SNM-10 Neutron detector

Got a B10-lined neutron detector "SNM-10" or "CNM-10".
It works in a "corona mode", which means noisy current (about 2... 2.5 uA) at 1650V in series with 50 MOhm.
The pulses will be about 20V or so, but I'm planning to measure the current with a common-base circuit, to avoid the capacitive load over the high series resistor.
This is what it looks like:

For the high voltage I will combine a switched DC-DC step up converter with a voltage multiplier, the schematic only shows the idea, I will use the MAX1771 not the LTC:

We can do the same thick without a transformer:

Better helium plasma

The previous movie only showed the plasma at low voltages before the feedthough broke.
We made a new feedthrough, fused quartz, should be able to handle 50kV.
This time we go beyond sparks, a stable plasma can be seen, it's clearly red (helium), and near the end (around 7.5 kV, about 3.5 mA) some Xray spots can be seen.