Building a nuclear physics lab in the 21st century

Abstract

For more than half a century, expensive and bulky modules (e.g. the standard NIM, Nuclear Instrumentation Modules) and electronic boards have been used in nuclear physics laboratory courses, in order to filter, shape and digitize the analog signals coming from particle detectors. Recently it has become technically possible to miniaturize these circuits within ASICs, but their high cost and specificity make them unsuitable in a didactic and general-purpose context. In this contribution we present an innovative system for reading and processing the signals produced by radiation detectors, which is based on simple, cheap and versatile components. The system is based on the "Red Pitaya STEMlab 125-14" a compact size board which implements: a CPU, a FPGA, a port for network connections (useful for remote access and control) and two 125 MS/s 14-bit digitizer channels. The software framework, necessary for the acquisition, processing, and storage of the signals, is based on the "ABCD" acquisition system. This system was experimentally tested in the Nuclear Physics Laboratory course of the Bachelor's Degree in Physics at the Insubria University, in Como (Italy). In particular, it was used to read the signals produced by a silicon photodiode and a Ce:LaBr 3 scintillator in alpha and gamma spectroscopy experiments. The system performance resulted to be equivalent to the one obtained with the traditional VME spectroscopic system. The main advantages of this new approach concern the compactness, versatility, and low cost, making it ideal also for high school laboratories.