Reports until 08:52, Thursday 18 January 2018
H1 PSL (PSL)
peter.king@LIGO.ORG - posted 08:52, Thursday 18 January 2018 - last comment - 06:17, Friday 19 January 2018(40167)
Laser trip 
Richard informed me that the laser had tripped this morning.  I reset the laser without any problems.

    I increased the current for head 1 to the maximum of 60A and increased the diode temperature for
diode 3 to 23 degC.  The output of diode box 1 has taken a bit of a dive since the weekend.  So much
so that I would start to become concerned that the thermal lens in the NdYAG rod isn't what it should
be to make the resonator stable.

    At this point in time, we have two options as I see it, depending on commissioning constraints:
  i. replace the diode box
  ii. revert to low power mode
Both would take about half a day to do.
Comments related to this report
peter.king@LIGO.ORG - 09:38, Thursday 18 January 2018 (40168)
Link 

I have not turned the power watchdogs back on.
Images attached to this comment
jason.oberling@LIGO.ORG - 15:27, Thursday 18 January 2018 (40176)
Link

Attached is a trend of the DB operating current increases, starting in April 2017.  The ongoing failure of DB1 can be seen in the large operating current increases that have been required over the last 2 weeks to keep the laser running.  The life of DB1 has been slightly extended by adjusting its operating temperature in lieu of adjusting its operating current, hence the flat spot near the end of the graph.

Images attached to this comment
patrick.oppermann@LIGO.ORG - 01:43, Friday 19 January 2018 (40187)
Link 

The power of diode 3 in DB1 has dropped by 50% of its original power. The TEC is already at the maximum of its performance.
You should lower the temperature further and observe the performance of the HPO.
The current for the diode boxes can be higher than 60A, if you enter the value directly and do not work on the plus and minus button.
The diode itself will not last much longer.
Images attached to this comment
matthew.heintze@LIGO.ORG - 06:17, Friday 19 January 2018 (40190)
Link

If your trying to stretch out the lifetime I seem to recall that you can actually run these diodes up to 65A in a pinch