Improvements to the second design

A project log for Gamma PIN - Semiconductor Radiation Detector

An attempt to design and deliver universal and accessible radiaton analyser to be used in nuclear spectroscopy

Marcin WachowiakMarcin Wachowiak 10/06/2018 at 12:240 Comments

The first prototype is quite fine but it has some errors that I noticed during the assembly and testing. The detector will be still developed. I hope that the second version will be satisfactory enough to meet the requirements for the first spectroscopy. During the tests I became acquainted with the STM32 ADC and DAC. The detector is so sensitive that uploading the program to the development board caused oscillations. Having noticed this to prevent additional digital noise I decided to use non-volatile programmable potentiometer. Once the value on the MCP4161 is set. It will be disconnected to except any distortions from the signal busses. I am currently working with NUCLEO-H743ZI but after the prototyping is finished the detector should run with a “Blue Pill” board featuring STM32F103C8 microprocessor that should handle everything easily. 

Things to improve:

The signal processing

Old version simulations with noise

V1 prototype with noise source added
Current pulses with noise background
Singal after processing with V1 simulation model
Signal after substraction

New version configuration

V2 simulation schematic
Signal after the first stage of substractor and rectifier
Previev of the signal shape through the circuitry
Output signal suitable for farther processing

Supply filtering


The case of undershoot and baseline restoration is still open and it will be verified whether the removal of the coupling capacitors and inverting amplifiers has solved the issue. If not, there are some proposed solutions in the nuclear research papers.  Another thing to consider is addition of pile up rejection circuit and coincidence detector.