An MCP unit of the present invention has a triode structure with a structure to achieve a desired time response characteristic independent of restrictions from a channel diameter of MCP, and is provided with an MCP group, a first electrode, a second electrode, an anode, and an acceleration electrode. Particularly, the MCP unit further comprises a ring member between the acceleration electrode and the anode, as s restriction structure for confining reflected electrons emitted from the anode in response to incidence of secondary electrons from the MCP group, within a space between the acceleration electrode and the anode.
