The 11th Symposium on Accelerator Science. and Technology, Harima Science Garden City, 1997

Design of Rb Cell for Polarized 3 He Ion Source Based on Electron Pumping
Katsuya YONEHARA, Yasushi ARIMOTO*, Takeshi TAKEUCHI,Masayoshi TANAKA**, Mamoru FUJIWARA* and Tamio YAMAGATA
Department of Physics, Konan University, Higashinada, Kobe, 658 JAPAN*Research Center for Nuclear Physics (RCNP),Osaka University, Ibaraki ,Osaka, 567 JAPAN**Kobe Tokiwa Jr. College, Nagata ,Kobe 653 JAPAN
Abstract
A new principle to produce a polarized 3 He ion,called "electron pumping" is recently proposed byTanaka et al. We have newly constructed this typeof polarized 3 He ion source at RCNP to prove the validity of this principle and to establish a practical ion
source based on this method. In this paper we present
design and performance of a Rb cell, whi<>h plays a critical role in this ion source. A thick Rb vapor morethan 10 15 atoms/cm 2 is successfully available with thisRb cell.

sleeve is monitored by a thermocouple. This output isused as a feedback signal of a heater to stabilize the celltemperature.

Duoplasmatron
Ion Source··1 Introduction
A polarized 3 He beam is a promising probe in a research on nuclear physics. However, there is no practicalpolarized ion source, so far, becausethere is no practicalmethod to polarize a 3 He particle. Recently, Tanaka etal. have proposed a new method to polarize a 3 He particle called "electron -pumping". (1] It has been expectedthat typical nuclear polarization of 3 He+ ion is -80% at
the vapor thickness ofthe Rb of 10 15 atoms/cm2 and 100% of an atomic polarization. In order to experimentally
prove the validity of the principle of "electron pumping"
and to establish a method for a practical polarized 3 Heion source of this type, we have constructed a new polarized ion source based on the "electron pumping" atRCNP, Osaka University [2]. Since this method is basedon multiple-electron capture and stripping collisions between an incident 3 He ion and polarized Rb atoms undera strong magnetic field, we paid special attention for designing the size and figure of the Rb cell since it must
produce thicker and higher atomic polarized Rb vapor
than that used in the ordinary optical pumping polarized
1on source.

Fig. 13He

The whole set up of the polarized 3 He ion
source based on electron pumping.

JM!,-_.

1F'Cooling Sleever--- Outer Sleeve

1c~- Innerr

ileeve·--Rb;.
jFig. 2ASlOOmm~

A cross sectional view of the Rb cell. A lengthof the cell is 296mm and a full aperture is 29mm

2 The Set Up of an Electron Pumping
Polarized 3 He Ion Source and Rb cell

3 Experimental Result and Conclusion

The whole set up of the polarized 3 He ion source
based on electron pumping is depicted in Figure-1 (3].
The Rb cell is located at the center of a superoonducting
solenoidal magnet. A cross sectional view of the Rb
cell is shown in Figure-2. The Rb cell consists of threecoaxial sleeves, i.e. an inner sleeve, an outer sleeve and acooling sleeve. Inside the outer sleeve, a solid Rb metal
is vaporized. The vapor diffuse into the inner sleevethrough four axial slits, so that the Rb vapor distributes
uniformly in the inner sleeve. The inner sleeve has anentrance and an exit aperture of 10 mm and its lengthis 296 mm. These two sleeves are located inside thecooling sleeve. A temperature of a wall of the inner

We measured the thickness of the Rb vapor by meansof the Faraday rotation effect (4]. We can measure theFaraday rotation angle in accuracy of ±0.05 °. The measured Rb thickness as a function of the cell temperatureis plotted in Figure-3 in comparison with those calculated by using a saturated Rb vapor pressure. Since atime constant of a cell temperature is small due to thepresent cell structure, a good stability of the Rb celltemperature of ±0.1 °C at 100 °C was obtained.
It is clear from the Figure-3 that the present Rb cell
can produce the vapor thicker than 10 15 atoms/cm 2 at
160°C. The stability of the Rb cell temperature is ±0.1°C at 100 °C.

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The 11th Symposium on Accelerator Science and Technology, Harima S.dence Garden City, 1997

This stability corresp~nds to a change of±4.0x 1011
atoms/ cm2 in the Rb thickness. Since the accuracy ofthe measurement ofthe Faraday rotation angle (±0.050 ) corresponds to ±1.91 x 10 12 atornsfcm 2 , the precisionof the measurement of the Rb thickness is determinedby the accuracy of the Faraday rotation angles.

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Ne 1016e"' 1015~~';; 1014]"' 1013••••!

.!:l.c 'E-t 1012

~
20

40

60

80

100

120

140

160

180200Rb Cell Temperature [ oc ]Fig. 3The measured Rb vapor thickness by the Faraday rotation method. The solid curve showsthat calculated from a saturated Rb vapor
pressure.

Acknowledgement
Professor Ejiri is greatly acknowledged for his support throughout this work.
References[1) M. Tanaka et al.,"Method for Production of a 3 He
Beam with High Polarizatiol! and High Intensity",
Phys. Rev. A52, (1995) p.392.
[2] T. Yamagata et al. ,"Development of RCNP polarized
3 He ion source besed on electron pumping", NIM A
in press.
[3) K. Yonehara et al.,"DESIGN_ AND CONSTRUCTION OF POLARIZED 3 He ION SOURCE BASEDON MECSIS'', RCNP Annual Report (1995) p.165.
[4) Y. Mori et al.,"MEASUREMENT OF ELECTRONPOLARIZATION OF OPTICALLY PUMPEDSODIUM ATOMS", NIM 220, (1984) p.264.

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