Particle accelerators are widely used in various fields from basic sciences such as high energy physics and nuclear physics to industrial applications. Among them, we conduct researches on electron accelerators and related subjects. There are three electron linear accelerators at the Institute of Scientific and Industrial Research and we make use of one of them to conduct research for producing a high-quality electron beam and for generating a new light beam called the quantum beam. Our research activities extend from basic physical processes to development of high-performance accelerators. The photograph shows a far-infrared free electron laser, which can generate a high-intensity laser beam in the wavelength region between light and the electromagnetic wave. The red device is called the wiggler, which wiggles the high energy electron beam to emit light, and it is a part of the free electron laser. The electron linac is located behind the wiggler.