K.V. Khlopenkov

N. Tamura

S. Sudo

National Institute for Fusion Science (NIFS-Repository)

§11. Construction of Tracer-Encapsulated Solid Pellet Injection System for LH 0 Tamura, N. (Grad. Univ. Advanced. Studies), Khlopenkov, K.V, Sudo, S. The tracer-encapsulated solid pellet (TESPEL) injection system has been installed for LI-ID in the 3rtl campaign of LI-ID experiment. Fig. 1 shows the schematic drawing of the TESPEL injection system. The TESPEL consists of polystyrene (-CH(CJIs)CHr) as outer shell and tracer particles as an inner core. In the preliminary experiment of the 3rtl campaign, the typical outer and inner diameter of the polystyrene shell are 450 - 650 fJ, m and 100 fJ, m, respectively. As the tracer particle, LiH or Si is used. The fabrication method ofTESPEL is described in detail in [1] . The TESPEL injection system consists of a TESPEL injector part and a differential pumping system with three expansion chambers isolated by fast gate-valves. The main parts of the TESPEL injector are a magazine with a rotating disk, gun barrel and observation chamber. The rotating disk has 60 holes with inner diameter of 0.99 mm. In one series of experiments, 59 pellets can be loaded in the disk. The AC servomotor, which can be controlled remotely, is connected to the disk, and rotates the disk. For positioning the next TESPEL on the. injection axis the disk can be I rotated, which is controlled through a PC in the LI-ID control room. That action will be finished within 40 sec, after the PC sends a corrunand. The method for accelerating the TESPEL takes the pneumatic method. A helium gas is used as the propellant gas and the typical pressure is about 25 atrn with duration of 3 msec, and the typical TESPEL velocity with this pressure is about 200 - 350 m/sec. In the next campaign, that pressure will be adjustable remotely, since the pellet velocity depends strongly on the propellant gas pressure. The TESPEL injector is connected to the 1 st expansion chamber through gun barrel with 1.0 mm as the inner diameter. The 1 st expansion chamber is connected to a buffer tank (volume: 100 I) in order to consume the pressure jump due to the propellant gas, and is evacuated by the common exhaust. And the 2nd and 3rd expansion chambers are evacuated by the turbo molecular pump (1MP) and common exhaust. These TMPs have been installed at about 6 m away from the connecting port with LI-ID, for avoiding an effect of the high magnetic field. The ultimate pressure at the 3rd expansion chamber is 2.6 x 10.{i Pa. The light emission from the TESPEL, injected to the LI-ID plasma, is collected by the optical system using a half mirror, and it is divided to one CCD camera and two photo multiplier tubes (PMT). The CCD camera and the PMT are equipped with an optical filter (either H a or Li I (or Li II)). The image of this CCD camera is a temporal integrated image and provides the information about the scattering angle from the TESPEL injection axis. And the PMT signal, which is spatial integrated signal by the lens, is obtained with high time resolution (up to 1 fJ,sec). The additional two compact CCD cameras have been installed at location with looking aslope at the TESPEL injection axis. From the light intensity profile in the CCD images of these two CCD cameras, the deposited location in the LI-ID plasma is obtained. The tracer particles, deposited locally, diffuse in the plasma as ions. This diffusion, especially in the radial direction, is measured by observing the Li2+ lights (A: 449.9 nm) arising from the process of charge exchange of Li3+ ions with neutral hydrogen atoms, originated from the NBI. In order to obtain the pure emission from charge exchange process in the core region, the Li2+ lights are observed at the location with NBI path and at that without NBI path, and the difference of these signal is used as a pure emission from the core region. In the 3rd campaign, five sight lines are equipped at each location. The photo multipliers are used as a detector with high time resolution (up to 10 fJ,sec). Reference: [1] K. Khlopenkov, S. Sudo, Rev. Sci. Inst., 1998,69, pp.319--323 RS-232C LHD Control Room Fig. 1 The schematic drawing of the TESPEL injection system 160 

Construction of Tracer-Encapsulated Solid Pellet Injection System for LHD

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)