Status of the Linux PC cluster for between-pulse data analyses at DIII-D

Abstract

Some analyses that survey experimental data are carried out at a sparse sample rate between pulses during tokamak operation and/or completed as a batch job overnight because the complete analysis on a single fast workstation cannot fit in the narrow time window between two pulses. Scientists therefore miss the opportunity to use these results to guide experiments quickly. With a dedicated Beowulf type cluster at a cost less than that of a workstation, these analyses can be accomplished between pulses and the analyzed data made available for the research team during the tokamak operation. A Linux PC cluster comprised of 12 processors was installed at DIII-D National Fusion Facility in CY00 and expanded to 24 processors in CY01 to automatically perform between-pulse magnetic equilibrium reconstructions using the efit code written in fortran, cer analyses using cerquick code written in interactive data language ( idl) and full profile fitting analyses ( n e, T e, T i, V r, Z eff) using idl code zipfit. This paper reports the current status of the system, the details of the between-pulse profile fitting analyses, and discusses some problems and concerns raised during the implementation and expansion of the system.