The electron-proton collider HERA is being upgraded to provide higher
luminosity from the end of the year 2001. In order to enhance the selectivity
on exclusive processes a Fast Track Trigger (FTT) with high momentum resolution
is being built for the H1 Collaboration. The FTT will perform a 3-dimensional
reconstruction of curved tracks in a magnetic field of 1.1 Tesla down to 100
MeV in transverse momentum. It is able to reconstruct up to 48 tracks within 23
mus in a high track multiplicity environment. The FTT consists of two hardware
levels L1, L2 and a third software level. Analog signals of 450 wires are
digitized at the first level stage followed by a quick lookup of valid track
segment patterns.
For the main processing tasks at the second level such as linking, fitting
and deciding, a multifunctional processing board has been developed by the ETH
Zurich in collaboration with Supercomputing Systems (Zurich). It integrates a
high-density FPGA (Altera APEX 20K600E) and four floating point DSPs (Texas
Instruments TMS320C6701). This presentation will mainly concentrate on second
trigger level hardware aspects and on the implementation of the algorithms used
for linking and fitting. Emphasis is especially put on the integrated CAM
(content addressable memory) functionality of the FPGA, which is ideally suited
for implementing fast search tasks like track segment linking.Comment: 6 pages, 4 figures, submitted to TN