Citation
　　 ‘Theoretical establishment of the strongly coupled plasma sciences and their applications not only to laboratory plasmas and plasmas in solid- or liquid-state materials including fusion plasmas but also to important astrophysical plasma phenomena including radiation and nuclear reactions.’

Scientific Accomplishments
　 ‘Setsuo Ichimaru led a theoretical group at the University of Tokyo, studying basic issues of STRONGLY COUPLED PLASMA SCIENCES from the fundamental point of view, concerned not only with magnetized fusion plasmas and hydrogen matter but also with dense substances in astronomical setting such as Sun, Jupiter and white dwarfs. Objects treated include dense classical plasmas, quantum electron liquids, plasma materials such as liquid metallic hydrogen, non-neutral cryogenic plasmas, and two-dimensional layers of electrons. Subjects investigated include thermodynamic properties (e.g., equation of states, phase diagrams, and phase transitions), transport processes (e.g., electrical and thermal conductivity and viscosity), fluctuations, relaxations, turbulence, and nuclear reactions. Approaches adopted include density functional formalisms, dielectric formulation with static and dynamic local-field corrections, and Monte Carlo simulations.  He has been extremely active and productive with more than 150 original contributions to leading academic journals including the ones with extremely high citations.
　　　Ichimaru organized a number of International Conferences on Strongly Coupled Plasma Sciences facilitating their advances in Asia Pacific area and exposing younger generations to research frontiers.  His highly-cited comprehensive review articles and well-organized and well-read textbooks have been quite useful even for experienced researchers as well as for starting graduate students.’ 

Professor Setsuo Ichimaru developed and established the theory of strongly coupled plasmas on the basis of statistical physics.  His scientific accomplishments summarized above cover all major issues of the strongly coupled plasma sciences as follows. 

(1) Dense classical plasmas and quantum electron liquids
　　　Strongly coupled systems of charged particles have no small parameters available for expansion-based schemes and their theory requires novel and powerful concepts.  For both classical and degenerate plasmas, we have the domains of parameters where the one-component plasma (OCP) serves as a well-defined model.  For OCP models in both cases, he developed the theory based on the state-of-the-art theoretical methods for the many-body systems and then took the effect of ion-electron coexistence into account.   In addition to comparisons with classical systems via simulations and observations of ion clouds in traps, he systematically developed the formulation for electron liquids at metallic densities, obtaining static and dynamic properties such as the plasmon dispersion, and successfully compared the results with experiments, showing usefulness of the method. 

(2) Dense hydrogen and plasma materials
　　　In order to apply to dense materials such as liquid metals and liquid metallic hydrogen, he further developed the theory emphasizing the aspect of two-component plasma (TCP) so as to obtain various thermodynamic quantities and transport coefficients, such as electric and thermal conductivities and shear viscosity, the stopping power and also the convergent collision terms.  Resultant values are shown to be in good agreement with available experimental results.  Thermodynamic functions, freezing transition, and phase diagram of dense carbon-oxygen mixtures in white dwarfs are obtained for applications to Supernova.  Studies of equations of state, phase diagram, and metal-insulator transition in dense hydrogen are compared with Livermore shock-compression experiments, giving the interpretation in terms of the first-order metal-insulator transition. 

(3) Enhanced fluctuations, turbulence, and transport
　　 As correlations in strongly coupled charged particle systems in thermal equilibrium, fluctuations also play the major role in systems out of thermal equilibrium. In his first paper which appeared in Physical Review Letters, he clarified the connection of the enhanced fluctuation spectrum in plasmas to the scattering of electromagnetic waves:  This is the first expression of this kind in plasma physics.  Starting from formulations firmly based on statistical physics, he explicitly derived the formulas for transport properties and applied them to important problems of magnetized fusion plasmas and astrophysical plasmas including the reconnection of magnetic fields.  The source of energy in astrophysical phenomena such as solar flares is often attributed to the reconnection of magnetic field.  He estimated the resistivity of electromagnetically turbulent plasmas and thereby gave proper explanation for empirical Alfven scaling of reconnection velocities. 

(4) Nuclear reactions
　　The rate of thermonuclear reactions can be modified by the correlation between reacting nuclei and ambient electrons. In dense plasmas, there exists the possibility of enormous enhancement of the rate through the argument of the exponential function giving its value.  While the enhancement is not so significant in inertial confinement fusion plasmas and the solar interior, the enhanced rate in dense astrophysical object such as white dwarfs has significant influence on their evolution and Supernova explosion.  Based on the theory of strongly coupled plasmas he constructed, he gave accurate estimations of reaction rate and applied to various cases.  He also applied his methods to the so-called cold fusion in metal hydrides and showed the most reliable result for the DD reaction at the room temperature which is too small to explain the claimed experiments. 

(5) Astrophysical applications
　　 Most of astrophysical activities take place in plasmas.  They need serious applications of the plasma theory and, at the same time, serve as a test.  The origin and behavior of extraordinary radiations from compact astrophysical objects have been homework for plasma physicists.  For Cygnus X-1, the first X-ray star of 1971 identified as a black hole, he gave the account for the bimodal behavior of radiation spectra in terms of the bimodal behavior associated with the onset of radiative-thermal instability for the first time.  This view has been supported by recent observations and the original paper in 1977 has been highly cited.  He also contributed to the problems including magnetohydrodynamic turbulence and magnetic field fluctuation in Galaxy, magnetic reconnections in solar flares and magnetospheres, and the solar neutrino problems.