Hi Matthew, Carlo,
On Tue, Nov 14, 2017 at 3:32 PM, Carlo Segre
HI Matthew:
One possibility is the Caen quad amplifier that they made for BPMs.
http://www.caenels.com/products/tetramm/
Carlo
Yes, I second this recommendation, at least in general. We've used caen amplifiers with thin-foil BPMs for awhile and they're good at going pretty fast (can definitely do 10 kHz) and giving a fairly low noise level. Nice features of the Tetramm include only two gain settings and the fact that it streams out floating point numbers in Amps. There is also decent Epics support. I played with using one of these for ion chambers and it works pretty well for large enough currents: the noise level on the lowest gain setting at 1kHz is around 0.7 pA, so it works well for measuring I0 of ~10 nA and above. So, I'm not sure how well it would work for doing feedback with currents of 0.1 to 1 nA. But, when I've talked to the Caen engineers they've been very knowledgable and helpful. --Matt