The dose mapping system for the electromagnetic calorimeter of the BaBar experiment at SLAC

An array of 116 p-channel radiation-sensitive MOSFET transistors (RadFETs) has been commissioned for the BaBar experiment at the PEP-II accelerator at the Stanford Linear Accelerator Center (SLAC). The aim of this system is to map the integrated dose absorbed by different regions of the calorimeter during the course of the experiment. This paper reports the design, characterization and installation of the sensors and briefly describes the readout system designed by co-workers. The response at low doses and the temperature coefficient for 130 RadFETs has been determined. At a “read” current of 160 μA an average shift in voltage of 51±4 mV was measured at an integrated dose of 30 rad with a temperature coefficient of 2.3±0.3 mV/°C. Calibration for high doses is also described. The system provides a novel method for real-time measurements of the spatial distribution of ionizing radiation dose within a large particle physics experiment.