This morning I tweaked the operating current and temperatures for the pump diodes for both PSL amplifiers (35W FE and 70W). The changes are summarzied in the below tables. This work was done with the ISS OFF.
Pump Diode Operating Currents:
| 35W FE Pump Diode Operating Current (A) | 70W Pump Diode Operating Current (A) | |||
| Old | New | Old | New | |
| D1 | 47.4 | 47.5 | 43.0 | 43.2 |
| D2 | 47.4 | 47.5 | 43.0 | 43.2 |
| D3 | 44.4 | 44.5 | 38.5 | 38.5 |
| D4 | 44.4 | 44.5 | 38.5 |
38.5 |
Pump Diode Operating Temperatures:
| 35W FE Pump Diode Operating Temperature (°C) | 70W Pump Diode Operating Temperature (°C) | |||
| Old | New | Old | New | |
| D1 | 26.5 | 26.3 | 28.0 | 28.0 |
| D2 | 22.3 | 22.3 | 21.8 | 21.8 |
| D3 | 26.8 | 26.8 | 21.8 | 21.8 |
| D4 | 26.8 | 26.8 | 22.2 | 21.8 |
When I began, the 35W FE had an output power of 32.3W, and after adjustment it had an output power of 32.4W. Not a big change, but it did bump up the transmitted PMC power by ~0.1W without changing the reflected power. Further increases in the current made things worse, so I stopped there. The temperature tweaks had a slight effect on the PMC Reflected power (~0.1W), so I moved on to the 70W amp.
The 70W amp was not happy with any change in the operating current for D3 and D4, but I did see an increase in PMC transmitted power without a corresponding increase in PMC reflected power when I slightly bumped up D1 and D2. As far as temperature tweaks, the 70W amp was not happy with any tweaks to the operating temperature of D1, D2, or D3 (temp up, temp down, didn't matter, PMC Refl increased and Trans decreased regardless). On the other hand, lowering the temp of D4 by 0.4 °C lowered the PMC reflected power by ~0.3W without changing the transmitted power; this change did lower the overall power out of the 70W by ~0.3W, but with no corresponding change in the transmitted PMC power, I think this small temp tweak removed some power from higher-order modes. The 70W amp is currently outputting just under 70W, at roughly 69.7W. I attached a screenshot of both PSL pump diode Beckhoff screen for future reference.
I also slightly tweaked the beam alignment into the PMC to see if I could further lower the PMC reflected power. With this complete, the PMC is now transmitting 54.1W (ISS OFF) and reflecting 10.0W. Upon turning the ISS back ON, the diffracted power was above our upper 3% limit, so I tweaked the ISS Reference Signal from -2.06V to -2.08V. This changed the ISS diffracted % to ~2.2%, which is where it's been sitting during normal operation. This change was accepted in SDF, both SAFE and OBSERVE.
To finish, I reset both PSL power watchdogs at 16:38 UTC (9:38 PDT). This completes FAMIS 10720.
