A study on the use of lead fluoride for electromagnetic calorimetry

A study has been made on the properties of lead fluoride as a Cherenkov material for use in electromagnetic calorimetry. A prototype calorimeter module consisting of a 5 x 5 array of 2.1 x 2.1 x 18.5 cm3 crystals has been built and tested in a test beam at the Brookhaven AGS. Results are given on energy resolution, shower size and e/pi separation for electrons and pions in the range from 1-4 GeV. The light output has been measured to give greater than or similar to 1000 photoelectrons per MeV in good quality crystals, and to provide useful signals down to as low as 32 MeV. Measurements were also made on radiation damage in lead fluoride using Co-60 gamma rays and high energy ionizing particles, as well as on thermoluminescence after irradiation. It was found that only modest damage occurs up to a level of approximately 30 Krad in large, calorimeter size crystals, and that the damage can be easily removed by optical bleaching.