  The test of gravitational force on antimatter in the field of the matter
gravitational field, produced by earth, can be done by a free fall experiment
which involves only General Relativity, and with a Mach-Zehnder interferometer
which involves Quantum Mechanics. This article presents a new method to produce
a tunable low energy (Ps ) beam suitable for trapping the (Hbar + ) ion in a
free fall experiment, and suitable for a gravity Mach-Zehnder interferometer
with (Ps). The low energy (Ps) beam is tunable in the [10 eV, 100 eV] range.
