544 



67 



ordinary copper coils and the inductive current drive may be 

 sufficient to ignite the plasma by ohmic heating alone; and (3) 

 compact toroids, which seek to combine the geometric simplicity of 

 mirrors with the benefits of toroidal confinement at high beta by means 

 of closed magnetic field patterns generated by the plasma itself. The 

 EBT, discussed in Appendix C, is distinguished by reliance on kinetic 

 effects of energetic electrons to stabilize the plasma. 



B. Scientific Contributions, Issues, Status 



The second line in Table I lists the Unique Physics Regime to which 

 each of the above lines of research has led. The present tokamak 

 continues to lead the way in attaining the long energy confinement 

 times required to achieve ignition and to explore fully the mechanisms 

 of energy transport across magnetic fields. On the other hand, unique 

 features of the other concepts have frequently led to new phenomena that 

 both enrich our understanding and. In some Instances, have anticipated 

 effects that later became important in the tokamak Itself or in other 

 concepts. A recent example is the possibility that electrostatic 

 thermal barriers, first utilized in tandem mirrors, may also account for 

 the Improved confinement in the so-called H-mode in tokamaks. Other 

 examples are the pioneering work on electron cyclotron heating In the 

 EBT program, and ion cyclotron heating In stellarators/heliotrons. 



The third and fourth lines of Table I state the major issues yet to 

 be addressed in each line of research and the present status of the 

 research. As can be seen from the table, the main question for the 

 tokamak, and its near- relative, the stellarator/heliotron, is the 

 ultimate limit on beta. By contrast, high beta has been demonstrated 

 for the tandem mirror, RFP and compact toroids (10 to 20%, 90% for the 

 FRC) but a key question Is heat confinement as one scales up from the 

 present experiments of moderate size. 



C. Facilities. Goals, Resources 



Table II lists by name the larger facilities existing or under 

 construction for each line of research. These facilities and their 

 functions are described in the Appendices, which also list some of the 

 smaller facilities not Included In Table II. 



Goals for the next 5 years are summarized in line 5 of Table I and 

 the present allocation of resources in line 6. No substantial changes 

 in percentage allocation are expected for the next several years, with 

 appropriate adjustments to accommodate the new facilities listed in 

 Table II. Note that the tokamak allocation Includes basic science and 

 technology that benefits all concepts and would be required even if only 

 one concept were pursued. Also, we have not attempted to separate 

 funding for Tokamak Improvements from other tokamak funding. 



