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The Bioscope System

The DEPFET Pixel Bioscope system has been developed by Peter Fischer, Wolfgang Neeser and Johannes Ulrici for autoradiography in biomedical applications. The system operates a full 64x64matrix of DEPFET pixels (total sensitive area 3.2 x 3.2 mm2). The DEPFET detectors are produced at the MPI Halbleiterlabor in Munich. Due to the very thin entrance window of only 200 µm and to the very low noise performance, a detection of low-energy beta emitting radiomarkers such as 3H (endpoint energy 18.6 keV, mean energy 5.7 keV) is possible. Because of the energy resolution of the system, different radioisotopes such as 3H and 14C can be separated geometrically in the same sample.

The project is a collaboration between the MPI Halbleiterlabor in Munich and the University of Bonn and is supported by the Deutsche Forschungsgemeinschaft under contract WE 976/2-1 and by the Ministerium für Wissenschaft und Forschung des Landes Nordrhein-Westfalen under contract IV A5 - 10600198.

System Description

The picture of a DEPFET Hybrid is shown in fig. 1. It consists of a 64x64 DEPFET matrix in the middle of the Hybrid and 2 dedicated ASICs for the readout. A biological sample can be placed on the backside of the detector. Both ASICs have been developed in our group and are connected to the sensor by wire bonds. The detector pixels are switched on and off by the steering chip SWITCHER 2.0 on the right-hand side of the detector. The SWITCHER also allows a row-wise reset of the matrix. Since only one of the 64 pixel rows is switched on at the same time, the transistor currents of this row can be read out and amplified parallely by the low-noise current amplifying chip CARLOS 2.0 on the bottom of the detector. The analog output signal of CARLOS 2.0 is digitized on a PCB. A second digital PCB controls the readout procedure and the communication with a PC.


Fig. 1: Picture of a DEPFET Hybrid.

The measurement data can be displayed by the PC in real-time. A system schematic is shown in fig. 2, a picture of the complete system can be seen in fig. 3 (the coloured circle indicates the position of the hybrid).


Fig. 2: Schematic of the DEPFET Pixel Bioscope System.


Fig. 3: Picture of the DEPFET Pixel Bioscope System.

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