Tilt adjustment for a portable absolute atomic gravimeter

For an atomic gravimeter, the measured value of the Earth's gravity acceleration g is the projection of the local gravity on the direction of Raman laser beams. To accurately measure the g, the Raman laser beams should be parallel to the g direction. We analyze the tilt effect of the Raman beams on g measurement and present a general method for the tilt adjustment. The systematic error caused by the tilt angle is evaluated as 0 (+0, -0.8) μGal (1 μGal=10 nm/s²) and the drift is also compensated in real time. Our method is especially suitable for the portable atomic gravimeter which focuses on the mobility and field applications.