55 -QT13.L 4537 9189 9333 9440 3322 1559 984 285 241 291 141 170 176 4545 9205 9350 9424 3327 1561 986 261 270 154 179 174 Tanaji Sen US-LARP: IR Upgrades

Dipole first optics Earlier layout (PAC 03) Present layout D1 dipole Additional TAS absorber in the present layout – per N. Mokhov IP D1a TAS2 D1b TAN Earlier layout (PAC 03) Present layout D1 dipole TAN absorber β* βmax 10m long After D1 0.26 m 23 km D1a 1.5m long, D1b 8.5m long TAS2, after D1a TAN after D1b 0.25 m 27 km Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

Gradients, beta max – dipoles first, triplets Quad B’[T/m] Left Right βmax[m] Coil aperture 2(1.1*9*σ+8.6+4.5+3) mm Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 QT11 QT12 QT13 -200 200 78 -104 80 -146 107 -92 230 170 161 -158 -Q1.L -Q2.L -Q3.L -112 137 -38 172 -196 31 -120 41 -156 -160 18478 26936 27135 8183 3441 2858 2185 953 1418 210 192 185 176 18619 27143 26926 8253 3845 932 3089 460 164 206 167 174 93 106 73 60 56 57 46 49 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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

Gradients, beta max – dipoles first, doublets Quad B’[T/m] Left Right βmax[m] Coil aperture 2(1.1*9*σ+8.6+4.5+3) mm Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 QT11 QT12 QT13 -200 200 46 -50 -155 -31 147 -204 186 -98 -27 92 Q1.L Q2.L Q3.L -Q4.L -Q5.L -Q6.L -Q7.L -147 205 -198 78 -44 -108 24446 4462 3908 1549 1354 443 388 267 199 185 168 176 3909 1547 1367 512 356 257 209 190 170 173 102 62 60 50 49 42 41 Tanaji Sen US-LARP: IR Upgrades

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, Tanaji Sen US-LARP: IR Upgrades

Chromaticity comparison Complete Q’x Insertion Q’y Inner Magnets Quads first Dipoles first – triplets Dipoles first - doublets -48 -99 -105 -96 -121 -44 -82 -103 -112 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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

Energy Deposition Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

Magnets Tanaji Sen US-LARP: IR Upgrades

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

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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. Tanaji Sen US-LARP: IR Upgrades

Beam-beam phenomena Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Emittance growth 50% larger Tanaji Sen US-LARP: IR Upgrades

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). Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

Backup Slides Tanaji Sen US-LARP: IR Upgrades

Doublet optics - dispersion Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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: TQS models: 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 Tanaji Sen US-LARP: IR Upgrades

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 Tanaji Sen US-LARP: IR Upgrades

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

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. Tanaji Sen US-LARP: IR Upgrades