Brief Description of Research Activities

My interests in experimental nuclear physics have evolved during my research at the Joint Institute for Nuclear Research (JINR, 1988-1997), Dubna, Russia; Idaho State University (ISU, 1997-2000); and in my present position at the Triangle University Nuclear Laboratory (TUNL)/Duke University. A brief summary is given below:

1. High Spin Isomeric States in Photonuclear reactions

I have developed the techniques and methods of analysis for studying high spin isomeric states using bremstrahlung spectrum from the Microtron electron accelerator at JINR, Dubna. My emphasis was on making precision measurements of cross sections and isomeric ratios in variety of photonuclear reactions as (g;g’), (g,n), (g,p), (g,a), and (g,f) at energies below neutron threshold to the maximum of the Giant Dipole Resonance. I measured the cross sections and isomeric ratios for more than 20 photonuclear reactions in wide mass region 80<A<238. Single-particle neutron or proton states, together with those for two-quasiparticle states have been investigated. Different phenomena of these isomers, such as mass, proton and neutron number dependence have been observed. The experimental results, published in peer-reviewed journals and presented in many International Conferences are reflected also in the National Nuclear Data Center file at the Brookhaven National Laboratory.

As a scientific worker at JINR, I participated in series of experiments on the frame of the ¹⁷⁸Hf(J^p =16⁺, T_1/2 =32 y) isomer, program. A method was proposed to production of nuclei only in the isomeric state in sufficient quantities to carry out nuclear reactions on high spin isomeric targets.

2. Heavy Ion Physics

My scientific activity in Dubna also overlapped with their heavy ion physics program. Differential characteristics of fission neutron emission in the region of compound nuclei with atomic number Z>92 have been obtained in ¹²C + ²³⁸U, ¹⁸O + ²³²Th, and a ± ²⁴⁶Crn reactions leading to the same A=250 compound nucleus with the same excitation energy and mean angular momentum. Measurements of pre-scission (n_pre) and post-scission (n_post) components from the total spectra of fission neutrons allowed as to understand the fission dynamics of these nuclei. For example from the n_pre measurements we may conclude that the time for asymmetric fission in which the nucleus descends from the saddle point to the scission point is substantially shorter that the time for symmetric fission.

In 1996, as Visiting Scientist at Hahn Meitner Institute in Berlin, I participated actively in an investigation of gamma transitions resulting from the decay of states based on the superdeformed minimum (shape isomers) in alpha cluster nuclei with mass numbers between 36-56. I was engaged in analysis of the experimental data using the FOFOS detector array at the Flerov Laboratory of Nuclear Reactions in Dubna and Hahn Meitner Institute in Berlin. This experiment was aimed at investigating hyperdeformed states in ⁴⁸Cr using the reaction ²⁴Mg + ⁴⁰Ca ® ⁴⁸Cr* + ¹⁶O*, with a subsequent decay of ⁴⁸Cr* into ²⁴Mg + ²⁴Mg.

3. Nuclear Application Development

In October 1997 I was invited in Idaho State University (ISU) to develop a fundamental photo-nuclear research program for the new Accelerator Center and to integrate this research with the current strength in applied nuclear science. Experimental photonuclear techniques have been applied to many practical problems that were the current emphasis of the Idaho Accelerator Center research in environmental, industrial and medical applications. For example the most recent investigations are connected with the possibility of using the ISU LINAC accelerator as an intense neutron source for Neutron Capture Therapy which is a cancer treatment. In this concept, relativistic electron beams from a 30 MeV LINAC impinge on a small uranium sphere surrounded by a cylindrical tank of circulating heavy water (D₂O). The photo-fission neutron spectrum from the uranium sphere is thermalized in deuterium and directed to the patient. The results of these calculations and recent experimental results demonstrated that photoneutron devices could offer quite a promising alternative approach to the production of epithermal source for Neutron Capture Therapy. The epithermal flux of more than 10⁸ n.cm^-2.mA^-1 was achieved.

Another activity was directed to study accelerator transmutation for effective radioactive waste remediation. “Burn-up” the spent fuel from fission reactor with electron accelerators, by transmute the long-lived fission products into short-lived or stable isotopes, and incineration of the transuranic isotopes via a fission reaction. These activities also applied to production of nuclear energy from heavy non-fissile elements. More conventional gamma and neutron activation analysis have been used to solve many of these analytical tasks.

4. Nuclear Astrophysics Related Studies

Techniques have been developed at TUNL for studying of proton capture reactions at energies of interest to nuclear astrophysics. Direct measurements of the slopes of S factors in the 10-160 keV range along with polarized beam measurements have allowed to obtain new and much more reliable values of the extrapolated S-factors and of the thermonuclear reaction rates in a number of cases. These studies have also provided new insights into the nature of proton capture reactions in this energy region, where Coulomb forces dominated. I am presently engaged in a studies the ratio of the ¹²C(p,g)¹³N/¹³C(p,g)¹⁴N reactions, ¹⁰B(,g)¹¹C, ⁷Li(p,g)⁸Be, ⁷Li(p,g)¹⁵O, and ²H(,g)⁴He reactions.

5. Polarized Gamma-ray Studies at HIGS (the TUNL/DFELL High Intensity Gamma Ray Source)

My primary focus at TUNL/Duke University is directed of using a highly intensive (>5 10^6 g/sec), 100% polarized and monoenergetic (DE/E<l%) gamma source at High Intensive Gamma Source. This “revolutionary” gamma source will reinvent many aspects on the traditional photonuclear physics. The quality and the quantity of the gamma beam allows us to have a deeper and more precise view of the mechanism of the nuclear reactions at broad range of energies from 1 to 220 MeV. For instance, recently the HIgS source was used to measure the parity of 88Sr and 138Ba nuclei in inelastic gamma scattering experiment. These experiments have started a new renaissance of the traditional Nuclear Resonance Spectroscopy and opens new chapter in experimental approaches to Nuclear Structure Physics. These investigations are strengthening by ongoing collaborations with colleagues from the Nuclear Institutes in Stuttgart and Koeln.

A considerable amount of my efforts have been involved with writing proposals, and developing independently funded research programs. In addition, I taught Quantum Physics for fall 1999 semester and advised four graduate students in research related activities at the Idaho Accelerator Center.