Jordan Palamos, Robert Schofield

Report attached: copying background and summary below

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Background

In early September as part of the PEM injection set we injected RF at specific frequencies where coupling to the interferometer was thought possible. The injections were done using dipole antennas and RF amplifier located by the water tank on site. For those injections the 9 MHz and 45 MHz injections were picked up by the PEM radio channels in the corner station electronics bay ~1000x louder than the background. Of the 10 frequencies chosen only the 45MHz injection showed up in the gravitational wave channel, barely visible over the noise. Those results have shown that RF coupling to the interferometer is small at these frequencies where coupling might have been expected and additionally for the coupling at 45Mhz any RF signal would have to show up very strongly in our auxiliary channels before it shows up in the gravitational wave channel. In order to check for strong and unexpected couplings outside of these frequencies we injected a swept sine spanning a wide range of frequencies.

Summary

We injected an rf sweep from 9 kHz to 100 MHz to check for coupling from environmental rf to the interferometer. We found no evidence for strong coupling at any frequency within the band. An initial upper limit for coupling is that a signal will need to show up with an SNR of 100 on the RF scanner to have an SNR of 1 in DARM, but further investigations may be able to lower that.