T. Yamamoto

Data acquisition system for steady-state experiments at multiple sites

A high-performance data acquisition (DAQ) system has been developed for steady-state fusion experiments at the Large Helical Device (LHD). Its significant characteristics are 110u2009MBu2009s−1 continuous DAQ capability and the performance scalability using an unlimited number of DAQ units. Incoming data streams are first transferred temporarily onto the shared random access memory, and then cut into definite time chunks to be stored. They are also thinned out to 1/N to be served for the real-time monitoring clients. In LHD steady-state experiment, the DAQ cluster has established the world record for acquiring 90u2009GB/shot. The established technology of this steady-state acquisition and store can contribute to the ITER experiments whose data amount is estimated in the range 100 or 1000u2009GB/shot. This system also acquires experimental data from multiple remote sites through the fusion-dedicated virtual private network in Japan. The speed lowering problem in long-distance TCP/IP data transfer has been improved by the packet pacing optimization. The demonstrated collaboration scheme will be analogous to that of ITER and the supporting machines.

Data Acquisition and Management System of LHD

Abstract The data acquisition (DAQ) and management system of the Large Helical Device (LHD), named the LABCOM system, has been in development since 1995. The recently acquired data have grown to 7 gigabytes per shot, 10 times bigger than estimated before the experiment. In 2006 during 1-h pulse experiments, 90 gigabytes of data was acquired, a new world record. This data explosion has been enabled by the massively distributed processing architecture and the newly developed capability of real-time streaming acquisition. The former provides linear expandability since increasing the number of parallel DAQs avoids I/O bottlenecks. The latter improves the unit performance from 0.7 megabytes/s in conventional CAMAC digitizers to nonstop 110 megabytes/s in CompactPCI. The technical goal of this system is to be able to handle one hundred 100 megabytes/s concurrent DAQs even for steady-state plasma diagnostics. This is similar to the data production rate of the next-generation experiments, such as ITER. The LABCOM storage has several hundred terabytes of storage in double-tier structure: The first consists of tens of hard drive arrays, and the second some Blu-ray Disc libraries. Multiplex and redundant storage servers are mandatory for higher availability and throughputs. They together serve sharable volumes on Red Hat GFS2 cluster file systems. The LABCOM system is used not only for LHD but also for the QUEST and GAMMA10 experiments, creating a new Fusion Virtual Laboratory remote participation environment that others can access regardless of their location.

Remote Participation for the LHD Experiment

Abstract Large Helical Device (LHD) experiments are executed with the collaboration of many universities in Japan. Therefore, remote participation plays an important role. In this paper, the authors introduce the current remote participation facilities for these experiments. National Institute for Fusion Science (NIFS) remote participation facilities fall into three categories. The first, remote access, allows direct access to the experimental network. This is the most flexible way to use computer resources remotely. For this purpose, virtual private network (VPN) service is available for coresearchers. In addition, several laboratories are connected directly via SINET3. Once researchers connect to the network, they can use the computer as if they are at the NIFS. The next is remote data reference. Users can view experimental data in a Web browser. Also, they can use a browser to retrieve basic information about experiments that is stored in a relational database. The last is video services. Remote researchers can use a videoconference system to communicate with researchers at the NIFS, and they can use Web browsers to watch the main monitor image displayed in the control room. For security reasons, the entire network is protected by a firewall, and one-time password authentication is used to realize secure VPN access.