Looking at the HV bias in a scope to see if it is the source of noise especially on the p+n side

Channel 1: HV Core channel 4
Channel 2: HV Braid Channel 4
Math: Ch1 - Ch2

100V bias (100 uA leakage current for 1 MOhm)

No obvious frequency components or large frequency components?
I do not know how this compares to RIKEN or STFC-DL

Updated to put the right frequency range (misread before)

Fig 3-4: Normalish looking data 

Fig 5-6: Examples of noise appearing randomly on math line

Fig 7: 1ms long trace, noise stopped appearing

Update 26.02.2020

Fig 8: Trace with all 4 HV channels off

Fig 9: Trace with only oscilloscope biased

Fig 10: Trace with braids unplugged from all 3 FEE64s (only channel 4 connected)

Things to try:

Joining clean earth & chassis ground?

Checking HV jumper?

Finding 'scope probes and testing NIM socket?