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Large Magnetic Volumes for Neutrino Factory DetectorsPowerPoint Presentation

Large Magnetic Volumes for Neutrino Factory Detectors

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- 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?

- Room temperature Cu or Al conductor - NO

Multiple Solenoids - Conceptual Layouts

Magnetic Tunnel

n

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

Magnetic Cavern

Magnet

Steel

n

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

- Don’t worry now about whether this is a cylindrical solenoid or a box.

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$) » 0.4(.5 X 3400)0.635» 45M$

- From Green and Lorant
- 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$

- Use stored energy and conclude formula overestimates by factor of 1.7 (93/54) based on CMS case
- 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$

- Use magnetic volume and conclude formula underestimates by a factor of 1.3 (54/41) based on CMS case

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

- The GEM Solenoid was to be the largest SC magnet ever built at 19 m in diameter and 30 m long (final engineering spec)

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

- 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

- For low-field case (B<.5T) scaling formulae may not be accurate due to the large size of magnets being considered
- The dimensions and a potentially non-circular geometry will be the cost drivers and will present the engineering challenges

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

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