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
Plan view of radial-sector magnet Type of PRISM-FFAG Magnet • Radial Sector Type • DFD Triplet • C type Center of • Magnetic Field Distribution D machine Positive Field F Negative � r Field • � k D B ( r ) = B 0 • r 0 • • r : distance from a center of a machine • r0 : average radius of beam orbit • B0 : magnetic field density at r = r0 • k : k value
z r θ 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 10/42 /0312 !*'+,"-+$#. /0/12 )"#$%&'( /0112 5"6431 !"#$%&'( 40412 5"3/31 /0112 )"#$%&'( 5"6711 /0/12 /0312 2 !*'+,"-+$#. 4 / 0 1
F D D Main coil Trim coil Coils of PRISM Magnet • Coils consist of main coil and trim coils which can adjust field distribution.
z r θ Form of PRISM Magnet • Aperture size : 9/,0316,: • 110 cm (horizontal) 9/,03=6:2 ;5,7316,: • 30 cm (vertical) %&$ • Gradient of magnetic !$$ <0,-6.56=,13,0.253=6:2 !#$ field is produced by !"#$ main pole &&$$ • Anisotropic inter pole '()$$* +,-./0123456737/18,023120.25 is used
Anisotropic Inter-Pole • Structure Ferromagnetic material • Layers of ferromagnetic and Paramagnetic material paramagnetic material • Advantage µ z = µ Fe • Fringe field distribution become Large uniform at different r-position. µ r 2 Small • Smoothing of fluctuation for field distribution caused by trim coil
3D Calculation by TOSCA Without inter-pole With inter-pole Effect of inter-pole 1 • Uniform fringing magnetic field distribution in different r r=600 cm r=600 cm 1 1 r=620 cm r=620 cm Normarized B z (Gauss) Normarized B z (Gauss) r=640 cm r=640 cm 0.8 0.8 r=660 cm r=660 cm r=680 cm r=680 cm r=700 cm r=700 cm 0.6 0.6 z=9cm z=9cm 0.4 0.4 0.2 0.2 0 0 -0.2 -0.2 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 � (Deg.) � (Deg.)
2D Calculation by PANDIRA Without inter-pole With inter-pole Effect of inter-pole 2 • Improvement of field fluctuation of local k caused by trim coils 6.2 6.2 N sub =8 z = 0 cm 6.1 6.1 z = 3 cm z = 6 cm z = 9 cm z = 12 cm 6 6 local k local k N sub =8 5.9 5.9 z = 0 cm z = 3 cm z = 6 cm 5.8 5.8 z = 9 cm z = 12 cm 5.7 5.7 480 485 490 495 500 505 510 480 485 490 495 500 505 510 r (cm) r (cm)
3D simulation of PRISM Magnet • Main pole shape and main coil current was optimized 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.)
Magnetic field distribution Calculation Results x 10 2 /export/home/arimoto/tosca/0407/17/tr432.op3 /export/home/arimoto/tosca/0407/17/tr432.op3 2000 5000 BL + r=580 cm 1750 BL - r=600 cm 4000 ’z = 0’ cm’’ r=620 cm 1500 r=640 cm BL z (Gauss*cm) r=660 cm 1250 3000 r=680 cm B z (Gauss) 1000 r=700 cm r=720 cm B F L 2000 750 z=0 500 B D L 1000 250 0 0 -250 -1000 580 600 620 640 660 680 700 720 0 2 4 6 8 10 12 14 16 18 r (cm) � (Deg.) ∫ B F L = B ( r ) B > 0 r d θ ∫ B D L = B ( r ) B < 0 r d θ
Calculation results F/D ratio = B F / B D /export/home/arimoto/tosca/0407/17/tr432.op3 10 7 9 k=(B i+1 -B i )r i / (r i+1 -r i )B i 6.5 8 7 6 k value + 1 F/D ratio 6 5 5.5 4 5 3 B F L 2 B D L 4.5 1 0 4 580 600 620 640 660 680 700 720 580 600 620 640 660 680 700 720 r (cm) r (cm) ∫ B F L = B ( r ) B > 0 r d θ ∫ B D L = B ( r ) B < 0 r d θ
RF Core Field Clamp Magnet Magnetic Field in RF core • Saturation of RF core by DC magnetic field is occurred more than 100 Gauss • Field clamp is installed to clamp magnetic field at RF Core
Magnetic field in the RF core Without Field Clamp With Field Clamp 400 Gauss 400 Gauss 0 Gauss 0 Gauss Effect of field clamp
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
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