Direct Observation of Runaway Electron Beams in EAST Yuejiang Shi Baonian Wan, Jia Fu, Huixian Gao, Fudi Wang, Jiahong Li, and EAST team Institute of Plasma Physics, Chinese Academy of Sciences,China ASIPP 4th US-PRC Magnetic Fusion Collaboration Workshop 5-6 May 2008, Austin, Texas, USA EAST

Self-Introduction I am the leader of the advanced spectroscopy diagnostic group for HT- 7 and EAST. This group includes charge exchange recombination spectroscopy (collaboration with FRC_UT),UV-VIS OMA Spectrometer for impurity measurement, and X-ray Imaging Crystal Spectrometer (collaboration with PPPL and KSTAR). Main interesting are LHCD physics, the thermal transport of plasma, the impurity transport in plasma. EAST

Outline I. Synchrotron radiation of the runaway electrons in tokamaks II. Experimental setup III. Experimental results IV. Summary EAST

Synchrotron radiation spectra of the runaway electrons The spectra of runaways with different energy EAST I. Synchrotron radiation of the runaway electrons in tokamaks The spectra of runaways with different pitch angle

The profiles of radiation power measured with XUV array The radiation patterns with different q and fixed pitch angle (  p = 0). EAST I. Synchrotron radiation of the runaway electrons in tokamaks Numerical simulated synchrotron patterns of the runaway beams The radiation pattern with  p = A parabolic-like q profile is assumed

Two color (RGB) cameras Wavelength range:380nm-750nm Sampling frequency:75fps Pixel number:640  480 Appointed purpose in EAST: Monitor discharge status and plasma shape EAST II. Experimental setup

Video of the camera The relation between the runaway energy and the ratios of the three color pixels. The shading bar are corresponded to the experimental data. Simulation of test particle dynamic equation:, …… Elim=47~49MeV,  p =0.06~0.07 for Te=0.5keV Elim=21~432MeV,  p =0.1~0.13 for Te=0.7keV ……………………. EAST III. Experimental results(1) Typical image in a circular- configuration shot Waveforms of the discharge in EAST From this image,  p and q(0) are estimated as 0.06 and 2.8, respectively

EAST III. Experimental results(2) The shell pattern of synchrotron radiation in EAST The shell is located around q=1 surface The shell is asymmetry in HFS and LFS

IV. Summary It is the first time to observe the synchrotron radiation emitted from runaway electrons with a common visible camera in EAST tokomak. Very clear synchrotron radiation images from runaway electron beams have been obtained in EAST tokamak. Both the pitch angle and energy limit runaway electrons have been self-consistent derived from the measurement of synchrotron radiation. The experimental results are partly consistent with the test particle dynamics numerical simulation. A strange stable shell shape of synchrotron radiation can be observed. The mechanism for the formation of this shell is unclear. EAST