Isolated, short dispersed pulses of radio emission of unknown origin havebeen reported and there is strong interest in wide-field, sensitive searchesfor such events. To achieve high sensitivity, large collecting area is neededand dispersion due to the interstellar medium should be removed. To survey alarge part of the sky in reasonable time, a telescope that forms multiplesimultaneous beams is desirable. We have developed a novel FPGA-based transientsearch engine that is suitable for these circumstances. It acceptsshort-integration-time spectral power measurements from each beam of thetelescope, performs incoherent de-dispersion simultaneously for each of a widerange of dispersion measure (DM) values, and automatically searches thede-dispersed time series for pulse-like events. If the telescope providesbuffering of the raw voltage samples of each beam, then our system can providetrigger signals to allow data in those buffers to be saved when a tentativedetection occurs; this can be done with a latency of tens of ms, and only thebuffers for beams with detections need to be saved. In one version of ourimplementation, intended for the ASKAP array of 36 antennas (currently underconstruction in Australia), 36 beams are simultaneously de-dispersed for 448different DMs with an integration time of 1.0 ms. In the absence of such amulti-beam telescope, we have built a second version that handles up to 6 beamsat 0.1 ms integration time and 512 DMs. We have deployed and tested this at a34-m antenna of the Deep Space Network in Goldstone, California. A thirdversion that processes up to 6 beams at an integration time of 2.0 ms and 1,024DMs has been built and deployed at the Murchison Widefield Array telescope.
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