Beam monitoring system for ion beam irradiation experiments

A compact ion beam irradiation system has been developed in our facility to study the mechanism of radiation effects on a variety of materials and devises. This system is designed to achieve beams of about 1 μm in minimum diameter and of about 1 nanosecond in minimum pulse width. The essential components of the system are shown in Fig. 1. The beam is extracted from the ion gun at the energy of 1-5 keV. Available ions are H+, D+, He+, Ar+, etc. and the maximum beam current is ∼300 nA. The extracted beam is pulsed by the electrostatic deflector and the aperture. The pulsed beam is accelerated to an energy < 50 kV by the accelerating tubes and is focused onto a target in the experiment chamber by the final electrostatic lens. Most of these components are commercially available and the configuration of the system can be easily rearranged according to experimental requirements. To constrain the divergence of the beam, apertures of 500 μm and 100 μm in diameter are placed at the entrance to the accelerating tubes and to the final electrostatic lens, respectively. And an adjustment to transport the beam through them is required at the beginning of irradiation experiments. The suitable monitoring of the position and profile of the beam at the apertures is necessary for the stable ion beam irradiation. This paper describes a simple method of monitoring the beam position and profile for the beam adjustment. First, this paper shows the overview of the present beam monitoring system and then describes results of its performance tests. (author)