CERN-CARE Workshop HHH2004, 8 November 2004 Technological Challenges for the LHC Upgrade W. Scandale CERN Accelerator Technology Department Thanks to the valuable contributions of D. Tommasini

Walter Scandale - 8 November HHH2004 workshop2 Present context A road map for the upgrade of the LHC luminosity Technological challenges High-field superconducting magnets for the LHC-IR Medium-field fast-cycling superconducting magnets for the LHC-injector complex SPL and RCS Conclusive remarks Outlook

Walter Scandale - 8 November HHH2004 workshop3 LHC in operation within about 30 months GSI program based on SIS100 and SIS300 approved EU-CARE activities settled HHH-network investigating Possible scenarios for LHC upgrade New concepts for Interaction Regions design Possible use of high-field and for medium-field fast-pulsed magnets NED-Joint Research Activity (NED-JRA) launching R&D for high-field Nb 3 Sn superconducting wire New concepts for the design of high-field superconducting IR magnets HIPPI-Joint Research Activity (HIPPI-JRA) launching R&D for high-intensity pulsed linear accelerators Optimization of up to 200 MeV Linac Beam dynamics and RF component design for Linac up to the GeV energy Potential interest of CEA-Saclay, CERN, GSI and INFN to strengthen the SC magnet R&D program US-LARP very active on high-field Nb 3 Sn superconducting quadrupoles (about 2 M$/year from DOE) Present Context

Walter Scandale - 8 November HHH2004 workshop4 A Road Map for the LHC Upgrade Baseline hardware: ultimate performance -> L max ~ 2.3x10 34 /cm 2 s -1 Ultimate bunch intensity -> I b = protons per bunch Requires RF batch compression in the PS or Linac4 Two collision points (instead of four) with = 315 rad (instead of 300) Luminosity increase by reducing * -> L max ~ 4.6x10 34 /cm 2 s -1 IR quadrupole upgrade (higher aperture - higher pole field) -> *=0.25 m larger crossing angle -> = 445 rad (Crab crossing RF-cavities?) Beam density increase and LHC turn-around upgrade RF upgrade for bunch compression in the LHC Super-PS and super-SPS injecting at 1TeV (first step for future LHC energy upgrade) Beam energy increase Higher field dipoles (14 T) and higher gradient quadrupoles (500 T/m) Mass production of a new superconductor (most likely Nb 3 Sn) See LHC Project Report 626

Walter Scandale - 8 November HHH2004 workshop5 A Time-Window for LHC-IR Upgrade Due to the high radiation doses to which they will be submitted, the life expectancy of LHC IR quadrupole magnets is estimated ~5-7 years IR-quadrupoles will have to be replaced in , thereby offering an opportunity of upgrading LHC IR optics to improve luminosity Mid-2010s is also the earliest time frame when one can expect to need final-focusing quadrupole magnets for any of the proposed projects of linear colliders. At least one needs very strong wide final triplets Radiation damage limit ~700 fb -1 Courtesy of F. Ruggiero and Jim Strait

Walter Scandale - 8 November HHH2004 workshop6 IR based on High Fields Magnets with reduced * New Interaction Regions: beam dynamics versus magnet technology and design See PAC03 pp blue DIPOLES red QUADRUPOLES green RF-CAVITIES

Walter Scandale - 8 November HHH2004 workshop7 R&D needed for High Field Magnets SC Cable High performance SC cable aiming at a non-Cu J C up to 1500 A/mm T at a temperature of 4.2 K or 1.9 K Insertion and magnet design Simultaneous optimization of optics and magnet design 15 T dipoles and 12 T mm quadrupoles of accelerator type (reasonable quench margin and good field region, easy to build) Particle loss hardness Upgrade of the Heat Transfer in SC cables; Comparative study among 4.2 K and 1.9 K solutions (imposing the constraint of the LHC cryogenic plant) Upgrade simultaneously radiation hardness (cable insulators and coil design) and local collimator layout

Walter Scandale - 8 November HHH2004 workshop8 SC conductor for High Field Magnets High Temperature Superconductors (HTS) are not yet ready for large-scale applications requiring high current densities under high magnetic fields. It will take at least another decade before they become competitive in terms of performances, yield and cost The upper critical field of MgB 2 is too low Nb 3 Al exhibits promising properties but there are serious manufacturing issues that have yet to be resolved At present, the only serious candidate to succeed NbTi, suitable for industrial production, is the intermetallic compound Nb 3 Sn (world production still rather low: ~15 t/year). R&D on Nb 3 Sn conductor started in the frame of CARE-NED See CARE-HHH-AMT workshop WAMS March 2004 Archamps

Walter Scandale - 8 November HHH2004 workshop9 High Field Magnets: recent results A series of record-breaking dipole magnet models, opening the 10-to-15 T field range (however, not yet of accelerator class) 11 T on first quench at 4.4 K in a 50-mm-bore (Twente University, 1995) 13.5 T at 1.8 K in a 50-mm bore (LBNL, 1997) 14.7 T at 4.2 K in a 25-mm gap (LBNL, 2001) MSUT (cos ) D20 (cos ) RD-3 (Racetrack)

Walter Scandale - 8 November HHH2004 workshop10 The poor man way: LHC-IR upgrade with new NbTi quadrupoles -> *=0.25 m The quadrupole aperture is matched to the real beam size Comparison between NbTi, NbTiTa and Nb 3 Sn conductors See EPAC 04 pp

Walter Scandale - 8 November HHH2004 workshop11 The main objective of the NED JRA is to develop a large-aperture (more than 88 mm), high-field (up to 15 T) dipole magnet model relying on high-performance Nb 3 Sn conductors (non-Cu J C up to 1500 A/mm T and 4.2 K). Such magnet is aimed at demonstrating the feasibility of the LHC-IR upgrade scenarios based on high field dipole and quadrupole magnets and is meant to complement the US-LARP. In addition, the NED model could be used to upgrade the CERN superconducting cable test facility (presently limited to T). The NED JRA proposal involves 7 collaborators (CEA/Saclay, CERN, INFN-Milan and Genoa, RAL, Twente University and Wroclaw University), plus several industrial sub-contractors. EU funding limited to 25 % of the original request -> new resources needed soon to complete the program The EU Joint Research Activity CARE-NED

Walter Scandale - 8 November HHH2004 workshop12 De-scoping CARE-NED Given the present State of the Art and the magnet requirements foreseen for LHC IR upgrade and for IRs of future linear colliders, we established the following road-map: revisit magnetic and mechanical designs to achieve enhanced performances with coils made from brittle conductors, address coil cooling issue under high beam losses, keep promoting high-performance Nb 3 Sn wire development (to ensure the survival of multiple suppliers including in EU), improve mechanical robustness and assess radiation hardness of Nb 3 Sn conductor insulation, put into practice all of the above in magnet models and prototypes.

Walter Scandale - 8 November HHH2004 workshop13 Beam Density Increase The upgrade of the injector chain is needed Up to 160 MeV: LINAC 4 Up to 2.2 GeV: the SPL (or a super-BPS) The superconducting way: Up to 60 GeV a SC super-PS Up to 1 TeV a super SPS SC transfer lines to LHC The normal conducting way: Up to 30 GeV a refurbished PS Up to 450 GeV a refurbished SPS A 1 TeV booster ring in the LHC tunnel may also be considered Easy magnets (super-ferric technology?) Difficult to cross the experimental area (a bypass needed?) Rich-man way: Poor-man way: RF upgrade for batch compression in the PS See CARE-HIPPI See CARE-HHH and CARE-NED

Walter Scandale - 8 November HHH2004 workshop14 Low Energy Injector Upgrade: LINAC4 & SPL particles at 2 Hz for the PS booster see CERN-AB particles at 50 Hz for the PS

Walter Scandale - 8 November HHH2004 workshop15 Upgrade of the Injector Rings: Booster, PS and SPS Basic investigations still needed Main constraints: Use the existing tunnels Increase the beam density and the beam intensity possibly by a large factor Fast repetition rate to speed-up the LHC injection process Expected challenges Fast-cycling SC magnets Powerful RF within a limited space Cryogenic, vacuum Ejection optimization, loss control, beam disposal, instrumentation

Walter Scandale - 8 November HHH2004 workshop16 Recent Activity on Fast Cycling Dipoles SIS 200 (abandonned) 4 T central field, 1 T/sec ramp Design based on RHIC dipoles Costeta, Rutherford cable One phase He cooling BNL model : optimize to higher ramp-rate Wire twist pitch 4 mm instead of 13 mm Stabrite coating instead of no coating Stainless steel core (2x25 microns) G-11 wedges instead of copper wedges Thinner yoke laminations (0.5 mm instead of 6.35 mm), 3.5 % silicon, glued with epoxy. Courtesy A.Ghosh and P.Wanderer Cable inner edge

Walter Scandale - 8 November HHH2004 workshop17 The BNL Fast Cycling Dipole Model Courtesy A.Ghosh Cross section of GSI-001 Prototype Magnet

Walter Scandale - 8 November HHH2004 workshop18 The SIS 300 Fast Cycling Dipole Model SIS T, 1 T/sec ramp, 100 mm bore Design based on UNK dipoles, bore from 80 mm to 100 mm 2-layers Cos, Rutherford cable One phase He cooling Challenges : high operational field for 4.2 K, pulsed, high losses Activity on cable development: Reduction of conductor AC loss adjusting filament hysteresis, strand matrix coupling current, cable crossover resistance Rc, and adjacent resistance Ra. A 3.5 micrometer filament diameter was chosen because it appears to be the minimum value that can be reached in a standard copper matrix strand without the onset of proximity coupling. The use of a Cu-0.5% Mn as an interfilamentary matrix material is also under consideration, to reduce both matrix coupling current losses (due to the high resistivity of CuMn ) and hysteresis losses. Coil Collars Key Iron yoke Shell C-Clamp Staples Courtesy of G.Moritz

Walter Scandale - 8 November HHH2004 workshop19 Cables for Fast Pulsed Dipoles A.D. Kovalenko, JINR, 2004

Walter Scandale - 8 November HHH2004 workshop20 R&D Still Needed (a non-exhaustive list) Lowering losses in pulsed magnets Industrialize filament size 3.5 microns or smaller, reduce twist pitch Electromagnetic design for minimum amount of superconductor Optimize cable (cable size, keystone angle, number of strands) Cored cables and strands with resistive coating : long term behaviour issues investigate limits of high Ra/Rc keeping acceptable current sharing Resistive matrix Alternatives to Rutherford cables, such as Nuclotron and CICC Other issues Thermal modelling of magnet cross section under helium flow Characterization of cable insulation schemes (dielectric/mechanical/thermal) Manufacture of a small scale prototype for thermal model/parameter validation, for cable testing/characterization, and as coil test facility Manufacture of an optimized prototype to prepare series production Field quality during the ramp : modellization and experiments Develop dedicated magnetic measurement systems for fast varying magnetic fields

Walter Scandale - 8 November HHH2004 workshop21 Pulsed Dipoles for PS and SPS? Initial considerations based on known technology Upgraded PS and SPS may require two different types of pulsed magnets 3T – 2T/s for the PS 5T – 1.5 T/s for the SPS The quench limit performance ican be achieved with present technology Modified RHIC dipoles or Nuclotron/CICC cable based dipoles for PS Modified (lower losses) « SIS 300 » type dipoles for the SPS

Walter Scandale - 8 November HHH2004 workshop22 Technological Challenges A SC dipole for the SPS may produce 70 W/m peak (35 W/m effective 140 kW for the SPS, equivalent to the cryogenic power of the LHC !) A rather arbitrary guess for beam loss is of about px100GeV/10s= 15 kW By dedicated R&D magnet losses should be lowered to 10 W/m peak (5 W/m effective 20 kW ), comparable to expected beam loss power 1 s 3 s 5 T Tentative SPS cycle Losses are a major concern -> Vigorous R&D program needed Study and evaluate different scenarios of beam losses in PS and SPS Study and evaluate a maximum allowed cryogenic budget Optimize the dipoles not only for good quench performance in condition of cable/iron losses, but also for cryogenic budget

Walter Scandale - 8 November HHH2004 workshop23 What about High Power Beams ? seeH.Schonauer EPAC 2000 pp Main Ring Cycle High power beams: what for? Improve LHC beam (yet to be seen) High flux of POT for hadron physics Feed -factory

Walter Scandale - 8 November HHH2004 workshop24 Possible parameters see H. Schonauer, April 03

Walter Scandale - 8 November HHH2004 workshop25 Technological Challenges in a 30 GeV RCS see H. Schonauer, April 03 Lattice and beam dynamics High t needed but difficult to have dispersion-free SS at the same time Constraint on 1 together with =0 and large dynamic aperture Potential coupled bunch instability during the long injection plateau RF Large RF voltage needed, but little space for RF-cavity in dispersion-free SS Injection capture in an accelerating bucket not truly an adiabatic process Demanding HOM damper Difficult adiabatic bunch compression at 30 GeV (too low synchrotron fr.) Capture loss versus injection energy Vacuum pipe and bean surroundings Large shielded ceramic chamber Tight impedance budget: Z/N < 2 ohms critical Dipoles and power supplies Large stored energy (some hundreds of kJ per dipole) Fast power supplies

Walter Scandale - 8 November HHH2004 workshop26 Conclusion A staged roadmap for the LHC luminosity upgrade needs R&D on: High-field (up to 15 T) superconducting cables and magnets Powerful and sophisticated RF devices for beam manipulations Medium-field fast-pulsed superconducting cables and magnets Accelerator design and integration to existing constraints Upgrading LHC complex is a unique opportunity to Share technological developments with other communities such as: Fusion (EFDA) Nuclear physics (GSI) NMR developers Boost the CERN accelerator complex for future applications such as: High intensity hadron and neutrino physics at intermediate energy Injector developments for neutrino factory Initial resources for R&D are presently provided by EU and CERN within the frame of CARE, in particular within the HHH-network and in the NED and the HIPPI JRAs (most likely, more support will be needed soon)

Walter Scandale - 8 November HHH2004 workshop27 Thank-you for your attention