Kyushu University Tandem Accelerator Laboratory Research Articles

Measurement of Double Differential Neutron Yields from Thick Aluminum Target Irradiated by 9 MeV Deuteron

Abstract Double differential neutron yields from a thick aluminum target irradiated by 9 MeV deuterons were measured at the Kyushu University Tandem accelerator Laboratory (KUTL). An NE213 liquid organic scintillator (50.4 mm thick and 50.4 mm in diameter) was used as a neutron detector. Neutron yields from the target were measured at nine angles between 0° and 140°. The neutron energy spectra were obtained by means of an unfolding method using FORIST code with the response function of the NE213 scintillator calculated by SCINFUL-QMD code. The experimental result was compared with other measured data at 5 and 40 MeV and the calculation based on intra-nuclear cascade of Liege (INCL) model in PHITS code.

Charge state distribution of 16O from the 4He(12C,16O)γ reaction of astrophysical interest studied both experimentally and theoretically

In astrophysics, 4He(12C,16O)γ reaction places an important role. At Kyushu University Tandem accelerator Laboratory (KUTL), the measurement of 4He(12C,16O)γ cross section is in progress in the energy range of astrophysical nuclear reaction. Since the charge state of product 16O ions after passing through the gas target is spread and only one charge state can be measured at terminal detector, it is necessary to know the charge state distribution of 16O ions passing through the He gas target precisely. Here, we report the charge state distribution of the 16O recoils both experimentally and theoretically. Experimentally, we measured the equilibrium charge state distribution of 16O ions in the windowless helium gas target with the beam energy of primary 16O ions at 7.2, 4.5, and 3.45MeV at KUTL. The measured results showed a Gaussian distribution for the charge state fraction. Theoretically, we proposed a framework for the charge state distribution study. Charge state distribution was computed by solving a set of differential equations including a series of charge exchange cross sections. For the ionization cross section, plane-wave Born approximation was applied and modified by taking target atomic screening as a function of momentum transfer into account. For the capture cross section, continuum distorted wave approximation was applied and the influence of the gas target density was taken into account in the process of electron capture. Using above charge exchange cross sections, the charge state evolution was simulated. According to the equilibrium distribution, we compared the theoretical calculation to the experimental data. After taking into account the density effects in the charge exchange process, the theoretical charge state distributions shows a good agreement with the experimental data. Both experimental and theoretical results are useful to understand the charge fraction of recoil oxygen created via 4He(12C,16O)γ reaction, especially in the energy range of astrophysical nuclear reaction.

Direct Measurement of 12C+4He Fusion Cross Section at E cm = 1.5 MeV at KUTL

12C+4He fusion reaction at Ecm = 0.3 MeV is one of the main reaction in 4He-burning in stars, and is very important in nuclear synthesis. However the fusion cross section has not been determined yet in spite of 40 years efforts in the world. Recently we succeeded in the measurement at 1.5 MeV. We have a plan to make direct measurement of the total fusion cross section down to 0.7 MeV at Kyushu University Tandem accelerator Laboratory (KUTL), and to determine the cross section at 0.3 MeV by extrapolation.

Measurement of Deuteron Induced Thick Target Neutron Yields at 9 MeV

The double differential thick target neutron yields from 9 MeV deuteron incidence were measured at the Kyushu University Tandem Accelerator Laboratory. A copper and a titanium foils which are thick enough for a deuteron to stop in the foils were placed at the center of a vacuum chamber. An NE213 liquid organic scintillator was employed to detect neutrons emitted from targets and placed at 9 directions from 0◦ to 140◦. To consider the contribution of scattered neutrons from the floor, we also measured neutron yields with an iron shadow bar located in front of the scintillator. Because incident deuteron beam was not pulsed and the Time-of-Flight method was not applied, the energy spectrum was derived from unfolding the light output spectrum using the FORIST code. The detection efficiency was calculated with the SCINFUL-QMD code. The experimental results were compared with the calculation data of the TALYS code, and it turned out that the calculation data does not reproduce the experimental ones satisfactorily.

Systematic measurement of the D(p, pp)n cross section at KUTL

Systematic measurement of the D(p, pp)n cross section at Ep = 13 MeV at star configurations at various inclined angle α is in progress at Kyushu University tandem accelerator laboratory (KUTL). The measured cross section at space star (α = 90°) is about 12% below the recent pd calculation. The next measurement is being made at 0° < α < 90° to see if the large anomaly of about 25% found by the Koln group (2006) at backward α exists also at forward α.

Facilities for direct measurement of 4He( 12C, 16O)γ reaction cross section at KUTL

A recoil mass separator designed to achieve a highest possible capability of the background rejection in the condition of inverse kinematics has been developed at Kyushu University tandem accelerator laboratory. Developments at accelerator have also been carried out to obtain a pulsed beam of high current and good emittance. With the mass separator and the pulsed heavy-ion beam, we are about to start the investigation of the 4He( 12C, 16O)γ reaction of astrophysical interest.