Accurate wavefront aberration measurement are essential for\nnext-generation Extreme Ultraviolet (EUV) Lithography. During the past\nyears several accurate interferometric techniques have been developed,\nbut these techniques have limitation. In this work we discuss a\ndifferent technique based on the Hartmann Wavefront Sensor that requires\nno interferometry. We present a mathematical model of this system and\ndescribe our experimental setup which demonstrates the feasibility and\nadvantages in terms of dynamic range and accuracy compared to\ninterferometric techniques.