A Multi-Beam Radio Transient Detector With Real-Time De-Dispersion Over a Wide Dm Range

Abstract

Isolated, short dispersed pulses of radio emission of unknown origin have been reported and there is strong interest in wide-field, sensitive searches for such events. To achieve high sensitivity, large collecting area is needed and dispersion due to the interstellar medium should be removed. To survey a large part of the sky in reasonable time, a telescope that forms multiple simultaneous beams is desirable. We have developed a novel FPGA-based transient search engine that is suitable for these circumstances. It accepts short-integration-time spectral power measurements from each beam of the telescope, performs incoherent de-dispersion simultaneously for each of a wide range of dispersion measure (DM) values, and automatically searches the de-dispersed time series for pulse-like events. If the telescope provides buffering of the raw voltage samples of each beam, then our system can provide trigger signals to allow data in those buffers to be saved when a tentative detection occurs; this can be done with a latency of tens of ms, and only the buffers for beams with detections need to be saved. In one version of our implementation, intended for the ASKAP array of 36 antennas (currently under construction in Australia), 36 beams are simultaneously de-dispersed for 448 different DMs with an integration time of 1.0 ms. In the absence of such a multi-beam telescope, we have built a second version that handles up to 6 beams at 0.1 ms integration time and 512 DMs. We have deployed and tested this at a 34-m antenna of the Deep Space Network in Goldstone, California. A third version that processes up to 6 beams at an integration time of 2.0 ms and 1,024 DMs has been built and deployed at the Murchison Widefield Array telescope.

Spectropolarimetric Analysis of FRB 181112 at Microsecond Resolution: Implications for Fast Radio Burst Emission Mechanism

“…The data presented here are derived from the ASKAP voltage capture system, which encodes the electric field saved by each antenna. A detailed overview of the ASKAP voltage capture system is given in Bannister et al (2019) and Clarke et al (2014), and a brief summary of the relevant aspects of the high time resolution data reconstruction is presented here. The scripts implementing the following data processing steps are available in the CRAFT git repository 1 .…”

A single fast radio burst localized to a massive galaxy at cosmological distance

“…We used a 6 × 6 hexagonal closed packed beam configuration (see (10), their figure S1). The beamformers produce fast-dump autocorrelation spectra by squaring and averaging the beamformed voltages over a 864 microsecond window (14). These spectra are streamed over Ethernet to a dedicated fast transient searching node and processed on a single graphics processing unit (GPU).…”

The Detection of an Extremely Bright Fast Radio Burst in a Phased Array Feed Survey

“…In the real-time CRAFT data pipeline, described in detail by Clarke et al (2014), the beamformed voltages are squared and averaged over an integration time of 1.265 ms and transmitted to a processing computer, which sums the polarizations and writes the data to disk.…”