VME–based DAQ system for the Deuteron Spin Structure setup at the Nuclotron internal target station

Abstract

The new powerful VME–based data acquisition (DAQ) system has been designed for the Deuteron Spin Structure setup [1] placed at the Nuclotron Internal Target Station [2]. The DAQ system is built using the netgraph–based data acquisition and processing framework ngdp [3, 4]. The software dealing with VME hardware is a set of netgraph nodes in the form of the loadable kernel modules. The specific for current implementation nodes are described, while specific software utilities for the user context are the following. The b2r (binary–to–ROOT) server converts raw data into per trigger and per accelerator spill representations, which are based on C++ classes derived from the ROOT framework [5] ones. This approach allows us to generalize the code for histograms filling and polarization calculations. The b2r optionally stores ROOT events as ROOT TTree in file(s) on HDD, and supports the design of some express offine. The histGUI software module provides an interactive online access for human operator to histograms filled by the r2h (ROOT–to–histograms) server, which obtains the ROOT event representations from b2r. The r2h supports the calculation and histograming of runtime configurable variables as well as raw data variables, and optionally stores ROOT histograms in file(s) on HDD. Since the spin studies at the Nuclotron require fast and precise determination of the deuteron and proton beam polarization, the polarization calculator software module is introduced. This calculator based on runtime configurable r2h code allows us to compute polarization values online and integrate them into the Web–based scheme of representation and control of the polarimeters [6, 7].