MeV Cluster Ion Beam–Material Interaction

Toshiaki Kaneko

doi:10.3390/qubs6010006

Abstract

This paper treats the characteristic topics of MeV/atom cluster ion beams produced using tandem accelerators both in the production stage and in the penetration stage from the viewpoint of fundamental processes. The former is related to atomic collisions in that production and decay of a cluster ion Cn+ (n=1−4) colliding with a charge-changing rare gas underlined through the electron-loss process. Regarding the latter, relatively small carbon clusters Cn+ (n=2−10) are treated. The reduction effect of the average charge of cluster ions in a material is first presented. Next, the electronic stopping power and the energy loss, the polarization force, and the coulomb explosion under cluster-ion impact are described in the dielectric function form. Alignment and structure effects are stressed. As a large and highly symmetric cluster, the electronic stopping power and the average charge are shown for a C60 cluster ion moving inside a solid. Throughout the paper, it is emphasized that the vicinage effect originating from correlation on spatial structure and orientation of constituent ions plays the key role. Moreover, results obtained in cluster production and penetration phenomena are mostly different from multiplication of those under single-ion impact.

Highlights

Since the development of accelerators, controlled single-ion beams have been intensively utilized in various fields of application, e.g., surface analysis, ion implantation, material modification, and cancer therapy
The knowledge accumulated for a long time on the stopping powers of materials for single ions and their ranges were compiled as a series of data book [4] and have been utilized in SRIM computer code [5]
Fundamental processes incorporated in the production and penetration stages of swift carbon cluster-ion beam are described

Summary

Introduction

Since the development of accelerators, controlled single-ion beams have been intensively utilized in various fields of application, e.g., surface analysis, ion implantation, material modification, and cancer therapy. Under cluster-ion impact, unique phenomena have been reported, e.g., on the sputtering yields [11,12], reduction of average charge per atom [13,14,15,16,17], enhanced and suppressed energy losses [18,19,20,21,22,23,24], suppressed low-energy secondary electron emission [25,26,27], and enhanced convoy electron emission [21] These situations intensively attract our attention to the size (the number of constituent atoms) of cluster ions and the spatial structures since those quantities are known to newly affect the irradiation effect.

Objectives

Results

Conclusion