R. Short, J. Oberling

As written in Jenne's alog here, upon finding the spare PSL NPRO SN1661 does not show the glitching we've been seeing with NPRO SN7974 we begsn swapping the PSL NPRO this afternoon.  We started by removing NPRO SN7974 and our glitch test setup, then installed NPRO SN1661.  We immediately noticed the readbacks in PSL Beckhoff were slightly wrong, meaning we need to adjust the potentiometers on the power supply's internal board that provides these readbacks.  With an injection current of ~0.9 A, which gave an output power of ~32 mW, we roughly aligned the beam to our alignment irises that sit between M02 and M03, using M01 to align to the first iris and M02 to align to the second.  We did remove the PSL EOM and lens L01 from the beam path; the EOM will be reinstalled once we have a mode matching solution, and L01 will have to be changed to a new lens (the current f=167mm lens installed for L01 gives us an uncomfortably small beam in the area of the EOM crystal).  We then set a power meter after M02 and turned up the NPRO injection current until the power meter read ~1.8W; the injection current is 2.144 A.  WP13 (a QWP) and WP14 (a HWP) were adjusted to maximize the power read by the power meter (these 2 waveplates serve as polarization clean up for the naturally slightly elliptical polarization of the NPRO beam).  We started with ~1.806 W and ended with ~1.814 W.  Moving the power meter to the output of the NPRO we measured ~1.86 W, so we're losing roughly 46 mW to wrong polarization.  We then calibrated the PSL Beckhoff reading for the NPRO power monitor PD, as well as the channel H1:PSL-PWR_NPRO_OUT_DQ that is also connected to this PD; these now read correctly at ~1.86 W.

We left the NPRO running overnight, so there will be more data collection for looking for glitches, although we also did not see any while working in the PSL enclosure this afternoon.  The enclosure environmental controls are also running, but the lights are off.

On deck for tomorrow:

• Tweaking the board in the NPRO power supply that provides the NPRO readbacks for PSL Beckhoff
• Find and implement a mode matching solution for NPRO to Amp1
  • This is likely to be a 3 lens solution, with 1 lens getting the beam the correct size for the PSL EOM (new L01), and 2 lenses between FI01 and M03 that mode match to Amp1
• Begin recovering the amplifiers