Fast silicon drift photodiodes free from bias connections on the light entering side

A new type of silicon drift photodiode intended to be coupled to large area scintillators is described. The diodes have a relatively large area (1 cm( 2)) and a short maximal drift time (300 ns). They operate without requiring any external electrical connection at the side of the photodiode coupled t o the scintillating crystal. These new photodiodes have almost identical ri ng structures on both sides with individual rings being at linearly increas ing potentials providing the required high electric drift field. A new feat ure of the presented photodiodes is a small modification of the electrode s tructure near the signal collecting anode. It allows a full depletion of th e photodiode and the highest drift field. Advantages and drawbacks of this kind of photodiodes are described. (C) 2000 Elsevier Science B.V. All right s reserved.