Response originally posted by Andrew Tgomas on muondetector groups.io mailing list 26/5/2026:
The picoMuon will behave oddly and even stop working if it gets too hot. This usually manifests as one scintillator either stopping counting or there being a significant dip in the count rate. High temperatures can also cause the device to shut down completely. Generally the count will return to normal as the device cools down.
The ultimate limit is the RaspberryPi pico cpu temperature reaching 85°C which usually causes a complete shutdown. At lower temperatures my suspicion is that the ADC operation is degraded.
I have tested the device up to an ambient temperature of 40°C and observed the fall in the count rate as the temperature got over approximately 37°C. The temperature inside the enclosure was higher than the external ambient temperature.
Similar observations have been made by groups fling a picoMuon on a high altitude balloon. The close attention was paid to stopping the instrument package getting too cold led to overheating.
The enclosure temperature is measured and recorded in the raw data file generated by the UKRAA Python software suite. Plotting the count rate with the temperature is a useful diagnostic tool.
Andrew Thomas