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

The first prototype of “superstrong” Permanent Magnet Quad. Integrated strength GL=28.5T (29.7T by calc.) magnet size.  10cm bore  1.4cm Field gradient is about 300T/m PHOTO Cut plane view Axial view PM Soft iron

Double Ring Structure –Adjustable PMQ- 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. ON Permanent magnet Pole material OFF First Quadrant shows the flux plot.

Definition of “Switched-On” Length 16 series of outer ring switching No. 8 cm 4 cm 2 cm 1 cm “Switched- on” length 1 ON 15cm 2 ON OFF 14cm 3 ON OFFON 13cm 4 ON OFF 12cm 5 ONOFFON 11cm 6 ONOFFONOFF 10cm 7 ONOFF ON 9cm 8 ONOFF 8cm 9 OFFON 7cm 10 OFFON OFF 6cm 11 OFFONOFFON 5cm 12 OFFONOFF 4cm 13 OFF ON 3cm 14 OFF ONOFF 2cm 15 OFF ON 1cm 16 OFF 0cm ON Cut Plane View

Design Parameter of the Adjustable PMQ Bore  1.0cm Outer radius of the inner ring  6.0cm Inner radius of outer rings  6.6cm Outer radius outer rings.  10cm Mechanical length 23cm Outer ring size along the axis 1.0cm,2.0.m, 4.0cm,8.0cm Max. integrated strength 25.1T(28T) Min. integrated strength 4.7T(7T) step 1.4T poleVanadium permendur Inner ring magnet NEOMAX38AH (Br=1.23T,iHc=28kOe) Outer ring magnet NEOMAX44H (Br=1.33T,iHc=16kOe) materialdimensions strength

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

Measurement with Rotation 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 Fig. shows the skew rotation angle as the function of switched-on length. This will be reduced by adjustment. 1cm_on 2cm_on 4cm_on 8cm_on 1,2,8cm_on strongest weakest Y=0.01x Y=0.0085x+1.365

Options for Various L* & X’ing Angles NBS (For Head on) MBS (For 7mrad) SBS (For 2mrad) LBS (2 nd prototype) (For 20mrad) NBS=No Beam Separation,SBS=Small Beam Separation MBS=Medium Beam Separation,LBS=Large Beam Separation Q-size  160mm  100mm Grad. With  20mm bore 212T/m (max) -23T/m (min) 175T/m (max) -77T/m (min) 208T/m (max) 26T/m (min) 186T/m (max) 31T/m (min) Grad. With  14mm bore 296T/m242T/m282T/m272T/m

Summary “Double ring ” Adjustable PMQ was fabricated. This PMQ generates GL from 3.48T to 24.2T by 1.4T 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.