Crystal Rainbow, Accelerators and Future of Science: Interview with Dr Nebojša Nešković
From Crystal Rainbows to New Scientific Discoveries
We usually associate rainbows with rain and light, but few people know that they also exist in the world of charged particles. The crystal rainbow is a phenomenon discovered thanks to the research of theoretical physicist Dr. Nebojša Nešković, a long-time researcher at the Vinča Institute of Nuclear Sciences in Belgrade and former head of the ambitious TESLA Project, which aimed to build advanced accelerator infrastructure. Dr. Nešković is currently the Vice President of the World Academy of Art and Science and the President of the Serbian branch of the Club of Rome. His research and contributions to science have left a lasting mark in the fields of physics and accelerator technologies.
In an interview for the University of Montenegro website, he discusses his research, the importance of scientific collaboration, and offers advice to future generations of researchers. The occasion for the conversation is his participation in the "Days of the Scientific Diaspora," an event organized by the University of Montenegro that gathers scientists from the region and around the world.
PR UMNE: Your research includes the transmission of charged particles through thin crystals and the phenomenon of the crystal rainbow. Can you explain in simple terms what this phenomenon is and why it is important for science?
Dr. Nešković: Everyone is familiar with the meteorological rainbow that appears in the sky after rain. It results from the refraction and reflection of sunlight by water droplets. Similar phenomena have been observed in the scattering of atoms on atoms and molecules, nuclei on nuclei, and atoms on crystal surfaces. Crystal rainbows occur during the transmission of charged particles through crystal channels. This means that bright lines appear in the angular distribution of transmitted particles, clearly separating bright and dark regions in that distribution. These lines are analogous to the rainbow in the sky after rain. The study of crystal rainbows is significant because, on the one hand, the conclusions drawn can serve as new guidelines for exploring rainbows in other areas, and on the other hand, the results can be practically applied to determine certain characteristics of crystals.
PR UMNE: What inspired you to focus on this specific segment of theoretical physics?
Dr. Nešković: I started working on the transmission of charged particles through crystal channels at the Oak Ridge National Laboratory in Tennessee, USA, where I was a postdoctoral researcher. Shortly after arriving at the laboratory, I realized that I could apply a model I developed during my doctoral studies at the Vinča Institute in Belgrade to the process of ion channelling in crystals, which had been researched there for several years. The result of this application was the discovery of the crystal rainbow phenomenon, which was soon experimentally confirmed in the same laboratory. Upon returning to the Vinča Institute, I continued to study this phenomenon with my younger colleagues. This led to the formulation of the theory of the crystal rainbow, as a proper theory of charged particle transmission through crystal channels and nanotubes.
PR UMNE: How has your theory helped to explain experimental results that were previously unclear?
Dr. Nešković: The conventional approach to the channelling process of charged particles in crystals was developed with assumptions that limited its application to thick crystals only. Moreover, this approach completely ignored the complex and catastrophic nature of the process, which is central to our approach. The crystal rainbow is a complex phenomenon because its root lies in the interference of contributions from rows of crystal atoms to the probability of particle transmission, demonstrating that a crystal is more than just a simple sum of these rows. On the other hand, it is a catastrophic phenomenon because the sudden change in transmission probability near the rainbow lines can be excellently described by catastrophe theory, which can be considered a mathematical theory of sudden changes. This approach led to the theory of crystal rainbows, which was then successfully used to explain a series of experiments with ions or electrons and thin crystals that had previously defied explanation.
PR UMNE: As a distinguished theoretical physicist, you have also worked on ion beam acceleration and their applications in various scientific and medical disciplines, as well as accelerator technologies. Which of these engagements do you consider the most important, and why?
Dr. Nešković: I graduated from the Faculty of Electrical Engineering and earned my PhD from the Faculty of Physics at the University of Belgrade. This enabled me to seriously engage first in theoretical physics and later in accelerator science and technologies, without abandoning theoretical physics. I consider both engagements important and challenging, although the second required a specific integrated approach to science, technology, medicine, and education, making it significant for the broader society. I find working with accelerator technologies particularly important because knowledge in this field is one of the prerequisites for a countrys collaboration with global scientific organizations, such as the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, and the Joint Institute for Nuclear Research in Dubna, Russia.
Accelerator Technologies and the TESLA Project
PR UMNE: You also served as the head of the TESLA Project at the Vinča Institute. How did the results of this project contribute to science, technology, and medicine, and how did they shape your career?
Dr. Nešković: The TESLA Project existed from 1991 to 2007 under my leadership. The team I led included around 90 scientists, engineers, and technicians. The project involved the construction and preparation for the use of the TESLA Accelerator Installation, a large facility for the production, acceleration, and application of ion beams in science, technology, medicine, and education, based on a decision by the Serbian government in 1989. The implementation of this endeavour was under strict supervision by two highly competent international bodies. As a result, numerous scientific, medical, and educational institutions from Serbia and the region became involved, as well as more than 50 Serbian companies interested in the development and application of accelerator technologies. The planned programs for using the installation included advanced research in physics, chemistry, and biology; the production of radioactive pharmaceuticals for diagnostics and therapy; proton therapy for eye tumours in medical institutions in Serbia and other regional countries; and research and education in nuclear energy with a small, safe fission nuclear reactor. However, despite the majority of the installation being completed, the Serbian government decided to terminate the project in late 2007 based on the report of a committee whose members were entirely unqualified in the field of accelerator construction and use. The project leadership believed this was done at the request of a strong foreign interest group to prevent Serbia from having too much influence on the development of science, technology, medicine, and education in the region. My stance was to do everything possible to maximize the use of the project’s results. I focused on this for an extended period while continuing my research on the interaction of charged particles with crystals.
International Scientific Collaboration
PR UMNE: You are the Vice President of the World Academy of Art and Science, a full member of the Club of Rome, and the President of its Serbian branch. How have these experiences influenced your work and your role in promoting science in this region?
Dr. Nešković: My engagement with the World Academy of Art and Science and the Club of Rome aims to connect and foster collaboration between scientific, technological, and educational institutions from Serbia and similar national, regional, and global organizations. It also involves promoting ideas and proposals that can contribute to establishing sustainable, secure, and peaceful development at all levels. These goals are based on the belief that continuous progress and excellence in science, technology, and education require a dialectical unity of national and global approaches to these fields. My experience working with these international organizations has been very positive.
Scientific Diaspora and the Future of Young Researchers
PR UMNE: The "Days of the Scientific Diaspora" at the University of Montenegro gather scientists from the region and around the world. As a participant, how do you assess the importance of this event for connecting scientists and exchanging knowledge across different scientific fields? What has your experience been like? What can this event mean for students?
Dr. Nešković: The "Days of the Scientific Diaspora" was a valuable and very pleasant event for me. I havent attended a gathering in a long time where I could hear so many interesting presentations from various scientific fields. Additionally, the event facilitated connections between researchers from different disciplines who work in different parts of the world and might otherwise never have met. I am confident that the event was very interesting for the University of Montenegro students who attended. I believe that future gatherings should also invite students from other universities in the region.
PR UMNE: What advice would you give to young physicists and researchers who want to pursue theoretical physics and accelerator technologies? What first steps can they take on their path?
Dr. Nešković: I believe that mastering mathematics, especially numerical analysis and programming, is crucial for serious work in theoretical physics. Additionally, one must master the deductive approach to quantum mechanics. I took such a course with Professor Fedor Herbut during my postgraduate studies at the Faculty of Physics at the University of Belgrade. I also advise young theoretical physicists to look up to Milutin Milanković, the renowned Serbian astronomer, climatologist, and geophysicist who formulated the astronomical theory of climate change. He said his goal was "to find an uninhabited area and acquire a modest scientific domain." On the other hand, there are practically no opportunities to work in accelerator technologies in this region, a direct consequence of the TESLA Projects termination in 2007. Researchers interested in this field should focus on one of the large accelerator centres, of which there are dozens worldwide.