Real-time measurement of the focal-spot intensity-distribution for megavolt flash X-ray machines

A new method for measuring the 2D intensity-distribution of the focal-spot of megavolt flash X-ray machines is demonstrated. A position-sensitive plane detector views the radiation source through an X-ray-opaque large square aperture. The square aperture was introduced in a previous publication [1] and it was shown that in this case, the focal-spot intensity-distribution is given by the second order mixed Cartesian partial derivative of the penumbral image intensity distribution. This technique is demonstrated by measuring the intensity distribution of the focalspot of a pulsed X-ray machine (1 MV, 40 kA, 50 ns). The results are compared with the physical damage visible on the metal target.