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

Development of Measurement and Control System for Polarized 3 He Ion Source
Based on Electron Pumping
Yasushi ARIMOTO, Katsuya YONEHARA*, Takeshi TAKEUCHI*,
Masayoshi TANAKA** and Tamio YAMAGATA*
Research Center for Nuclear Physics, Osaka University,lbaraki, Osaka 567, JAPAN*Department of Physics, Konan University,Higashinada, Kobe 658, JAPAN**Kobe Tokiwa Jr. College,Nagata, Kobe 653, JAPANAbstract
A polarized 3 He ion source based on electron pumping has been developed at RCNP, Osaka University. The
measurement system mainly consists of two parts. One
is a part where a polarization of a Rb atom is measured
based on the Faraday rotation effects. Another one isa part where a nuclear polarization of a 3 He particle ismeasured by the beam-foil spectroscopy. To reduce thestatistical errors in these measurements, a helicity of a
pumping laser is changed by controlling a pockels cell.
These measurements and a controlling are operated by
the SUN workstation.

ToADCFig. 1

1 Introduction
A new polarized 3 He ion source based on electron
pumping[1] is being developed at the Research Center for Nuclear Physics, Osaka University[2]. It isnecessary to measure a Rb atomic-polarization and a
3 He nuclear-polarization to investigate a performance of
the ion source. The Rb atomic polarization is measured by using of the Faraday rotation effects whichcauses a rotation of the plane of a polarization of
the light penetrating into an atomic-polarized medium
along the magnetic fields[3]. On the other hand, the3 He nuclear-polarization is measured by the beam-foil
spectroscopy[4][5]. In the beam-foil spectroscopy wemeasure a circular polarization of photons emitted fromthe polarized 3 He particle after transversely go througha carbon foil, 5J-tg / cm 2 in thickness.

2 Measurement of Rb atomic polarization
A set up for a measurement of the Rb atomicpolarization is shown in Fig. 1. A linearly polarized
light from a diode laser goes through a Rb oven located in the magnetic field (2.....,3T) and a >./2 plate andis splitted into a parallel and a perpendicularly polarized lights to the plane of the incidence by a polarizing
beam splitter. These splitted lights are respectively detected by photo-diodes. Electric currents generated by
the two photo-diodes are converted into voltages signals
using operational-amplifiers and are feed into the ADC.
The Faraday-rotation angle is measured rotating the >./2
plate with a stepping motor which is controlled by theSUN workstation.
In Fig. 2 plotted points are the observed ratio of thetwo components of the lights splitted by the polarizing

The experimental set up for a measurement of
the Rb atomic polarization.

beam splitter. From this figure the Faraday rotation
angle is determined in the precision of ± 0.05 degrees
when the Rb oven temperature is 20 °C. This precision
corresponds to that of the Rb atomic- polarization of ±0.03.
.

3 Measurement of 3 He nuclear-polarization
The 3 He nuclear-polarization produced by the 3 Hepolarized ion source is measured by the beam-foil
spectroscopy[4][5]. A schematic view of this equipment isshown in Fig. 3. We observe circularly polarized photons
emitted via the transitions between the 33 PJ (J=2,1,0)
and 23 S 1 states of 3 He I. Fig. 4 shows a typical photon spectrum (closed circles) for a 4 He incidence instead of a 3 He observed by a monochromator locatedat the polarimeter position. It is shown from Fig. 4that the 33 P-23 S transition is relatively intense. The
life time of this transition ("-'100 ns) is known to bemuch longer than hyperfine interaction periods, therefore, this transition is suitable for the beam-foil spectroscopy. To observe this transition selectively, a 391.5
nm wavelength-filter (a transmission efficiency of 41.5%
at 20 nm FWHM) is inserted between a convex lens anda >./4 plate. A spectrum with this filter is also shown inFig. 4 (open circlesJ. It is seen that the filter successfully
chooses only the 3 P-23 S 389 nm transition.
Thus, the 3 He nuclear-polarization is obtained bymeasuring the intensity asymmetries of the circularly polarized light for the 33 P-23 S transition[5]. However,
because of a failure of a power supply of a pumping laser-14-The lith Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

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IJ2 Plate Rotation Angle [Degree]
Fig. 2Intensity ratio of a parallel polarized light to aperpendicularly polarized light to the plane ofthe incidence vs. the >./2 plate rotation-angle
at three different temperature of the Rb oven.

for the Rb (an alexandrite pulsed laser), we cannot produce the polarized 3 He beam at the moment.
To investigate an overall performance of the 3 He polarimeter a test of this system by using a 17.9 keY 4 Hebeam (with no nuclear-polarization) instead of the 3 He
beam was performed. Fig. 6 shows the asymmetries of
the 389 nm photons observed by the polarimeter as afunction of time starting from the pumping laser ignition. From this measurement an obtained asymmetry RFig. 3

A schematic view of a 3 He polarimeter basedon the beam-foil spectroscopy.

ISR = 0.9978 ± 0.0077,
and a resulting polarization P isp = R- 1 = 0.9978 - 1 ± 0.0077 = _ 0011 ± 0 037
A0.207.
.
'

where A is an analyzing power for the circular polarization measurement. Since the measurement wasperformed with the 4 He incidence with no nuclearpolarization, no asymmetry should be observed. The

1200~

1000~ 800

result is in reasonable agreement with no polarization.

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4 Data taking and Control system
To flip a helicity of the pumping laser light, a pockels
cell is used by controlling a high voltage supplied to thepockels cell by using an I/0 register board.
The ADC, GPIB and 1/0 resister boards are on
the YME and these boards are virtually addressed ona memory of the workstation by YME/Sbus interface
board (SFllO:Solflower Computer Inc.) and controlled
by this workstation CPU[6].

200o~~~~~~~~~~~~~~~

Fig. 45 Conclusion
The measurement and control system for polarized
3 He ion source recently installed at RCNP is designedand constructed.

-15-350 375 400 425 450 475 500 525 550 575 600
Wave Length [ run 1

Photon spectra emitted from an incidence of
17.9 keY 4 He beam on a carbon .foil. Closed
circles were data taken by a monochromator
without a filter, while open circles were takenwith a filter.

The lith Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

1.6c;--------------------,._g 1.4
C'l 1.2~1;>..

.~ 0.8~ 0.6

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o~~~5~0L00~~~~~00~00~~~~~50L00~~~2~00L00~~~2~5L00~0~

Time [ f.!sec ]Fig. 5An asymmetry of intensity of the 33 P-23 S
photons by the 4 He incidence. A data aquisition time is 3600 sec.

By these system it is confirmed that the Rb atomicpolarization is measured in the precision of 0.03, and the
3 He nuclear-polarization is in that of 0.037 in 1 hour.
Acknowledgement

The authors thank the director of RCNP, Prof. Ejiri
and cyclotron crew of RCNP for their warm support
during this work.
References[1] M. Tanaka at al.,"Method for Production of a 3 He
Beam with High Polarization and High Intensity",
Phys. Rev. A52, (1995) 392.
[2] T. Yamagata at a/.,"Development of RCNP Polarized 3 He Ion Source Based on Electron Pumping",
Nucl. Inst. and Meth. in Phys. Res. A, in press.
[3] F .Strumia," Magnetic Rotatory Power of OpticallyPumped Na Vapour and its Application to the Studyof Longitudinal Relaxation Time and of Buffer-GasPressure Broadening of Optical Lines", N uovo Cim.
44B, (1966) 378.
[4] H.J. Andra," Fine Structure, Hyperfine Structureand Lamb Shift Measurements by the Beam-foilTechnique", Physica Scripta 9, (1974) 257.
[5] T. Ohshima at a/.,"Production of a Nuclear Polarized
3 He Beam", Phys. Lett. B274, (1992) 163.
[6] Y. Arimoto at al.,"The Data Taking and Control
System for Polarized 3 He Ion Source Based on MECSIS", RCNP Annual Rep. (1995) 180.

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