Preface

Gamma rays were discovered by Villard more than a hundred years ago. Rutherford gave the name -rays to the electrically neutral radiation emitted by the naturally occurring radioactive materials.

Gamma rays are electromagnetic radiation, photons, which arises due to energy changes in the nucleus. It does not appear as an independent form of radiation, but it follows and *β* decay, in those cases when the newly created core of the offspring is found in the excited state. This state is very short, while the excited nucleus in its transition to a lower energy level or the primary energy state, mosty usually transmits - photons or transfers the energy to some of the atom electrons. The product nuclide in such an excited state either falls directly to the ground state or descends in steps to lower energy states through the dissipation of energy as gamma radiation.

So, it's the word about the deexcitation process that usually occurs immediately after excitation of the core to some of the higher energy levels. The energy of the emitted photon is strictly determined by the difference of energy states of the nucleus at this transition. Therefore, the energy spectrum of - radiation is linear, i.e. we are talking about a discrete energy spectrum of the emitted - rays.

Gamma rays bombard our bodies constantly. They come from the naturally radioactive materials in rocks and the soil. We take some of these materials into our bodies from the air we breathe and the water we drink. Gamma rays can be produced in labs through the process of nuclear collision and also through the artificial radioactivity that accompanies these interactions. The high-energy nuclei needed for the collisions are accelerated by devices such as the cyclotron and synchrotron.

Gamma radiation is of interest to persons working in a wide spectrum of disciplines. These include scientists, physicians, engineers, and technicians whose work entails the preparation, utilization, or disposal of radioactive materials and the measurement of radioactivity in the environment. Among these are persons working in the fields of radiopharmacy, radiobiology, radiochemistry, industrial applications, nuclear medicine, health physics, nuclear power, nuclear waste management, etc.

Gamma radiation is the basis of gammaspectrometry, a central nuclear method for the quantitative and qualitative analysis of radioactive materials in all ambient

#### XII Preface

environments. Gamma rays can be used to examine metallic castings or welds in oil pipelines for weak points. The rays pass through the metal and darken a photographic film at places opposite the weak points. In industry, gamma rays are used for detecting internal defects in metal castings and in welded structures. Gamma rays are also used in nuclear reactors and atomic bombs.

Gamma rays are used in medicine to kill and treat certain types of cancers and tumors. In radionuclide imaging diagnostics, metastable gamma emitters are most favorable for use, while the beta radiation is absorbed by the body, causing an unnecessary radiation overload. Gamma rays passing through tissue of the body produce ionization in tissue, and thus can harm the cells in our body.

Gamma rays are often used in the food industry. The radioisotopes preserve foods. Gamma radiation is a modern, efficient, economical and fast method for the commercial sterilization and microbial decontamination. Gamma radiation is used in many ways in the food industry and agriculture. In the pharmaceutical industry, gamma radiation is used for cold sterilization.

The book contains 15 chapters which are grouped into five areas: Nuclear physics, Environmental sciences, Materials science, Radiation Biology, Agriculture and Forestry.

From the most chapters of this book can be seen great progress in applying gamma radiation in certain scientific disciplines, which will undoubtedly provide new guidelines for research in these and other scientific fields. And that is the aim of this project. The book which treats such important issues, required the contribution of scientists from a wide range of scientific disciplines. I noted with satisfaction the participation of scientists from different parts of the world, who have made special contributions to the quality of the book. I believe that with such a concept it will bring benefit to scientific workers who have contacts with gamma radiation, as well as those who intend to enter the world of applications and problems of gamma radiation. I hope that this extensive research field will be continued with new contents and integrated in future releases of Intech.

I am grateful to the authors, scientific workers from all parts of our beautiful but agitated planet, who have made valuable contributions to the concept of this book, and to Ms Daria Nahtigal (Publishing Process Manager) who brilliantly coordinated activities on this project, and the visionary editorial team of Intech which promotes global scientific solidarity in best way.

> **Prof. Feriz D. Adrovic**  Faculty of Science Univerzity of Tuzla Bosnia and Herzegovina
