PERMANENT MAGNET QUADRUPOLE FOR THE LINAC 4 CCDTL Linac4 Beam Coordination Committee Meeting 15/02/2011 Alexey Vorozhtsov, Evgeny Solodko, Pierre-Alexandre Thonet TE-MSC-MNC

Outline Permanent magnet solution Permanent magnet quadrupole general view Permanent magnet material Magnetic design Fabrication of the prototype Magnetic measurements Conclusions & Future actions 2 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Permanent magnet solution Why a PM solution? Only 204 mm available between 2 CCDTL accelerating tanks. Beam energy will remain the same at each magnet emplacement. Savings (power supply, cables, instrumentation and operation of the magnets). Requirements:   Number of magnets : 14 installed + 3 spares   Integrated gradient (Max): 1.6 Tesla   Integrated gradient (Min): 1.3 Tesla   Inner diameter (Min): 0.040 m   Outer diametre (Max): 0.200 m   Length : 0.100 m   Gradient  integral error (rms): ± 0.5 %   Magnetic versus geometric axis: < 0.1  mm   Harmonic content at 15 mm radius: Bn/B2 for n=3,4,... : <   0.05   Yaw/pitch/roll: 1 mrad   Each quadrupole has a different gradient   Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Permanent magnet quadrupole general view Return yoke C10R steel. Tuning blocks C10R steel, to compensate the possible p.m. inequalities and set the field gradient (up to a reduction of 6 % of the nominal value). Mechanically movable up to 6 mm, independently for each pole. The exact position of the blocks is assured by non-magnetic spacers of different thickness. Pole tip C10R steel, smooth the possible differences on the easy axis orientation of the permanent magnet blocks. Permanent magnet blocks Sm2Co17, as a flux generator. Core aluminium, structure maintaining all the parts together, giving a high precision on the poles positioning. Advantage of this design: Possibility to compensate the differences on the permanent magnet blocks. Possibility to set the field gradient. 3 types of quadrupoles (low, medium and high gradient) cover an integrated gradient range from 1.3T to 1.6T. 4 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Permanent magnet material Samarium Cobalt Sm2Co17 Maximum specific energy product fulfils with the magnet design. Small temperature coefficient: 0.035%/°C. Good radiation resistance. Acceptable corrosion stability without protective coating. Sm2Co17 Recoma 30S from “ARNOLD MAGNETICS” High remanent field Br=1.12 [T]. Small deviation of the magnetic characteristics (maximum 3% from the nominal values on Br and Hc). ±2[deg] maximum error of easy axis orientation. Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Opera 2D model Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Field quality 2D model (ideal case) Field gradient = 18 [T/m] which is 2 T/m higher than the requirements. 3D modeling suggested that, due to the short magnet length and relatively large aperture, the central gradient Grad(z=0) is not as high as in 2D model (end effects domination). Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Opera 3D model ~1.7 [T/m] difference due to the 3D effects Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Integrated relative field components at R=15mm Minimum dodecapole component is mandated for chamfer height between 5 and 6 mm Chamfer height [mm] Integrated relative field components ∫Bndz/∫B2dz at R=15 [mm] B6 B10 B14 -2.8E-03 3.57E-05 -1.31E-05 1 -2.28E-03 -4.66E-05 -5.27E-06 2 -1.54E-03 -8.59E-05 -9.3E-06 3 -9.14E-04 -8.71E-05 -1.21E-05 4 -4.43E-04 -7.99E-05 -1.29E-05 5 -1.12E-04 -7.42E-05 -1.32E-05 6 1.10E-04 -7.30E-05 -1.28E-05 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Relative dodecapole component B6(z) at R=15mm Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Fabrication of the prototype (1) Fabrication of ≈80 mm long permanent magnet blocks and gluing by pair. Cutting and magnetization of slices for each block to check the magnetic properties. Gluing of the blocks together with the soft steel pole tip. Final grinding. Magnetization and measurement of magnetic properties of each pole assembly. Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Fabrication of the prototype (2) The aluminium core was made by EDM cutting. All the soft steel parts were machined and ground. The assembly of the magnet was done carefully by hand. 12 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Magnetic measurements First Results: An integrated gradient of 1.77 T.m/m has been measured with a rotating coil which is exactly the value of the Opera 3D model. The average field harmonics have been measured without shims on the tuning blocks and they are already much lower than the requirements. n bn an Unit Tolerance 3 -5.2 8.5 units @15 mm 500 4 6.1 0.5 5 -0.3 -1.3 6 -2.2 (-1.12) 0.8 7 0.1 0.0 8 9 -0.1 10 -0.6 (-0.7) 11 12 13 14 Field harmonics measured at 17mm and corrected at 15mm Next measurements: We could improve field quality by moving tuning blocks (but already 100 times better than requirements). Measurement of minimum quadrupole gradient by adjusting the tuning blocks. Measurement of the magnetic center vs geometric center. Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Conclusions & Future actions The first results from the magnetic measurements confirm the excellent field quality provided by this design. Definition of an adapted positioning system of the magnet function of measurements results of magnetic center vs geometrical center and tilt. Writing of a technical design report once all the tests will be completed. Production of the 17 magnets (14 installed + 3 spares) after the final validation (delivery time ≈ 12 months). Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Thank you for you attention! 15 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Additional slides 16 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

p.m. easy axis orientation errors 17 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Positioning of the magnet in space The magnet will be positioned on the referential plate with a key (x axis). The referential plate will be machined in order to have the magnet center well positioned. An adjustment will be possible on the z axis. Referential plate y x z Key 18 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011

Budget Price for the prototype (CHF) Unit price for 19 magnets (CHF) Permanent magnet blocks 5000 2900 Magnet assembly 900 Magnetic and non magnetic parts 3800 2000 Tooling (machining and assembly) 2600 Unit price 12300 5800 Total price for 17 magnets 98600 Pierre-Alexandre THONET Linac4 BCC - 15.02.2011