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Large Magnetic Volumes for Neutrino Factory Detectors. Bross ISS Detector Phone Meeting July 3, 2006. Options. We have begun looking into the engineering realities of trying to magnetize very large (>30k m 3 ) volumes

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Large magnetic volumes for neutrino factory detectors

Large Magnetic Volumes for Neutrino Factory Detectors


ISS Detector Phone Meeting

July 3, 2006


  • 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


Multiple solenoids conceptual layouts
Multiple Solenoids - Conceptual Layouts

Magnetic Tunnel


15 m x 15 m x 15m modules; B = 0.5T

Magnetic Cavern




Cost modeling
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

Cost extrapolations for baseline nf detector magnet
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$

Magnet costs
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

World s largest magnet never built
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)

Gem solenoid
GEM Solenoid

Coil module » 1.2m long

12 Coil modules stacked to

produce half coil

Magnet cost estimate ii
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


  • 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

Conclusions ii
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