Development and application of intermittent electron irradiation technique with a high voltage electron microscope

Abstract. 2014 For the purpose to observe and analyze the transient phenomena after the start of irradiation and the relaxation phenomena after the cessation of irradiation, techniques for intermit-tent electron irradiation are developed with a high voltage electron microscope, utilizing the STEM function installed in H-1250ST. One of the two methods developed is to make move the electron beam along a circle passing the area of interest in each cycle, which has an advantageous feature of invariant accumulated irradiation time regardless of the frequency. In another method, the electron beam goes back and forth between two positions, in which there is a free choice of the combination of the on- and off-time of electron beam. Dynamical control of electron beam position is made with two deflection coils placed at a right angle, which are driven by a computer loaded with two-phase-signal oscillator through D/A converter. Examples of applications are quoted on the relaxation effect of accumulated point defects on the nucleation and growth of interstitial clusters introduced in metals by electron irradiation