Soon after starting the MEG electronics, as they warm up, there is sometimes large noise from the system itself. We regularly see this during the empty-room noise recordings, and have to wait a few minutes and redo the noise recording. As such, please always plan to start the electronics 5-10 minutes before you collect the empty-room recording and if you do see the artefact, wait 2-3 minutes for it to disappear. As always, keep me informed of anything new or unusual, like if this startup noise lasts more than a few minutes.
Please be aware this issue can sometimes be worse, either taking much longer to appear after starting the system, or even lasting longer, up to an hour. I’m still working on minimizing it, but for now we can keep the system on, e.g. overnight for morning bookings.
Importantly, it seems to need to be in acquisition preview mode to finish warming up, not just the electronics turned on. So even if we keep the system on, it’s best for now to still put it in preview for say 30 minutes before recording, to be safe.