Nanodosimetry: Present and perspectives
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Nanodosimetry: Present and perspectives Mircea Chipara Indiana University Cyclotron Facility, Bloomington, IN
ABSTRACT The reasons to develop a nanodosimetry theory are critically reviewed. The necessity of such an approach is proved. The main features of nanodosimetry are analyzed. The predicted enhanced sensitivity of nanomaterials to ionizing radiation is demonstrated. It is concluded that the lifetime of nanomaterials in the harsh conditions of the space environment has to be accurately estimated.
INTRODUCTION The huge scientific and technological effort focused on the synthesis and fabrication of nanomaterials and nanostructured materials resulted in a wide variety of materials and structures with new or improved properties. Some of these materials are changing already our life, while many others are expected to be used in a wide variety of applications in the near future. The space exploration depends critically on the availability of light materials, on the advances of large-scale integration, and on low energy consumption. Additional features such as multifunctionality, self-healing, and self-awareness will accelerate the space exploration. All these requirements justify the central role of nanomaterials in the space exploration. Little attention has been paid to degradation processes occurring in nanomaterials and nanostructured materials. While the Earth environmental conditions are considered as mild, the harsh conditions of the space environment may reduce significantly and even destroy the functionality of devices based on nanomaterials and nanostructured materials. The most important contribution to the degradation of nanomaterials and nanostructures exposed to the space environment comes from the radiation component of the space environment. The goal of this contribution is to dissect the radiation-induced modifications within these emerging materials and structures in order to quantify the potential danger of ionizing radiation and to estimate the lifetime of nanomaterials and nanostructured materials in the space environment. Nanodosimetry, microdosimetry, and dosimetry It is generally accepted that the effects of ionizing radiation on materials and structures are related to the amount of energy deposited within the target by the impinging radiation. The dose, D, quantifies the energy deposited by the incident ionizing radiation per unit mass of the target [1, 2]. It is the fundamental concept of dosimetry at macroscopic scale. Qualitatively, the dose reflects the statistical character of the interaction between the incident beam and the target. The recent successful development
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of microdosimetry [3] revealed the need for a more accurate analysis of the balance between the incoming and outcoming energy contributions. The refined expression for the energy balance showed that the energy of the incident radiation is not completely absorbed and retained within the sample. A certain flux of particles (or/and radiation) and an associated energy are leaving the target (reflected beam,
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