J. Oberling, E. Merilh
On June 23rd we swapped the laser on the ETMx oplev, see alog 19290. We spent the next couple weeks tweaking the operating power of the laser to get it in a stable zone; this has to be done since the thermal environment is different between the end station VEA and the LSB lab the laser was originally stabilized in. After I got back from vacation last week I've been looking at quiet times (no apparent optic movement; I looked at the pitch & yaw oplev signals and picked times where the optics were quiet) to see if the laser is stable and glitch-free. I've attached 3 spectrograms of quiet times during the last week
- 2015-7-13 for 3 hours starting at 11:00:00 UTC (4:00 am PDT)
- 2015-7-15 for 2 hours starting at 13:30:00 UTC (6:30 am PDT)
- 2015-7-19 for 4 hours starting at 14:00:00 UTC (7:00 am PDT)
There is no obivious glitching in the ETMx oplev laser as shown in these spectrograms. I think it is safe to say this oplev is healthy. I have also attached a spectrum of the ETMx oplev pitch & yaw signals for the same 4 hour stretch on 2015-7-19 as the attached spectrogram.
As usual if anyone notices anything not right with any of the optical levers, let me know.
Glitch Performance evaluation of diode lasers:
It is sometimes difficult to see whether a laser is glitch free because of the tools we employ display the data. It is good to compare performance of a laser under test with one that is known to be glitch free and another known to be glitchy. This way the display tool is validated (since it shows the glitches in the glitchy laser). At the same time we would know if the laser under test has achieved the Reference Laser's performance level.
Please see my post on laser evaluation. And it would be preferable if the same kind of plotting tools (ligodv) are used as in the past in order to make the comparisons easier.