Calibration of the L3 Bgo Electromagnetic Calorimeter With a Radiofrequency Quadrupole Accelerator

Abstract A new calibration technique based on radiative capture of protons from an RFQ accelerator in a lithium target, which makes use of the resultant high intensity flux of 17.6 MeV photons, has been developed and tested. The technique is capable of calibrating the thousands of BGO crystals in the L3 electromagnetic calorimeter at once, with an absolute accuracy of better than 1% in 1–2 h. Systematic errors in the calibration, which have been studied earlier through Monte Carlo simulations, have been experimentally proven to be small and calculable, and are expected to be much less than 1%. When installed in the L3 experiment at LEP, this system will help ensure that the high resolution of the L3 electromagnetic calorimeter is maintained during running.