1 Large Magnetic Volumes for Neutrino Factory Detectors A.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 m 3 ) volumes  What we are considering is something much much larger than what has been built to date u But has been studied it some detail – See GEM Solenoid  Technologies u Room temperature Cu or Al conductor - NO s Power dissipation is MUCH too high u High T c superconductor – NO * s At this point in time for the same Ampere-Turns: 200X more expensive than convention SC s * However, development progress in recent years has been rapid so the situation could change in the near (5 yr) future. u Conventional SC s Lots of experience, but this size is new. s Technically – certainly doable s BUT WHAT IS THE COST?

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

4 Cost Modeling  Green and Lorant is a good starting point u “Estimating the Cost of Large Superconducting Thin Solenoid Magnets” – 1993 u C(M$) = 0.5(E s (MJ)) C(M$) = 0.4(B(T)V)  We can also take the CMS Coil as-built cost (  $55M) as a more recent reference point u B = 4T u V = 340 m 3 u Stored Energy – 2.7 GJ  For the NF case take a 15 X 15 X 15 m 3 volume with B=0.5T u Don’t worry now about whether this is a cylindrical solenoid or a box. s This will of course be very important mechanically

5 Cost Extrapolations for Baseline NF Detector Magnet  Cost via stored energy  Stored energy  340 MJ u From Green and Lorant  C(M$)  0.5(340)  24M$  Cost via Magnetic Volume u From Green and Lorant  C(M$)  0.4(.5 X 3400)  45M$  Reference Point – CMS Solenoid  C(M$)  0.5(2700)  93M$ (Stored energy)  C(M$)  0.4(4 X 370)  41M$ (Magnetic volume)  Most Optimistic Extrapolation u Use stored energy and conclude formula overestimates by factor of 1.7 (93/54) based on CMS case s Then NF magnet extrapolated cost – 14M$  Most Pessimistic Extrapolation u Use magnetic volume and conclude formula underestimates by a factor of 1.3 (54/41) based on CMS case s 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. u P 0 = 0.33 S 0.8 Price of equiv. zero energy magnet in MCHF u P E = 0.17E 0.7 Price of magnetization in MCHF u P = P 0 + P E Price of magnet in MCHF u Where s S = Surface area of the cryostat s V = Magnetized volume s E = Stored energy s NOTE: Model includes cost of power supplies, cryogenics and vacuum plant u 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 u ALEPH (R=2.65m, L=7m, B=1.5T, E=138MJ, P=14M$) u CMS (R=3.2m, L=14.5m, B=4T, E=3.0GJ, P * =53M$) u 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 12 Coil modules stacked to produce half coil Coil module  1.2m long

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 u P 0 =.33(900) 0.8 = 76 MCHF u P E =.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: u For low-field case (B<.5T) scaling formulae may not be accurate due to the large size of magnets being considered s Vacuum loading (vacuum vessel) will be a major consideration and will strongly impact cost s Superconductor itself is not a cost driver –Based on recent MICE order, cost for baseline NF magnet discussed here is <0.5M$ s Magnetization Costs are not driving factor in low-field case s On-site fabrication required u Magnets of this size can certainly be built, but better cost estimates will only come after some real engineering analysis s 3-6 month effort u Savings will come with “INNOVATION” in vacuum vessel –We have started looking at the vacuum vessel here at Fermilab u 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 T c SC could change this picture u Reduction in cost of the high T c conductor itself u Possibility for non-vacuum insulated vessels (Icarus example) for SC operating at 77K u There is a long way to go to make this viable