[Niko, Suresh]

Motivation:   

    We suspect that the He-Ne Laser power supply may be generating an unacceptable amount of EMI.  To check this we installed a magnetometer close to the power supply of the laser.

Updated He-Ne laser setup:

   1) we moved the power supply close to the laser (see pictures attached) and placed the magnetometer near them on the ground.

   2) the optical fiber was rerouted to minimise dangling.  The fiber has been supported close to the laser and the oplev transmitter to decrease fiber motion.

   3) To check if the large (39dB) whitening gain was introducing noise into the oplev signals.  We temporarily reduced the gain to 19dB and then after about an hour put it back to 39dB.  This change did not seem to have an effect on the noise level in the oplev signals. 

   4) The Magnetometer signals are connected (X,Y,Z) to inputs (1,5,6) on PEM BNC breakout panel which show-up in CDS channels H1:PEM-EY_ADC_0_08_OUT_DQ, H1:PEM-EY_ADC_0_12_OUT_DQ and H1:PEM-EY_ADC_0_13_OUT_DQ.

Results Pending further analysis:

Will look at data with Robert and report on the EMI issue next week.

Will look at oplev data to see if rerouting the fiber has made any difference.