Swift Heavy Ion Synthesis and Modifications of Nanophosphors for Dosimetric Application: Effect of Swift Heavy Ion Irradiation

Introduction

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  Swift Heavy Ion: Swift means very fast, i.e. having very high velocity. It is well known that if any object with a mass m traverses with velocity v, it will gain the kinetic energy indicated as 1/2mv².As the energy of the substance is directly proportional to the square of the velocity, the word swift indicates that it is having an elevated energy. Therefore, highly energetic heavy ions are generally known as Swift Heavy Ions. The present chapter deals with swift heavy ion induced synthesis and modification of phosphor materials mainly for dosimetric applications. This chapter will describe the history and the types of the radiation in brief along with its interaction with matter. Based on this discussion, this chapter will introduce different luminescence phenomena. Various simulation procedures will be revealed to obtain an idea of the suitability of the materials for dosimetric appliances.

Before going into the details, the outset of some prologue to theindispensable concepts and terminology of the radiation physics is necessary to be first mentioned. This interesting subject starts with the discovery of X-rays by Wilhelm K. Rontgen in the 1890s along with the foundation of radium by the Curies and radioactivity by Henri Becquerel. From then, X-rays havebecome handy paraphernalia in the practice of medicine, diagnostic radiography within a brief duration and hence setting some kind of record for the hasty implementation of innovative machinery forindustrial applications. However, the chronological advancement of the knowledge of radiological physics draws the research attention since then and has become an imperative partof the materials physics.

The radiation falls on an object and can excite and ionizethe atoms i.e., carries sufficient energy tofree electrons from atoms or moleculesof matter with which they interact are known as ionizing radiation. It is well known that at least 4- 25eV energy isrequired to craft a valenceelectron free from the atom and thereby the radiations which carry energies greater than the above-mentioned energy will be named as “ionizing.” Ionizing radiation can be classified in two different ways as directly or indirectly ionizing radiation based on the nature of the radiation that creates the ionizing consequence.

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  Directly Ionizing: If any radiation of charged massive particle carries adequate kinetic energy to ionize target atoms unswervingly by elementary interaction through the Coulomb force, these ionizing radiation will be categorized as directly ionizing radiation. It includes electrons,protons, nuclei, muons, pions, and so on. In general, alpha particles and beta particles defined as the Helium nuclei evicted from atomic nuclei, and electrons ejected usually at relativistic speeds respectively are also in this category.

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  Indirectly Ionizing: The electrically neutral substances when falling on an object, indirect ionization occurs due to secondary ionizations. Therefore these substances do not interact sturdily with the target. The neutron radiation is one of the examples of indirectly ionizing radiation.

These ionizing radiations have many militaries, industrial, and medical uses along with the appliances in materials science. Therefore, the present chapter deals with the basic understandings of ionizing radiation and its application for thedosimetric purpose.

Background

The highly energetic cosmic rays (Figure 1) constitute a serious dosimetric problem for aircrew and space dosimetry. The component used in various subsystems of the spacecraft near the lower earth orbit gets exposed to these high energy heavy ion radiations. (Vij et al., 2010)This necessitates the concurrent development for the measurement of doses/ fluences of such energetic particles with great precision of accuracy especially while dealing with human beings. Recently, there is a huge demand for experimental and theoretical efforts for the dosimetry of the ionizing radiation due to its diagnostic and therapeutic purposes.(Manjunatha et al., 2013) However, the ability to emit visible light radiation when suitably excited makes the phosphor materials suitable for TL dosimeter (TLD).