Starting at the Chopper the interaction region begins. We measure the H₂ molecules formed here from Associative Detachment interactions between laser induced H atoms and H- ions. In this section the overlap between the Ion and Neutral beams are measured using two NEC Beam Profile Monitors (model 80).

Beam Profile Monitors

To measure our beam position and profiles using a National Electrostatics Corporation (NEC) Beam Profile Monitor Model 80 (BPM). The BPM operates by rotating a helical wire through the beam. The axis of rotation is 45o to the horizontal plane of the beam. The wire rotates at 19 cycles per second. During one complete rotation the wire passes through the beam once horizontally and once vertically due to the shape of the wire. When the wire passes through the beam, secondary electrons are released and collected. This electron current is measured as a function of time. By matching the corresponding signal within the timing of one rotation you can measure the electron current induced when the wire scans vertically and horizontally. The magnitude of the electron current is prortional to the magnitude of the beam current, hence giving us our vertical and horizonal profiles.

Gas Cell