500 MeV PROTON BEAM LINE FOR KEK BOOSTERSYNCHROTRON UTILIZATION FACILITY
I. Sakai, H. Someya, T. Adachi, Y. Irie and H. Sasaki
National Laboratory for High Energy Physics
Magnet System
The layout of the 500 MeV proton beam line is shown in Fig.i. The total
length of the beam line is about 80 m. The magnet system is composed of 23
quadrupole magnets, 2 horizontal bending magnets, 1 pulse magnet for beamswitching, and 6 steering magnets.
Quadrupole Magnet
The dimensions of the quadrupole magnet are as follows. The bore radius
is 57 mm, and geometrical length is 300 mm. The pole face is hyperbolic, andend cut coyrection was made for uniformity of effective length of the fieldgradient. 1
About all of 23 quadrupole magnets, transverse distribution of
the field gradient and the effective length of the field ~radient were measure~
carefully by the method of displacing twin search coils. 2The accuracy ofthe measurementswere better than 1 X 10- 4 of the field_gradient on the medi~nplain. The example of the measured value is shown in Figs. 2 and 3. The
integrated values of nonlinear field over the useful ar".rture, ± 75 lllll! on themedi~n plain, were less than 0.1 % of the field gradient on the medium plain.
The measured value of each magnet is expanded in Taylor series as,a2 Bz (x);aB z (O)"oX-"-- =LG(X )/LG(O)

oX

=

b4 2
b5 3
b. 6 4b7 5
bz + b 3X + -21• X + -31• X + 7T
X+ -"fX'!.
-'•

L0 + L lX + 2!
Lz X 2 + Ls
L4 X 4 + Sf
Ls X 53! X 3 + 4TCoefficients
correspond to multipole components. The distribution of each
multipole component of 23 quadrupole magnet is shown in Fiy.4. The effect of
the fablication error to the nonlinear field is estimated 3 , and the value wasconfirmed experimentally by making intentional deviation of the pole. The
sextupole component b2 is induced by aSYlllll!etrical error of the magnet. As inFig.4, the average value of the bz is 8 x 10- 5 (cm- 1 ), and the standard deviation is 1.6 x 10- 4 (cm- 1 ). The corresponding estimated value of asymmetricaldeviation of the pole face is about. 30 flm with average value and about 58 ~tmwith standard deviation. The octupole component b3 is induced by symmetricalof the magnet. As in Fig.4, the average value of the b3 is - 1.6 x 10- 5(emand the standard deviation is 6 x 10- (cm- 2 ). The corresponding
estimated value of symmetrical deviation of the pole face is about 9 flm withaverage value, and 34 flm with standard deviation. Absolute value of theeffective length was obtained by the point-to-point measurement of the field
gradient along the magnet axis. It is 341 mm long, and the radial distribution is less than 1 mm over the useful aperture.

The vacuum chambers of the beam line were mainly composed of aluminumalloys for the purpose of reducing residual radioactivity. Metal gasketswere
used at all of the flange connection. A quantity of leakage from each flange
connection and welding portion are less than 1 x 10- 10 Torr ~s- 1 for helium.
The beam line is evacuated by a ion pump of 1000 ~s- 1 , the maximum pressureless than 10- 6 Torr was easily performed.
-3 3-Beam Transfort
Proton beam had been transported to Utilization Facility seccessfully.
The beam profiles are observed by secondary emmition type profile monitors andthe beam intensity monitors. The observed profile is shown in Fig.5. The
abscissa is graduated in em. The monitoring positions are indicated in Fig.1,
good agreement between observed and designed values was obtained. The lostbeam through the beam line is negligible small.
Reference
M. Kumada et al; Proceeding of the 2 nd symposi~ on accelerator scienceand technology (1978) p.73.
M. Kumada et al; Proceeding of the 2. nd symposium on accelerator scienceand technology (1978) p.75.
Robert J. Lari et al; Caluculation of the harmonic content of asymmetricalquadrupole magnets January 24, 1967, RJL/GJB-2, Argonne •1)
2)

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.• I
II

j_ I j lI

1.001

IT'';.

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Fig. 4

Fig. 5-34-10