H." Funaba

I. Yamada

J. Kohagura

K. Kawahata

K. Nagasu

M. "Yoshikawa

M. Ichimura

M. Sakamoto

T. Imai

T. Minami

Y. Nakashima

Y. Shima

Y. Shimamura

National Institute for Fusion Science (NIFS-Repository)

    The GAMMA 10/PDX device has open magnetic field configuration and improvement of the plasma confinement with potential formations in both parallel and perpendicular directions to the magnetic field line has been demonstrated. By using the controllability of plasma parameters, divertor-simulation experiments at the end-cell region have been performed with strong ICRF and ECH systems. The ITER relevant level heat flux of 10 MW/m2 at the end-cell has been obtained. Recently, the divertor simulation experimental module (D-module) has been installed on the west end of the device.  This module has a V-shaped target plate and closed divertor structure. The V-shape plate can be changed its angle and the pumping speed in the D-module is controllable. Two tungsten plates are mounted on the V-shaped plate and these plates can be heated up to 300 degrees centigrade for studying interactions between plasma and wall materials under high temperature. Gasses are injected into the D-module for realizing detached plasma operation and the clarification of radiation cooling mechanism toward the development of future divertor systems. In addition to the divertor simulation experiments, the development of high power gyrotrons is also main subject of the GAMMA 10/PDX device.  At the GAMMA 10/PDX end cell, high plasma temperature of Ti = 100 – 400 eV and Te = 30 eV has been produced under the high magnetic field around 1 Tesla. In the experiment, target plasmas are produced and heated with ICRF waves in the central cell. The maximum ion temperature becomes more than 10 keV in the perpendicular direction in the central cell. Recently, additional ICRF antennas have been installed in the anchor and plug/barrier cells in order to increase both particle and heat fluxes at the west end. A remarkable increase of the end-loss flux up to 1023 m-2sec-1 has been observed when ICRF waves are injected in both east and west anchor cells at the same time. Figure 1 shows the temporal evolution of (a) diamagnetic signal in the central cell, (b) electron temperature and (c) electron density on the target plate in the D-module in cases without additional gas injection and with H2 and H2+Ar gas injections. As shown in the figure, remarkable reduction of electron temperature and increase of electron density are observed in the case of H2+Ar gas injection. The reduction of electron temperature from a few tens eV to a few eV in the linear device with an inherent feature of short connection length of the magnetic field line indicates the possibility of the GAMMA 10/PDX device contributed to boundary plasma research. The electron density more than 1018 m-3 was obtained by injecting H2 and Xe gasses in the D-module. In University of Tsukuba, gyrotrons with wide range of frequencies from 14 to 300 GHz are developed in collaboration with JAEA, NIFS and TETD. Heat flux more than 10 MW/m2 at the end mirror throat has been observed when ECH with gyrotron of 380 kW power has been performed in the plug/barrier cell. The heat flux increaseswith gyrotron power.  Recently, output power of 1.25 MW at 28 GHz and 0.87 MW at 35.45 GHz from the same gyrotron tube have been achieved with design improvement, which is the first demonstration of the dual frequency operation in lower frequency tube. The output power of 600 kW for 2 sec at 28 GHz is also demonstrated.  This tube is applied to QUEST on Kyushu University and has given a new operating region of EC non-inductive driven current in higher density plasma. In the joint program with NIFS, The power of 1.9 MW gyrotron at 77GHz and a new frequency of 154 GHz with TE28,8 cavity, which delivered 1.16 MW for 1 sec, has been successfully developed. The total power of 4.4 MW to LHD plasma with other three 77 GHz tubwes,which extended the LHD plasma to high Te region. Figure 2 shows the summary of gyrotron development in Univ. Tsukuba.  (a)(b)(c) Fig.1 The temporal evolution of (a) diamagnetic signal in the central cell, (b) electron temperature and (c) electron density on the target plate in the D-modulein cases without additional gas injection and with H2 and H2+Ar gas injections. 0 0.5 1 1.5 214283577154300Short Pulse ( < 1sec ) Long Pulse ( > 1sec )㻜 㻜㻚㻡 㻝 㻝㻚㻡 㻞Power    [ MW ]Frequency    [ GHz ]Under designUnder test with JAEA Fig.2  The summary of gyrotron development in Univ. of Tsukuba An yttrium-aluminum-garnet (YAG) Thomson scattering (TS) system was constructed and applied to the tandem mirror GAMMA 10 device to measure the electron temperature and density. A large solid-angle TS light-collection system was achieved by use of a spherical mirror system and large numerical aperture of bundled optical fiber. We constructed two five-channel polychromators with new avalanche silicon photo diodes. We carried out the Rayleigh and Raman scattering experiments for system settings and calibrations, and applied the YAG-TS system to the GAMMA 10 plasma. We applied the new charge to digital converter (QDC) system (CAEN, V792) for multi-channel and multi-period TS signal measurements with 50-channel high-speed amplifier system. The YAG-TS system is constructed with the laser, the incident optics, the light collection optics, the signal detection electronics, and the data recording system. Details of the system is shown in elsewhere. We prepared the newpolychromator systems (TS-030 and TS-136) with new APDs (Perkin Elmer, C30659-1060-3A). Moreover, we made an improvement of preamplifier circuit for Hamamatsu APD (S8890-30) in the polychromator TS-143.  Then we can obtain the Thomson scattering signals by TS-143. The signals are recorded by using the high speed oscilloscopes, a DPO 4034 (Tektronix) and two DS5524 (IWATSU). We can measure three radial positions’ electron temperatures and densities in a single plasma shot (Fig. 1). Fig. 1 (a) and (b) show the radial electron temperature and density, respectively. The linearity of both QDC system and 50-channel amplifier system were checked and their linearities were confirmed. We applied them to measure the electron temperature.  Figure 2 shows the TS spectrum measured by using QDC system.  We successfully obtained the electron temperature (15s2 eV) by using this QDC system.01020304050607080-20 -15 -10 -5 0 5 10 15 20#227086Electron temperature [ eV ]X [ cm ](a) 05 10111 10121.5 10122 10122.5 10123 1012-20 -15 -10 -5 0 5 10 15 20#227086Electron density [ cm-3 ]X [ cm ](b) Fig. 1: (a) and (b) show the radial profiles of the electron temperature and density, respectively.-500501001502002503001020 1030 1040 1050 1060 1070 1080 1090 1100Thomson scattering spectrum #229480Intensity [ Arb. units ]Wavelength [ nm ]  Fig. 2: TS spectrum obtained by using QDC system.501§2. Electron Temperature and Density Measurements by Using the Thomson Scattering System in GAMMA 10Yoshikawa, M., Nagasu, K., Shimamura, Y., Shima, Y.,  Kohagura, J., Sakamoto, M., Imai, T., Ichimura, M., Nakashima, Y. (Univ. Tsukuba),  Minami, T. (Kyoto Univ.),  Kawahata, K., Yamada, I., Funaba, H.

Electron Temperature and Density Measurements by Using the Thomson Scattering System in GAMMA 10

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Electron Temperature and Density Measurements by Using the Thomson Scattering System in GAMMA 10

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