RIKEN Accel. Prog. Rep. 50 (2017)

Research Activities 1991–2016

Experiments at SMART and related activities
Hideyuki Sakai ∗1,∗2
The E4 experimental room is now occupied withthe fixed-frequency Ring Cyclotron (fRC), a part of
the RIBF accelerator complex. It was once occupiedby the Swinger and Magnetic Analyzer with Rotator
and Twister (SMART). SMART was a versatile magnetic spectrometer primary designed for the spectroscopic study of nuclei by means of the missing-energy(mass) method induced by intermediate-energy heavyion beams (A/Z ≥ 2) from the RIKEN Ring Cyclotron(RRC), and it was active during 1990–2005.
Here, some of the research programs conducted at
SMART as well as related activities of the author’sgroup are brieﬂy described.

solid-angle (20 msr) and wide-momentum-acceptance(δp/p = 40%) spectrometer with a momentum resolution of p/Δp = 4, 000. With the full conﬁguration(QQDQD) having the second focal plane FP2, it works
as a high-momentum-resolution (p/Δp = 12, 000) spectrometer with a moderate solid angle (10 msr) and momentum acceptance (δp/p = 4%).
The construction of SMART was ﬁnished in 1990,
following which commissioning works were conducted.
Regrettably, SMART was decommissioned in 2005 tocreate space to install fRC.

SMART magnetic spectrometer

Although the deuteron beam at the RIKEN Accelerator Research Facility (RARF) with a maximum energyof 270 MeV was already unique at the time, the author’s group realized that it would become truly unique
if the polarization degrees of freedom are available.
We proposed the construction of an atomic-beamtype Polarized Ion Source (PIS) dedicated to thedeuteron beam in 1990 (Fig. 2). It was accepted by
RARF. PIS construction was ﬁnished by 1992. The
beam intensity achieved was about 140 μA with 80%
polarization.2) At the exit of PIS, a Wien ﬁlter system
was equipped to rotate the deuteron polarization axis,
i.e., the spin quantization axis. Owing to the single-

Construction of polarized ion source

The SMART magnetic spectrometer was designed
and constructed by the SMART Group,1) led by Hajime Ohnuma of the Tokyo Institute of Technology.
SMART, shown in Fig. 1, consisted of a beamswinger and a magnetic spectrometer. To change thescattering angle of a reaction, the incident beam isswung with respect to the target, and the spectrometer stays still. The magnetic spectrometer was composed of three quadrupole magnets and two dipole magnets in the quadrupole-quadrupole-dipole-quadrupoledipole (QQDQD) conﬁguration.
The ﬁrst three components (QQD) having the ﬁrst
focal plane FP1 were designed to work as a large-

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Fig. 1. Photograph of the SMART magnetic spectrometerin the E4 experimental hall.
∗1∗2

SPIN ROTATOR

Senior Visiting Scientist from the University of Tokyo (1993–2010)
At present RIKEN Nishina Center

Fig. 2. Atomic-beam-type polarized ion source of RIKEN.

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RIKEN Accel. Prog. Rep. 50 (2017)

turn extraction for both the AVF injector cyclotron
and RRC, the polarization axis is maintained during
the accelerations, which allows us to control the polarization axis to any direction at the target positionof SMART. This is the ﬁrst facility in the world thatrealized this unique feature.

270 MeV.
The measured results together with Faddeev-type
three-body calculations employing the modern twonucleon force (2NF) are shown in Fig. 4. A surprisingly
large discrepancy of about 30% in the cross-sectionminimum region of 100◦ –150◦ was found between our
measurement and the Faddeev calculations.
This discrepancy led us to get deeply involved in the
study of the three-nucleon force (3NF).

Polarization measurement with d + p scattering
After the successful construction of PIS and subse
quent acceleration of the polarized deuteron beam (d)to 270 MeV, we needed to measure the absolute magnitude of the polarization. At the time, it was notknown which reaction (scattering) should be chosen forpolarimetry sensitive to both vector and tensor polarizations. Our ﬁrst choice was the d + p scattering.
The complete analyzing powers (Ay , Axx , Ayy , Axz )for the elastic d + p scattering were successfully measured and published in Ref. [3] by using the beamline polarimeter system together with the cross sections. Since all analyzing powers showed moderatemagnitudes, it was concluded that the d + p scattering
could be an ideal scattering reaction for polarimetry atThree-nucleon force study
Soon after the above study, the full Faddeev calculation with 2NF plus 3NF became available.4) Meanwhile, we extended our d + p scattering measurements
to SMART, which allowed us to measure wide scattering angles θc.m. = 10◦ − 180◦ . Moreover, the polarizay p) scatteringtion transfer coeﬃcients Kij
for the 1 H(d,were measured for the ﬁrst time at Ed = 270 MeV. The
scattered proton polarization was measured by the polarimeter (DPOL) set at FP2 of SMART. DPOL will
be described later.
The results obtained at SMART were published inRef. [5] together with the state-of-the-art Faddeev calculations with the modern 2NF + Tucson-Melbourne(TM) 3NF, as shown in Fig. 5 for cross sections andspin observables.
The cross-section diﬀerence is beautifully explainedby the calculation, which is the ﬁrst conﬁrmation of
the 3NF eﬀects in the three-nucleon continuum (scattering) system. This was the milestone of the 3NF
study. In contrast, some polarization observables were
not described well with calculations, which indicatessome deﬁciencies in the spin-dependent part of 3NF.
After this study, 3NF eﬀects have been seriously
considered not only in few-body systems but also innuclear-structure calculations particularly for neutronrich nuclei as well as for high-density matter such asa neutron star. For example, for the nuclear structure

Fig. 3. Vector and tensor analyzing powers. Dashed andsolid curves show the results of Faddeev calculations
with the Argonne v14 2NF for j ≤ 3 and j ≤ 4, respectively. See Ref. [3] for details.

Fig. 4. Diﬀerential cross sections. The ﬁgure is taken from
Ref. [3] with modiﬁcation. The dashed and solid curves
are the same as in Fig. 3.

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Research Activities 1991–2016

 2 He) reaction
Spin-isospin responses with (d,calculation for neutron-rich Ca isotopes, see Ref. [6].
In SMART, measurements were extensively extended
for the study of 3NF:

The (d, 2 He) reaction has a very interesting quantum
selection rule as a reaction probe. It excites exclusively
spin-isospin ﬂipped states ΔT = 1 and ΔS = 1, while
the (n, p) reaction excites, in principle, ΔT = 1 and 2 He) reaction is suited for
ΔS = 1 and 0. Thus, the (d,the study of the Gamow-Teller (GT) state 1+ as well
as spin-dipole states 0− , 1− , and 2− starting from a
0+ target. Those transitions are in the β + direction,
which plays in some cases an essential role in the evolution of star burning or supernova explosion processes.
Here, 2 He indicates the two-proton coupling to form thespin-singlet state [1 S0 ]. To ensure [1 S0 ] experimentally,
one needs to detect two protons in a small momentum corn (p1  p2 ), resulting in a small relative energy( < 1 MeV). These conditions are not necessarily simple to satisfy by experimentally at an intermediate energy. The detection system for 2 He was constructed at
FP1 of SMART.15) The ﬁrst results without polarization degrees of freedom were published in Refs. [16,17]
to show the usefulness of the (d, 2 He) reaction as a spectroscopic tool for GT transitions.
The tensor analyzing powers Axx and/or Ayy of the =• Complete dσ/dΩ, Ady , Axx , Ayy , Axz at E(d)7)
140, 200, and 270 MeV.


y
y
y
• Polarization transfer Kyy , Kxx
, Kyy
, Kxz
, P y for
 = 270 MeV.8)
θc.m. = 90◦ –180◦ at E(d) =• Resolving the dσ/dΩ discrepancy at E(d)9)
270 MeV.
• Polarization transfer for the breakup process of d+10)p → p + p + n at E(d) = 270 MeV.
Now this comprehensive data-set has become a world
standard for theoretical studies of 3NF eﬀects.
The 3NF study was further extended to higher
deuteron energies at the RIBF by constructing the
BigDpol polarimeter: = 500 and• Complete Ady , Axx , Ayy , Axz at E(d)11)
596 MeVand = 380 MeV.12)
at E(d)A four-body system was also studied by theH(2H, 3 He)n and 2 H(2H, 3 H)p reactions at Ed = 140,
200, and 270 MeV for wide scattering angles θc.m. =0◦ −110◦ . The physics interest here was that the tensor
analyzing powers Axx , Ayy , and Axz could be sensitive
to the D-sate (L = 2) property in 3 He/3 H. Ambiguityin the reaction mechanism prevented us from drawing
a clear conclusion.13,14)
2

Fig. 5. Angular distributions of cross section, analyzing
powers, and polarization transfer coeﬃcients.
See
Ref. [5] for symbols and theoretical curves.

Fig. 6. Excitation energy spectra of cross section and Axx .
The ﬁgure is taken from Ref. [18].

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Research Activities 1991–2016

RIKEN Accel. Prog. Rep. 50 (2017)At θ ∼ 5◦ , it takes another extreme value of Azz ∼ +1,
demonstrating very strong angular dependence. The
present experimental Azz value of the peak at Ex =9.3 MeV is an angle-integrated value over θc.m. = 0◦ −1◦ and, therefore, Azz ∼ −1.2 instead of −2.

 2 He) reaction are very useful as a spectroscopic tool(d,in identifying the spin-parity J π , in particular, for the
spin-dipole states (J π = 0− , 1− , 2− ). Finding a possible collective enhancement of 0− states through its
coupling to the pionic degrees of freedom in nuclei wasof particular interest.
For natural-parity states, the tensor analyzing power
predicted with PWIA tends to have an extreme valueof
Axx ∼ +1 d ) with DPOLΔS = 1 and 2 excitations via (d,Isoscalar spinﬂip states (T = 0, S = 1) are least
known because the eﬀective interaction Vσ responsible
for the excitation is weak and there is no good experimental means to isolate the state.
The deuteron inelastic scattering (d, d ) is very attractive to explore the isoscalar spinﬂip states. Since
the deuteron has an intrinsic spin of S = 1, the inelastic
scattering could have single spinﬂip ΔS = 1 and double spinﬂip ΔS = 2 processes in addition to a strong
non-spinﬂip ΔS = 0 process. The ΔS = 1 and ΔS = 2
spinﬂip processes may be connected to the target spin
excitations of S1 and S2 , respectively. They are expressed in terms of polarization observables as follows:for 1− or 2+ ,while that for the unnatural-parity 0− state is
Axx ∼ −2
for 0− ,Ayy = +1
for the scattering angles in which the cross section becomes maximum. Note that the tensor analyzing power
can take a value +1 ≥ Aij ≥ −2.
At θ = 0◦ , Azz takes an extreme value,
Azz (0◦ ) = +1◦

Azz (0 ) = −2

for 1− or 2+ ,for 0− .

 
1
y y
),
(4 − P y y − Ayy − 2Kyy
9
 

1
y y
),
S2 =
(4 + 2P y y + 2Ayy − 9Kyy + Kyy
18

S1 =

Note that Axx = Ayy at θ = 0◦ and Axx + Ayy +Azz = 0. It should be remarked that the result of
Azz (0◦ ) = −2 for 0− is a model-independent one owing
to the parity conservation in the spin-parity structureof 1+ + 0+ → 0+ + 0− .
The usefulness of the tensor analyzing powers was,
 2 He)12 B
for the ﬁrst time, demonstrated by the 12 C(d,18)
reaction at Ed = 270 MeV.
The result is shown in
Fig. 6.
A striking feature is the conspicuously large Axx observed at energies corresponding to 2+
1 (0.95 MeV) and
1−
(2.62
MeV),
which
agreeswiththesimple prediction
1
above that Axx becomes close to +1 for natural-parity
states. The bump at Ex = 7.5 MeV in residual 12 B has
been believed on the basis of many theoretical calculations and studies of (p,n) reactions to be dominatedby 1− states. However, the Axx values corresponding
to the bump are found to be almost similar to that of2−
2 (4.5 MeV), which clearly indicates that the bumpis dominated by 2− .
A spectroscopic study on the neutron-rich light nuclei 6 He, 9 Li, and 11 Be was also performed.20,21)
A model-independent spin-parity determination of
the 0− state was applied for the ﬁrst time to the12 2 He)12 B reaction by measuring the tensor anC(d,alyzing power Azz at θ = 0◦ .19) The measurement was
performed by preparing the tensor polarized deuteronbeam aligned to the beam direction (pzz beam), andthe result is shown in Fig. 7.
It is indeed very remarkable to ﬁnd that the Azz ofthe peak at Ex = 9.3 MeV takes a very large negativevalue of ∼ − 1.2. Thus, it is unambiguously concluded
that the bump at 9.3 MeV is dominated by 0− states.
It is noted that Azz = −2 holds only at exactly θ = 0◦ .

Fig. 7. (a) Double-diﬀerential cross sections at θc.m. = 0◦ –1◦ as functions of 12 B excitation energy for pzz = −1.16
and +0.79 polarized beams. (b) The result of peak ﬁtting, and (c) the corresponding Azz spectra. Azz foreach peak obtained by the ﬁtting is shown by the closed
circle, while that for the continuum binned in 1 MeV isshown by open circles. The ﬁgure is taken from Ref. [19].

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RIKEN Accel. Prog. Rep. 50 (2017)

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where A, P , and K refer to the analyzing power,
induced polarization, and polarization transfer coeﬃcient, respectively. The vector and tensor polarizations of scattered deuterons have to be measured, whichis experimentally very diﬃcult and complicated. To
measure S1 and S2 , we constructed the Deuteron POLarimeter (DPOL) at FP2 of SMART.22) DPOL utilizes the d+C
elastic scattering and the 1 H(d, 2 He) reaction for vector and tensor polarization analysis, respectively.
 d ) reaction and 12 Si(d, d ) reaction were
The 12 C(d,measured and S1 and S2 were derived for the ﬁrst
time.22,23) The result is shown in Fig. 8 for the crosssection and the single- and double-spinﬂip cross sections. The S1 value for the 2+ state is close to zero,
while that for the well-known 1+ state at 12.71 MeV
is large. This fact clearly indicates that S1 will be an
excellent spectroscopic tool to investigate isoscalar spin
excitations.
It is quite surprising to ﬁnd that the S2 values are
consistent with zero over the measured excitation energy region, and no clear indication of the double spinﬁlp (ΔS = 2) state was found.

HICEX reaction
Giant resonances represent major modes of collective
motion of nuclei, and various multipole modes exist,
reﬂecting isospin (T ) and spin (S) degrees of freedom.
Among them, an isovector non-spinﬂip quadrupole resonance (IVGQR), which is supposed to be a coherent
state of 1p-1h excitations across two major shells (2h̄ω),
was studied by the heavy-ion charge exchange reactionof 60 Ni(13 C, 13 N)60 Co at E/A = 100 MeV.24) The measurement was performed at the FP2 of SMART, wherea pair of the cathode readout drift chambers 25) was
placed for 13 N detection.
Figure 9 shows typical energy spectra, which clearly
display two prominent bumps at Ex = 8.7 ± 0.5 MeV
with Γ = 2.8 ± 0.8 MeV and at Ex = 20 ± 2 MeV
with Γ = 9 ± 2 MeV. To determine the multipolarities
for those bumps, standard DWBA calculations were
performed. The angular distributions of bumps were
well ﬁtted with the angular momentum transfers with
L = 1 and L = 2, respectively. Based on this, it is concluded that the bump at Ex = 8.7 MeV is due to thewell-known isovector giant dipole resonance (IVGDR)
and the bump Ex = 20 MeV is due to IVGQR. Thus,
IVGQR was unambiguously identiﬁed. It is interesting to note that an isovector giant monopole resonance(IVGMR), which is also expected at a 2h̄ω excitationenergy and therefore should overlap with IVGQR, was
not distinctly observed.
EPR paradox with EPOL
It is an intriguing and fascinating problem to verify
the basic idea of quantum mechanics. It is well known
that Einstein, Podolsky, and Rosen (EPR) 26) asserted
that quantum mechanics is incomplete in terms of lo-

Fig. 8. Excitation energy spectra for the 12 C(d, d ) reactionat Ed = 270 MeV integrated over θlab = 2.5◦ –7.5◦ . (a)An excitation energy spectrum. (b) The spectrum multiplied by S1 . (c) The spectrum multiplied by S2 . The
ﬁgure is taken from Ref. [23].

Fig. 9. Energy spectra of the 60 Ni(13 C, 13 N)60 Co reaction
for the angular bins of (a) θlab = 0◦ − 0.2◦ and (b)θlab = 0.8◦ − 1.0◦ . The ﬁgure is taken from Ref. [24].

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RIKEN Accel. Prog. Rep. 50 (2017)

The quantum-mechanical prediction of the spincorrelation function is
SQM (Φ) = 3 cos Φ − cos 3Φ,while that of Bell-CHSH states satisﬁed by local realistic theories is
SCHSH (Φ) ≤ 2,irrespective of Φ (opening angle between spins of a
proton pair). For the deﬁnition of Φ, see Refs. [29,30].
It is amazing to ﬁnd that the experimental data follow the quantum-mechanical prediction faithfully forthe entire angular region and exceed Bell-CHSH’s limit
over a wide angular range.
At Φ = π/4, the measured value of the spincorrelation function isFig. 10. Spin-correlation function S(Φ) vs Φ. The solid
circles are experimental results compared with SHCH
and quantum-mechanical predictions. Errors are shownby the blue band. The ﬁgure is taken from Ref. [30].

Sexp (π/4) = 2.83 ± 0.24sta ± 0.07sys ,which violates Bell-CHSH inequality at the 99.3% conﬁdence level. This is the ﬁrst Bell-CHSH test using
massive particles with signiﬁcant accuracy. A characteristic feature of this experiment is that it is freefrom the loopholes of post-selection, causality (partially
fulﬁlled), perfect detector eﬃciency (charged particle),
and an ‘event-ready’ detection system.
Thus, EPR assertion does not seem to hold, andthe ‘Spooky action at distance,’ phrased by Einstein against quantum-mechanical non-local phenomena, does exist.
Later, the Bell-CHSH inequality test was attemptedwith a proton-neutron pair in a singlet state via the(d, pn[1 S0 ]) reaction. For that, a neutron polarimeter
SMART-NPOL was constructed. Since the EPOL for
proton and SMART-NPOL for neutron were separated
by a few meters, a loophole of causality (space separation) could be overcome. Unfortunately, the statisticalaccuracy did not allow us to draw any conclusion.31)

cal realism, a classical physicist’s conception of nature. Bell 27) rendered this argument quantitative andamenable to experimental veriﬁcation, as he showedthat any local hidden variable theory will result in
an inequality, which can contradict quantum mechanical predictions, i.e., Bell’s inequality or equivalently
the Clauser, Horne, Shimony, and Holt (CHSH) inequality.28) The Bell-CHSH formulation concerns experiments where spin orientations have two possible
outcomes (up/down). Many experiments have been
performed with entangled photon pairs with great accuracy. However, there have not been any experimentswith spin- 12 particle pairs having mass with a statistically signiﬁcant accuracy.
To conduct an experimental test of the Bell-CHSH
inequality with massive particles, viz. two protons, two
protons coupled to a spin singlet state [1 S0 ] as the initial state must be prepared, and the spin correlation of
two separated protons satisfying the locality property
in the ﬁnal state must be measured. The two-proton
system in the spin singlet state is nothing but 2 He,
which is very familiar to us as an ejectile of the (d, 2 He)
reaction. It should be mentioned especially that theuse of 2 He has a huge merit. Since 2 He entangled by
the strong interaction is an unbound two-proton system, two protons are automatically separated in a very
gentle manner by the electromagnetic Coulomb force
between them keeping their entanglement.
A spin polarimeter (EPOL) dedicated to measure thespins of two protons simultaneously was constructed
and set up at FP2 of SMART.29)
Entangled proton pairs were produced as a decay of
2
He formed in the 1 H(d, 2 He) reaction at a 270 MeV
deuteron beam. The experimental result is shown in
Fig. 10.29,30)−→  4p) He reaction
Polarized 3 He target and 3 He(d,The ground state of deuteron is a mixture of S- andD-states with orbital angular momenta of L = 0 and 2,
respectively. Although the D-state plays an importantrole in determining various properties of the deuteron,
it is not well determined, in particular at the high momentum region, owing to a lack of experimental means
to directly access the D-state component.
A new approach to access the D-sate component using the polarization correlation measurement by the
→  4
3−
He(d,
p) He reaction was proposed.32) The polarization correlation coeﬃcient C// can be deﬁned in termsof PWBA asC// =w2 (kpn )9,2
4 u (kpn ) + w2 (kpn )(1)

where u2 (kpn ) and w2 (kpn ) are the S- and D-state wave

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RIKEN Accel. Prog. Rep. 50 (2017)

Research Activities 1991–2016

functions of deuteron in momentum space, respectively,
and kpn is the internal momentum. It is remarkable tosee that C// is directly proportional to w2 (kpn ).
 p)4 He reaction was performed with the d,
The 3 He(
vector- and tensor-polarized deuteron beam of 270 MeV
and a vector polarized 3 He target at θlab = 0◦ . For
this purpose, a spin-exchange-type polarized 3 He gas
target was constructed.33) The 3 He nuclei were polarized via the spin-exchange reaction with the optically
pumped Rb atom. The 3 He gas density was 2.2×1020
atoms/cm3 with a polarization of 0.12. The result 32)
is shown in Fig. 11. Neither DWBA nor PWBA calculations could reproduce the present result, which casta question on the relevance of the reaction mechanism.

at 100 K by transferring a large population diﬀerence
among the photo-excited triplet states of pentacene tothe hydrogen nuclei. The proton polarization achieved
was about 0.2.
The ﬁrst RI beam experiment to measure the analyzing powers (Ay ) for the 6 He(p, pgnd )6 He scattering
was conducted in inverse kinematics.36) The 6 He beamwith 71 MeV/nucleon was provided by the RIKEN
Projectile-fragment Separator (RIPS).
Figure 12 shows the ﬁrst results, in which the analyzing powers are compared with those of 6 Li(p, p0 )6 Li
scattering. Although the statistics are poor, the backward angular behavior of Ay seems to be very diﬀerent
from each other, even though the shapes of cross sections are similar. A very simple optical model analysis
indicates that the spin-orbit potential for 6 He is locatedoutside by about 0.8 fm compared to that for 6 Li. It isnoted that the present Ay behavior resembles that of
the 4 He(p, p0 )4 He scattering.
Later, the 6 He(p, p0 )6 He scattering experiment was
repeated with a higher proton polarization and improved detection system.37) Further, scattering from amore exotic nucleus 8 He(p, p0 )8 He, was performed.38)

Polarized proton target and 6 He(p, p0 )6 He scattering
It is quite exciting if we could extend spin-observablemeasurements to radio-isotope (RI) beams. In the RI
experiments, a high-density target is necessary to gain
suﬃcient luminosity since the intensity of the RI beams
is typically less than 106 particles/s. In this respect, asolid target, rather than a gas target, is desirable. For
the proton, a polarized solid proton target (PSPT) isavailable. However, a conventional PSPT system requires a high magnetic ﬁeld (≥ 2.5 T) and a very low
temperature (≤ 1 K), which is very inconvenient for
the RI beam experiments because it inevitably utilizes
inverse kinematics for the scattering, i.e., it is necessary to detect very-low-energy recoiling protons. We
constructed a PSPT system that overcomes such experimental diﬃculties.
Since the construction of the PSPT system is described in Refs. [34,35] in detail, only an outline isgiven below. Protons in a single crystal of naphthalene(C10 H8 ) doped with pentacene (C22 H14 ) with a size of
4×5×2 mm3 are polarized in a magnetic ﬁeld of 0.3 T

Neutron radiology study
Radiological studies such as the neutron yield induced by heavy-ions 39) or radioactive cross sections by

Fig. 12. Cross sections and analyzing powers. The solid anddashed lines are the results of optical model analyses
ﬁtted to the cross sections. The ﬁgure is taken from
Ref. [36].

Fig. 11. Present datum in a black dot with statistical error.
Solid and dashed lines are DWBA and PWBA calculations, respectively. The ﬁgure is taken from Ref. [32]with modiﬁcation.

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Research Activities 1991–2016

RIKEN Accel. Prog. Rep. 50 (2017)quasi-mono energetic neutrons 40,41) were conducted by
Shouji Nakamura of Tohoku University and his collaborators using the swinger part of SMART. Obtained
data provide very useful bases for designing radiation
shields of accelerator facilities.

sult of our cooperative but critical discussions. Without him, the scientiﬁc achievements described here
could not be accomplished.
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SHARAQ; successor of SMART
Although SMART was decommissioned and disassembled in 2005, its scientiﬁc motivation/tradition waspartly succeeded by the SHARAQ project of the Center for Nuclear Study (CNS), the University of Tokyo.
SHARAQ stands for Spectroscopy with High-resolution
Analyzer of RadioActive Quantum beams.
The SHARAQ project was born while the author was
the Director of CNS. The intention was to construct
a high-resolution magnetic spectrometer dedicated to
the RI beam experiments at RIBF. To achieve a highmomentum resolution together with high angular resolution, SHARAQ was designed to have dispersionand angular-matching functions utilizing the momentum dispersion of BigRIPS. The idea of ‘an exothermic
charge-exchange reaction with unstable RI beams to
explore exotic spin-isospin responses in nuclei with amagnetic spectrometer’ was approved by JSPS.42) The
construction of SHARAQ started in 2005, and its commissioning started in 2010.
It should be mentioned that the ﬁrst dipole magnet of SMART was reused in SHARAQ, again as theﬁrst dipole magnet in a QQDQD conﬁguration. Thus,
SHARAQ carried forward not only the scientiﬁc motivation but also a dipole magnet of SMART.
Summary and acknowledgments
In summary, various nuclear sciences were promoted
exploiting the SMART magnetic spectrometer by manyusers. SMART was active for 15 years. During that
period, 63 peer-reviewed papers were published, and17 graduate students earned their Ph.D degrees.
Our group consistently pursued nuclear physics utilizing spin degrees of freedom of beam, target, andscattered particles. For that aim, we constructed PIS,
DPOL, EPOL, SMART-NPOL, a polarized 3 He target,
and PSPT. Strong support by RARF is greatly appreciated, in particular on for PIS, the polarized 3 He target,
and PSPT constructions.
I am very much indebted to many collaborators andgraduate students, who were the main contributors to
the works mentioned above. Without their incessant
hard working eﬀorts of day and night, nothing could
have been achieved. For lack of space, I regret that thenames of contributors cannot be explicitly mentioned.
However, I cannot help but mention my esteemed collaborator Hiroyuki Okamura (deceased). The construction of various devices and scientiﬁc works were the re-S-21