1. 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

2. 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

3. 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

4. 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

5. 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

6. Opera 2D model
Pierre-Alexandre THONET
Linac4 BCC

7. 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

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

9. 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

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

11. 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

12. 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

13. 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 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

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

16. Additional slides 16
Pierre-Alexandre THONET
Linac4 BCC

17. p.m. easy axis orientation errors17
Pierre-Alexandre THONET
Linac4 BCC

18. 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

19. 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