Search

The BABAR detector at PEP-II will operate in a high-luminosity [e.sup.+][e.sup.-] collider environment near the [Gamma](4S) resonance with the primary goal of studying CP violation in the B meson system. In this environment, typical physics events of interest involve multiple charged particles. These events are identified by counting these tracks in a fast first level (Level 1) trigger system, by reconstructing the tracks in 'real time.' For this purpose, a Binary Link Tracker Module (BLTM) was designed and fabricated for the BABAR Level 1 Drift Chamber trigger system. The BLTM is responsible for linking track segments, constructed by the Track Segment Finder Modules (TSFM), into complete tracks. A single BLTM module processes a 360 MBytes/s stream of segment hit data, corresponding to information from the entire Drift Chamber, and implements a fast and robust algorithm that tolerates high hit occupancies as well as local inefficiencies of the Drift Chamber. The algorithms and the necessary control logic of the BLTM were implemented in Field Programmable Gate Arrays (FPGAs), using the VHDL hardware description language. The finished 9U x 400 mm Euro-format board contains roughly 75,000 gates of programmable logic or about 10,000 lines of VHDL code synthesized into five FPGAs.

The CP violation experiment HERA-B at DESY [1] requires a highly selective on-line filtering of data due to high interaction rates and low signal to background ratio. This demands a hierarchical trigger system and a data acquisition with high bandwidth. A complete level of the trigger hierarchy and the DAQ chain can be built from a single unit type: a single slot 6U VME unit carrying six ADSP21060 (SHARC) DSPs [2]. The six SHARCs communicate via the common bus or via their link ports, which are all accessible from the front panel. Up to 350 units will be used in the experiment. Prototype units have been built and are operating successfully.

A 24 x 24 [cm.sup.2] asymmetric multiwire proportional chamber, with 7.5 x 7.5 [mm.sup.2] photosensitive CsI pads, has been tested with Cherenkov radiation of 3 GeV/c electrons in the T24 test beam at DESY. The performance of the chamber with specially designed low-noise, charge-sensitive preamplifiers is described. The parameters of the CsI-MWPC are compared to those of a TMAE photon detector in order to evaluate their potential as Ring Imaging Cherenkov (RICH) counters for the HERA-B experiment at DESY.