Measurement of Edge Localized Mode using Fast Camera in NSTX

This paper describes the ELMs measurement by a fast camera in NSTX. The images obtained by the fast camera reveals the ELMs behavior near the divertor region, and the X-point movement can be seen clearly at a first time. The X-point moves inner and down during large ELM. On the other hand the X-point moves up and down during tiny ELM. The difference of these ELMs behavior is also briefly discussed.