Executive summary
Heavy Ion Accelerator Laboratories provide a powerful set up for formation and study of exotic nuclear states. These nuclei span a range of neutron proton numbers corresponding to those that are stable or nearly stable (like those that are present on our earth) and also more exciting ones that are involved in creating these stable nuclei through complex astrophysical processes. A variety of nuclear shapes get stabilized and get accessible for studies through high-energy photon spectroscopy, with appropriate techniques for formation and selection of these states. A host of advanced facilities requiring high investment exist or are under development in the laboratories both in US and in India which facilitate picking up of these exotic states from the enormous plethora of highly complex nuclear states that are produced in heavy ion collisions. The primary purpose of the proposed workshop is to get a first hand interaction between the scientists from such laboratories in order to set out interesting scientific projects leading to collaborative research and development in the field of nuclear structure and dynamics.
Background, concept and purpose
Heavy Ion Projectiles deliver a very large amount of angular momentum and energy into the reacting systems, thus producing exotic nuclei far away from the line of stability. The subsequent de-excitation of the product nuclei may induce fission, nucleon- or cluster-emissions and, finally, gamma ray emission from the normal yrast or the super-deformed bands. The formation of these exotic isotopes occurs at extremes of excitation, spin, and isospin. The mechanism of formation through heavy-ion fusion around the barrier and above poses interesting departures from the light-ion physics and is of high current interest from the basics of nuclear rearrangement processes, and from the viewpoint of stellar nucleosynthesis processes. The mechanisms of cooling down of the hot rotating nuclear system revealed through the study of emission of light particles and high energy gamma-rays provide a rare glimpse of this otherwise inaccessible rapid cool down of nuclei formed following fusion and other nuclear processes. The cooled-down system has still a lot of spin that it has to shed off. This happens dominantly through a series of electromagnetic transitions amongst the cooled yrast states of the rotating nuclei involving emission of discrete photons and electrons. The properties of the ground states of the rare isotopes thus reached are measured through beta decay and subsequent processes.
The field of nuclear spectroscopy using detectors for the cascade of gamma rays/electrons emitted from the exotic nuclear states identified through special tagging techniques involving gamma rays, evaporation residues, and light particles, is a very active research field in the studies of nuclear structure and dynamics. Energy spectroscopy and the dynamics of their decay provides a wealth of information giving an insight into the intricacies exhibited by the strongly interacting multi-fermion system forming the nuclei. Stability of (lowering of the associated binding energy of the states) various exotic shapes that the nuclei exhibit as we vary the spin, the isospin and mass of these nuclear states is truly remarkable. Prolate shape, a preference by most of the nuclei, is an artifact of strong shell structure effects that control these shapes. Heavier nuclei, where much diverse shape structures may occur at relatively low excitation energies, is recognized as a nuclear region where shell and angular momentum effects get to play the most crucial role in controlling such shape stabilization; the otherwise dominant Coulomb force and the surface tension (generated by the attractive nuclear force) nearly cancel each other. On the other hand, very light nuclei have now been made prone to full scale mean field structure calculations where in new and exciting phenomena such as Island of inversion, shell quenching etc. are attracting a series of high intensity investigations. Oblate shape may get a preference vis a vis shell effects in some regions, such as neutron rich side around mass 100.
A host of advanced facilities requiring high investment exist or are under development in the laboratories, both in US and in India, which facilitate picking up these exotic states from the enormous plethora of highly complex nuclear states that are produced in heavy ion collisions. The main aim of the proposed workshop is to get a first hand interaction between the scientists from such laboratories in order to set out interesting scientific projects leading to collaborative research and development in the field of nuclear structure and dynamics.
Specific need for a bilateral event
The field of nuclear structure and dynamics demands enormous human resources in the form of experimental and theoretical scientists and research scholars. The possibility of collaboration between the research communities of US and India needs to be defined so as to take a systematic approach towards realizing a strong collaboration between the two countries. A workshop is proposed towards this end with a view to provide structured discussion/presentations on the aspects of interest in this important field. In particular, with the recent identification of the construction of the Rare Isotope Accelerator (RIA) as among the top priorities of the U.S. Department of Energy projects in the short term, such collaborations are most imperative. RIA would be a unique facility and would require global collaborations to fully harness its capabilities.
Fundamental research in nuclear sciences has had a long and rich tradition in India. It has received a strong impetus in recent years with the availability of accelerator facilities accessible to researchers at Indian universities, the Universities Accelerator Center in New Delhi being the prime such facility. In general, contemporary research in this field has become highly collaborative, with select facilities worldwide being used for specific experiments and with scientists of several countries joining hands in conducting research. Such collaborations are even more imperative in light of the proposed construction of the Rare Isotope Accelerator in the U.S. The primary purpose of the proposed Indo-US Workshop would be to bring together active researchers, primarily from Indian and US Universities, for discussion on possible collaborations in the near and medium-term future in the fields of nuclear structure and nuclear reactions, with emphasis on use of radioactive ion beams. We will explore the complimentarity in skills, manpower, available equipment, and facilities that would lead to synergistic and most efficient use of the available resources in the two countries. The first part of the Workshop would involve talks by the participants presenting their current research and exploring the commonality of interests. The participants would then divide into several working groups to discuss in detail the possibilities and modalities of the proposed collaborative efforts. It is during the discussions in these working groups that detailed contours of such collaborations will be worked out. This might include possible joint experiments, ways to optimally utilize the facilities and manpower available in the two countries, and division of responsibilities in the proposed joint experiments. It is intended that out of this Workshop will come a strong proposal to be submitted jointly by the US and Indian counterpart-PI's to the U.S. National Science Foundation and the Department of Science and Technology, Government of India, for support of this effort under the Indo-US Scientific Collaboration program.
Number of US & Indian participants with affiliation (including any other country)
- From US 10
- From India 20
The tentative list of Indian and US Speakers and Participants is available on this website.
The final list will be selected on the availability of the speakers out of this list.
Vvenue and dates, preliminary agenda listing proposed speakers
Venue is Chandigarh . Workshop is planned for 3 days and will consist of presentation of research programme (first day) which will be followed by two days of comprehensive presentation and discussions on specific experimental/theoretical projects of interest form the scientists from the US and India.
Expected outcome specifically in terms of furthering bilateral cooperation/interactions and other products
We expect well-formulated collaborative research projects in the field of nuclear structure and dynamics between Scientists from various universities and laboratories from India and US which may be executed with support from funding agencies.
|