A DEPFET pixel matrix system for the ILC vertex detector

The DEPFET detector offers radiation detection and amplification jointly by embedding a field effect transistor into fully depleted silicon. Due to the excellent noise performance ( ENC = 2.2 e - for single pixel at room temperature and 6 μ s shaping time) and the high spatial resolution of the device ( 4.3 μ m at 22 keV using 50 × 50 μ m 2 pixels), the DEPFET concept is attractive for X-ray astronomy, for biomedical application and for tracking in particle physics. For the vertex detector of a future TeV-scale linear collider, like the proposed ILC (International Linear Collider), a highly granulated pixel system operated row-wise with line rates of 20 MHz at a noise level below 100 e - is needed. Addressing these requirements, improved DEPFET sensors with 22 × 36 μ m 2 pixel size have been fabricated. A prototype system has been developed that uses dedicated chips for steering and readout of a 64 × 128 DEPFET pixel matrix. Due to the current based readout mode provided by the readout chip, a thousand times faster matrix operation than achieved so far is possible. The performance of the single components of the system will be summarized and first results obtained with the entire system will be presented.