Measurements of focal spot size for X-ray source by using polycapillary collimator

The method of measuring the focal spot size of X-ray source was designed by using a monolithic glass polycapillary X-ray collimator (MGPXRC). The MGPXRC is composed of 105 capillaries with an inner diameter of several microns. The divergent X-ray beam emitted from X-ray source became a quasi-parallel beam after collimated by MGPXRC. The quasi-parallel beam size is related to the focal spot size of X-ray source. Therefore, the focal spot size of X-ray source can be obtained by using the linear fit based on the quasi-parallel beam size at various distance from the output of the MGPXRC. The focal spot size of a micro X-ray source was measured by using the MG-PXRC method and conventional pinhole imaging method, and the measured results are 60.8 and 59.4 μm, respectively. The MGPXRC can be used to measure the focal spot size of X-ray source with a larger emitting angle than the critical angle of the total reflection of X-rays. And the MGPXRC method has a potential application in the measurement of X-ray source with a spot size of a submicron or even smaller. (authors)