Dipole magnet design and construction

The mechanical design of the dipole magnet is depicted in figure 22 and table 12 summarizes parameters of the dipole magnet. The bending angle is 70$^\circ$ and the radius of the magnet center is 2.7 m (the radius of the beam center is 2.663 m to use good field region as much as possible). The required integral magnetic field is 4.8 T$\cdot$m for 1.2 GeV/$c$ particles and thus an average magnetic field of 1.44 T is required for normal operation. Figure 23 shows the result of the 3D TOSCA calculation for HKS-D magnet. At the center of the magnet, $1 \times 10^{-3}$ field uniformity could be achieved for $\pm$40 cm from the beam central trajectory. Near the edges of the magnet, the field uniformity becomes worse, but most of the region would be covered by the $1 \times 10^{-2}$ uniformity region. The corner of the outer yoke will be cut for the space of the photon and electron beam pipes.

表 12: Dipole magnet parameters

Item	D
Pole gap height (mm)	200
Pole length (mm)	1560
Max. Ampere turns (A turns)	291840
Number of turns	256
Conductor size	22 $\times$ 22 ($\phi$12 hole)
Max. Field (T)	1.53
Max. Current (A)	1140
Resistance (@47.5 $^\circ$C) (m$\Omega$)	145
	Gap side	Yoke Side
Cooling Water Flow rate (l/m)	66.3	68.8
Pressure drop (MPa)	0.32	0.35
Number of Coolant circuits	8	8
Total Magnet Weight (ton$^*$)	210
$^*$metric ton.

Figure 24 is the picture of the completed D magnet. The precise magnetic field mapping is in process (section 4.6.)