Lines in the spectra of the lasers and in the dark fringe....

Alessio Thu Oct 08, 2009 5:33 pm

Tonight the ITF has been relocked. Looking at the spectrograms of the dark fringe, a new large line has been discovered arounf 75Hz and moving in time.

Lines in the spectra of the lasers and in the dark fringe.... Spectr10

It has been identified to come from the TCS. We then looked at the spectrograms of the TCS PDs. Since we installed the intensity stabilization, there are a lot of lines on both PDs. These lines move in the same way in time. They all seems to be daughters of the (in)-famous 575Hz line coming from the beating of the NI RF driver.

Lines in the spectra of the lasers and in the dark fringe.... Spectr11

Lines in the spectra of the lasers and in the dark fringe.... Spectr12

Lines in the spectra of the lasers and in the dark fringe.... Spectr13

Lines in the spectra of the lasers and in the dark fringe.... Spectr14

It seems that there is a coupling between the AOM RF drivers and the NI laser RF driver, so that this line and all her daughters are fed into the TCS beams in both benches...