A Technique for Directly Measuring the Gravitational Acceleration of   Antihydrogen
  The gravitational force on antimatter has never been directly measured. A method is suggested for measuring the acceleration of antimatter $(\bar g)$ by measuring the deflection of a beam of neutral antihydrogen atoms in the Earth's gravitational field. While a simple position measurement of the beam could be used, a more efficient measurement can be made using a transmission interferometer. A 1% measurement of $\bar g$ should be possible from a beam of about 100,000 atoms, with the ultimate accuracy being determined largely by the number of antihydrogen atoms that can be produced. A method is suggested for producing an antihydrogen beam appropriate for this experiment. 
Thomas J. Phillips (Physics Department, Duke University Durham, NC,   USA)