1. Elastic scattering measurements using weakly bound nuclei at well above the Coulomb barrier energy
DREB th International Conference on Direct Reactions with Exotic Beams
4-8th June 2018
Matsue
Presented by
Dipika Patel
(IMP, CAS, China)
DREB D. PATEL-IMPCAS

2. Outline Introduction Motivation
Some of the recent measurements carried out using weakly bound nuclei by our group at IMP, CAS, Lanzhou
Elastic scattering of the proton drip line nuclei 8B and 9C
Elastic scattering using 10Be beam
Summary
DREB D. PATEL-IMPCAS

3. Introduction
Breakup coupling effects studied Experimentally and theoretically mainly by two different tools
Elastic scattering
Fusion cross sections
Breakup coupling effects are understood in terms of the Breakup Threshold Anomaly (BTA)
Unlike Threshold Anomaly(TA) in case of tightly bound nuclei
Typical Observation made in neutron halo nuclei at near the Coulomb barrier energy
Extensive study with fusion measurements
Enhancement at below the barrier and suppression at above the barrier has been observed
Interests have been devoted to the study using exotic projectiles as the observation of enhancement in fusion cross sections might facilitate the formation of super heavy nuclei
A very interesting result is the observation of a strongly destructive Coulomb-nuclear
interference, since the Coulomb component is larger than the total breakup cross section at sub-barrier energies
for heavy targets. This behaviour can be observed even at energies slightly above the barrier. Otomar et al. [14]
have shown that the nuclear breakup cross section increases linearly with A1/3
t , for the same Ec.m/VB energy,
where At and VB are the target mass and height of the Coulomb barrier, respectively. For the Coulomb breakup,
the cross section increases linearly with the Zt .
>>> Interestingly strong destruction of Coulomb-nuclear interference was observed
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4. What are Halo Nuclei? Characterized by weak bindings,
large spatial extent and few body structure
Well defined core+ one or more valance nucleons
Large transfer/break-up probability
The scattering with such projectile beams are very different from the scattering of tightly bound nuclei.
Elastic scattering is an ideal tool to study the information of the exotic structure and reaction mechanism of the weakly bound nuclei.
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5. Elastic scattering of 9,10,11Be on 64Zn target
How about proton-halo nuclei ?
At above-barrier energies ?
Motivation
Elastic scattering of 9,10,11Be on 64Zn target
Many experiments of elastic scattering measurments:
for neutron halo nuclei(6He, 11Li and 11Be )
for proton halo nuclei above the Coulomb barrier are still scarce
Coulomb Nuclear Interference Peaks (CNIP) for 11Be is suppressed.
The effect of the breakup on elastic scattering is strong.
(Effect of 11Be halo structure on nuclear reaction mechanism)
What about the
proton halo nuclei?
A. Di Pietro et. al., Phys. Rev. Lett. 105, (2010)
DREB D. PATEL-IMPCAS . . . . . .

6. 1p-halo 2p-halo 1p-ha lo 1n-halo 2n-halo 4n-halo
There are less than 300 stable nuclei, but about 2000 unstable nuclei can be produced in accelerators
Recently more focus has been given to study using 9,10,11C, 9Li,7,10,11Be, and 8B projectile beam at energies three times above the Coulomb barrier
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7. 8B elastic scattering
The Coulomb Nuclear Interference Peak (CNIP) is not suppressed.
The effect of the breakup on elastic scattering is small.
The very low breakup threshold ( MeV for 8B −→ 7 Be +p) has a small influence on the elastic scattering.
Within the experimental errors the angular distributions are identical fro 6Li,7Be, 8B projectiles
Y.Y.Yang, J.S.Wang et al., PRC 87, (2013)
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8. More investigation at different energy and target is required
8B and 11Be elastic scattering
valence neutron
∼ 1.4 times the Coulomb barrier
medium target 64 Zn
valence proton
∼ 3.3 times the Coulomb barrier
heavy target nat Pb
More investigation at different energy and target is required
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9. At lower energies, the breakup coupling effect is stronger.
Some observations in cases of 8B and 11Be nuclei at different energies and target masses
For neutron-rich projectiles, the breakup coupling effect is remarkable.
At lower energies, the breakup coupling effect is stronger.
For 11 Be: the coupling effect is stronger on heavier target but for 8 B: no influence.
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10. Recent measurement using 9C beam
Elastic scattering of the proton drip line nucleus 9C on a lead target at well above the Coulomb barrier energy
primary beam: 12C
primary target: Be target of 2652µm thickness
secondary beam: 500 pps for 9C, pps for 8B
9C, separation energy ~1.43 MeV.
In 1997, B. Blank et al. measured the one proton removal cross sections (σ1p) for 8B and
9C and the two proton removal cross section (σ2p) for 9C on targets varying from carbon 10
11 to lead at the energy of 285 MeV/nucleon, based on the projectile-fragment separator of
12 GSI [B. Blank et al., Nucl. Phys. A 624, 242 (1997).].
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11. Elastic scattering AD of both 9C and 8B nuclei along with the results from CDCC calculations
CDCC calculations by considering
For 9C->7Be+2p cluster structure
For 8B-> 7Be+p cluster structure
The present measurement for proton rich nuclei 9C shows a negligible suppression of the Coulomb rainbow, similar to that of 8B.
CDCC calculations for the elastic scattering angular distributions of 9C on 208 Pb at 227 MeV (upper) and 8B on 208Pb at 178 MeV (bottom), with all barriers (dashed line) with only the centrifugal barrier (dashed-dotted line) and with no barriers (dotted line), together with the experimental data.
This fact can be interpreted that the valence particle is proton, rather than neutron, so that the Coulomb and centrifugal barriers (if any) counteract the breakup coupling effects and result in the absence of the Coulomb rainbow suppression for proton-rich nuclei such as 9 C and 8 B.
The results from both CDCC calculations show more or less consistent each other and both reproduce the experimental results within the errors well, suggesting that the configuration of the one-proton or two-proton halo has a tiny influence on the couplings of the breakup and elastic scattering channels.
Communicated to Phys. Rev. C
Y.Y.Yang, J.S.Wang et al., et. al, (2018)
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12. (9C 7Be+2p). [B. Blank et al., Nucl. Phys. A 624, 242 (1997).].
CDCC calculations assuming 9C to have 7Be+2p cluster structure is observed to give similar elastic scattering cross sections as that of a 8B+p structure.
However, their breakup cross sections differ quite much at around the Coulomb rainbow angles.
This suggests that the breakup cross sections, instead of the elastic scattering ones, are more sensitive to the structure of proton-rich nuclei at incident energies around three times of Coulomb barriers.
The measured 2p values are 2-3 times larger than those of 1p, depending slightly on the target nuclei, markedly suggesting a di-proton configuration for 9C.
(9C 7Be+2p) [B. Blank et al., Nucl. Phys. A 624, 242 (1997).]. θ
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13. Elastic scattering angular distribution measurement for the 10Be+natPb system
Experimental setup
Experiment was carried out using 10Be beam provided by RIBLL facility at Institute of Modern Physics, Lanzhou, China
Primary beam :16O
Primary target : Be target of 2652µm thickness
A self supporting foil of 208Pb with a thickness of around 4.2 mg/cm2
Performed at around three times the Coulomb barrier (~48 MeV) of this reaction
Two position-sensitive Parallel-Plate Avalanche Counters (PPACs) with a position resolution of 1 mm.
Each PPAC has 80 gold-plated tungsten wires, 20µm in diameter, in both X and Y directions with sensitive area of 80×80mm2
Schematic layout
Two position-sensitive Parallel-Plate Avalanche Counters (PPACs) with a position resolution of 1 mm were used to reconstruct the position and incident angle of the incoming beam at the target event by event.
Each PPAC has 80 gold-plated tungsten wires, 20µm in diameter, in both X and Y directions with sensitive area of 80×80mm2. The scattered particles were detected by four sets of ∆E-E detector telescopes.
Each telescope consists of one double sided Si strip detector (DSSD) of 150 µm in thickness and 48X48mm2 in area.
Each DSSD has 16 strips on both sides and the orientations are perpendicular to each other.
The DSSDs were used to determine the energy loss and the position of the particles passing through the detector with an accuracy of 3×3 mm2. The QSDs were used to detect the remaining energy.
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14. Detectors setup The typical TOF spectra for the secondary beam
Scattered Particle detection by four sets of ∆E-E detector telescopes.
Each telescope consists of one DSSD of 150 µm in thickness and QSD of 1000 µm in thickness.
Each DSSD has 16 strips on both sides and the orientations are perpendicular to each other.
The DSSDs were used to determine the energy loss and the position of the particles passing through the detector. The QSDs were used to detect the remaining energy.
The typical TOF spectra for the secondary beam
Detectors setup
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15. Some preliminary results from the experiment using10Be beam on a lead target
2D spectrum and corresponding x and y- projections for one of the telescope
10Be
PRELIMINARY RESULTS
One channel cal. (Fresco)
Measured scattering angles for one of the telescope
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16. Summary
The results of elastic scattering angular distributions measurement using 8B, 9C, 10Be beams at IMP-CAS is presented at above the Coulomb barrier energies.
Continuum descritized coupled channels (CDCC) calculations also have been performed using Fresco code.
The present work shows that the Coulomb Nuclear Interference Peak (CNIP) is not suppressed for proton drip-line nuclei, in contrast to the neutron halo one.
Further, data analysis are being carried out for the 10Be projectile !!
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17. Thank you for your attention!!
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18. Group members at IMP-CAS, Lanzhou
J. S. Wang, Y.Y. Yang, P. Ma, X. Liu, J.B. Ma, S.L. Jin, Z. Bai, Hu Qiang, D. Patel, Q. Wang, W.H. Ma, F.F. Duan, Z.H. Gao, Y.C. Yu, Z.Y. Sun, Z.G. Hu, S.W. Xu, S.T. Wang, D. Yan,Y. Zhou, Y.H. Zhang, X.H. Zhou, H.S. Xu, G.Q. Xiao, and W.L. Zhan
List of collaborators
China Institute of Atomic Energy (CIAE)：
Chengjian Lin, Xinxing Xu, Huiming Jia
Beihang University：
Danyang Pang
Instituto de F´ιsica, Universidade de S˜ao Paulo,
Prof. V. Guimar˜aes
Instituto de F´ιsica, Universidade Federal Fluminense,
Prof. J. Lubian
The Andrzej Sołtan Institute ,Warsaw, Poland：
N. Keeley, K. Rusek
M. S. University of Baroda, India：
S. Mukherjee
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19. Results of CDCC calculations for reaction
of 12N projectile on a lead target
small breakup coupling effects as expected in case of well bound nuclei.
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20. Heavy ion research facility at Lanzhou
CSRe
CSRm
1000 AMeV (H.I.),
2.8 GeV (p)
RIBLL1
RIBs at tens of AMeV
RIBLL2
RIBs at hundreds
of AMeV
Schematic layout
RIBLL (Radioactive Ion Beam
Line in Lanzhou) is a typical
Projectile Fragmentation (PF)
type facility.
RIBLL has three focal points (T0,T1 and T2) and two focal planes (C1 and C2).
Please give some details here???
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