Reversed Field Pinch Historical Review (6)
At the end of the 70's and in the early 80's a consolidated opinion was formed on the need to investigate thoroughly the RFP configuration as a possible approach to Thermonuclear Fusion using larger machines and more intense plasma currents than in devices operating at that time.
The RFX project, a machine with minor radius of 0.5 m, major radius of 2 m and a maximum plasma current of 2 MA, was proposed initially as an European undertaking to be built at Culham with the financial and scientific support of Los Alamos and Padova.
But at the end of 1981 the U.K. Government curtailed its financial support to fusion research. In 1984 the project was reassigned to the Padova group, whose staff was composed of people from CNR (Ionized Gases Institute), Padova University (Fusion Research Center) and Culham Laboratory, with financial support of ENEA and EURATOM.
The RFX construction involved a total investment cost of 140 billions of Lire and scientific-technical work equivalent to 600 person-year, as in the project forecasts.
The RFX construction was completed in 1991 and the first plasmas were produced in 1992.
As a conclusion of this short history of the RFP configuration it is worth presenting a synoptical diagram of the main results obtained by the different important RFP machines. The diagram evidences the almost linear relationship between the energy confinement time 'TauE' and the following parameters of each experiment:
TauE = a2 I1.5 (I/n)1.5
where 'a' is the minor radius of the toroid; 'I' is the plasma current; 'n' is the ion density; 'TauE' is the energy confinement time, i.e. the ratio between the plasma thermal energy and the power losses. Along with temperature and density, energy confinement time determines the fusion relevance of each experiment ("Lawson criterion").
For further information we suggest the following reading list:
- Woltjer I., (1958), Proc. Natl. Acad. Sci. U.S.A., 44,489
- S. Glasstone, R.H. Lovberg, "Controlled Thermonuclear Reactions", D. Van Nostrand Company Inc. (1960)
- J.B. Taylor, (1974), Plasma Phys.and Contr.Nucl. Fus.React. (IAEA, Vienna, 1975), Proc. 5th Int.Conf. Tokyo, Japan, Vol.1, 161
- H. A. Bodin, A.A. Newton - "RFP Research" -, Nucl. Fus. Vol.20, No 10 (1980), 1255 - 1324
- S. Ortolani, D.D. Schnack, "Magnetohydrodynamics of Plasma Relaxation", World Scientific (1993)