Development of a high dynamic range read-out system using multiple photodiodes for the total absorption calorimeter of the CALorimetric Electron Telescope

Read-out systems using Si-PIN photodiodes and front-end circuits(FEC) were studied to measure the energy deposit with a dynamic range from 1MIP(Minimum Ionization Particle) to 106 MIPs in a BGO bar of the total absorption calorimeter (TASC) of the CALET (CALorimetric Electron Telescope) instrument. Three types of FEC were tested for the photodiode read out. Two were A225(AMP-TEK), which consists of a hybrid charge sensitive preamplifier and a shaping amplifier, and MPX-08 (NOVA), which is a charge-integrating chip. It was confirmed that the A225 has a resolution of about 0.31 fC and a maximum range of about 2 pC. It was found that the use of the A225 makes a wide range measurement with six orders of magnitude possible using three photodiodes. A new hybrid integrated circuit is being developed to measure a BGO signal with a dynamic range of seven orders using two photodiodes. This FEC consists of two preamplifiers, one for a smaller photodiode and one for a larger one. A high-gain preamplifier was developed and its performance was evaluated. The resolution is about 0.5 fC and the maximum range is more than 25 pC. This makes a dynamic range with four orders of magnitude possible using one photodiode. The outline of a read-out systems using each type of FEC and the state of the development of each system is described below