The present invention concerns an apparatus for spectral and intensity profile characterization comprising: a diffractive element; a beam block (3) attached to the diffractive element, the beam block (3) being positioned so as to block the passage of the direct incoming beam (1) which is not incident on the diffractive element; a device for translation of the beam block (3) and the diffractive element; reflective element (4); fixed detector (5) positioned on the axis of the incoming beam (1). The invention also concerns use and a method thereof. Such a compact system provides application in the field of spectrometry and diagnostics of the beam intensity profile, especially in the area of XUV and soft X-rays.