1. F. Kircher CLIC concept meeting 12/15/08 1 Some points about the superconducting magnet for a CLIC detector F. Kircher (CEA Saclay/DSM/Irfu/SACM) December 15, 2008

2. F. Kircher CLIC concept meeting 12/15/08 2 Summary 1.Introduction 2.Geometrical, electrical, magnetic and mechanical parameters 3.Limits 4.Conductor possible improvements 5.ILD detector magnet 6.Conclusions

3. F. Kircher CLIC concept meeting 12/15/08 3 Summary

4. F. Kircher CLIC concept meeting 12/15/08 4 Introduction  CMS magnet tests were very successful  For the next colliders (ILC, CLIC), most of the detector magnets are CMS-like  Nevertheless, some questions may be asked, such as:. what are the relevant parameters?. what is the ultimate limit for such magnets?. which improvements can be done on CMS elements?  We will give some directions in this presentation (technical aspect, not cost)

5. F. Kircher CLIC concept meeting 12/15/08 5 Summary

6. F. Kircher CLIC concept meeting 12/15/08 6 - Three basic parameters for the design: B 0 : central field R i : coil inner radius (typically: R i = R bore + 250 mm) L: coil length - Other relevant parameters: Field homogeneity Fringing field Coil thickness (in term of radiation length) Magnet parameters

7. F. Kircher CLIC concept meeting 12/15/08 7 CMS Detector (Compact Muon Solenoid). Superconducting solenoid: 6 m bore diameter 13 m length 4T central field + iron yoke. No special request on field homogeneity. Cold mass thickness: 3.9 X 0

8. F. Kircher CLIC concept meeting 12/15/08 8 From design to realization : 1998-2006 Central field : 4 T Nominal current : 20 kA Stored energy : 2.6 GJ Cold mass Length : 12.5 m Internal diameter : 6.4 m Weight : 220 t

9. F. Kircher CLIC concept meeting 12/15/08 9 Stored energy of SC magnets Among detector magnets,, CMS has both :  the largest stored energy (2.6 GJ)  the largest density of stored energy (11.6 kJ/kg) A value around 12 kJ/kg is now considered as a safe standard for CMS-like magnets An important parameter for magnet safety

10. F. Kircher CLIC concept meeting 12/15/08 10 Stored energy/per unit of cold mass E/M (from A. Hervé)

11. F. Kircher CLIC concept meeting 12/15/08 11 CMS parameters and what can be varied (from A. H.)?

12. F. Kircher CLIC concept meeting 12/15/08 12 Important parameter:. for the workers around (or in) the magnet. for some hardware (relays, pumps…). for the other detector in push-pull operation Unfortunately, in these huge yoke structures, gaps are needed, both for cable passages and for assembly reasons CMS has an in equivalent iron thickness of about 1.5 m, and is rather field-leaking (typically 500 G near the outside part of the barrel yoke) For ILD, the foreseen iron thickness is more around 3 m. Nevertheless, because of the gaps, the fringing field is still around 200 G at 2 m outside the yoke As the mass of iron is huge, both specifications and gaps must be as reasonable as possible Note also that the metallic structure of the buildings affects the calculations Fringing field

13. F. Kircher CLIC concept meeting 12/15/08 13 Summary

14. F. Kircher CLIC concept meeting 12/15/08 14 Actual limitations My personnal criteria (from experience) B 0 2 * R c ≤ 60 T 2 * m (complementary to the other criteria, where neither B 0 nor R i appear). CMS: 4 2 *3.2 = 51 T 2 *m. LDC: 4 2 *3.6 = 58 T 2 *m. SiD: 5 2 *2.6 = 65 T 2 *m These are physical, and cost, and not so much technical limitations The length L is important in the aspect ratio L/Rc for field homogeneity and efficiency of A*t

15. F. Kircher CLIC concept meeting 12/15/08 15 Summary

16. F. Kircher CLIC concept meeting 12/15/08 16 CMS conductor Superconducting cable (32 strands) Thermal stabilizer: very high purity aluminium: 99.998% Mechanical reinforcement: Aluminium alloy 6082 T5 Electron beam welding

17. F. Kircher CLIC concept meeting 12/15/08 17 Improved CMS conductor (1) Replace pure aluminum stabilizer by: o cold drawn Al-0.1wt%Ni alloy o developed for the ATLAS thin solenoid superconductor (A. Yamamoto et al.)

18. F. Kircher CLIC concept meeting 12/15/08 18 Improved CMS conductor (2) This proposal was done by several labs involved in the CMS magnet few years ago Unfortunately, up to now, no funding could be found Nevertheless, this development is important to be done for future projects:. the electrical stability will not be affected (RRR* of 500 for CMS overall conductor, starting from a RRR of 3 000 for very pure Al) * RRR = resistivity at 300 K / resistivity at 10 K. the mechanical stability will be improved (about 100% of structural material in the conductor, vs about 60% for CMS).

19. F. Kircher CLIC concept meeting 12/15/08 19 Changing the mechanical stabilizer welding This is an other way The EBW (electron beam welding) method used for CMS is costly (about 40 % of the total cost of the conductor) and tricky Other ways were foreseen during the CMS conductor R&D phase, but not too much time was available for the necessary developments:. soft soldering. friction. laser beam As some of these methods have been progressing in the last 10 years, it is worthy to do at least some research and reflexion

20. F. Kircher CLIC concept meeting 12/15/08 20 Cable in conduit conductor? Developed for fusion magnets, with very high fields (10 -12 T range), and high losses Developed for fusion magnets, with very high fields (10 -12 T range), and high lossesDrawbacks:. low current density. short unit length. expensive Not suited for medium-range field, DC magnets, as are detector magnets

21. F. Kircher CLIC concept meeting 12/15/08 21 Summary

22. F. Kircher CLIC concept meeting 12/15/08 22 Version ILD-V2 Saclay Parameters used for ILD-V2 detector magnet:. B 0 = 4 T nominal, 3.5 T operation. R int coil = 3 590 mm. R ext coil = 3 940 mm. L coil = 3 672 * 2 mm Stray field (@ 3.5 T):. B ext ≤ 200 G @ z=10 m from I.P.. B ext ≤ 50 G @ at 15 m in the radial direction Homogeneous field in the TPC volume: z max  l (R) = ∫ (B r (R) / B z (R) dz ≤ 10 mm 0 within the TPC volume: z max = 2.25 m, R max = 1.8 m

23. F. Kircher CLIC concept meeting 12/15/08 23 Version ILD-V2 Saclay: field homogeneity The field homogeneity is ajusted with: a FSP (Field Shaping Plate) inside the endcap yoke and correction currents in some places of the coil (3 inner layers of the two modules at extremities).

24. F. Kircher CLIC concept meeting 12/15/08 24 ILD-V2: main outputs Electrical parameters (4 T) I nom (kA) 15.9 Eng. J (A/mm 2 )9.6(for I nom )  I cor (kA)18.1(3 layers * 2 modules) Stored energy (GJ)2.0 W s density (kJ/kg)12.2 Integral homogeneity in TPC volume (mm) ≤ 9 Yoke dimensions R out barel yoke (mm)7 110 Z out endcap yoke (mm)7 190

25. F. Kircher CLIC concept meeting 12/15/08 25 ILD-V2 Br/Bz(z=0 to 2.25 m) for r=0 to 1.8m  (Br/Bz) vs r (z=0 to 2.25 m) ILD-V2 SACLAY configuration @ 4 Tesla Iron : up to R=7.110m (2.76m thick), up to Z=+/-7.190m (3.27m thick) + 100 mm FSP (Field Shaping Plate) Coil : 4 layers,7.35 m length subdivided in 5 parts Bz(r=0) B(z) (8m<r<9.5m) 600 Gauss

26. F. Kircher CLIC concept meeting 12/15/08 26 Summary

27. F. Kircher CLIC concept meeting 12/15/08 27 Conclusions CMS detector magnet was a huge step from detector magnets of the LEP generation (Aleph, Delphi) Because of physical and economical reasons, a similar step is not realistic for the after-LHC detector magnets Nevertheless, the CMS, and also the ATLAS, experience must be used for the design and realization of the future magnets Some basic parameters, limitations and directions for R&D concerning the conductor have been mentionned in this presentation. As an application, the work going on for an ILC detector magnet has been briefly presented