A large memory VME data acquisition system for the jet heterodyne radiometer upgrade

A large memory VME data acquisition system was developed for the JET heterodyne radiometer upgrade, which is capable of acquiring/storing 576 MB of data per JET pulse. The implementation of the system integration software, which includes a CGI-based control interface and the data acquisition software is described as well as the development and architecture of the transient recorders. The system maximum data throughput is 288 MB/s when all the 48 channels acquire at the maximum rate of 3 MSPS. The system hardware is composed by the following components: (i) A VME controller module, with a Pentium III processor running Linux, 128 MB of RAM, 100 Mbits/s Ethernet channel and a 40 GB disk; (ii) Six on-site-developed transient recorder modules, each having 8 input channels, 12 bit resolution, 6 MSample/channel of memory and sampling rate up to 3 MSPS. Optimal VME device drivers were developed to minimize the data transfer time to the local disk. The acquired data on disk is remotely available through a HTTP server. The system has been reliably in operation since January 2003.