Still not desired resolution (new scint from GEO)

[ChristofferBraestrup]

So I've been optimizing my setup quite a bit, and it turns out most of my problems still lie with preamplification.

From different sources (esp. the Hamamatsu PMT handbook) I gather that preamp time constant (R*C of feedback net) should be LONGER than the scintillation time constant, which is about 250 ns for NaI(Tl). The Ortec 113A scintillation preamp uses about 50 µs as decay constant (=50 pf over 1 Mohm), and I'm currently experimenting with 20 µs.

The only worrying things left that can be attributed to the detector are a lot (multi-counts per sec!) very very big pulses, that completely saturates my preamplifier. Thankfully, these 12V clipping pulses are over the detectable range for my MCA so they just disappear but my big worry is if they stem from arcing in the divider circuit. I feel my biggest weakness is never having worked with a functioning gamma spectrometer to know what behavior is normal. These show up regardless of voltages (600-1000V tested)