Reliability study of custom designed ADC for the Jiangmen underground neutrino observatory

Objective The Jiangmen underground neutrino observatory(JUNO)is the largest and most precise liquid scintillator detector under construction in the south of China.The front-end readout electronics system will be installed very close to the photomultiplier tubes under water.Therefore,the system’s absolute reliability is mandatory.As an important piece,the failure rate of the custom designed analog-to-digital convertor(ADC)must be measured.Methods The Arrhenius High Temperature Operating Life(HTOL)model is usually used to calculate the standard reliability value failure rate(λ).A temperature acceleration test of the ADC is performed with a 115℃ambient temperature based on a custom aging system.The performance of ADC is compared before and after aging,and the most significant bit(MSB)of the digital output is monitored during the test.Results The result of a 2400-hour-long test shows that there were no failures.The upper limit of the failure rate is calculated as 5.8FIT,which can be added to the failure rate of other components to meet the overall failure rate requirements(84FIT).Conclusion With the test system,we established a method based on the HTOL model to obtain the upper limit of the ADC reliability for overall failure rate calculation in JUNO.This method can be applied to the reliability measurement for any other custom designed ADC.This experiment can be repeated with a new set of parameters to get a satisfactory failure rate according to other overall system requirements.