aLIGO LHO Logbook

H1 ISC

stefan.ballmer@LIGO.ORG - posted 16:20, Wednesday 04 May 2016 - last comment - 08:35, Thursday 05 May 2016(27011)

10msec transients every 100msec are from RFID

With the ring antenna and the battery powered scope I chased down the time-domain transients that I observed on the L2 coil cable (10msec burst every 100msec). They are due to the RFID tag, and get huge close to the RFID stations (35Vpk when the antenna is held close to the RFID board).

Attached are 4 scope traces, as well as a 3MHz span spectrum. The frequency content is 124kHz plus (mostly odd) harmonics. The y-axis is arbitrary, as the gain depends on the distance from the source.

Images attached to this report

Comments related to this report

stefan.ballmer@LIGO.ORG - 16:23, Wednesday 04 May 2016 (27013)

Link

I also verified that these time-domain bursts disapear in the L2 coil cable common signal. However, most of the high frequency junk on those cables is still there - as expected only the 124kHz and harmonics disapear.

stefan.ballmer@LIGO.ORG - 19:39, Wednesday 04 May 2016 (27022)

Link

Robert and Nutsinee tested the effect of turning the RFID system off in alog 23169.

robert.schofield@LIGO.ORG - 08:35, Thursday 05 May 2016 (27026)

Link

In iLIGO we did switch off the RFIDs as a precaution, however, there was a desire to keep them on for aLIGO to monitor access to the experimental areas. It may be that this is not longer as important now that we have made a detection.

The on/off tests dont probe below the noise floor, so we should keep doing these tests as our sensitivity, especially in the 10 Hz region, increases. However, I think it will be obvious if RFID begins to affect DARM so I have been and continue to be OK with leaving them on. This is because the RFIDs are pulsed at 10 Hz and so produce sharp peaks at 10Hz and harmonics. The CW group monitors for such combs and would let us know even if the peaks were not obvious in second-scale spectra.