Research in Fusion Energy
My Ph.D. research at M.I.T. was in the area of “fusion” energy. It can be a major energy source for the next generation. “Fusion” means that two atoms (e.g., hydrogen) “fuse” together to form another atom (e.g., helium). During this process high energy particles (e.g., alpha particles) are produced. Fusion reactors can be built to harness these high energy particles to generate energy. Some of the advantages of fusion energy are (1) it adds little to global warming because no carbon is produced, (2) it can be generated steadily, unlike solar and wind, and (3) fusion reactors are relatively safe because they do not have uncontrolled chain-reaction. Radioactive materials are generated from fusion, but their harmful duration is generally short.
If fusion energy has so many advantages, why we don’t have it? The reason is that fusion is VERY difficult to achieve. It involves confining lots of very high temperature atoms (called “plasma”) in a tight space. The temperature we are talking about is at the level of the temperature of the sun. Basically we try to create a small sun in a fusion reactor. High temperature atoms have great ability to escape confinement because they are energetic. At this time we are not able to confine enough high temperature atoms in a reactor to create enough fusion.
I can give one example to show the difficulties. The largest experimental fusion reactor today is called International Thermonuclear Experimental Reactor (ITER). 35 countries cooperated on this project because the international community recognized the benefits and difficulty of fusion energy. ITER was proposed in 1988. Site construction began in 2007 and construction is projected to complete almost 20 years later in 2025. With luck, we may be able to have a working experimental reactor that can lead to commercial deployment (probably after 2035). The ITER has a complex donut-shaped design called "tokamak". It uses extremely powerful magnetic field to confine the plasma. The word "Токамáк" is a Russian word and is an acronym of "тороидальная камера в магнитных катушках" (translation: toroidal chamber with magnetic coils).
My research was on the movement of high energy alpha particles within the confinement. Alpha particles are generated from fusion reaction and can cause turbulence in the plasma. I found out that the turbulence leads to undesirable movement (I called it “anomalous transport”), and this "anomalous" movement needed to be considered in a reactor design.
The results of my Ph.D. research were published in a prestigious scientific journal named “Nuclear Fusion.” It was administered by the International Atomic Energy Agency.
My career path changed immediately after receiving my Ph.D. degree from M.I.T., and I left academic research as a result. In my life I have published only one research paper. Click below to see the first page of my 1978 journal paper titled
Anomalous Alpha-Particle Transport in Thermonuclear Tokamak Plasma.
From time to time a journal invites an author to write a “review paper” on a topic of interest. The review paper summarizes important development in a field of research. The author is typically a prestigious scientist who is an authority in the field. In 1980, Nuclear Fusion invited a leading Soviet Union fusion scientist, Kolesnichenko, to write a review paper titled “The Role of Alpha Particles in Tokamak Reactors.” At that time Soviet Union was the top country in the world on plasma and fusion research. For example, the "tokamak" design used in the ITER was invented by the Soviet Union. Many fusion scientists then agreed that the research of Soviet Union was more advanced than that of USA. Many of the plasma books I studied were translation of Soviet Union books.
The review paper devoted a section on my research. It named my research the “Sigmar-Chan theory of α-particle diffusion induced by an Alfven instability due to trapped particles.” (Professor Sigmar was my thesis advisor). Click below to read the relevant pages of
The Role of Alpha Particles in Tokamak Reactors.
I admit that my research was merely a minor addition to scientists' knowledge of alpha particles. Nonetheless, I was immensely pleased because a leading scientist considered my research significant enough to name the discovery as the "Sigmar-Chan" theory.
My research was mentioned in a chapter of a 1983 book (name of the book: “Advances in Nuclear Science and Technology”). The chapter, titled “Fusion Reactor Development: A Review”, was written by
Professor Stacy wrote: "Several mechanisms have been suggested for the loss of alpha particles due to microscopic fluctuations before they have deposited their energy in the plasma. The potentially most dangerous of these seems to involve ExB transport in the fluctuating electric fields arising from unstable shear Alfven waves that are excited by the alpha particles (16)." (This "most dangerous" loss was my research discovery and reference 16 is my journal paper, as can be seen on the list of references at the end.). I was pleased again because not many research are significant enough to be mentioned in a book.
Europeans also thought highly of my research. Click below to read relevant pages of a 1987 report by
Anderson, Hamnen, and Lisak of Sweden
According to the authors, the report was written to describe “important aspects of the alpha particle physics and diagnostics in a fusion tokamak plasma.” The authors devoted more than two pages to analyze my research in order to determine design conditions that can reduce anomalous alpha particle losses. They then conceded that the conditions "may be very difficult to achieve in a practical fusion reactor."
Finally, about 15 years after I identified the disturbing anomalous transport, this obstacle was overcome in 1994 by
Fisch and Herrmann of Princeton University, USA
They found a method to harness the plasma turbulence generated by alpha particles. Thus the undesirable effects of the turbulence can be channeled to beneficial uses.
(Note: Professor Fisch is the Director of the Princeton University Program in Plasma Physics. He was elected Fellow of the American Physical Society. He received a Ph.D. from M.I.T. in 1978.)
I am glad that my research has a happy ending!
Note: If you are interested in learning more about fusion energy, you can read this brochure published by the International Atomic Energy Agency.