Limited Validity of the Lawson Criterion for Magnetic Fusion - Reported to American Physical Society

SAN ANTONIO, March 5, 2015 /PRNewswire-USNewswire/ -- A radical revision of the "Lawson Criterion" - the guiding light in fusion research for the past half a century - was proposed at the 2015 March Meeting of the American Physical Society in San Antonio, Texas, on March 5.

Lawson Criterion was never endorsed by the author himself. Lawson made it clear that the Criterion was only a theoretical paper "designed for idealized conditions to illustrate the essential features of the problem, and is by no means sufficient for the successful operation of a thermonuclear reactor."¹ According to Generalized Criterion for Controlled fusion in Non-Ideal Systems, ^2,3, 12 terms are missing from Lawson Criterion.

Although it was derived for inertial fusion with zero magnetic field, Criterion has been inaccurately applied to all magnetic fusion systems of 146 past and 35 current tokamaks. While the popularly known version states that the product of the fuel density and energy confinement time must be at least 10²⁰ per cubic meter-seconds, it is often forgotten that this product is valid only for "the 1% burn-up criterion"¹; for a meaningful power production, at least 50 times more stringent conditions will apply.

According to Lawson, there is a jump-start "critical temperature "below which the reactor cannot ignite: it is 30 million degrees centigrade or 3,000 -electron volt or 3 KeV. In their paper "Evidence for Critical Energy for Ion Confinement in Magnetic Fusion reactors," three authors point out that critical temperature, to be referred to as to "critical energy," is nearly 100 times higher, i.e. 200 KeV. Above 200 KeV, colliding beam fusion device known as auto-collider or migma ^4,5 has achieved a confinement time of 24 seconds at 700 KeV.  By contrast, confinement times are fraction of a second at thermonuclear temperatures. Physical meaning of critical energy is that the ion laboratory velocity is greater than the orbital velocity of the electron in hydrogen atom.

Lawson Criterion is concerned only with nuclear reactions, neglecting the atomic ones; specifically, the plasma destroying "charge transfer" reaction with a giant cross section of about 1 Gigabarn, a trillion times higher than that for fusion, was ignored because - at the time of Lawson criterion - its counter reaction, ionization, was believed to be 100 times larger than charge transfer. Measurements at Belfast ⁶ of the 1980's, hitherto ignored, have shown the opposite: neutralization (charge transfer) is 100 times larger at thermonuclear temperature below 200 KeV. On the other hand, above 200 KeV, ionization becomes dominant. Another consequence of the higher cross section for neutralization is that the burnout process cannot take place, hence that ultra-high vacuum pumps with bakeout of the reaction chamber for outgassing, must be used.  Neutral beam injection is a magnetic fusion reactor poison⁷.

The misconception that ionization dominates neutralization below 200 KeV led the ITER designers to believe that ionization will act as ultra-high vacuum pump by itself; as a result, ITER has been designed without UHV pumps and without a bake-out facility.

Paper was submitted by B.C. Maglich, Dan W. Scott and T. Hester of California Science & Engineering Corporation of Irvine, California, contact: Tim Hester (949) 474-5002

References

1. Lawson JD, Proc. Phys. Soc. B70 (1957).
2. J. Appl. Phys. 46, 2925 (1975).
3. J. Appl. Phys. 46, 344 (1975).
4. Phys. Rev. Lett. 54,769 (1985).
5. Aneutronic Energy, NIM A 271 1-288 (1988); Inst. Advanced Study Princeton Symposium, (north0Holland Physics Publishing Division).
6. Physics Scripta, 23, 143 (1981).
7. "Fundamental physics oversight of critical ion energy in International Thermonuclear Experimental Reactor (ITER) and proposed remedy," Maglich BC, Scott DW, Hester T, online at: http://world-scientific-education.net/
8. "Experimental evidence for absence of thermonuclear fusion power production in tokamak fusion test reactor (TFTR) – prototype of international thermonuclear experimental reactor (ITER)," Maglich BC, Scott DW, Hester T, online at: http://world-scientific-education.net/

SOURCE California Science & Engineering Corporation