The basic principle is a scintillating screen which can be flipped into- and out of the beam path. Observation is via an embedded window in the mounting flange. A camera above such window transmits the image to the control room.

Each pixel on the camera CCD chip can subsequently be used for a readout of the target light intensity versa the light spot cross-sectional area. Flipping action will be facilitated via a magnet- or via an air actuated mechanism.

Different scintillating materials are possible, but the most common one is CHROMOLUX. – Important is the power dissipated on the screen and MIGHT require back-side cooling.

Light emissions are not necessarily linear over the whole energy range!