ACCELERATION OF PROTONS WITH THE SPIN AXIS
IN THE HORIZONTAL PLANE
K. Hatanaka, T. Saito, N. Matsuoka, H. Sakai, K. Nisimura*,
H. Shimizu*, K. Hosono and M. Kondo
Research Center for Nuclear Physics, Osaka University,Suita, Osaka, Japan* Department of Physics, Kyoto University, Kyoto, JapanAbstract
Protons with spin in the horizontal plane were accelerated
by the AVF cyclotron at RCNP. The maximum polarization of thebeam accelerated up to 65 MeV maintained about 70% of the initialvalue at ion source. The dependence of the final beam polarization on various parameters of the cyclotron was also investigated.

1.

Introduction

It has been believed that the beam polarization would belost when an along beam (a beam with spin in the horizontalplane) was accelerated with circular accelerators. The along
beam has been, therefore, accelerated only by linear accelerators, for example, by the Van de Graaff accelerators. This isa reason why the tensor analyzing power T21 could not be measured
at higher energies than 15 MeV. However it may be possible toaccelerate the along beam with a cyclotron, if a good conditionof turn-separation can be obtained. It is important to measure
the T 21 above the Coulomb barrier for the study of the tensor
interactions between the deuteron and the nucleus.
Before the acceleration of deuterons, a test was performed
for a proton beam with spin in the horizontal plane. It was
found that the maximum polarization of 65 MeV protons was about
70% of the initial value at ion source and was very large. We
also investigated the dependence of the final beam polarization
on various parameters of the cyclotron.
Measurements and Results
The test experiments were performed with 65 MeV polarized
protons accelerated by the AVF cyclotron at RCNP. Polarized
protons were produced by the atomic beam type ion source. The
beam quantization axis (the beam's spin) was rotated in a vec . ical plane by a Wien Filter located just after the ion source.
The beam polarization was measured by a polarization monitor
system with two turn tables in the horizontal (left, right) andvertical (up, down) planes.
The vertical and horizontal components of the beam polarization can be determined from measurements of left-right and updown asymmetries, respectively. The magnetic and the electricfields of the Wien Filter were adjusted to minimize the absolutevalue of the vertical polarization. The decrease of beam intensity was recovered with slight re-adjustment of the parameters of
the injection system. When the Wien Filter was rotated aroundthe beam axis, the measured up-down asymmetry varied on a sine
curve as expected, and is shown in fig. 1. The Wien Filter wasfixed at the angle which gave the maximum up-down asymmetry.
The parameters of cyclotron were changed to investigate theeffects on the asymmetries. An example is given in fig. 2, where

2.

-7 7-

the dependence on the Dee voltage is shown. Other parametersinvestigated were trim-coil and valley-coil currents. It was
found from these measurements that the final polarization wasinsensitive to the condition of the central region of the cyclotron and was mainly determined by the number of the rotations of
the beam in the cyclotron and then the condition of the turnseparations. We now intend to make a test with polarized deuterons
at 56 MeV.

E0.1
Fig. 1. Up-down asymmetries
as a function of the angle ofthe Wien-Filter. The line
presented is only the eyeguide.

0- 0.1120.

240°

W.F. ANGLE
E0.2
0-0.2

2 223vDEE <RELATIVE)

Fig. 2. Up-down asymmetries as a function of the Deevoltage. The line is only the eye-guide.

-78-