Laser system for testing radiation imaging detector circuits

W.Zubrzycka, K.Kasiński, "Laser system for testing radiation imaging detector circuits"

Performance and functionality of radiation imaging detector circuits in charge and position measurement systems need to meet tight requirements. It is therefore necessary to thoroughly test sensors as well as read-out electronics. Detector systems can be characterized using radioactive sources or a particle beam. The major disadvantages of these approaches are high financial expenses and limited accessibility. As an alternative short pulses of well-focused laser beam are often used for preliminary tests. There are number of laser-based test devices available on the market, but very often their applicability in this field is limited.
This paper describes concept, design, development and validation of laser system for testing silicon sensor based radiation imaging detector circuits. The greatest emphasis is put on keeping low cost while reaching all required functionality: mobility, flexible parameters of laser beam, remote control and possibility of carrying out automated tests.
The main part of the developed device is an optical pick-up unit used in optical disc drives. The hardware includes FPGA-controlled dedicated drivers for controlling lens and movement stage and fast laser diode driver. The FPGA precisely controls the timing and current of the laser diode short (few ns) pulses. The system is controlled via USB interface by a dedicated LabVIEW-based application. Setting all system parameters, executing single commands and also automated tests are possible.