DESIGN OF INJECTION SYSTEM FOR THE IPCR SSC (I)Y. Yano, A. Goto, T. Wada, H. Takebe, Y. Obana, N. Kishida,
N. Nakanishi, S. Motonaga and H. Kamitsubo
The Institute of Physical and Chemical Research
Besides a principal role to guide a beam transported from the injectors
onto the first equilibrium orbit in the sse, the injection system must possess functions to satisfy some conditions imposed upon the beam at the position where it enters the first equilibrium orbit. These functions are indispensable for one to get well-centered accelerated orbits for particles withwide range of mass and energy, and to accelerate the beam efficiently. The
conditions of the beam to be adjusted are a position and direction, dispersion in radial direction, and beam ellipse in six dimensional phase space.
The third condition is met by the transporting preceding the systemdescribed here. The injection system should be designed so that these matching procedure may be done as easily as possible.
Having investigated three different types of injection method (i.e. radial injection, axial injection and injection by charge stripping), we decided
to employ the method of axial injection as shown in fig. 1. In this method,
firstly the beam which is injected vertically down into the open valley isinflected onto the median plane by two 45° bending magnets and secondly it .is
led to the first equilibrium orbit by means of a bending magnet (BMl), twomagnetic inflection channels (MIC1,MIC2) and an electrostatic inflection channel (EIC). The MIG's are inserted between the magnetic poles of the sector
magnets to add the necessary bending power to the sector field. The characteristics of these injection elements are listed in table 1. Face angles ofBMl are determined to match the dispersion in radial direction. The Q magnet
between the 45° bending magnets makes the achromatic trqnsportation of beam
in vertical direction possible. The advantage of the present method is thatthe beam focusing elements can be arranged down to the central region. In theradial case, no such elements can be arranged along the injection trajectorythrough the long valley region because the accelerated beam exists. The circumstance that the. beam line of linac as the injector is about 14m higher thanthe median plane of SSC is also one of primary factors for our decision. A
considerable effort was devoted to the feasible design of the injection equipments, since they must be capable of bending particle of large magnetic rigidity up to about 800 kG-em and be located in the limited available space ofthe sse central region.
Fig. 2. shows the cross section of bending magnet (BMl) designed. Thismagnet is of modified window-frame type with the ends having the unsaturated(Rogowski) profile. The material of the yoke and pole is pure iron. A 1/1scale model of this magnet whose bending angle is 50° has been built. The mapof the magnetic field produced by this magnet was measured at excitations of 7,12, 15 and 18 kG. The measurement of the field strength was made with Hallelements which was moved in azimuthal direction automatically by computer controlled driving system. Fig. 3. shows magnetic field distribution along radial direction measured at the position inner enough from the magnet edge when
the clearance o between the coils underneath the pole and the pole was taken
to be 2.5 mm. Using the measured data, the beam passing through the magnet
was traced by numerical calculations (see "Design of Injection System (II)").
The MIG's were designed to consist of a iron shim and coils, a model ofwhich is now under construction. The EIC is of conventional structure.
Through the present study, it has been concluded that the proposed methodof beam injection is feasible for the IPCR SSC.

-43-

Q magnet
ST: Magnetic stet'rer~M:

BM: Bending mngnel
HIC: ~1.1gm•tic Jnflf'ction chann£'1ETC: El('ctrmll.1tfc lnf](•ctlnn ch.wnt·l

SECTOR MAGNET

PM: Profllt· monitor
DP: Differential probe',,2nd E.O.

00. 5lrn

Fig. 1. Layout of central region of the IPCR separated sector
cyclotron. The injection trajectory drawn through STl, ST2and QM is in the plane perpendicular to the median plane.
Table 1.
Element

Characteristics of injection elements.

Bend angle

BM245°

BM1110°Aperture(cm}Radius(cm)Maximum field

Face angle

(H)

(V)

10

4. 4

46

17.1

kG

22.5/22.5

4. 4

46

17.1

kG

14/-130/00/0(entrance)/(exit)

MIC286.9°43(15.2)+3kG

MIC137.2°

48(15.2)+1.2

kG

EIC

3.6°

450

62

kV/cm

8/B.~---.----.----.--

460R

Fig. 2 Cross section of the bending
magnet (BMl).

-44-Fig. 3. Magnetic field distribution along radial direction
measured at the position innerenough from the magnet edge.