Abstract：Based on the operating principle of an interferometric absolute gravimeter, a deviation of the measured gravitational acceleration value introduced by Gaussian laser beam is analyzed. And then a practical method, 90/10 knife-edge method, to measure the beam waist radius for diffraction correction is presented and the relative value of diffraction correction is obtained. Experimental results indicate that the beam waist radius is 1.1586mm and the relative value of diffraction correction is 7.56×10-9. The solution to determine diffraction correction applies to every interferometric absolute gravimeter.
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