Measured power output of X-arm laser to be 56.3W directly after laser.  Thermopile in laser has a lower V/W sensitivity (0.116V/W) than others measured. I've updated the calibration to reflect this so that the channel H1:TCS-ITMX_CO2_LSRPWR_HD_PD_OUTPUT now gives correct laser output power.

I have also redone the calibration of the rotation stage using a second power meter on the table at the output to the CP.  The rotation stage position for a minimum output was correctly set at (37 degrees) giving a zero reading on a 100W and 10W power meter heads (we can go to a more sensitive power meter also, but here I'm measuring the full range of the rotation stage).  Maximum is seen at 82 degrees giving 5.44W.

Attached is a plot of angle to power for both power meters.

I've checked the calibration of the rotation stage, which was almost correct, and have slightly altered the maximum power output setting for this.  Minimum power and minumum power angle were both correct.

It looks like we are seeing the rotation stage not always going to exactly the requested angle.  This results in non-zero power output when minumum power is requested.  This is not an issue with the power meter - it is real.  So when there is a non-zero power reading on the power meter it means there is power going to the CP.  Repeated presses of the 'Go to minimum power' button result in the rotation stage eventually going to the correct angle.  If it still won't go to zero, then using the 'Home' button can reset the rotation stage position.