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Department of Physics,National Taiwan University

Faculty(by Directory)

Kwo-Ray Chu

Name   朱國瑞
 Kwo-Ray Chu
Title   Distinguished Chair Professor for Research
Education   Ph. D., Cornell University (1972)
Office   710
Tel   02-3366-5113


  • 1973-1977, Research Scientist, Science Applications International Corporation, Virginia, U.S.A. 
  • 1977-1983, Supervisory Research Physicist, Naval Research Laboratory, Washington, D. C. 
  • 1983-2010, Professor/Distinguished Chair, Department of Physics, National Tsing Hua University, Hsinchu, Taiwan 
  • 2010-present:, Distinguished Chair, Department of Physics, National Taiwan University, Taipei, Taiwan
  • Science 50 Achievements, National Science Council, Taiwan (2009). 
  • Outstanding Alumni, National Taiwan University (2007). 
  • Outstanding Achievement Award, Phi Tau Phi Honor Society (2006). 
  • Science and Technology Award, Executive Yuan, Taiwan (2004). 
  • Presidential Science Prize, Taiwan (2003). 
  • Academician, Academia Sinica, Taiwan (2002). 
  • Academic Award, Ministry of Education, Taiwan (2002). 
  • Plasma Science and Application Award, IEEE Nuclear and Plasma Sciences Society (2001). 
  • K J Button Medal and Prize, British Institute of Physics (2001). 
  • Fellow, IEEE (1997). 
  • National Chair, Ministry of Education, Taiwan (1997). 
  • Fellow, Physical Society of the Republic of China (1994). 
  • Outstanding Research Award, National Science Council, Taiwan (1986-1995). 
  • Fellow, American Physical Society (1983).

Kwo Ray Chu specializes in plasma physics and, in particular, the generation of coherent electromagnetic waves via the electron cyclotron maser (ECM) interaction. The ECM is based on a stimulated cyclotron emission process involving energetic electrons in gyrational motion. It constitutes a cornerstone of relativistic electronics, a discipline that has emerged from our understanding and utilization of relativistic effects for the generation of coherent radiation from free electrons. Over a span of four decades, the ECM has undergone a remarkably successful evolution from basic research to device implementation while continuously being enriched by new physical insights. By delivering unprecedented power levels, ECM-based devices have occupied a unique position in the millimeter and submillimeter regions of the electromagnetic spectrum, and find use in numerous applications such as fusion plasma heating, advanced radars, industrial processing, materials characterization, particle acceleration, and tracking of space objects. 

His academic activities include (1) In-depth mathematical formulation and physics studies of the ECM in the framework of relativistic kinetic equations, which led to the discovery of a competitive relationship between the fast-wave ECM and the slow-wave Weibel instabilities and provided a definitive identification of the physical mechanism responsible for the cyclotron emission observed in early experiments; (2) Development of a fully relativistic theory which led to the design and subsequent demonstration (at the University of Maryland) of a 10 GHz gyroklystron at a power level (30 MW) two orders of magnitude beyond the state-of-the-art, a scheme currently explored for driving the next-generation accelerators; (3) Invention, fundamental studies, and demonstration of a novel Ka-band gyrotron traveling wave amplifier with record performance in bandwidth, power, gain, and efficiency. This scheme has been employed in the US for the upgrade of space radars; (4) Participation in national scientific programs, in particular, the synchrotron light source project, defense electronics system research, and the establishment of Taiwan's microwave tube industry; (4) Physics of high-power terahertz radiation mechanisms (since joining NTU in 2010).

Selected Publications
  1. S. H. Kao, C. C. Chiu, K. F. Pao, and K. R. Chu, “Competition between Harmonic Cyclotron Maser Interactions in the Terahertz Regime,” Phys. Rev. Lett. 107, 135101 (2011).
  2. C. C. Chiu, C. Y. Tsai, and S. H. Kao, K. R. Chu, L. R. Barnett and N. C. Luhmann, Jr., “Study of a High-Order-Mode Gyrotron Traveling-Wave Amplifier,” Phys. Plasmas 17, 113104 (2010).
  3. L. R. Barnett, N. C. Luhmann Jr., C. C. Chiu, and K. R. Chu, “Relativistic Performance Analysis of an Advanced High-Current-Density Magnetron Injection Gun, ” Phys. Plasmas 16, 093111 (2009).
  4. C. C. Chiu, K. F. Pao, Y. C. Yan, and K. R. Chu, “Nonlinearly Driven Oscillations in the Gyrotron Traveling-Wave Amplifier,” Phys. Plasmas 15, 123109 (2008).
  5. K. F. Pao, C. T. Fan, T. H. Chang, C. C. Chiu, and K. R. Chu, “Selective Suppression of High Order Axial Modes in the Gyrotron Backward-Wave Oscillator,” Phys. Plasmas 14, 053108 (2007).
  6. T. H. Chang, C. T. Fan, K. F. Pao, S. H. Chen, and K. R. Chu, “Stability and Tunability of the Gyrotron Backward-Wave Oscillator,” Applied Phys. Lett. 90, 191501 (2007).
  7. K. F. Pao, T. H. Chang, C. T. Fan, S. H. Chen, C. F. Yu, and K. R. Chu, "Dynamics of Mode Competition in the Gyrotron Backward-Wave Oscillator," Phys. Rev. Lett. 95, 185101 (2005).
  8. K. R. Chu, "The Electron Cyclotron Maser," Rev. of Modern Phys. 76, 489 (2004).
  9. S. H. Chen, T. H. Chang, K. F. Pao, and K. R. Chu, " Study of Axial Modes in Gyrotron Backward-Wave Oscillators," Phys. Rev. Lett. 89, 268303 (2002).
  10. T. H. Chang, S. H. Chen, L. R. Barnett, and K. R. Chu, "Characterization of Stationary and Non-stationary Behavior of Gyrotron Backward Wave Oscillator," Phys. Rev. Lett. 87, 064802 (2001).
  11. S. H. Chen, K. R. Chu, and T. H. Chang, "Saturated Behavior of Gyrotron Backward-Wave Oscillator," Phys. Rev. Lett. 85, 2633 (2000).
  12. K. R. Chu, H. Y. Chen, C. L. Hung, T. H. Chang, L. R. Barnett, S. H. Chen, and T. T. Yang, "An Ultra High Gain Gyrotron Traveling Wave Amplifier," Phys. Rev. Lett. 81, 4760 (1998).
  13. K. R. Chu, H. Guo, and V. L. Granatstein, "Theory of the Harmonic Multiplying
  14. Gyrotron Traveling Wave Amplifier," Phys. Rev. Lett. 78, 4661 (1997).
  15. K. R. Chu, L. R. Barnett, H. Y. Chen, S. H. Chen, Ch. Wang, Y. S. Yeh, Y. C. Tsai, T. T. Yang, and T. Y. Dawn, "Stabilization of Absolute Instabilities in the Gyrotron Travelling Wave Amplifier," Phys. Rev. Lett. 74, 1103 (1995).
  16. C. S. Kou, S. H. Chen, L. R. Barnett, H.Y. Chen, and K. R. Chu, "Experiments Study of an Injection Locked Gyrotron Backwave Wave Oscillator," Phys. Rev. Lett. 70, 924 (1993).
  17. K. R. Chu and A. T. Lin, "Harmonic Gyroresonance of Electrons in Combined Helical Wiggler and Axial Guide Magnetic Fields," Phys. Rev. Lett. 67, 3235 (1991).
  18. L. R. Barnett, L. H. Chang, H. Y. Chen, K. R. Chu, W. K. Lau, and C. C. Tu, "Absolute Instability Competition and Suppression in a Millimeter-Wave Gyrotron Traveling-Wave Amplifier," Phys. Rev. Lett. 63, 1062 (1989).
  19. K. R. Chu and A. T. Lin, "Gain and Bandwidth of the Gyro-TWT and CARM Amplifier," IEEE Trans. Plasma Science PS-16, 90 (1988).
  20. K. R. Chu, V. L. Granatstein, P. E. Latham, W. Lawson, and C. D. Striffier, "A 30 MW gyroklystron Amplifier Design for High Energy Linear Accelerators," IEEE Trans. Plasma Science PS-13, 424 (1985).
  21. Y. Carmel, K. R. Chu, M. E. Read, A. K. Ganguly, D. Dialetis, R. Seeley, J. S. Levine and V. L. Granatstein, "Realization of a Stable and Highly Efficient Gyrotron for Controlled Fusion Research,'' Phys. Rev. Lett. 50, 112 (1983).
  22. Y. Y. Lau and K. R. Chu, "Electron Cyclotron Maser Instability Driven by Loss Cone Distribution,” Phys. Rev. Lett. 50, 243 (1983).
  23. H. Guo, L. Chen, H. Keren, J. L. Hirshfield, S. Y. Park, and K. R. Chu, "Measurement of Gain for Slow Cyclotron Waves on an Annular Electron Beam," Phys. Rev. Lett. 49, 730 (1982).
  24. R. M. Gilgenbach et al. (15 authors), "Heating at the Electron Cyclotron Frequency in the SX-B Tokamak," Phys. Rev. Lett. 44, 647 (1980).
  25. K. R. Chu and J. L. Hirshfield, "Comparative Study of the Azimuthal and Axial Bunching Mechanisms in Electromagnetic Cyclotron Instabilities," Phys. Fluids 21, 461 (1978).
  26. K. R. Chu, "Theory of Electron Cyclotron Maser Interaction in a Cavity at the Harmonic Frequencies," Phys. Fluids 21, 2354 (1978).
  27. K. R. Chu and R. W. Clark, "Dynamical Model for Magnetic Signal Interpretation in Relativistic Electron Beam Heated Plasmas," Phys. Rev. Lett. 38, 704 (1977).
  28. W. M. Manheimer, K. R. Chu, E. Ott and J. P. Boris, "Marginal Stability Calculation of Electron Temperature Profiles in Tokamaks," Phys. Rev. Lett. 37, 286 (1975).
  29. K. R. Chu, R. W. Clark, M. Lampe, P. C. Liewer and W. M. Manheimer, "Ion Heating by Expansion of Beam-Heated Plasma," Phys. Rev. Lett. 35, 94 (1975).
  30. C. A. Kapetanakos, W. M. Black, and K. R. Chu, "Plasma Heating by a Rotating Relativistic Electron Beam," Phys. Rev. Lett. 34, 1156 (1975).
  31. K. R. Chu, N. Rostoker, "Interaction of a Rotational Relativistic Electron Beam with a Magnetized Plasma," Phys. Fluids 17, 813 (1974).
  32. K. R. Chu, N. Rostoker, "Relativistic Electron Beam Neutralization in a Dense Magnetized Plasma," Phys. Fluids 16, 1472 (1973).