UTILAZATION OF CRIB SPECTROMETER FOR DIRECT MEASUREMENT OF (α,p) REACTIONS BY VIETNAMESE GROUP Le Hong Khiem Institute Of Physics (IOP), Vietnam Academy of Science and Technology (VAST)

CONTENT The role of CRIB for Vietnamese nuclear physicists Direct measurement of (α,p) reactions Conclusion

I. The role of CRIB for Vietnamese nuclear physicists VN Government always attache importance to the development of science. The level of science of VN is very modest compared to developed countries. To make quick changes, we need to take advantage of the help of countries with a high level of science. International cooperation will help VN having an opportunity to catch up the delay. Therefore, the issue of international cooperation in scientific research at high-level and training of human resources in science is becoming urgent, and is encouraged by the Government. IOP was established in 1969 and is one of the largest institutions of VAST. Seeing clearly the importance of international cooperation, IOP has always considered international cooperation plays a crucial role and gives a special interest in this issue. Our Center for Nuclear Physics, which belongs to IOP has spent a lot of effort for international cooperation. An agreement on academic exchange between graduate school of science and IOP was signed (2009). This is a useful umbrella for our cooperation. This agreement allows the exchange of researchers, students and academic information between CNS and IOP. Under this agreement, Vietnamese group has been involved in the experiments performed at CNS.

I. The role of CRIB for Vietnamese nuclear physicists (cont.) For many years the VN Nuclear Physical Society has a dream to create an experimental nuclear physics group having enough experience. However, we have not any facilities. In order to maintain our research, a most efficient way is to go to world-wide famous nuclear physics centers in Japan (RIKEN, CNS, RCNP,…). By this way, we have opportunities to participate or to conduct the experiments using mordern nuclear physics facilities and detectors. In addition, these studies will help us for having good man power in future for our nuclear power plant projects. CNS has CRIB for study of nuclear astrophysics with RIBs at low energy with high purity, and is one of the premier facilities in the world for research in the field. The facility is also suitable for studying nuclear physics. From our point of view, CRIB is very useful for foreign researchers and graduate students, especially for VN nuclear physicists since it is not so complicated for operation in comparison with other huge nuclear physics facilities. VN graduate students and researchers have came to CNS to participate in the experiments at CRIB, and carried out their own. The cooperation between our center and CNS has been considered as a best effective one among many other international cooperation created so far by IOP.

Thanks to CRIB, we are now successful in creation of a small experimental nuclear physics group in VN, all the members of this group have accumulated their experience through the experiments using CRIB (without CRIB, it is impossible!!!) By using CRIB, we can learn physics using RIBs, development of RIB technique and many other necessary practical skills needed for modern experiments. VN students and researchers time by time come to visit CNS. We have intensively involved in the experiments performed at CNS. Recently, we have performed the direct measurement of 21 Na( ,p) 24 Mg nuclear reaction at the energy of astrophysical interest using CRIB. Another experiment for studying 22 Mg(α,p) 25 Al reaction was approved and will be done in very near future. These experiments are the part of an ongoing collaboration with the group of Prof. Shigeru Kubono at CNS. These experiments are the main subjects for Ph.D thesis of our students. I. The role of CRIB for Vietnamese nuclear physicists (cont.)

II. Direct measurement of (α,p) reactions Nuclear Astrophysics: study of nuclear reactions involved in nucleo-synthesis process inside astronomical objects. In recent years, this field has seen a remarkable expansion and exciting developments (introduction of more sophisticated stellar models, increased precision in the experimental determination of stellar reaction rates….) It’s still rare to find exp. values of nuclear reaction rates at the energies needed as inputs to stellar models. Reasons: the reaction cross sections at energies at which they occur in astrophysical environments are very low and very difficult for direct measurement. By using CRIB, we are able to measure directly the cross sections of nuclear reactions induced by  particles in proton- rich isotopes which are of astrophysical interest. For illustration: 21 Na( ,p) 24 Mg and 22 Mg( ,p) 25 Al.

Direct Measurement of (α,p) Reaction Using a 21 Na RI-Beam From Nov. 24th 2008 to Dec. 3rd Scientific motivations: - An expected galactic γ-ray emitted following a β + decay of 22Na -The Ne-E problem in meteorites for the high temperature stellar environments like in X-ray bursts and supernovae. 2. Objective: - Resonant alpha scattering on 21Na - 21Na(α,p)24Mg reaction cross section directly for the first time using a 21Na RI beam

20 Ne(d,n) 21 Na in inverse kinematics 6.2 MeV/u 21 Na Beam production F2 F3 21 Na beam condition: Energy: 39.5 ± 0.9 MeV Purity: 80 – 95 % Intensity: ~ 5x10 5 pps 21 Na 11+

Excitation function of α-scattering cross sections Dead layer 5 resonances were observed  α Scattering Data Analysis

R-Matrix Muti-channel Analysis

21Na(α,p)24Mg reaction rate calculation We tried to measure the total cross sections of the 21Na(α,p)24Mg reaction by direct measurement in inverse kinematics. There are significantly large proton transitions to highly states in 24Mg at around MeV were observed.

The experiment for studying (α,p) reaction induced by 22Mg beam We have proposed to measure directly the 22Mg(α,p)25Al reaction cross section at stellar energies corresponding to the Gamow window, which is relevant for the reaction flow in X-ray busters. The reaction is important as it provides a path to bypass 22Na/22Ne and hence it is relevant for our understanding of the 22Ne anomaly in meteoritic samples and for the prediction of gamma-fluxes arising from 22Ne decay. The latter has been one of the primary observational goals of the INTEGRAL mission, however, yet without success. The experiment aims to measure the cross section in a thick-target method performed via inverse kinematics. Two beam energies will be used, which will allow to cover the complete Gamow window for the relevant temperatures T9 = 1-3. We expect to observe all resonances in this energy range with a width of 100 keV and large. We will determine the resonance parameters by R-matrix analysis to the measured cross sections for the ( ,p) reaction and for elastic alpha scattering, which will be performed simultaneously. The proposal has been accepted for full time requested by the 7th RIBF-NP-PAC meeting. We planed to carry out the experiment in July of Unfortunately, due to a big problem with AVF cyclotron, our experiment was postponed. We expect the experiment will be performed as soon as the problem can be fixed.

Studying 22Mg(alpha,p) reaction using CRIB Run time: Beam production test of low energy 22 Mg beam 2.0 days Tuning with RI beams and electronics for data run 2.0 days High energy run 4.0 days Background run for high energy run 1.0 days Changing setup and re-tuning electronics 0.5 days Low energy run 6.0 days Background run for low energy run 1.0 days Calibration of silicon detectors 0.5 day Total: 17 days.

III. Conclusions CRIB facility is still having a very high performance for production of low-energy RI beams from our point of view. Therefore, it is necessary to find some way for continuation of CRIB operation. In conclusion, CRIB facility is still having a very high performance for production of low-energy RIBs from our point of view. Therefore, it is necessary to find some way for continuation of the CRIB operation. On behalf of IOP, I gratefully acknowledge CNS for continuous invaluable support and train Vietnamese group. Especially, I am greatly grateful to Prof. S.Kubono, who gives us a chance to come to CNS to work and to teach us many things. I also would like to thank to Japanese and foreign colleagues who participated in the experiments presented in this report.