30 MHZ HARDWARE DIGITAL-FILTER FOR SIGNALS OF THE ZEUS FORWARD TRACKING DETECTOR

Here we describe the FADC modules for the 5184 channels of the forward tracking detector of the ZEUS experiment at HERA (DESY), which conver t the incoming analogue signals on a 104 MHz clock and apply a hardwar e digital filtering and zero suppression procedure on the acquired dat a. A module works on 32 input channels, nine boards are grouped in a 9 HU crate. On a given trigger, the data are sequentially transferred to an output buffer for final acquisition, passing a 30 MHz digital filt er and zero suppression hardware. The module uses a 9 bit signed FIR f ilter with eight tabs, where the eight filter coefficients are freely programmable. Only signals with two successive filtered values above a certain threshold are stored for output. Due to the filter procedure the data reduction rate is greater than 95%. The system provides a pro cessing power of 600 mops per board for the foreseen application. In a ddition to the data reduction the main benefit of the filtering proces s is the significantly improved separation of double signals.