Optical setup

The optical setup is shown in figure 1, and is made of:

• A optical table (stainless steel) supporting one breadboard (anodized aluminum);
• Seven infra-red diode lasers (four for longitudinal pumping and three for transverse pumping) located on one side of the table, with optical fiber bundles.
• Seven lens to have each laser beam focused at the pumping cell;
• Seven beam splitters to split each laser beam to two beams;
• Fourteen $\lambda$/4 waveplates to transform each beam from linear polarization to right or left circular polarization;
• Fourteen dielectric mirrors to reflect each split beam back into the pumping cell;
• One transparent window on the RF enclosure and one transparent window on the oven to allow the combined transverse laser beam to pass through;
• Two dielectric mirrors to reflect the combined longitudinal laser beam into the pumping cell;
• One pumping cell to absorb all the laser beam power;
• Three mirrors for monitoring the pumping cell;
• One spectral-analyzer for monitoring the pumping cell.

Figure: Optical Setup in the Laser Hut

The optical table will be about 2 meters from the platform. The laser beams will be from about 15 cm to 105 cm above the table Each of the 795 nm diode laser light, after passing through the lens, will be split into two beams. Each one will go through a $\lambda$/4 waveplate to transform linear polarization to circularly right or left polarization. All beams, after passing some windows and being reflected by some mirrors, will shoot into a glass pumping cell filled with mixture of Rb vapor and $^3$He gas. The laser beams will be completely absorbed by the pumping cell. The total path length from the lasers to the pumping cell is about 5 meters. The pumping cell is inside an oven and connected to a target cell. The whole target assembly is inside two pairs of Helmholtz coils, which provide a magnetic field for the polarization of the target. A NMR system with a set of RF drive coils and a set of separate pickup coils, and an EPR system are used to measure the polarization of the target.