Uwe and I were able to get some noise testing done before the ESR was closed with asbestos exposure. We used the new flange so didn't address any issues with the old flange. Our main findings were:
1. majority of noise comes from the connection to the ESR. Compare the two scope pics attached with a) the detector isolated from the ESR, and b) the detector in the pocket. It is clear that the large high-frequency spikes of amplitude 40mV plus some low
frequency modulation is coming from the ESR.
2. The signal loop for the MS Pads is through both the MPR-32s and the MSI-8s, so ensuring those preamps are collectively grounded is paramount. Having a short grounding cable that connects all of them to the NIM crate containing the preamp power supply
is ideal. Wrapping in aluminium foil also seemed to help.
a. Perhaps creating a Lemo to preamp ground signal would also help directly connect the flange to the preamps.
3. Shielding of the preamp cables seemed to help a bit, but not a huge amount. It may be worth investigating more the effects of shielding, but my feeling is that the above two sources are more important so shielding may not be worth the hassle.
Remaining tasks to investigate:
1. Try and quantify impact of isolation from ESR by wrapping mounting system in Kapton tape. If this makes a big difference, perhaps we can create something more purpose built.
2. Quantify impact of noise on our signal from data analysis to see if its worth all this effort. |