D. X. Jiang

Study of the halo nucleus 6He through the direct nuclear reactions

Differential cross sections for quasi-elastic scattering, breakup reaction as well as 1n- and 2n-transfer reactions induced by 6He at 25 MeV/nucleon from a 9Be target are reported. The experimental data were analysed in the context of the coupled-channel calculations. The internal structure of 6He is discussed and further studies are proposed.

Efficiency calibration of a large-area neutron detector by using Am/Be neutron source

Neutron detection efficiency for a long wedge-shaped plastic scintillation detector was measured by using the Am/Be neutron source. The overall efficiency attains 23% at around 2 MeV and decreases to 15% at about 5 MeV. The experimental results are in agreement with the Monte Carlo simulation calculations.

Neutron removal reactions of 17C

Measurement of one-, two- and three-neutron removal cross sections of 17C at 79 A MeV on a 12C target has been carried out using the fragment separator RIPS of RIKEN. The one-neutron removal cross sections were compared with the few-body Glauber calculations coupled with the spectroscopic factors from the shell model. A fair agreement between the calculation and the experimental data was found. The prediction of the relation between the reaction cross sections and one-neutron removal cross section can be well satisfied, which means that 17C could be described by a core plus valence neutron system. The two- and three-neutron removal cross sections of 17C are reported for the first time.

Knockout reaction induced by 6He at 82.3 MeV/u

A knockout reaction experiment was carried out using a 6He beam at 82.3 MeV/u impinged on carbon and hydrogen targets. The recoil protons were detected in coincidence with the forward moving charged fragments and neutrons. It is demonstrated that through the correlation between the recoil protons and forward moving charged fragments, the core fragment knockout and valence nucleon knockout reaction mechanisms can be discriminated at energies around 100 MeV/u. The 5He ground-state resonance was reconstructed based on the selection of the valence nucleon knockout mechanism. The resonance parameters were obtained for both carbon and hydrogen targets, which are consistent with those previously reported in the literature. The importance of selecting appropriate reaction mechanisms is discussed based on reconstructions using events with larger transverse momentum transfer.

8He cluster structure studied by recoil proton tagged knockout reaction

Knockout reaction experiment for 8He at 82.3 MeV/u on Hydrogen target was carried out at the RIPS beam line in RIKEN. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The quasi-free knockout mechanism is identified through the polar angle correlation and checked by various kinematics conditions. The absolute differential cross sections for 6He core cluster are obtained and compared with the simple Glauber model calculations. The extracted spectroscopic factor is close to unity and a shrinking of the cluster size is evidenced.

Study on the 8He ground state via 8He(p, d)7He and 8He(p, t)6He reaction at 82.3 MeV/nucleon

The differential cross sections for reactions 8He(p, d)7Heg.s and 8He(p, t)6He2+ were measured by the coincidence of d + 6 He and t + 4He in a wide angular range from 15 to 130 degree in the center-of-mass system. The cross sections of the 8He(p, t)6Heg.s reaction were extremely lower than that of 8He(p, t)6He2+ reaction, and was not obtained from the present data. The experimental results were compared to the preliminary theoretical calculations in the frame of adiabatic distorted-wave approximation with the code Fresco. The results show that the configuration of (1p3/2)2(1p1/2)2 may have some probability in the ground state wave function of 8He. The cluster structure of 8He = 5H + 3H could not be neglected.

Recoiled Proton Tagged Knockout Reaction for 8He

Recently recoiled proton tagged knockout reaction experiments were carried‐out for 8He at 82 MeV/nucleon. The purpose of the experiment are: (1) Through the core knocked out technique, to study the correlation of the valence neutrons in the ground state of 8He. This should provide new experimental information to the neutron coupling and neutron matter, including the BCS pairing and BEC pairing. (2) Through the valence neutron knocked out technique, to study the resonant states 7He and the related single particle states. This will be complementary to the previous similar measurement but with better selection of the reaction mechanism.Some new recoiled proton telescopes and the forward neutron spectrometer was applied in the experiment. Performance of the detection system and very preliminary experimental results are shown here.

Elastic 3He‐transfer Reaction of 6He on the 9Be Target at 25 MeV/nucleon

Angular distribution of the cross sections of the elastic 3He‐transfer of the 6He nucleus on the 9Be target were measured at the incident energy of 25 MeV/nucleon. The experimental data at the backward angles were analyzed within the finite‐range DWBA framework. A large spectroscopic amplitude of 1.41 for the 3He‐cluster in the ground state of the 9Be nucleus was needed for this experiment, which is much larger than its theoretical prediction of 0.286.