D.K. Avasthi

A BRAGG CURVE SPECTROSCOPY DETECTOR FOR ERDA STUDIES

The design and use of a Bragg curve spectroscopy (BCS) detector for depth profiling of elements in materials using the elastic recoil detection analysis (ERDA) technique is discussed. The detector when used to identify recoils from samples in an ERDA experiment using a 170 MeV Ag beam showed a clear separation between Fe (Z = 26) and Cu (Z = 29) recoils. Measurements near Z = 11 yielded ΔZZ of 134 showing a Bragg peak resolution of 2.9%. For typical applications, the detector can be effectively used for neighbouring charge identification up to Z ∼ 30.

Coupled channel description of 16O+142,144,146Nd scattering around the Coulomb barrier using a complex microscopic potential

Abstract Angular distributions of elastic scattering and inelastic scattering from 2 + 1 state are measured for 16 O+ 142,144,146 Nd systems at several energies in the vicinity of the Coulomb barrier. The angular distributions are systematically analyzed in coupled channel framework. Renormalized double folded real optical and coupling potentials with DDM3Y interaction have been used in the calculation. Relevant nuclear densities needed to generate the potentials are derived from shell model wavefunctions. A truncated shell model calculation has been performed and the calculated energy levels are compared with the experimental ones. To simulate the absorption, a ‘hybrid’ approach is adopted. The contribution to the imaginary potential of couplings to the inelastic channels, other than the 2 + 1 target excitation channel, is calculated in the Feshbach formalism. This calculated imaginary potential along with a short ranged volume Woods–Saxon potential to simulate the absorption in fusion channel reproduces the angular distributions for 16 O+ 146 Nd quite well. But for 16 O+ 142,144 Nd systems additional surface absorption is found to be necessary to fit the angular distribution data. The variations of this additional absorption term with incident energy and the mass of the target are explored.

Preparation and characterization of a sandwiched target of enriched neodymium oxide

Abstract The preparation of enriched neodymium oxide targets sandwiched between two carbon foils is discussed. The concentration of oxygen in a prepared target was measured using low-angle Rutherford scattering and Elastic Recoil Detection Analysis (ERDA) technique. The analysis indicated that the prepared target had 31 at.% of oxygen as compared to the expected concentration of 60 at.% relative to neodymium. It shows that neodymium oxide loses oxygen during evaporation.

In-vacuum target transfer facility

Abstract In order to transfer highly oxidizing and hygroscopic targets in-vacuum or in controlled atmosphere and to change the target ladder without affecting the chamber vacuum, an in-vacuum target transfer system has been designed, fabricated and installed. It consists of a transfer body, compatible flanges with gate valves at the bell jar and the chamber. Ca, being a highly oxidizing element, was taken as a test case to stress the utility of the in-vacuum target transfer system. Using the elastic recoil detection analysis (ERDA) technique, we could see that there was only 11.5% of O 2 in the target when it was transferred from the bell jar to the scattering chamber using the in-vacuum target transfer facility. When the target was exposed to air for 35 min the O 2 content rose to 63.5 at.%

Study of alpha-transfer Reaction 28si( 7li,t) 32S

The 28Si( 7Li,t) 32S reaction has been studied at 48 MeV. Using a t potential overlap based on a microscopic cluster model, the full finite-range distorted wave Born approximation analysis was carried out for nine low-lying states; 0.0 MeV (0+), 2.23 MeV (2+), 3.78 MeV (0+), 4.46 MeV (4+), 5.01 MeV (3-), 5.80 MeV (1-), 6.76 MeV (3-), 7.43 MeV (1-) and 8.49 MeV (1-) of the residual nucleus. A re-analysis was also done for the same states of 32S having an d overlap for the reaction 28Si (6Li, d) 32S at 75.6 MeV. Theoretical spectroscopic factors have been calculated for the measured even-parity states of 32S using the shell model code OXBASH. The spectroscopic factors were compared for both the reactions.

Study of alpha-transfer reaction28Si(7Li,t)32S

The 28Si( 7Li,t) 32S reaction has been studied at 48 MeV. Using a t potential overlap based on a microscopic cluster model, the full finite-range distorted wave Born approximation analysis was carried out for nine low-lying states; 0.0 MeV (0+), 2.23 MeV (2+), 3.78 MeV (0+), 4.46 MeV (4+), 5.01 MeV (3-), 5.80 MeV (1-), 6.76 MeV (3-), 7.43 MeV (1-) and 8.49 MeV (1-) of the residual nucleus. A re-analysis was also done for the same states of 32S having an d overlap for the reaction 28Si (6Li, d) 32S at 75.6 MeV. Theoretical spectroscopic factors have been calculated for the measured even-parity states of 32S using the shell model code OXBASH. The spectroscopic factors were compared for both the reactions.

Study of -transfer reaction 28Si( 7Li,t) 32S

The 28Si( 7Li,t) 32S reaction has been studied at 48 MeV. Using a t potential overlap based on a microscopic cluster model, the full finite-range distorted wave Born approximation analysis was carried out for nine low-lying states; 0.0 MeV (0+), 2.23 MeV (2+), 3.78 MeV (0+), 4.46 MeV (4+), 5.01 MeV (3-), 5.80 MeV (1-), 6.76 MeV (3-), 7.43 MeV (1-) and 8.49 MeV (1-) of the residual nucleus. A re-analysis was also done for the same states of 32S having an d overlap for the reaction 28Si (6Li, d) 32S at 75.6 MeV. Theoretical spectroscopic factors have been calculated for the measured even-parity states of 32S using the shell model code OXBASH. The spectroscopic factors were compared for both the reactions.

WIDE-ANGLE α-t COINCIDENCE MEASUREMENT IN THE BREAKUP OF 7Li ON 27Al

We have performed wide-angle in-plane coincidence measurements of the alpha particles and tritons emitted in the 48-MeV 7Li projectile breakup reaction on 27Al. The data have been analyzed using the post-form distorted-wave Born-approximation (DWBA) theory of breakup reactions where Coulomb and nuclear breakup as well as their interference terms are included. The theory is able to provide a good description of the experimental data particularly at large relative angles between the fragments. The interference between the Coulomb and nuclear breakup modes is found to be significant.

A microscopic complex potential description of elastic, inelastic cross section in the Coulomb nuclear interference region in the 28Si on 28Si system

Abstract Elastic and inelastic angular distribution and excitation functions were measured for the 28 Si + 28 Si system in the vicinity of the Coulomb barrier. While the elastic data could be described very well by using fully microscopic complex potential, the inelastic cross sections were found to be more sensitive to small variations in the potential. In particular the Coulomb nuclear interference dip observed in the inelastic excitation functions could not be fitted satisfactorily with calculation. Inclusion of an energy dependent term of Gaussian shape to the associated matrix element with the reorientation coupling in the phenomenological calculations leads to a better fit the inelastic excitation functions.