Device for recognizing the impact site of a charge carrier beam on a target

DETAILED DESCRIPTION The invention is therefore based on the task of obtaining an actual position signal of the impact point of an electron beam on a target which is independent of the melt material level.
This task is solved according to the features of the present invention.
The advantage achieved with the present invention consists in particular in that the exact position of the impact site of an electron beam on the surface of a target can be determined even if the level of the melt material changes which is of significance with all vaporizer installations in which no continuous feed of material occurs during the vaporization process.
Moreover with the impact position of the electron beam on the target surface the level of the crucible can also simultaneously be monitored and hence a burning-in of the electron beam into the bottom of the crucible can be prevented.
Furthermore, with the present invention the determination of all three spatial coordinates of the impact site of the electron beam in different systems of coordinates (for example Cartesian coordinates, polar coordinates, spherical coordinates) is possible.
The impact site of the charge carrier beam is understood to be the location of the center of gravity of the power density distribution of the charge carrier impinging on the target surface.
It is also possible with the present invention to determine precisely the coordinates of the impact site--thus including the z-coordinate--even if the detectors are disposed near the target surface.
A change of any coordinate no longer has any influence on the others, i.
e.
the non-correlated determined coordinates.
In a series of application cases a precise determination of the beam position at all points of the target surface is not required, but rather only fixing the impact area in the center of the target surface is desired.
For these cases a simplified version of the invention in the form of a center-position sensor can be applied.
In contrast to known position sensors this simplified version also permits the precise determination of--even of only a single--a distinct position, for example the center position, even if the the melt material level and hence the z-coordinate of the impact point changes