The negative-ion based NBI System(N-NBI) for JT-60U was completed in 1996 for the studies of a non-inductive current drive and plasma core heating experiment with high energy neutral beam injection into high density plasma. The N-NBI is designed to deliver a neutral beam injection power of 10 MW at 500 keV for 10 seconds. In this paper, we review an overview of the computer control and data acquisition system of the N-NBI system, including the design concept, the hardware constitution, and the functions.

The control system of the N-NBI system required important functions for operating two negative ion sources, power supplies, etc. First, we designed the hardware constitution and functions of the control system of the N-NBI similarly to the control system of the positive-based NBI for JT-60U. That is to say, the control system is composed of two systems, one is control panels system and the other is a computer control and data acquisition system. The control panels system consists of a programmable controller, a timing system, etc., and plays only basic roles, such as system protection control and interlock, time sequence control, etc. On the other hand, the computer system plays more applicative roles. Second, we designed the hardware constitution of the computer system a UNIX network system which consisted of workstations and VMEbus systems. Furthermore, a real-time operating system(OS) compatible with the UNIX was adopted for the VMEbus systems. As a result, the software development environment for both the workstation and the VMEbus system has been unified with the UNIX, and we can, thus, develop the software more efficiently. The function of the computer system is classified into two types, "device control" and man-machine interface. The first one includes the functions of operation management, data acquisition, data processing, system monitoring, and data communication with external control devices. The second one, which has all kinds of graphical displays using X Window on the workstations, is for setting of operating parameters and for monitoring waveforms of a set of high voltage power supplies and thermocouples of various beamline components to analyze beam performance. Thus, this system can facilitate ion source operation.

The first beam injection into JT-60U plasma with the N-NBI was conducted in March 1996 using the newly developed software, As of February 1997, the neutral beam injection of 350 keV, 2.5 MW with deuterium and 350 keV, 3.2 MW with hydrogen have been achieved.