Fusion Engineering and Design 60 (2002) 273 – 278 A large memory, high transfer rate VME data acquisition system for the JET correlation reflectometer Nuno Cruz a, *, Rita Pereira a , Miguel Correia a , Luis Cupido a , Carlos Correia a,b , C.A.F. Varandas a a Associac ¸a ˜o EURATOM/IST, Centro de Fusa ˜o Nuclear Instituto Superior Te ´cnico, 1049 -001 Lisbon, Portugal b Grupo de Electro ´nica e Instrumentac ¸a ˜o, Departamento de Fı ´sica, Uniersidade de Coimbra, 3004 -516 Coimbra, Portugal Abstract The current paper presents a large memory giving special emphasis to the architecture and suitability of the Linux OS for this type of applications. The system will be used on the joint european torus new correlation reflectometers composed by four microwave channels with four analogue signals each. All sixteen signals will be acquired by 12-bit VME fast acquisition channels at 2 Msamples/s achieving a total data rate of 60MB/s. Slower VME acquisition channels, with 16-bit resolution and sampling rates up to 250 ksamples/s, can also acquire these 16 signals. Two dedicated digital signal processors run an algorithm over this acquired data to avoid the use of the old KG8B root mean square analogue circuits as well as to control and to generate all the timing and acquisition clocks needed by the system. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Data acquisition; Digital signal processing; VMEbus; Transient recorder; Reflectometry; Real-time OS www.elsevier.com/locate/fusengdes 1. Introduction Correlation reflectometry with high temporal ( 1 s) and spatial ( 1 cm) resolutions is an adequate tool for the study of the influence of electrostatic turbulence on improved operation regimes particularly during the occurrence of in- ternal transport barriers [1]. The new joint european torus (JET) X-mode correlation reflectometry will have four mi- crowave channels, each one delivering four ana- logue signals. During the complete JET discharge 10 – 20 correlation measurement series shall be performed, each one corresponding to the acquisition of 10–20 frequency plateaux at a sampling rate of 2Msamples/s (MSPS) with at least 1 ksample acquired data per plateau. On the other hand, real-time plasma monitoring at a slower sampling rate is also required to detect the turbulence. This paper describes the VME data acquisi- tion system that fulfils the above-mentioned re- quirements. It has 16 fast and 16 slow input channels with large local memory, providing data transfer rates up to 60MB/s to accomplish minimum dead time between measurement se- ries. * Corresponding author. Tel.: +351-239-410108; fax: + 351-239-829158. E-mail address: nunocruz@lei.fis.uc.pt (N. Cruz). 0920-3796/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0920-3796(02)00020-0