RIKEN Accel. Prog. Rep. 48 (2015)

Ⅱ-1. Nuclear Physics

Interaction of 8B, unstable and loosely bound, with 208Pb: scattering andbreakup
C. Signorini,*1 A. Boiano,*2 C. Boiano,*3 C. Manea,*4 M. Mazzocco,*4 C. Parascandolo,*2 D. Pierroutsakou,*2A.M. Sánchez-Benítez,*5 E. Strano,*4 D. Torresi,*4 M. La Commara,*2 H. Yamaguchi,*6 D. Kahl,*6 Y. Hirayama,*7H. Ishiyama,*7 N. Imai,*6,*7 N. Iwasa,*8 S.C. Jeong, *7,*13 S. Kimura,*7 Y.H. Kim,*7 S. Kubono,*6,*9 H. Miyatake,*7M. Mukai,*7 T. Nakao,*7 Y. Sakaguchi,*6 T. Teranishi,*10 Y. Wakabayashi,*9 Y.X. Watanabe,*7 C.J. Lin,*11 H.M. Jia,*11L. Yang,*11 and Y.Y. Yang*12
The main motivation of this experiment was toinvestigate of the reaction dynamics induced by theradioactive ion-beam 8B, extremely loosely bound with Sp=137keV, at Coulomb barrier energy: i.e., reaction crosssection deduced from elastic scattering, as well as thetransfer and/or breakup processes. The 8B beam, providedby the CRIB facility, was produced via the inverse
kinematics reaction 3He(6Li, n)8B. The primary 6Li beam
intensity ranged from 1 to 3 eA, resulting in a 8B intensityof ~104 Hz, with an energy of 50±1 MeV. The 6Li ion
source had to be retuned twice owing to the total
consumption of the lithium material. This resulted in a
beamtime loss of two days, allowing us to accumulate
statistics for four days beamtime on target. As expected, the8B beam was contaminated by 7Be, via the 3He(6Li,pn)7Be
reaction, by 3He, recoiling from the 3He material of theproduction gas target, and by some 6Li halo (originatingfrom the primary beam, that was around 108 times more
intense than the secondary one); thus, the 8B beam purity
achieved was approximately 20%. The contaminations were
not problematic since each beam species was identified via
a time of flight technique. The light charged particles
produced in the reaction were detected and identified withsix E-E telescopes, consisting of 40–50 m + 300 mdouble sided silicon strip detectors. The detectors werearranged symmetrically around the target at a distance ofpproximately 11 cm. All the detectors with the related
electronics were brought from Italy, INFN1. For theE-detectors we utilized for the first time, ASIC digitalelectronics, whereas we used for the E detectors low-noiseelectronics; these electronics were also fully developed in
Italy2,3. The charged particles identified were 8B, 7Be, 6Li,4He, 3He, and protons (Fig. #1), confirming our preliminary
estimates: namely, the existence of a consistentFig. 1. E-Eres identification of the different ions producedin the scattering of the cocktail 8B-7Be-3He beam onto a208
Pb target.
amount of transfer (p transferred with 7Be out) and breakup
processes (→7Be+p, and possible subsequent 7Be breakup→3He+4He). Preliminary data from the angular distributionof the 8B elastic scattering confirm our expectations of astrong absorption occurring in the 8B-induced reactions.
In all the runs we were able to verify the good
capabilities of the homemade electronics2,3 for identifying
the various ions detected by the E silicon via the built-in
risetime detection. Fig. #2 shows a typical spectrum: signal
rise time vs. E, with the related ion identification.

*1

INFN, LNL, Legnaro
Department. of Physics and INFN, Napoli*3
INFN-Sezione di Milano*4
Dept. of Physics and Astronomy and INFN, Padova*5
University of Lisbon, Nuclear Physics Centre*6
CNS University of Tokyo, RIKEN
*7
KEK
*8
Department of Physics, Tohoku University*9
RIKEN Nishina Center*10
Department of Physics, Kyushu University*11
China Institute of Atomic Energy*12Institute of Modern Physics, Chinese Academy of Sciences*13
Institute for Basic ScienceFig. 2. Performances of the homemade electronics of thethin E detectors. The measurement of the risetime signal
vs. the energy loss allows for clear ion identification.

*2References

1) E.Strano et al., Nucl. Instr. and Meth. B317(2013)657
2) C.Boiano et al.; IEEE Nucl.Science Symposium and MedicalImaging Conference. (NSS/MIC)14-34(2012)865
3) C. Boiano et al.; IEEE Nucl.Science Symposium, Conference
Records 1-173(2009)1399.

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