In order to achieve a total output of 100 J, we conducted independent adjustments for each amplifier, PFN voltage, SHG crystal optimization, and energy tuner optimization to produce beam energies slightly higher than 25 J (at 527 nm). It was recommended that the PFN voltage should not exceed 2400V. Figure 9 illustrates a simplified architecture of the final beam combining and delivery system. The two west arms, AB and EF, were combined using the west thin film polarizer (TFP), while the two east arms, IJ and GH, were combined using the east TFP. Multiple high reflectivity (HR) mirrors were placed between each SHG crystal and TFP. To verify the P and S throughput, we measured the SHG energies before and after the TFPs. It was observed that the east TFP did not function optimally, as the maximized transmission and reflection angles were not complimentary. Consequently, the total efficiency was below 90%, resulting in a total output of 95 J. To address this issue, we ordered a new TFP from Lattice-Electro-Optics and replaced it on February 16. With the new TFP correctly aligned, we calibrated the energy meters and measured the energy inside the chamber, resulting in a measured output of 107.9 J with an rms fluctuation of 0.8 J (west arm: 54.5 J, east arm: 53.4 J), as shown in Figure 9.
For the 50 mm amplifier, an energy ramp-up was conducted as depicted in Figure 10, with the GH arm exhibiting a higher output compared to the AB, IJ, and EF arms. We also measured the efficiency for each SHG crystal. With this information, we were able to control the output energy slightly higher than 25 J for each arm.
Finally, the combined east and west beams were expanded using a pair of telescopes before being delivered into the target chamber. To maintain consistent beam size and collimation in the target chamber, the final pair of telescopes underwent modifications. The original lens combination and magnification were (f1 = -500, f2 = 1000, M = 2). The new lens combination and magnification were adjusted to (f1 = -660, f2 = 1000, M = 1.5).
Figure 9. The energy measurement before and after change the east side TFP ,which IJ and GH beams are combined
Figure 10. IR energy vs voltage plot of 50 mm amplifiers: IJ, AB, EF, and GH