ASTM E2903 Effective Focal Spot Size of Mini and Micro Focus X-ray Tubes

Scope:

The ASTM E2903 method is advantageous as it allows users to do geometric calculations to determine the practical focal spot dimensions of the X-ray source. The results of this method are used for maintaining the desired maximum magnification possible or degree of geometric unsharpness, or both, for a given radiographic imaging application.

Test Procedure:

The ASTM E2903 method is based on indirect measurement of the focal spot size by determining the geometric unsharpness, then using a geometric calculation to determine the effective focal spot dimensions. For this purpose, edges are imaged either on a film or a radioscopic or digital radiographic device using a relatively high geometric magnification.

Specimen size:

The specimen’s focal dimension must be from 5 μm up to 300 μm with 225 kV tube voltage.

Data:

The following formula is used in ASTM E2903 to determine the geometrical magnification,

M_{L, W}  = D_L,W /D_eal 

where: D_W and D_L are the diameters of the test object in the width and length direction and D_real is the real diameter.

Conclusion:

The ASTM E2903 method is advantageous as it allows users to do geometric calculations to determine the practical focal spot dimensions of the X-ray source.