NIM stuff is typically fast risetimes and short pulses and often comes from nuclear counting instrumentation (so nuclear folks have been sticking their instrumentation in NIM bins for 40-50 years at least). I haven't messed with this stuff in 40+ years (and I didn't do any electronics with it then), but I can say that it will require some high speed techniques (use ECL?). OP, if you want to get help, you'd better specify your problem's conditions carefully like crutschow asked about...