ACCELERATION OF HORIZONTALLY POLARIZED PROTONS AND DEUTERONSBY THE RCNP CYCLOTRONK. Hatanaka, T. Saito, N. Matsuoka, H. Sakai, H. Tamura,
K. Imai*, K. Nisimura** and M. Kondo
Research Center for Nuclear Physics, Osaka University*Department of Physics, Kyoto University**Institute for Nuclear Study, Tokyo University
Abstract
Polarized protons and deuterons with their polarization
axis in the horizontal plane were successfully accelerated
by the AVF cyclotron. To obtain a high beam polarization,
test experiments were performed to distinguish the turnnumbers of the beam in the cyclotron.
Previously, polarized protons and deuterons with theirpolarization axis in the horizontal plane were successfully
accelerated by the RCNP cyclotronl) . Rotation of the beampolarization axis was achieved by using a Wien filter
installed just after the atomic type polarized ion source(fig. 1). The performance of the Wien filter was described
The measured vertical polarization of 56 MeVelsewherel)
deuterons is shown in fig. 2 as a function of the magneticFig. 3 shows an example
field strength of the Wien filter.
of the up-down asymmetries as a function of the Dee veltage.
It was found that the horizontal beam polarization was mainly
determined by the turn number of the beam in the cyclotron.
The period of the oscillation of the up-down asymmetries
should correspond to seven turns due to the deuteron anomalous magnetic moment. Actually, a periodical variation of
up-down asymmetry with the Dee voltage was observed (fig. 3).
The measured maximum horizontal beam polarization was about
It was also
70% of the initial value at the ion source.
found that the final beam polarization was sensitive to thevarious parameters of the cyclotron.
If the turn number of the beam in the cyclotron can bedetermined, high beam polarization can be obtained. A
preliminary test was performed to distinguish the turn numberof beam. A pulsed beam was generated at the Wien filter byadding an appropriate voltage. The accelerated beam wasdetected by a plastic scintillator inserted in the beam line.
By selecting a proper duty-cycle, one can observe the disFig. 4
tributions of the turn number of the extracted beam.
shows the case of 1/48 duty-cycle, where multi-turn extraction is observed. The turn number were descreased to 2 or 3
by a careful tuning of the cyclotron parameters associatedwith the use of the phase-defining slit. Efforts are now inprogress to increase the beam intensity and to reduce themixture of the turn numbers.
Reference1)

K. Hatanaka et al., Proc. Ninth Int. Conf. on Cyclotrons
and Their Applications, Caen, les Editions de Physique(1981) p. 453.
-57-Pv
5c00t-40.5-·~ •""\N....
0•00...

0u3

Ed=56MeV

0.

-....

\....\Cll>

02B ( KG )Fig. l. Cross sectional viewof the Wien filter. l:polepiece, 2:electrode, 3:coil,4:yoke, 5: vacuum housing.

c:I: 0.4120-oc (d. d) 12 c
Ed=56MeVIa.
:lFig. 2. Rotation of deuteronspin by the Wien filter.
Solid line shows the curveof Pv=0.72 0.433 cos(B/Bo/2), where Bo=2KG and 0.72
and 0.433 are beam polarization and the vector analyzing power of the l2cpolarimiter.

0.2

IllEE 0.
>-Ill

<27.5VoEE

2 8. 02 8. 5(arbitrary)

Fig. 3. Up-down asymmetries of
56 MeV deuterons as a functionof the Dee volgate. Opencircle.s were measured using aphase-defining slit. Thelines drawn through theexperimental data are only foreye guide.

-58-Fig. 4. Distribution of theturn numbers observed by aplastic scintillator in the
beam line. A duty cycle isl/48.