Nuclear Physics

The study of Nuclear Physics aims at understanding Nuclear Structure  and the forces holding the nucleus together. To achieve this understanding it studies Nuclear Reactions  and the Radioactivity  they produce. In addition, since the produced radiation is characteristic of the emitting nuclei, it serves as a diagnostic tool for almost all sciences.

We mention here:

The use of Radioisotopes for medical diagnosis and therapy.

The use of radiations for the Microanalysis of Trace elements  with sensitivities of the order of one in a million (i.e. one gram in a ton of material) and applications in Environmental  Biology , the Characterization of New Materialsand Archeometry

The study of reactions contributing to the Production of Energy and the Evolution of Stars

Nuclear Structure

In nature there are 92 Elements. They are distinguished by the number of their electrons (Atomic Number, Z) which determines their chemical properties. Every element (Atom) has a nucleus which contains as many protons as the atomic electrons. It also contains neutrons. The sum of protons and neutrons (the nucleons) is the Mass Number (A) of the element. With these numbers every nucleus is fully specified.

Nucleons are confined in very small space where the laws of Quantum Mechanics are valid. The only information we can obtain is about the Energy States  of the nucleus, the Probability to find it in one of these, as well as, its decay to other states of lower energy which we present in an Energy Diagram.

Radioactivity

The mass of the isotope differs from the sum of the masses of its nucleons. This difference, the Mass Defect, is equal to the Binding Energy or Internal Energy.  Part of the Mass has been converted to energy in order to bind the nucleons. Thus elements with the same Α, the isobars, have different Internal Energy.

Nature always seeks states with lower energy. Thus the isobars of the diagram, decay (or transmute) to Aluminum, emitting either electrons (β^-) or positrons (β⁺, EC), they are Radioactive.

We measure the Activity in Bequerel (1Bq = one decay per second) or Curie (1Ci= 3.7´10¹⁰ Bq ). For medical applications the important quantities are the Absorbed Dose measured in Grey (Gy) and the Effective Dose measured in Sievert (Sv)

Nuclear Reactions

For the study of the structure and the properties of the nucleus we provoke Nuclear Reactions. We use Ions which have been accelerated, i.e. they have obtained kinetic energy by an Accelerator . With these we “bombard” the “target” nuclei. The nuclei absorb the energy of the “projectile” or they are transformed, absorbing all or part of the projectile. We end up with nuclei, which have excess energy and will decay to states of lower energy, emitting photons or particles, they become Radioactive .

X-Ray Spectrometry

The X-ray fluorescence technique is an important analytical tool for the non-destructive, simultaneous and multielemental analysis of samples with interest in various disciplines, from advanced materials, biomedicine, geology, to the environmental science and archaeometrical research. The Institute of Nuclear Physics of NCSR ‘Demokritos’ is equipped to produce X-rays from ions (using the TANDEM accelerator) or from electrons (using a variety of X-ray tubes of different power). The research in the field of X-ray spectroscopy includes studies in basic research as well as studies of multidisciplinary nature.