In this contribution I present some exploration into high energy radiation detection and the suitability of the Arduino R4 minima to realize a multichannel analyzer (MCA). The latter then can be used to obtain a energy spectrum of the radiation. This endeavor (in part) was triggered by a recent purchase of a Radiacode radiation detector (www.radiacode.com/de ) , which is a tiny device using a small CsI scintillation crystal in combination with a so called “silicon photo multiplier” (i.e. an array of avalanche photodiodes). While this is a “black box” and here just serves as reference for comparisons, the following circuitry, Arduino application and closer inspections are made with an Ebay acquisition of a used NaI-scintillation detector head. The latter combines a NaI-scintillation crystal with a “conventional” vacuum photomultiplier (PMT). Since it came without documentation the first task was some try-an-error and guess-work to identify the connection scheme of the 12 socket pins. 

 
Physical background

If energetic radiation quanta (here mainly -rays) are stopped in a scintillation crystal (NaI, CsI, …; doped with Tl) a fraction of the absorbed energy is converted to light. Typically, a few 1000 visible photons are released. By putting the crystal in a reflecting (and light tight) enclosure and in contact with a sensitive photodetector, a photo-multiplier tube (PMT) one tries to register the total light output in terms of an electric pulse with corresponding intensity. 

The photon emission after the -absorption event extends over a typical decay time, which is about for NaI(Tl). To get an electrical pulse height that is proportional to the gamma-quantum energy, the PMT (current) output must be integrated over several times the decay time. 

In this prooject a tiny analog circuit is  presented that does the pulse integration and  supplies the pulse height together with a trigger signal. These signals are processed by an Arduino R4 Minima thus realizing amultichannel analyzer for the pulse heights.

Compared to a gas filled (small) Geiger tube, the scintillation counters are way more sensitive.
Some examples for this are also shown.