jason.oberling@LIGO.ORG - posted 09:14, Tuesday 22 December 2015 - last comment - 10:16, Wednesday 23 December 2015(24382)
BS/SR3 OpLev Laser Power Increased (WP5667)
I increased the power on the BS and SR3 oplev lasers this morning by ~5%. I used the voltage read out of the "Current Monitor" port on the back of the laser (this port monitors the laser diode current, outputs a voltage). The old and new values are listed below, as well as the new SUM counts. Since I had to open the coolers the lasers are housed in they will need ~4-6 hours to return to thermal equilibium; at that point I can assess whether or not the glitching has improved.
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BS OpLev
- Old voltage: 0.987 V
- New voltage: 1.036 V
- New SUM: ~33500 counts
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SR3 OpLev
- Old voltage: 0.889 V
- New voltage: 0.933 V
- New SUM: ~40900 counts
Links to todays DetChar pages (look at the SUM spectrograms, both standard and normalized, at the top of the page) for these oplevs, showing data after the power increase and subsequent return to thermal equilibrium (data starts at 0:00 UTC 12/23/2015, or 16:00 PST 12/22/2015): BS, SR3. As can bee seen, SR3 quieted up significantly (go back a day or two and compare), one more small power adjustment should take care of it; will do that at the next opportunity (probably the next maintenance day, 1/5/2016). The BS on the other hand has not seen much improvement. I'm starting to think maybe I've overshot the stable range... Will perform another adjustment (probably also on the next maintence day), this time targeting a region between my last 2 adjustments. I will keep WP5667 open as this work is still ongoing.
On a brighter note, I have been testing the laser removed from the BS oplev in the LSB optics lab and can find nothing wrong with it. I'm currently adjusting the TEC temperature setpoint to bring the stable region to a more useful power level and the laser will be ready for re-installation (back into the BS if the current laser proves too finnicky or into another oplev (likely ITMy)).