Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 47 (2014)

Design of experiment for search of 10N resonances with resonant scattering of9C off polarized proton
E. Milman,＊1,＊2 T. Teranishi,＊3 S. Chebotaryov,＊1,＊2 N. Imai,＊4 T. Kawahara,＊1 S. Sakaguchi,＊3K. Tateishi,＊1 and T. Uesaka＊1
The 9C+p elastic resonant scattering has been proposed
for search of resonances in the unbound 10N nucleus whose
structure is almost unknown at present. Theoretically, four
low-lying 10N levels are expected as two very broad 2s1/2and two very broad 1p1/2 proton single-particle resonances,each of which has a width much larger than 1 MeV. These
resonances overlap each other and may not be clearly
identifiable in the 9C+p excitation function. The level
information obtained in the experiment is useful for
discussing resonances in 10Li because 10N and 10Li aremirror partners that are expected to have similar structures.
The 10Li structure provides us with valuable information for
constructing the three-body model of the borromean 11Li
nucleus.
We proposed to measure analyzing power to resolvethese broad resonances1). The combined information of theexcitation function and an analyzing power spectrum will
enable us to impose more strict constraints on analysis ofthe resonances.
The range of center-of-mass energy was set to 1–5 MeV
to cover the ground state of 10N, predicted at around 1.5
MeV, and several excited states (one experimentallyobserved at 2.6 MeV2)). For the measurement of analyzing
power and excitation function, we considered to adopt thethick-target method in inverse kinematics (TTIK), wherethe excitation function can be scanned with a single beamenergy utilizing the energy loss of the beam particle in thetarget.
We conducted LISE++ simulation to produce 9C beam on
RIPS with a low energy of 5 MeV/A. In the simulation,using a 12C primary beam with 70 MeV/A and 200 pnA, 3.5mm-thick Be target, and 583 mg/cm2-thick Al wedge
degrader at F1, beam intensity obtained at F2 was ∼3.5 ×
104 pps with a purity of >90%. RF deflector can be used toreduce the rate of contamination because the rate ofcontaminations such as 8B and 7Be is one order magnitudelarger than the simulated value in the proton rich side. We
also planned to replace Al wedges with (CH2)n wedges todecrease the multiple scattering effect.
Polarized target is required for the measurement ofanalyzing power. A polarized proton solid target for
low-energy beam experiments3) has been designed based on
existing system for intermediate energies4).

A single crystal of p-terphenyl doped with pentacenemolecules with a concentration of 0.05 mol% was chosen as
the target material, which allows us to operate the target invacuum environment at room temperature. Thickness of thetarget was chosen to be 110 μm to cover the range of thesecondary 9C beam. Strength of the magnetic field waschosen to be 0.2 T to maintain the polarization, and thisdoes not severely affect the particle trajectory. The
estimated polarization was 15% at this magnetic field.
Production and polarization of thin films (7 μm) haverecently been realized at Osaka University5), where the sizeof the grown single crystal was 3 × 4 mm2. However,production of large sized single crystals, with a desired
diameter of 2 cm, remains a challenge. We designed atechnique to grow a crystal between two thin films.
We consider use of silicon detector for detection of
protons with energies of 3–18 MeV. Each telescope consistsof one 65 μm-thick double sided silicon detector (DSSD)
and two 1.5 mm-thick DSSDs with a detection area of 50
mm × 50 mm. Two telescopes are planned to be placed atboth left and right sides of the beam line at a laboratory
angle of ±22.5◦, where the vector analyzing power isexpected to have large absolute values. We plan to place
another telescope at 0◦. The distance between the target andthe telescopes is 250 mm.
TTIK method allows us to archive an ECM resolution ofapproximately 76 keV with a proton energy resolution of120 keV.
��� �1��1
�� �����������������1��� ��� �� �Equation 1 shows dependence of ECM on recoil protonenergy, where A= 9 for 9C and θp is proton scattering angle
in laboratory frame.
In conclusion, we proposed the first low energy RI
experiment with polarized proton target. RIKEN polarized
proton target has been redesigned for use with low energy
RI beam. We plan to construct the target in the next fiscal
year.
References
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2)
3)

RIKEN Nishina Center
Department of Physics, Kyungpook National University＊3
Department of Physics, Kyushu University＊4KEK＊14)＊2

5)- 24 -T. Teranishi, S. Sakaguchi, T. Uesaka et al., AIP Conf. Proc.
1525, 552 (2013).
A. L é pine-Szily et al., Phys. Rev. C 65, 054318 (2002).
S. Sakaguchi et al., Nuclear Instruments and Methods inPhysics Research B 317, 679-684 (2013)
T. Uesaka et al., Nuclear Instruments and Methods in Physics
Research A 526, 186 (2004).
K. Tateishi et al., J. Phys. Soc. Jpn. 82, 084005 (2013).