Jason, Sheila
There have been some glitches on the ETMX oplev, which don't seem to correspond to motion of the optic, the attached screen shot shows an example. I think that I have seen glitches like this that were much larger in amplitude, but am not sure.
One question for detchar is if they have a tool that can search for glitches like these, and give us some information about how often they are happening, how large they are, and maybe monitor to see if they are happening on other op levs.
Another issue is that sometimes the lasers fail, which is often foretold by a several seconds oscillation in the oplev sum. Can detchar set up some kind of monitoring for that?
Of course the real question is how can we fix it......
Hi Jason and Sheila, here at LLO Olmo Cerri, a summer student from UMISS, looked at the possible causes of glitches in OPLEVs. He worked with Suresh. Suresh earlier found that the the temperature variation could cause changes in the cavities of OPLEV laser and thereby changing the laser intensity which would look like glitches. Olmo looked at week long strecthes of data from a few OPELVs and charactersized how many glicthes we see (he wrote a matlab script to find the such gltiches). They also implemetned a simple temperature stabilization method (LLO a-log) to reduce the gltiches. It seemed to work well. Here is a presentation by Olmo on this work which shows data before and after the temperature stabilization setup. He is now looking into implemneting an online version of the code.
I set Olmo's code to run on a cron job with the results here: https://ldas-jobs.ligo-wa.caltech.edu/~codyca/MHoF_results/ We still need to put together a better way to present the results. The code is set to remove glitches caused by human interaction by looking at the OPTICALIGN offsets. Also, the results for LLO can be found here: https://ldas-jobs.ligo-la.caltech.edu/~codyca/MHoF_results/