A vacuumed enclosure has a window formed of an X-ray transmissive material. The vacuumed enclosure encloses an electron beam source for generating an electron beam and a target which, irradiated by the electron beam, generates a primary X-ray. The target is smaller in the outer dimension than the window and located on the center of the window such that it irradiates, through the window, the primary X-ray onto a sample located outside. The vacuumed enclosure further encloses an X-ray detector located such that it can detect a fluorescent X-ray and a scattered X-ray coming from the sample through the window. The X-ray detector generates a signal representative of energy information of the fluorescent X-ray and the scattered X-ray. The vacuumed enclosure further encloses a thermally and electrically conductive metal extending through the target across the widow.