Nuclear Instruments and Methods in Physics Research A 510 (2003) 122–125 FPGA-based data acquisition system for a Compton camera $ K. Nurdan a,b, *, T. C¸ onka-Nurdan a,c , H.J. Besch c , B. Freisleben b , N.A. Pavel c , A.H. Walenta c a CAESAR (Center of Advanced European Studies and Research), Friedensplatz 16, Bonn D-53111, Germany b Uni-Siegen, FB Elektrotechnik und Informatik, Ho¨lderlinstrr. 3, Siegen D-57068, Germany c Uni-Siegen, FB Physik, Emmy-Noether Campus, Walter Flex Str. 3, Siegen D-57068, Germany Abstract A data acquisition (DAQ) system with custom back-plane and custom readout boards has been developed for a Compton camera prototype. The DAQ system consists of two layers. The first layer has units for parallel high-speed analog-to-digital conversion and online data pre-processing. The second layer has a central board to form a general event trigger and to build the data structure for the event. This modularity and the use of field programmable gate arrays make the whole DAQ system highly flexible and adaptable to modified experimental setups. The design specifications, the general architecture of the Trigger and DAQ system and the implemented readout protocols are presented in this paper. r 2003 Elsevier B.V. All rights reserved. PACS: 07.05.Hd; 87.59.Àe Keywords: Compton camera; Data acquisition systems (DAQ); Field programmable gate arrays (FPGA) 1. Introduction A Compton camera (CC) is a gamma-ray imaging system, which consists of two radiation detectors a scatter detector and an absorption detector. A gamma-ray incident on the camera can be imaged when it Compton scatters in the scatter detector producing recoil electron and the scat- tered photon is detected in time coincidence at the absorption detector. A monolithic array of 19 silicon drift detectors [1] as the scatter detector and an Anger Camera without lead collimator as the absorption detector are used in the prototype system [2,3]. 2. System hardware The data acquisition system (DAQ) presented in this paper covers the electronics between the front- end analog electronics (FE) and the image reconstruction computer (Fig. 1). The DAQ per- forms the reconstruction of Compton event data and its system hardware is based on two types of ARTICLE IN PRESS $ Work Supported by CAESAR (Center of Advanced European Studies and Research). *Corresponding author. Address for correspondence: Uni- versity of Siegen, ENC FB7, Walter Flex Str. 3, Siegen D-57068, Germany. Tel.: +49-271-740-3534; fax: +49-271- 740-3533. E-mail address: kivanc@alwa02.physik.uni-siegen.de (K. Nurdan). 0168-9002/03/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0168-9002(03)01688-7