Keita, PeterK, Rick

Keita and I went out to the laser room to make some RIN measurements.

Short summary:

     Front end RIN seems normal both with the high power oscillator (HPO) running and with it off

     High Power Oscillator RIN much higher (>factor of 10).  Glitches (few cycles of 500 kHz) at abouyt 37 kHz on the hight power oscillator light, but not the front end light

     More tomorrow regarding this.

After shutting the laser (front end and HPO) down to reset the Long Range Actuator (via the reset button on the back of the control box), the HPO only came back up with about 1/4 of the expected power.  Troubleshooting and brainstorming on the phone with Peter, we tried increasing the diode currents by 1 A (left the laser in this condition).  This due to the low power and because the head 4 output dropoed from about 96% to about 91%, i.e. it came back about 5% lower after switching the laser off to reset the LRA and turning it back on.

HPO power (with internal shutter open, front end off) still only came up to about 50 W (expecting close to 200).

Peter suspects that some internal optic has been damaged.  We decided to shut the system completely down - lasers and chillers - and try a cold start in the morning.

I plan to talk with MattH and Olli Puncken at LLO first thing in the morning to see if they have any ideas or suggestions.

It's looking pretty likely at this point that we aren't going to have a high-power laser until we can go into the HPO to inspect the optics and assess the state of the HPO.  This would start next week on Tuesday at the earliest, when PeterK returns from vacation.

Assuming that the cold start in the morning is not successful, we will have to decide is we want to try to get a the 15 watts reflected from the HPO aligned and modematched to the PMC so we will at least have a low power beam to work with until next week.