[Alastair, Jason, Ben, Vern, Dave]

Thanks to everyone for their help getting this work done.  The Y-arm TCS laser is now running full power, and the table is fully aligned.  The in-loop photodiode is also now working again.  Details below.

Tuesday we discovered the laser on the table (SN 20306-20419D) had previously been paired with the driver that went with the spare laser ( 20816D-20510).  The laser had been outputing 40W at the time.  When the Hanford team had swapped in the 'spare' driver they actually were putting in the one that matched up with the laser (SN 20419D-20306) and the power went down to 16W.  First thing we did on Tuesday was to add irises to the table to define the optical axis after the laser.  We added blocks to the table to define laser position We then swapped in the spare laser (20510-20816D) and aligned to the blocking, and we found the power outputs were ~14W with its mating driver, and ~40W with the driver SN20419D-20306.

Checks on as much of the electronics as we could test showed no problems (RF distribution system, controller voltages, power etc).

Wednesday we decided the fastest way to diagnose the drivers was to swap them in to the working X arm table.  Driver SN 20419D-20306 gave a power output of 58W.  Driver  20816D-20510 gave 42W.  Swapping back to the original X arm laser (SN 20706-21015D) and driver combo gave 60W so at this point we left the X-table in its previous working condition.  Conclusion was that driver SN 20816D-20510 has now given output of ~40W on three separate lasers and appears to have some issue.

Moving back to the Y-table, two issues were noticed.  Firstly there was very minor discoloration on one pin of the power cable for the laser.  Ben also said that the pin looked badly seated and did some corrective work on this (we should check with him if he thinks this needs further work).  Secondly the power meter height was adjusted to make sure the aligment to the laser gave the largest apeture possible - this could with a little misalignment oclude part of the beam.

We repeated measurement of spare laser SN20510-20816D with driver 20419D-20306 getting 49W output.  We then completed the cycle of tests by putting in laser 20306-20419D with its matching driver 20419D-20306 and getting 58.6W output.  It's not clear what fixed the problems - the power cable seems a likely candidate but behavior of the laser still doesn't seem totally consistent with this (if one half of the driver was getting no current we would expect ~25W output).  We also might want to test driver  SN 20816D-20510 to check whether the power connector (which looked okay when visibly inspected) might be a cause for its performance drop.

After the laser swaps the final laser configuration was aligned to the blocking on the table and then to the optical axis with some minor tweaking of the actuators on the first mirror on the table.  The laser was aligned through the whole table.  At the mask we aligned by maximizing transmitted power, then using the FLIR camera on remote desktop (yes this works now - thanks Dave Barker) we tweaked the alignment to make the beam symmetrical after the mask.  We then aligned to the irises at the output of the table which define the optical axis into the vacuum system.  We changed the alignment onto the power meter that gives the power output to the CP because the head was too close to a focus.  We checked the calibration of the power output to the CP and this was confirmed accurate.  Finally we aligned to the two photodiodes on the table.  Inloop was not giving an output but we swapped cables with outofloop and were able to get a signal to align to.

The problems with the in-loop photodiode were traced to being a bad ADC board which has now been swapped for the spare (thanks Ben & Jason for tracking this down).

The Y-table will have the output to the vacuum system unblocked so the system is ready to go.  The laser will be left keyed off, with the rotation stage set to minimum power.  When the system is needed it just needs keyed on at the rack in the LVEA, and then power increased at the rotation stage.