MEASUREMENTS OF ELECtRON-SPIN ORIENTED
SODIUM ATOMS FOR KEK POLARIZED H- ION SOURCE
K. Ito, Y. Mor:t, A. Takagi and S. Fukumoto
National Laboratory for High Energy Physics
The construction of the polarized H preinjector has been started sinceApril in 1980. In this project, a new type polarized ion source (APOLON) which
utilizes the charge-exchange reactions beyween fast protons and electron-spin
The principle of this polarized ion
oriented sodium atoms is to be employed. 1source is shown in Fig.l. There are two ways to obtain the electron-spinorientyd sodium atoms; Stern-Gerlach method with an inhomogeneous ma~~eticThefield 2 and optical pumping method with the circular polarized light.
intensity of polarized H- ion beam depends strongly on the density of electronspin oriented sodium atoms. We have measured the density and the electron
polarization of sodium atoms for both methods described above.
Experimental setup for the measurement of the density of sodium atoms which
are oriented by passing through the 6-pole magnet is shown in Fig.2. The typicaltemperature of the oven was 480°C and the orifice diameter was 3 mm. The maximum
edge field of the 6-pole magnet was about 8 K gauss. Sodium atoms were detectedby the surface ionization detector placed at the exit of the magnet. In Fig.3
is shown a schematic set-up of this detector. The positive voltage was applied
to the tungsten filament heated up to about 1500°C and the wall of the anode wascooled by a liquid freon. The distance between the filament and the anode was5 mm.
Acceptance of the 6-magnet for the sodium atomic beam can ~e ealculated
analitically for each atomic. state of m. = + 112 or m. = - 112 4 and the results
are shown in Fig.4. In this figure n i~ the parametel concering for the atomic
Ivelocity:(1)n = (4kTim) 1 2 lv
where v is the velocity of sodium atom, T the source temperature, m the atomic
weight and k the Boltzmann constant. The number of atoms per second which leavean oven of pressure p and orifice radius Rs within the solid angle S1 is given by,c Q

pTI

R~I(TM) 1 I 2(2)1.115 x 10 2 2 ( °K amu) 1 I 2ATorr cm 2 sr sec). Fig. 5 shows the output
where ccurrent from the surface ionization detector as a function of the oven temperature. The saturated current was varied with an applied bias voltage becauseof the space charge effect. The measured sodium density was 5 x 10 10 atoms/cm 3at the temperature of 480°C and it was consistentwith the value calculated
from eq. (2) .
In Fig.6 is shown a schematic sep-up for the polarization measurementsof optically pumped sodium atoms. Sodium atoms flowing from the oven is exposedin the teflon coated cell to a circular polarized light whose wave length is 5896
as same as that of the Dl spectrum line in sodium atoms. Teflon coating
prevents from depolarization induced by the collisions with the metal wall. The
oriented sodium atoms are analyzed by the 6-pole magnet and the polarization isestimated in the following equation,Ap

N1 - Nz
N1 + Nz(3)

where N1 is the intensity of the sodium atomic beam pumped by a left circular
light and Nz by right circular light. The measurements a:r:e now in progress.

-7 5-References1)

Y. Mori et al., Proc. of the 4'th Symp. on Ion Sources and Ion Application
Technology, Tokyo (1980), 59.
G.J. Witteveen, Nucl. Inst. Meth., 158 (1979), 57.
L.W. Anderson, Nucl. Inst. Meth., 1~(1979), 363.
V.W. Hughes, et a1., Phys. Rev. A.,~ (1972), 195.

2)
3)
4)

SIX-POLE MAGNET

H+H++Na(et)=H 0 (et)+Na

H 0 (p t)

H (p t)+Fig.l Block diagram of Pol. H
ion-source.

5001/sFig.2 Experimental arrangement forSodium atom density
30:....

200•.

10Fig.3 Surface ionization
detector'l 00

T=400'cx ~T=3 80°C..
.
0lFig.5
Output current
from surface
ionization detector

..

(sr.)

5001000(V)

SPECTROSCOPE.:--COLO TRAP

SIX-POLE MAGNET.

~~t-f-H ~:~ER HL_A_R_Go_L~_SE_~~-N-'",~.ill§ "~Y~.M_

Fig.4 Acceptance 6-pole magnet

Fig. 6 Experimental set-up for optical_
pumping method-7 6-