The 9th Symposium on Accelera1or Science and Technology, Tsukuba, Japan 1993

A Dual-Optically-Pumped Polarized Negative Deuterium Ion Source
M. Kinsho*, Y. Mori, K.Ikegami, and A.Takagi*Graduate University fur Advanced Studies
Oho 1-1, Tsukuba-shi, Ibaraki-ken 305, JAPANNational Laboratory for High Energy Physics (KEK)
Oho 1-1, Tsukuba-shi, Ibaraki-ken 305, JAPAN(abstract)
An optically pumped polarized H- source (OPPIS), which
is based on the charge exchange between H+ ions and electronspin-polarized alkali atoms has been developed at KEK[l].
Just by applying this scheme to a deuteron beam, it is difficult
to obtain a highly vector polarized deuteron beam. To obtainhighly vector polarized o- ions, we have developed a "dual
optical pumping type" of polarized o- source. With thisscheme, a 100 % vector nuclear-spin polarization foro- ionsis possible in principle. In a preliminary experiment, a 60 %of vector nuclear-spin polarized o- ions was obtained.

+D Beam

Production
RegionElectron
Oriented

Zero CroM FieldRbAtoms(Sona Transition)n· + Rb ( e I>
- D0 (c I>+ Rb•Do<IonizingIf ,I 0)

IIIIIRegion

II. INTRODUCTION
Polarized protons have been successfully accelerated inthe KEK 12-GeV proton synchrotron (KEK-PS) since 1985.
Many experiments have been carried out with polarized proton
beams so far. Recently, several proposals for the physics
experiments with polarized deuteron beams in the KEK-PS areunder discussion.
An OPPIS has been used for acceleration of polarized
proton beams in the KEK-PS so far. The idea of this type ofpolarized ion source was proposed by Anderson[2] and the first
operational ion source has been successfully developed atKEK. [3] Afterwards, various institutes have developed an
optically pumped polarized ion source (OPPIS) for their
1accelerators. [4][5][6]It has been believed that this type of polarized ion
source is not useful to produce a highly nuclear-spinpolarized(vector and tensor) deuterium ions. In 1988, Schneiderand Clegg[?] proposed a new nuclear-spin state selection
In spite of this possibility of making a highlyscheme.
polarized deuteron beam by optical pumping, they concluded
eventually in their paper that this dual optical pumping
scheme might be not practical because efficient opticalpumping of the thick target in the ionizer is difficult due toradiation trapping. However, we have re-examined the dualpumped scheme in detail and found that radiation trapping was
not a serious problem and highly polarized deuterons could beobtained with the dual-pumped scheme.[8]In this paper, we report the preliminary experimental
results which showed that the highly vector polarized negative
deuterium ions could be produced by the OPPIS with dualoptically-pumped technique.

Fig. 1 Block diagram of the dual-optically-pumped polarized
ion source.
These electron-spin polarized deuterium atoms equally
populate three hyperfine sub-levels lz=+ 1, 0, and -1 in a highmagnetic field, which are labeled the states 1, 2, and 3,
respectively in Fig.2. Using the Sona transition, the state 1(mj =+1/2, Iz=+l) goes to the state 1' (mj =-1/2, lz:=-1), thestate 2 (mj =+ 1/2, Iz=O) goes to the state 2' (mj =+ 112,Iz:=-1),
and the state 3 goes to the state 3' (mj =+ 1/2, Iz=O),
respectively as shown in Fig.2. Therefore, the deuterium
atoms with only the hyperfine level of Iz=-1 (state 1' in Fig.
2) has an opposite electron-spin state, mj =-1/2, of the othertwo sub-levels (2' and 3') after Sona transition.
EnergyIz=+l 4'
Iz=O 3'
Iz=-1 2'

1 Iz=+l2 Iz=O
3 Iz=-1Iz = -1 1'
Iz=O 6'
Iz=+1 5'4 Iz = -1
S Iz=O
6 Iz=+l0
Magnetic Field

II. OPPIS FOR DEUTERONS
A block diagram of the dual-optically-pumped polarized
ion source is shown in Fig.l schematically. The idea of thisscheme is as follows: After picking up the polarized electrons
from optically pumped alkali atoms, for example, deuterium
atoms are electron-spin polarized in the state of mj =+ 1/2 asshown in Fig.2.

Fig. 2 Hyperfine sub-levels of deuterium atom in Sonatransition.
When the alkali atoms in the ionizer are also optically pumped
and their electrons are to be spin polarized in the mj =+ 1/2-217-

state, only deuterium atoms with the electron-spin state of mj=-112 ( state 1' ) can form negative ions because of the PauliThis process is shown in Fig.3
exclusion principle.
The nuclear-spin state of the negative
schematically.
deuterium ions' in this case is lz=-1, the nuclear vector
polarization becomes -I. The nuclear tensor polarization is,in this case, -l. Using a proper rf transition simultaneously, apure nuclear tensor polarization of -2 may become possible.
III. EXPERIMENT OF DUAL OPTICAL PUMPING
In order to check this dual-pumped scheme
experimentally, we have used a following simple method.
When the alkali atoms in the ionizer are dectron-spin
polarized by optical pumping, deuteron atoms which are stayedin the state of mj=+ 1/2 can be permitted to form negative ionsin the charge-exchange reactions with alkali atoms of whichelectron-spin state is mj=-112, from the Pauli exclusion
principle. Contribution of the each hyperfine sub-level of
deuterium atoms after the Sona transition to the intensity of
the negative deuterium ions can be expressed in the following
equation.

I ( 1 ·) =I ( 2 .) =·= fog -C-/on =.!. It• ~UN:t.
3f 0g

•

(3)

It is clearly seen from this equation that e: depends only on
When the electron-spin polarizationPrj) and PJONZ.
directions of the alkali atoms in both neutralizer and ionizer

are parallel, e: becomes positive. On the other hand, when theelectron-spin polarization directions of the alkali atoms in eachcell are anti-parallel, E becomes negative.

Rb~ i+ ~0 (1 + ~oNz) a 0 l ,t~0 (1 - PIONZ) (J 0 l ,i+

1 . N0J(3 )= -3l + - (/ - ~ONZ) (J 0 {'2.

1 . N0.

3 2 (/ + ~ONZ) 0 / '1(4 )=3 t2 (1-~oNz)crol,
J(5 )=Here, we defme ease= Ooff-lon) 110 ff, where 10ftand 10 n are the beam intensities when the pumping laser for
the ionizer is off and on, respectively. Thus, from eq.(2) e canbe expressed in the following form.

(1)

neutralizer

1 . N0l_

mF+112
1.::+1
1...-i!
1.::-1. 1 . N0
(1 + ~oNz) cr o l.
Land I ( 6 ) =3 2Here, l(k') k=l,2... 6 is the negative deuterium ion currents
contributed from the each hyperfine sub-level k 'of deuterium
atoms which is shown in Fig. 2. And, No the density of thePwm the electron-spin
alkali atoms in the ionizer,
polarization of the alkali atoms in the ionizer, (J 0 is the spin
independent electron pick-up cross section to form negative
deuterium ions and l the ionizer length, respectively. Ineq.(l), i + and L are the intensities of the deuterium atoms
with the electron-spin states of mj=+ 1/2 and mj=-1/2, andand( = I v• (1 + Pv•)aswrittenaretheseIi_ = ~ (1- Pv• }, respectively. Here lrfJ is the intensityof electron-spin polarized deuteron atoms in the neutralizer andPrj) the electron-spin polarization of deuteron atoms in theneutralizer. Therefore, the total beam intensity of negative
deuterium ions after the ionizer can be written in following
equation.

Iv.No
I= -6-( 3- Pv•~oNzJ Uo l.

HSona transition Hionizer ~ o· (lz=-1)(J(2)

As can he clearly seen from this equation, theintensity of electron polarized deuteron atoms ( /rfJ ) is
determined by both electron-spin polarization of the deuteronatoms after the neutralizer and the alkali atoms in the ionizer.

mF+112 1111=-112~=-1
1.:·11.:0~ • Dual Op6cal Pumping"

Fig. 3 Principle of the dual-optically-pumped polarized
negative deuterium ion source.
Figure 4 shows the changes of the beam intensities ofnegative deuterium ions in each case that the electron-spin
polarization directions of the alkali atoms in the neutralizer
and the ionizer are parallel and anti-parallel, respectively. The
upper trace shows the beam intensity of negative deuterium
ions when the rubidium atoms in the ionizer are electron-spin
polarized whose polarization direction is parallel to thepolarization direction of the electron-spin polarized deuterium
atoms after the neutralizer. The lower one corresponds to thatwhen the polarization directions of rubidium atoms in theionizer and deuterium atoms after neutralizer are opposite. The
middle trace shows the beam intensity when the opticalpumping of the ionizer is off. Apparently seen from thisfigure, the negative deuterium intensity is increased ordecreased according to the polarization of rubidium atoms in
the ionizer as expected from eq.(3). In this preliminary
experiment, the electron polarization of rubidium atoms inionizer ( Pwm) was 1, therefore, the polarization of deuteronatoms ( PrJ)) was estimated to be 0.42.

-218-limited to less than 80%. This is because the spin-orbit
coupling in neutral deuterium atoms, which are created bypicking up polarized electrons from the optically pumped
alkali atoms in the neutralizer, reduces the electron-spin
polarization at this magnetic field strength. Thus, theobtained nuclear-spin polarization of negative deuterium ions
was almost 70% of the maximum limiting value. This is avery encouraging result and it can be said that the dualoptically pumped scheme for producing highly polarized
negative deuterium ions has worked in principle.

Fig. 4 The changes of the beam intensities of negative
deuterium ions.
From these experimental results, it was confirmed that thisdual optical pumping scheme for generating a highly polarized
negative ion worked well.

Calculation of PvFrom definition, the deuteron vector polarization ( Pv- ) ts
written as follows,(4)

Here h is the beam fraction of the deuteron nuclear spincomponent of mp+l, L the fraction of mp-1 and Io thefraction of mpO, respectively. From eq.(l), numerator anddenominator of eq.(4) can be written as,

f. -T_ =-{Do N0 fbo a 0 l,
3respectively. Then, eq.(4) can be rewritten as,

P. _ =(S)-2Pvo
3- Pv•~oNZ
nFrom eq.(S) and eq.(3), Pn· ts given by the followingequation
PIONZ (I - £). (6)The relationship between Pv· , Puwz

o.os

0.1

0.15

0.2

0.25

0.30.35£ ((1 .. -1.)/ 1,.)

Fig.S Relation between Pn- and £. The closed circle inIV. CONCLUSIONlno No
and[++ 10 +I_= - 6-(3- Pn•~oNz) 0 0 l,-2£0the figure shows the experimental result.

1Pv- =-~~~~~~~~~~~~~~

and£ areshown in Fig. 5. With the measurements of PwNZand £ ,we can estimate the deuteron vector polarization of negative
deuterium ions ( Pv-) from eq. (6) .
The result of the preliminary experiment is also
shown in Fig. 5. The closed circle in the figure shows theexperimental result. The electron-spin polarization of alkali
atoms in the ionizer (PwNZ) was meao;ured with a Faraday
rotation method. The errors shown in the tigure present thefluctuations of the data taken at different times. We obtained
In thePD- =-0.55±0JJ4 in the preliminary experiment.
present apparatus where the magnetic tield strength at theneutralizer is !.IT, the theoretical maximum polarization is

A new dual-optically-pumped scheme to obtain a highdeuteron-spin polarization in an optically pumped polarized
ion source has been examined in detail. The results of thepreliminary experiment are very encouraging and it is shownthat the new scheme, in principle, has worked. It wa'l
previously thought that the optically pumped polarized ion
source was not useful for producing highly polarizeddeuterons. Our results may open up a new possibilities forthe optically pumped polarized ion sources.
REFERENCES[ 1]Y .Mori et a! ; contributions for this conference.
[2] W.L.Anderson: Nucl. Instr. and Meth. 167,363(1979).
[3] Y.Mori, K.Ikegami, Z.Igarashi, A.Takagi,andS.Fukumoto: AlP Proc. 117,New York(l983)123.
[4] R.L.York, O.B. VanDyck, D.R.Swenson and D.Tupa:
Proc. of the Int. Workshop on Polarized Ion Sources andPolarized Gas Jets, KEK Report 9();.15(1990),page 142.
[5] L.Buchmann,C.D.P.Levy, M.McDonald, R.Ruegg, andP.W.Schmor: ibid page 161.
[6] A. Zelenskii, S.A.Kokhanovskii, V.G.Polushkin and K.N.
Vishnevskii:ibid page 154.
[71 M.B.Schneider and T.B.Clegg: Nucl. Instr. andMeth.,A254,630(1987).
[8]Y.Mori ; submitted to Nucl. Instr. Meth.

-219-