Large Magnetic Volumes for Neutrino Factory Detectors

1. Large Magnetic Volumes for Neutrino Factory Detectors Bross ISS Detector Phone Meeting July 3, 2006

2. Options • We have begun looking into the engineering realities of trying to magnetize very large (>30k m3) volumes • What we are considering is something much much larger than what has been built to date • But has been studied it some detail – See GEM Solenoid • Technologies • Room temperature Cu or Al conductor - NO • Power dissipation is MUCH too high • High Tc superconductor – NO* • At this point in time for the same Ampere-Turns: 200X more expensive than convention SC • *However, development progress in recent years has been rapid so the situation could change in the near (5 yr) future. • Conventional SC • Lots of experience, but this size is new. • Technically – certainly doable • BUT WHAT IS THE COST?

3. Multiple Solenoids - Conceptual Layouts Magnetic Tunnel n 15 m x 15 m x 15m modules; B = 0.5T Magnetic Cavern Magnet Steel n

4. Cost Modeling • Green and Lorant is a good starting point • “Estimating the Cost of Large Superconducting Thin Solenoid Magnets” – 1993 • C(M$) = 0.5(Es(MJ))0.662 C(M$) = 0.4(B(T)V)0.635 • We can also take the CMS Coil as-built cost (»$55M) as a more recent reference point • B = 4T • V = 340 m3 • Stored Energy – 2.7 GJ • For the NF case take a 15 X 15 X 15 m3 volume with B=0.5T • Don’t worry now about whether this is a cylindrical solenoid or a box. • This will of course be very important mechanically

5. Cost Extrapolations for Baseline NF Detector Magnet • Cost via stored energy • Stored energy »340 MJ • From Green and Lorant • C(M$) » 0.5(340)0.662» 24M$ • Cost via Magnetic Volume • From Green and Lorant • C(M$) » 0.4(.5 X 3400)0.635» 45M$ • Reference Point – CMS Solenoid • C(M$) » 0.5(2700)0.662» 93M$ (Stored energy) • C(M$) » 0.4(4 X 370)0.635» 41M$ (Magnetic volume) • Most Optimistic Extrapolation • Use stored energy and conclude formula overestimates by factor of 1.7 (93/54) based on CMS case • Then NF magnet extrapolated cost – 14M$ • Most Pessimistic Extrapolation • Use magnetic volume and conclude formula underestimates by a factor of 1.3 (54/41) based on CMS case • Then NF magnet extrapolated cost – 60M$

6. Magnet Costs • Another extrapolation model has been used by V.Balbekov, E.Black, C. Darve, D. Elvira, J.M.Rey (MuCool Note 215) based on scaling laws developed by A. Herve. • P0 = 0.33 S0.8 Price of equiv. zero energy magnet in MCHF • PE = 0.17E0.7 Price of magnetization in MCHF • P = P0 + PE Price of magnet in MCHF • Where • S = Surface area of the cryostat • V = Magnetized volume • E = Stored energy • NOTE: Model includes cost of power supplies, cryogenics and vacuum plant • This model does take into account difficulties in dealing with size separately from magnetic field issues • Balbekov et. al. used three “as-builts” to derive the coefficients (0.33, 0.8, 0.17, and 0.7) in the above equations • ALEPH (R=2.65m, L=7m, B=1.5T, E=138MJ, P=14M$) • CMS (R=3.2m, L=14.5m, B=4T, E=3.0GJ, P*=53M$) • GEM (R=9m, L=27m, B=0.8T, E=1.8GJ, P*=98M$) *estimated cost at the time

7. World’s Largest Magnet Never Built • The GEM Solenoid was to be the largest SC magnet ever built at 19 m in diameter and 30 m long (final engineering spec)

8. GEM Solenoid Coil module » 1.2m long 12 Coil modules stacked to produce half coil

9. Magnet Cost Estimate II • The GEM magnet is certainly relevant to the coils we are considering and as such is an good reference point for the cost estimate even though it was never built. • Using this estimating model we have for one of our coils • P0 = .33(900)0.8 = 76 MCHF • PE = .17(340)0.7 = 10 MCHF • P= 86 MCHF » 69M$ • What we see is that the cost is driven by the size (= vacuum can) and is at the high-end+ of the Green-Lorant estimating model

10. Conclusions • Conclusions: • For low-field case (B<.5T) scaling formulae may not be accurate due to the large size of magnets being considered • Vacuum loading (vacuum vessel) will be a major consideration and will strongly impact cost • Superconductor itself is not a cost driver • Based on recent MICE order, cost for baseline NF magnet discussed here is <0.5M$ • Magnetization Costs are not driving factor in low-field case • On-site fabrication required • Magnets of this size can certainly be built, but better cost estimates will only come after some real engineering analysis • 3-6 month effort • Savings will come with “INNOVATION” in vacuum vessel • We have started looking at the vacuum vessel here at Fermilab • The dimensions and a potentially non-circular geometry will be the cost drivers and will present the engineering challenges

11. Conclusions II • At this time it appears that a large volume air-core magnetized Totally sampling detector for a neutrino factory is not feasible from cost considerations, but is certainly technically feasible • R&D aimed at the mechanical engineering issues is required to see if the costs can be reduced. • Developments in high Tc SC could change this picture • Reduction in cost of the high Tc conductor itself • Possibility for non-vacuum insulated vessels (Icarus example) for SC operating at 77K • There is a long way to go to make this viable