Evaluation of the diffraction correction during the 10th International Comparison of Absolute Gravimeters (ICAG-2017)

The curved wavefronts of a Gaussian beam used in absolute gravimeters introduce a systematic error in the measured gravity value. Diffraction correction is defined to denote the correction of the error. This paper presents an evaluation of the diffraction correction for some absolute gravimeters participated in the 10th International Comparison of Absolute Gravimeters. An automatic M-2-measurement instrument is introduced to achieve an efficient and accurate measurement of the beam waist diameter. On the basis, the diffraction corrections are calculated and estimated. The results indicate that the waist diameter of two laser beams deviates from the typical value. After optimized, the diffraction corrections of all the estimated AGs are less than 2.4 mu Gal. The accuracy of the correction is better than 0.1 mu Gal. This work is of great significance for improving the accuracy of the gravity measurements in the comparison.