372596208

12

RIKEN Accel. Próg. Rep. 24 (1990)

111-1-3. Coulomb Breakup Reaction of 90 MeV/u ¹⁴0

T. Takei, T. Motobayashi, K. leki, H. Murakami, Y. Ando, N. Iwasa, M. Kurokawa, C. Perrin, F. Merchez, S. Kox, D. Rebreyend,

S. Kubono, M. Ishihara, S. Shimoura, T. Kubo, and N. Inabe

NUCLEAR REACTIONS, ²⁰⁸Pb(¹⁴0, ¹³Np), E(^uO)/A = 91 MeV/u; measured correlation between proton and ^UN, CsI(Tl) scintillator array, position sensitive Si detectors, plastic hodoscopes.    )

The Coulomb breakup process, ¹⁴0 —> ^uN+p, in the field of ²⁰⁸Pb nucleus was studied at 91 MeV/ u. It can be related to the inverse reaction ^l:iN(p,y)¹⁴0, which is of great astrophysical interest, because it is a key reaction for the hot CNO cycle. The process via the 1 State of ¹⁴0 (£_cx=5.14 MeV) is important, and our purpose is to determine the transition probability between the ground 0⁺ and 1“ States or the radiative width r_r of the 1“ State.

Unstable ^l40 ions of 91 MeV/u were provided by the RIPS facility at RIKEN. Outgoing proton and ¹³N were detected in coincidence with the EMRIC device.^l) It consisted of plastic hodoscopes for angle measurement of protons, 24 two-dimensional position-sensitive Silicon detectors for the angle determination and particie identification of heavy ions, and 24 CsI(Tl) crystals coupled with PMTs for the identification of protons and total energy measurement (Fig. 1).

^I40 beam    plastic    PSD+Csl(Tl)

scintillator

hodoscope{Y,X)

Fig. 1. Schematic view of the experimental setup.

Figurę 2 shows a two dimensional plot of the energies of the proton and ¹³N in coincidence. Events are concentrated on the linę of Q_v=0, where Q_r denotes the excitation energy of the residual nucleus ²⁰⁸Pb. About 4xl0⁴ events were collected and they are to be used to deduce r_Y after correcting for an experimental back ground.

150---i-1-r— • -«--1-> • no

²⁰⁸Pb( ^l40.^ISN p)    -96

Z

L so

^    E-90 MeV/u

o - . —---*-1 -    »    *-

o    50    100    150

E_v (CHANNEL)

Fig. 2. Correlation between the energies of proton and ^l3N. The kinematical locus of Q_r = 0 is shown by the solid linę.

References

1) F. Merchez, S. Kox, C. Perrin, J. Mistretta, J.C. Gondrand, L.N. Imouk, P. Gretillat, and E. Schwarz: Nuci. Instrum. Methods, A275, 133 (1989).