Magnet Design for the PRISM-FFAG Y. Arimoto Osaka U. - - PowerPoint PPT Presentation

Magnet Design for the PRISM-FFAG

• Y. Arimoto Osaka U.

Contents

• Type of PRISM-FFAG Magnet
• Form of PRISM-FFAG Magnet
• Anisotropic inter pole
• 3D simulation
• Summary

Type of PRISM-FFAG Magnet

• Radial Sector Type
• DFD Triplet
• C type
• Magnetic Field Distribution
• • r : distance from a center of a

machine

• r0 : average radius of beam orbit
• B0 : magnetic field density at r=r0
• k : k value

B(r) = B0 r r0 k

D F D Center of machine

Negative Field Positive Field

Plan view of radial-sector magnet

Form of PRISM Magnet

• F and D have their return yoke in common.
• Field clamps are installed not to leak magnetic field to RF Core

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r θ z

Coils of PRISM Magnet

• Coils consist of main coil and trim coils which can adjust field

distribution.

F D D Main coil Trim coil

Form of PRISM Magnet

• Aperture size :
• 110 cm (horizontal)
• 30 cm (vertical)
• Gradient of magnetic

field is produced by main pole

• Anisotropic inter pole

is used

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r θ z

Anisotropic Inter-Pole

• Structure
• Layers of ferromagnetic and

paramagnetic material

• Advantage
• Fringe field distribution become

uniform at different r-position.

• Smoothing of fluctuation for field

distribution caused by trim coil

µz = µFe µr 2 Large Small

Ferromagnetic material Paramagnetic material

Effect of inter-pole 1

• Uniform fringing magnetic field distribution in different r
• 0.2

0.2 0.4 0.6 0.8 1 1 2 3 4 5 6 7 8 9 10

(Deg.) Normarized Bz (Gauss)

r=600 cm r=620 cm r=640 cm r=660 cm r=680 cm r=700 cm

z=9cm

• 0.2

0.2 0.4 0.6 0.8 1 1 2 3 4 5 6 7 8 9 10

(Deg.) Normarized Bz (Gauss)

r=600 cm r=620 cm r=640 cm r=660 cm r=680 cm r=700 cm

z=9cm

Without inter-pole With inter-pole

3D Calculation by TOSCA

Effect of inter-pole 2

• Improvement of field fluctuation of local k caused by trim coils

5.7 5.8 5.9 6 6.1 6.2 480 485 490 495 500 505 510

r (cm) local k

z = 0 cm z = 3 cm z = 6 cm z = 9 cm z = 12 cm Nsub=8

5.7 5.8 5.9 6 6.1 6.2 480 485 490 495 500 505 510

r (cm) local k

z = 0 cm z = 3 cm z = 6 cm z = 9 cm z = 12 cm Nsub=8

Without inter-pole With inter-pole

2D Calculation by PANDIRA

3D simulation of PRISM Magnet

• Main pole shape and

main coil current was

• ptimized to meet

flowing conditions over the aperture of the magnet.

• local k = 4.6
• F/D = 6
• BL integral = 8.6 Tm/half cell
• Calculation program:

TOSCA (Opera3d Vector field co.)

Calculation Results

/export/home/arimoto/tosca/0407/17/tr432.op3

• 250

250 500 750 1000 1250 1500 1750 2000 x 10 2 580 600 620 640 660 680 700 720

r (cm) BLz (Gauss*cm)

’z = 0’ cm’’

/export/home/arimoto/tosca/0407/17/tr432.op3

• 1000

1000 2000 3000 4000 5000 2 4 6 8 10 12 14 16 18

(Deg.) Bz (Gauss)

z=0

BFL = B(r) B>0r

∫

dθ BDL = B(r) B<0r

∫

dθ

BFL BDL Magnetic field distribution

Calculation results

/export/home/arimoto/tosca/0407/17/tr432.op3

1 2 3 4 5 6 7 8 9 10 580 600 620 640 660 680 700 720

r (cm) F/D ratio

4 4.5 5 5.5 6 6.5 7 580 600 620 640 660 680 700 720

k=(Bi+1-Bi)ri / (ri+1-ri)Bi

r (cm) k value + 1

BFL BDL F/D ratio =BF /BD

BFL = B(r) B>0r

∫

dθ BDL = B(r) B<0r

∫

dθ

Magnetic Field in RF core

• Saturation of RF

core by DC magnetic field is

• ccurred more

than 100 Gauss

• Field clamp is

installed to clamp magnetic field at RF Core

RF Core Field Clamp Magnet

Effect of field clamp

Magnetic field in the RF core

Without Field Clamp With Field Clamp

400 Gauss 400 Gauss 0 Gauss 0 Gauss

Summary

• PRISM FFAG magnet is DFD radial sector triplet

magnet, which have large aperture.

• Anisotropic inter-pole is used, which have following

merits

• Make uniform magnetic field distribution at fringe
• Damp the undulation of local k due to trim coils
• Magnetic field at RF core is clamped by the field

clamp