Letter of Rossi to Peggs (agred with Schmickler and Devred) April 2005

1. Letter of Rossi to Peggs (agred with Schmickler and Devred) April 2005 • We strongly believe that the major steps in the near term are: • 1) Construction of a quadrupole model, full cross-section, with parameters that are really significant for the LHC upgrade : G  250 T/m ,  90 mm….Otherwise there is the risk we give the impression we keep selling goods that never materialize. • 2) Construction of simple systems that may address the long magnets issues. We insist on this, as you know since our last recommendation, because we feel that it is vital … The system should be simple, in order to be low cost with fast turn-around, but should contain elements relevant for the actual costheta design… • In longer (but not too much longer, i.e. FY2009) terms, the main focus should be to pursue a 5 m long quadrupole, with characteristics almost final. The manufacturing of a successful prototype for 2009 is real vital to the whole magnet program, on both side of the Atlantic. Failing to produce such a prototype in the proper time may reinforce the idea that technologies beyond NbTi are too difficult and complicated for real accelerator magnets.

2. Letter LR continue • Examining alternative routes may be interesting, and eventually it may be very useful, but it should be a second priority in LARP, at least in my vision. We always understood that LARP should be complemented by a vigorous basic program, that is the most suitable to assess the feasibility of alternative routes without diluting the scope (and the resources) of LARP. • Without entering into the details of the activities and on the subdivision among different laboratories, which I do not want to comment on, I strongly support in its global figures and scope the program that S. Gourlay is going to present at the BNL meeting. I consider this essential if the US wants to play a crucial role in the LHC after LHC commissioning.

3. US LHC Accelerator Research Program Magnet Systems Provide options for future upgrades of the LHC Interaction Regions Primary Focus: Demonstrate by 2009 that Nb3Sn magnets are a viable choice for an LHC IR upgrade • The major issues:Nb3Sn technology, consistency, bore/gradient (field), length • Three phase approach 1. • Predictable and reproducibleperformance • TQ models (1 m, 90 mm aperture, Gnom > 200 T/m, Bcoil > 12 T) • Long magnetfabrication • LQ models (4 m, 90 mm aperture, Gnom > 200 T/m, Bcoil > 12 T) • High gradient in large aperture • HQ models (1 m, 90+ mm aperture, Gnom > 250 T/m, Bcoil > 15 T)

4. TQS/C - Predictable and Reproducible Nb3Sn Performance • Technology Quadrupoles (TQ) • 90 mm aperture • Gradient > 200 T/m • Explore alternate shell and collar structures using “identical” conductor / coils, form basis for more ambitious designs • Major initial emphasis to prove Nb3Sn technology • Coil production process developed across laboratories • Tests of TQS01 and TQC01 completed—Excellent First Results • Coils for TQC/S02 in process

5. TQ Coil Design and Fabrication • Design features: • Double-layer, shell-type • One wedge/octant (inner layer) • TQ01: OST-MJR strand, 0.7 mm • TQ02: OST-RRP strand, 0.7 mm • 27-strand, 10.05 mm width • Insulation: S-2 glass sleeve Winding & curing (FNAL - all coils) Reaction & potting (LBNL - all coils)

6. TQS01 SSL 3.2K SSL 4.5K TQS01 Quench History Started training at 80% of short sample reach 87% plateau on the 12th quench. Quenches typically in single coil, at given location High axial tensile stress measured in the island Potential problem pointing at a high strain area between island sections Rebuild addressing problem area and other production lessons learned underway

7. TQC01 Quench History 4.5K plateau with erratic behavior 1.9K plateau at 85% of the expected critical current limit Highest current is at ~12000A 200T/m Training quenches tend to be in inner coil pole, in area of low prestress. Last quenches moved to outer coil. Disassembly and investigation underway

8. LR/LQ: Long Magnet Fabrication Long Racetrack • Coil fabrication scale-up based on well-understood sub-scale coils • Explore length scale-up of coils in shell-based support structure • BNL practice winding, procurement of necessary oven and tooling underway Mirror dipole scale-up via FNAL core program • 2m practice coils under reaction, winding of 2m coils underway Long quadrupole (LQ) • 3.6 m quadrupole based on TQ cross-section—initial coils and tooling designs in study

9. HQ: High Gradient in a Large Aperture High Gradient Quadrupole (HQ) • Explore field and stress limits to performance • Increase peak field on the coil to ~ 15 T • Precursor to larger aperture • Push Nb3Sn technology based on TQ experience • Develop reasonable parameter space for final LHC Upgrade design Example: 4-layer, G=280-310 T/m Current subject of design studies --set up basis for iteration between magnet design possibilities and IR operating conditions

10. US LHC Accelerator Research Program Magnet Systems FY07 is an exciting transition year Initial TQC/S results are very promising • Coil production technology converged • In depth understanding of results underway • Development of improved 2nd iterations in process • Technological basis is being formed Length experiments coming on-line • Practice coils wound • 4m oven installation done at FNAL, in process at BNL Studies and Designs for the next steps ramping up • LQ detail designs start • HQ parameters becoming understood 1.

11. Feedback and interations • Through frequent exchange and contacts, either at conferences or ad hoc meeting (Jim Kirby visited CERN as soon as he has taken over the charge of S. Gourlay this spring). • Through common workshops: WAMS, WAMDO, CARE general meeting, LUMI, etc. • No participation of the Magnet R&D linkman (L. Rossi) to the LARP collaboration meeting. Amended starting next meeting in Port Jefferson 25-27 October 2006. • membership of CERN magnet people to many reviews: Fermilab director review (Fen 2006, L. Rossi chair), DOE LARP review June 2006 (E. Todesco, P. Fessia), DOE LARP reviews and LAPAC permanent membership (A. Devred). NED/HHH are fully in the game. • I think we have an excellent relation with LBNL and BNL; a good but not so excellent one with Fermilab (simply they have a strong basic program where they pursue their scopes and this they do not necessarily fully discuss with us: should they?)