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Nb3Sn wiggler development

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Presentation on theme: "Nb3Sn wiggler development"— Presentation transcript:

1 Nb3Sn wiggler development
Laura García Fajardo CERN Low Emittance Rings 2014 Workshop 17-19 September. INFN-LNF, Frascati, Italy

2 Outline Overview Nb3Sn wiggler model. 2D optimization
CLIC DR requirements, Nb3Sn wiggler background… Nb3Sn wiggler model. 2D optimization Selection of the main wiggler parameters (winding configuration, coil thickness, gap, B in gap, period length…) Design of the impregnation mould Conclusions Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

3 Overview - CLIC damping rings requirements
Plots and specifications by Fanouria Antoniou From the point of view of the magnet design, to get low emittances we should reach the highest Bw at the lowest possible λw, considering the IBS effect CLIC damping rings 26 wigglers per each straight section of the DR (52 wiggler per DR, 104 wigglers in total for CLIC) Bw: Maximum magnetic field density in the gap λw: Period length Lw: Total length of wigglers in the damping rings εr: Emittance with effect of intra-beam scattering Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

4 Overview - Wiggler design
Pictures taken from Daniel Schoerling Ph.D. Thesis Vertical design Important wiggler’s parameters Vertical design advantages Period length not limited by the bending radius Possibility of continuous winding Bw: Maximum mag. field dens. in the gap Bp: Mag. field dens. in the pole tip Bs: Maximum mag. field dens. in the conductor’s surface By: Vertical component of the mag. field dens. Bmod: Norm of the mag. field dens. λw: Period length g: Magnetic gap zc: Width of the square aperture Superconducting material (Nb3Sn) advantages Larger parameter space available (than with NbTi) Higher T and enthalpy margin (than with NbTi) Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

5 First vertical racetrack magnet (5 coils) tested in 2011
Overview - Background Photos courtesy of Jacky Mazet Short model sample First vertical racetrack magnet (5 coils) tested in 2011 Strand: OST, RRP Period length: 41.8mm Strand’s diameter [mm] 0.81 Jc SC [A/mm2] at B=12T and T=4.3K 2963 Magnet test interrupted after reaching 75% of max. current because of short circuit between the conductor and the iron parts (shorts to ground) Need to increase the insulation thickness between the poles and the cables This implies either increasing the period length or using a more efficient strand Short model sample inside the impregnation mould Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

6 Overview - Strand options
Technology: RRP Provider: OST Price: ≈5€/m Strand insulation: Fiberglass braiding, 0.07mm thick Strand specification Strand specification d [mm] 0.70 # of filaments 132/169 Sub-element size [µm] 41 Jc SC [A/mm2] at B=10T and T=4.3K 3421 Jc SC [A/mm2] at B=12T and T=4.3K 2176 SC fraction 44.44% d [mm] 0.85 # of filaments 132/169 Sub-element size [µm] 48 Jc SC [A/mm2] at B=12T and T=4.3K 2450 Jc SC [A/mm2] at B=15T and T=4.3K 1400 SC fraction 45.45% d: Strand diameter Jc SC: Critical current density of the superconducting material Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

7 Nb3Sn model. 2D optimization - Selection of the winding configuration
Photos courtesy of Jacky Mazet and Paolo Ferracin Goal: Finding the most efficient way to wind the magnet It means: the winding configuration with the highest packing factor It means: the highest ration between the area occupied by the cables and the area of the square aperture Winding configuration of the short model: Odd number of layers that have the same number of turns Insulation layers will be added between the wire bundle and the iron poles Plasma coating + fiberglass = 0.5mm Cross section of the short model Square aperture of the short model Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

8 Nb3Sn model. 2D optimization - Selection of the winding configuration
Comparing the packing factor (f) of different winding configurations f(2) is always greater than f(1) f(3) is greater than f(4) if n < 2m+1 Finally, f(3) is greater than f(2) if n < 2m It means that the winding configuration #3 has the highest packing factor if the height and width of the square aperture meet the following relation: (1) Centred layers – even number (2) Displaced layers – even number n: number of layers m: number of turns of the lowest layer a: height of the square aperture b: width of the square aperture D: diameter of the insulated strand Winding configuration selection (3) Centred layers – odd number (4) Displaced layers – odd number Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

9 Cable unit length saving ≈19%
Nb3Sn model. 2D optimization - Selection of the wire bundle thickness Previous studies (Schoerling, 2012) have shown that the optimal cross-section dimension in terms of maximum Bp* is yc ≈ zc ≈ 0.30*λw Cable saving. Comparing the maximum Bw for R=0.30 and R=0.27 (R=zc/λw): R=0.30 R=0.27 Bw gain ≈1% Cable unit length saving ≈19% Ratio of Bp achieved with a cross-section yc and zc to the maximum Bp* for a given period length λw. But zc has to be an integer multiplier of the insulated strand’s diameter! Period length vs. maximum Bw for R=0.27 and R=0.30. Strand diameter=0.70mm Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

10 Nb3Sn model. 2D optimization - Selection of the magnetic gap
Fix ratio: R=0.27 As zc has to be an integer multiplier of the cable’s diameter, for different strand diameters we get different period lengths Magnetic gap selection: g=15mm (clear bore gap=10mm) 1-period Bwy profile for different period lengths Strand diameter 0.70mm 1-period Bwy profile for different period lengths Strand diameter 0.85mm Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

11 2 possible options using Nb3Sn:
Nb3Sn model. 2D optimization - Selection of the max. magnetic field density in the gap Magnetic gap: 15mm Working point: 80% Nb3Sn strand Diameter: 0.85mm Jc SC at B=12T and T=4.3K: 2450 A/mm2 NbTi Bochvar strand Jc SC at B=5T and T=4.3K: 3088A/mm2 2 possible options using Nb3Sn: Bw=3.5T Bw=4.0T Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

12 Period length selection: Cable unit length saving
Nb3Sn model. 2D optimization - Selection of the period length and the strand Period length selection: λw=44mm for a maximum Bwy ≈3.5T λw=48mm for a maximum Bwy ≈4.0T Period length: λw=40, 42, 44, 46, 48, 50mm Ratio: 0.27 ≤ R ≤ 0.30 λw [mm] Bw [T] Cable unit length [m] d-strand: 0.70mm 0.85mm 44 3.63 3.58 99 69 48 4.06 119 93 λw [mm] Bw gain Cable unit length saving d-strand: 0.70mm d-strand: 0.85mm 44 ≈1% ≈30% 48 0% ≈22% Strand selection: Diameter=0.85mm Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

13 Nb3Sn model. 2D optimization - Bw profile in one period of the wiggler
λw=44mm λw=48mm Air Iron yoke Coil Winding pole Side pole Half gap Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

14 Nb3Sn model. 2D optimization - Parameters of the selected options
CS: Critical surface; WP: Working point; L: Cable unit length; CC: Critical current Parameters of the selected options λw [mm] L [m] R % of CC I-strand [A] J-strand [A/mm2] Bs [T] Bw [T] Bw/Bs 44 69 0.27 100 % 1365 2406 7.81 4.32 55 % 80 % 1092 1925 6.26 3.58 57 % 48 93 0.29 1232 2172 8.40 4.92 59 % 986 1737 6.73 4.06 60 % Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

15 Nb3Sn model. 2D optimization - Behaviour of the maximum Bw respect to λw
Red plots: R=0.27 Blue plots: 0.27 ≤ R ≤ 0.30 Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

16 Design of the impregnation mould
Drawings by Javier Parrilla Leal This piece does not compress the cables Wiggler prototype on the bottom piece of the mould Assembly of the top piece of the mould Assembly of the side pieces of the mould Assembly of the front and back pieces of the mould Previous wiggler prototype inside its impregnation mould, 2011 Wiggler prototype inside its impregnation mould Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

17 Conclusions It is possible to build a wiggler magnet using Nb3Sn strand, that meets the emittance requirements of the CLIC DR In this work, the 2D optimization of a Nb3Sn wiggler that aimed at reaching the highest Bw at the lowest possible λw, was presented Important parameters of the wiggler’s configuration were set: Winding configuration (odd number of centred layers) Wire bundle thickness (~0.27*period length) Magnetic gap (15mm) Maximum magnetic field density in the gap (3.5T or 4.0T) Strand (OST RRP, d=0.85mm) Period length (44mm or 48mm) Two possible scenarios were selected for constructing the 5 coils wiggler prototype: Period length=44mm for a maximum field density in gap ≈3.5T (better for total wiggler length decrease) Period length=48mm for a maximum field density in gap ≈4.0T (better for IBS effect decrease) The final design of the impregnation mould allows avoiding leaks during the impregnation process (o-rings), eases its manufacturing (box shape) and protects the coils during assembly (curved pieces on the sides) Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

18 People involved in the project at CERN
Laura García Fajardo Paolo Ferracin Jacky Mazet Javier Parrilla Leal Thomas Sahner Daniel Schoerling References A Multi-TeV Linear Collider Based on CLIC Technology. CLIC Conceptual Design Report. Geneva, 2012 Ferracin, P. et al., Report on CLIC Nb3Sn wiggler magnet. Local report, CERN. Schoerling, D., Superconducting wiggler magnets for beam-emittance damping rings. Ph.D. Thesis, CERN. Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014

19 THANK YOU FOR YOUR ATTENTION!
Nb3Sn wiggler development. Low Emittance Rings 2014 Workshop. Frascati, Italy 18/09/2014


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