High Power Oscillator Flow Sensors
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We replaced the water sensor block in the high power oscillator because the flow rate sensor for head 4 was not working and appeared to be jammed.  Inspection of the water filters in the water sensor block revealed a number of particles and remnants of PTFE tape.  After installation of the spare water sensor block, we noticed that the sensor for head 4 was not working, so a sensor from the previously installed block was removed and substituted in.  Re-installation of the spare water sensor block was successful.  The water was left on for a period of time to check for water leaks, none appeared.  The chiller flow rate was between 18.9 and 19 litres per minute.

Photos of the filters are attached.  The filenames correspond to the head number.  The last image is one of the flow sensor body.

After completion of the installation, the frontend laser was fired up.  The FSS and PMC were locked.  Some problems were experienced with the ISS.  We could lock the ISS but only with a relatively high diffracted power (~15-20%).  Efforts to reduce the diffracted power were thwarted by the control signal to the AOM oscillating, even with the servo gain turned down.



O. Puncken, P. King