Thick Target Inverse Kinematics Technique Research Articles

Hints of quasi-molecular states in 13B via the study of 9Li-4He elastic scattering

This paper reports on elastic scattering excitation functions for the reaction 9Li+4He measured at backward angles in the centre of mass energy range 5 MeV ≤ E≤c.m.9.5 MeV, with the aim of investigating the possible existence of molecular resonances which have been predicted to exist in the case of neutron-rich B-isotopes. Due to the short lifetime of 9Li, the experiment necessitated the use of inverse kinematics on a gaseous 4He target. The Thick Target Inverse Kinematics technique was used which allowed for the measurement of the full excitation function in a single 9Li run. Broad resonances were observed in the excitation region for 13B 15 MeV ≤ Ex≤20 MeV. To understand the nature of such broad structures, various theoretical attempts are reported concerning possible reaction mechanisms for this neutron rich reaction. The most promising approach to interpret the data is within the orbiting reaction scenario.

Structure of Ne20 states in resonance O16+α elastic scattering

Background The nuclear structure of the cluster bands in $^{20}$Ne presents a challenge for different theoretical approaches. It is especially difficult to explain the broad 0$^+$, 2$^+$ states at 9 MeV excitation energy. Simultaneously, it is important to obtain more reliable experimental data for these levels in order to quantitatively assess the theoretical framework. Purpose To obtain new data on $^{20}$Ne $\alpha$ cluster structure. Method Thick target inverse kinematics technique was used to study the $^{16}$O+$\alpha$ resonance elastic scattering and the data were analyzed using an \textit{R} matrix approach. The $^{20}$Ne spectrum, the cluster and nucleon spectroscopic factors were calculated using cluster-nucleon configuration interaction model (CNCIM). Results We determined the parameters of the broad resonances in \textsuperscript{20}Ne: 0$^+$ level at 8.77 $\pm$ 0.150 MeV with a width of 750 (+500/-220) keV; 2$^+$ level at 8.75 $\pm$ 0.100 MeV with the width of 695 $\pm$ 120 keV; the width of 9.48 MeV level of 65 $\pm$ 20 keV and showed that 9.19 MeV, 2$^+$ level (if exists) should have width $\leq$ 10 keV. The detailed comparison of the theoretical CNCIM predictions with the experimental data on cluster states was made. Conclusions Our experimental results by the TTIK method generally confirm the adopted data on $\alpha$ cluster levels in $^{20}$Ne. The CNCIM gives a good description of the $^{20}$Ne positive parity states up to an excitation energy of $\sim$ 7 MeV, predicting reasonably well the excitation energy of the states and their cluster and single particle properties. At higher excitations, the qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.

α-cluster resonances in light nuclei

Thick target inverse kinematics technique was combined with Time of Flight method to study resonance reactions induced by heavy ions at low energy, to minimize background and to identify various possible nuclear processes in extended target. The 17 O, 20 Ne spectrum, the cluster and nucleon spectroscopic factors were calculated using cluster-nucleon configuration interaction model.

Study of12C excited states decaying into threeαparticles using the thick target inverse kinematic technique

We will show that the Thick Target Inverse Kinematics (TTIK) technique can be used to investigate the breakup of excited selfconjugate nuclei into many alpha particles. Two test runs were performed at Cyclotron Institute of Texas A&M University to study the reaction 20 Ne+α at maximum beam energies of 10 and 12 AMeV. Due to the limited statistics, only events with alpha multiplicity up to three were analyzed. The analysis of the three α -particle emission data allowed the identification of the Hoyle state and other 12 C excited states decaying into three alpha particles. The results will be shown and compared with other data available in the literature.

Alpha clustering in Ti isotopes:40,44,48Ca +αresonant scattering

Measurements were made of the 4He(40,44,48Ca,α) resonant scattering reactions at 180° and up to Ec.m. ~ 11.5MeV, using the Thick Target Inverse Kinematics technique. These measurements are discussed, with a focus on assessing their usefulness for investigating α-clustering in medium mass 44,48,52Ti nuclei

The thick target inverse kinematics technique with a large acceptance silicon detector array

An experimental technique for studying elastic scattering using a thick gas target is described, with a measurement of the α(24Ne,α) reaction used as an example. Advantages such as ease, detector efficiency, and the possibility of measuring the cross section at 180° in the centre-of-mass are discussed. It is shown that a resolution of tens of keV is practical at zero degrees, and that the dominant contribution to the resolution for large angles is angular straggling of the beam in the entrance window. The use of helium gas as the target allows direct measurement of a-cluster states.

Elastic alpha-particle resonances as evidence of clustering at high excitation in 40Ca

The elastic-scattering reaction 36Ar + α was studied using the Thick Target Inverse Kinematics technique. Data were taken at a beam energy of 150 MeV in a reaction chamber filled with 4He gas, corresponding to the excitation region of 12–20 MeV in 40Ca. Using a simplified R -matrix method of analysis energies, widths and spin assignments were obtained for 137 resonances. The structure is discussed within the concept of α-cluster structure in the quasi-continuum of 40Ca and is compared to other nuclei in the same mass region.

Highly excited alpha-cluster states in 34S

The elastic-scattering reaction 30Si + $ \alpha$ was studied using the Thick Target Inverse Kinematics technique. Data were taken at a 30Si beam energy of 150MeV in a reaction chamber filled with 4He gas, corresponding to the excitation region of 12-24MeV in 34S . The data were treated in the framework of a simplified R -matrix approach, and energies, widths and spin assignments were obtained for 111 resonances in an approximative manner. The structure is discussed within the concept of $ \alpha$ -cluster structure in the quasi-continuum of 34S and is compared to recent data for 32S .

EVIDENCE OF ROTATIONAL BEHAVIOR OF ALPHA-CLUSTERS IN32S,34SAND40Ca

Elastic alpha-particle scattering from the nuclei28Si ,30Si and36Ar has been examined using the Thick Target Inverse Kinematics technique. Excitation functions for high excitation energy in the intermediate nuclei32S ,34S and40Ca have been constructed and analyzed in an approximative manner using a simplified R -matrix approach. The analysis reveals many similarities between the three cases, and shows groups of resonances of increasing spin with increasing energy, consistent with a picture of a rotating surface of a few alpha-particles orbiting an inert core.

Highly excited alpha-cluster states in 32S studied with the thick-target inverse kinematics method

Excitation functions of elastic 28Si + $ \alpha$ scattering were measured employing the relatively new thick-target inverse kinematics technique, confirming the usefulness of the method. Data were taken at a 28Si beam energy of 150MeV in a reaction chamber filled with 4He gas, corresponding to the excitation region of 10-24MeV in 32S . Results are compared to earlier studies, in order to validate the method and explore its limitations. The data were treated in the framework of a simplified R -matrix approach. Energies, widths and spin assignments were obtained for 129 resonances in this mid-shell nucleus. The structure is discussed within the concept of $ \alpha$ -cluster structure in the quasi-continuum of 32S .

T=3/2states inC13

Background: Experimental information on the structure of low-lying levels with isospin 3/2 in systems with 13 nucleons can be used to evaluate the quality of modern theoretical predictions for the light exotic systems. This level structure is poorly known at present. Purpose: Search for $T=3/2$ states in $^{13}\mathrm{C}$ was performed in this work. Method: These states were observed in the resonance elastic scattering of radioactive beam $^{12}\mathrm{B}$ on protons using the thick target inverse kinematics technique. Results: Six new states in $^{13}\mathrm{C}$ were identified as $T=3/2$ states. Tentative spin-parity assignments are suggested. Comparison to the previous knowledge of the level structure of $T=3/2$ $A=13$ system and to shell-model predictions is given. Conclusion: The elastic scattering of neutron-rich beams on proton target is a convenient tool for isobaric analog states search. The observed $^{12}\mathrm{B}$$+p$ excitation function is determined by the $T=3/2$ states and no features associated with $T=1/2$ states were found. Although the level scheme of $T=3/2$ states in $A=13$ systems is still far from being complete the emerging picture shows significant disagreements with predictions of contemporary shell models.