Laser System

The laser system provides 795nm circularly polarized light for optical pumping of the target. The light is generated by seven solid-state diode lasers, which are located in a shielding hut several meters away from the target, and polarized by passing through a polarizer (beam splitter) followed by standard $\lambda/4$ waveplates. Each laser emits roughly 30W of power. Because of the invisibility and high intensity of the laser beam, the lasers present a significant safety hazard.

The system generates two independent laser beams for optical pumping of two different target spin directions: parallel and perpendicular to the electron beam. In the standard configuration, four lasers are used for the parallel and three for the perpendicular direction. Further, it is possible to reverse each of these polarization directions by 180$^\circ$ (``flipping'' the target spin). This requires the rotation of the target holding field (see Chapter ) and reversal of the pumping light helicity. The light helicity can be inverted by inserting a $\lambda/2$ waveplate into the beam path of each laser.