CALIBRATION OF ELECTROMAGNETIC CALORIMETERS IN HIGH ENERGY EXPERIMENTS WITH A RADIO FREQUENCY QUADRUPOLE ACCELERATOR

Abstract A fast, effective calibration technique has been developed for future Superconducting Supercollider (SSC) calorimeters based upon the radiative capture of protons from a pulsed Radio Frequency Quadrupole (RFQ) accelerator in a fluoride target. The intense flux of low energy photons acts as a clean “pulse generator” calibration signal equivalent to 20 GeV or more. This calibration technique has been demonstrated with a bismuth germanate (BGO) detector array, as well as with several barium fluoride detector crystals, to provide a calibration accuracy of 0.5% within two minutes. The SSC calibration has resulted from the development of this novel technique by Caltech over the past five years for the L3 BGO electromagnetic calorimeter, which uses a lithium target for the production of 17.6 MeV low energy photons for the calibration source. Proven techniques have been developed to provide an in situ calibration for all 11 000 BGO detector crystals, with an accuracy of 0.8% obtainable in 1–2 h. The result of the experimental test by using the AccSys RFQ accelerator is reported, as is the preliminary concept of a small storage ring that can be used to compress the output beam pulse from the RFQ accelerator into a target beam pulse of 100 ns or less.