PuMa-II: A wide band pulsar machine for the westerbork synthesis radio telescope

The Pulsar Machine II ( PuMa- II) is the new flexible pulsar processing back- end system at the Westerbork Synthesis Radio Telescope ( WSRT), specifically designed to take advantage of the upgraded WSRT. The instrument is based on a computer cluster running the Linux operating system, with minimal custom hardware. A maximum of 160 MHz analog bandwidth sampled as 8 x 20 MHz subbands with 8- bit resolution can be recorded on disks attached to separate computer nodes. Processing of the data is done in the additional 32 nodes allowing near real time coherent dedispersion for most pulsars observed at the WSRT. This has doubled the bandwidth for pulsar observations in general, and has enabled the use of coherent dedispersion over a bandwidth 8 times larger than was previously possible at the WSRT. PuMa- II is one of the widest bandwidth coherent dedispersion machines currently in use and has a maximum time resolution of 50 ns. The system is now routinely used for high- precision pulsar timing studies, polarization studies, single pulse work, and a variety of other observational work.