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Each row of two frames represents one snapshot-pair of laser on (on the right side) and laser off (on the left side) with unchanged configuration. One can see a clear increase from these pictures, proof that the laser accelerates the 20 mega electron volts electron beam in vacuum. Pictures of the beam momentum spread after the spectrometer taken with the laser off (left column) and the laser on (right column). The length of the beam image reveals the energy spread of the beam. The experiment recorded 30 shots. Twenty shots were high intensity and showed effects of the laser on/laser off difference. Four shot examples are shown here. Pictures are taken from spectrometer on Beam Line #1 at BNL-ATF.