ADJUSTABLE STRONG PERMANENT MAGNET FOR FINAL FOCUS QUADRUPOLE

ADJUSTABLE STRONG PERMANENT MAGNET FOR FINAL FOCUS QUADRUPOLE T. MIHARA, Y. IWASHITA M. KUMADA C. M. Spencer Kyoto University N. I. R. S. S. L. A. C.

The first prototype of “superstrong” Permanent Magnet Quad. Soft iron PM Cut plane view Axial view PHOTO Integrated strength GL=28. 5 T (29. 7 T by calc. ) magnet size. f 10 cm bore f 1. 4 cm Field gradient is about 300 T/m

Double Ring Structure –Adjustable PMQ- First Quadrant shows the flux plot. ON Pole material OFF Permanent magnet The double ring structure PMQ is split into inner ring and outer ring. Only the outer ring is rotated 90 around the beam axis to vary the focal strength.

Definition of “Switched-On” Length 16 series of outer ring switching ON Cut Plane View No. 8 cm 4 cm 2 cm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ON ON OFF OFF ON ON OFF OFF OFF ON ON OFF ON ON OFF ON OFF ON “Switched - on” length 15 cm 14 cm 13 cm 12 cm 11 cm 10 cm 9 cm 8 cm 7 cm 6 cm 5 cm 4 cm 3 cm 2 cm 1 cm

Design Parameter of the Adjustable PMQ material dimensions pole Vanadium permendur Bore F 1. 0 cm Inner ring magnet NEOMAX 38 AH (Br=1. 23 T, i. Hc=28 k. Oe) Outer radius of the inner ring F 6. 0 cm Outer ring magnet NEOMAX 44 H (Br=1. 33 T, i. Hc=16 k. Oe) Inner radius of outer rings F 6. 6 cm Outer radius outer rings. F 10 cm Mechanical length 23 cm Outer ring size along the axis 1. 0 cm, 2. 0. m, 4. 0 cm, 8. 0 cm strength Max. integrated strength 25. 1 T(28 T) Min. integrated strength 4. 7 T(7 T) 1. 4 T step

An adjustable PMQ Outgoing beam line is 7 cm distant from incoming beam line. Outer ring is rotated by DC motors.

Measurement with Rotation Coil @SLAC Rotating Coil Temperature 21. 7± 0. 2 C. Preliminary data: • integrated strength • center shift by changing strength • skew rotation angle by changing strength

Strength variability Integrated strength is proportional to the “switched-on ” length It allows us simple adjustment This PMQ can generates GL 1/5 of the maximum GL.

Magnetic Center Shift when Integrated Gradient is Changed X center and Y center shift when GL is changed. Mechanical adjustment may reduce shift.

Skew rotation angle by changing strength strongest 1, 2, 8 cm_on Y=0. 01 x 8 cm_on 4 cm_on This will be reduced by adjustment. Y=0. 0085 x+1. 365 2 cm_on 1 cm_on weakest Fig. shows the skew rotation angle as the function of switched-on length.

Options for Various L* & X’ing Angles NBS Q-size Grad. With f 20 mm bore Grad. With f 14 mm bore SBS MBS LBS (For Head on) (For 2 mrad) (For 7 mrad) (2 nd prototype) (For 20 mrad) f 160 mm f 100 mm 212 T/m(max) 175 T/m (max) 208 T/m(max) 186 T/m(max) -23 T/m (min) -77 T/m (min) 26 T/m (min) 31 T/m(min) 296 T/m 242 T/m NBS=No Beam Separation, MBS=Medium Beam Separation, 282 T/m 272 T/m SBS=Small Beam Separation LBS=Large Beam Separation

Summary • “Double ring ” Adjustable PMQ was fabricated. This PMQ generates GL from 3. 48 T to 24. 2 T by 1. 4 T step. • Magnetic center shift was measured; good reproducibility was observed. • Measurement of Skew rotation angle shows the relative rotations of the rings. • Shifts and rotations will be adjusted. • Configurations can be changed to meet with various beam separations.