Theta pinch

This fact has been used to measure electron and ion temperatures in a theta-pinch plasma 28i), and a dense plasma (/tg = 10 cm ) produced in a carbon arc 282). Both experiments employed pulsed ruby lasers as light sources. 

Theta-pinch concepts belong to the so called high-0 devices since the ratio of the kinetic pressure of the plasma to the pressure of the external confining magnetic field is relatively high ... 

A Joint Report by Argonne Nat. Lab. and Los Alamos Sci. Lab. on Eng. Design Study of a Reference Theta-Pinch Reactor 1977-82... 

Linear Theta-Pinch (LTP) Reactor (Los Alamos Scientific Laboratory)... 

E-Beam-Heated-Solenoid Laser-Heated Solenoid Linear Theta-Pinch... 

Linear Theta-Pinch (LASL) Blanket 5 years 160 Modules 3.4m O.D. X 2m wide 70 tonnes 12 1) Largest number of modules 2) Sealing problem will be extremely difficult because of the method of sealing 3) Fairly light module 4) Electrical connections may be difficult... 

The plasma physics basis for CT reactor projections is derived from MHD stability theory and experimental observations of macrostability, and from postulated transport scaling or scaling of related devices (tokamak and diffuse, toroidal pinch). A central issue, on which different reactor projections can be based, centers on the observed macrostability of certain CT s (reversed field theta-pinch Toroidal apparent contradiction with MHD stability theory. Although the conflict may be resolved by inclusion of finite-ion-larmor radius (FLR) effects in the theory, scaling assumptions to reactor conditions may or may not invoke FLR. 

Table 8. C.T. Reactor Based on the Field-Reversed Theta Pinch ...

Theta Pinches," Proceedings of the High Beta Workshop at LASL ERDA-76/108, July 28-August 1, 1975, p. 470. J. Hammer, private communication 1980. 

Fig. 13 The plasma formation scheme one is the Marshall gun approach and the other is reversed field theta pinch approach...

The plasma gun production methods have been theoretically modeled and analyzed by the Livermore group and the theta-pinch scheme has been investigated by the Columbia and Maryland groups. The details may be found in Ref [33/34]. Here/ the quasi-static approach proposed by Princeton will be discussed in detail. 

There have been a number of proposals for r-f heating of plasma columns by a variety of modes, both radial and axial.A certain amount of analytical theory as well as numerical simulations have been carried out, but to date no scaling laws for reactor relevant plasmas have been reported. An experiment on radial acoustic mode heating of a 2-meter long low density (10 ) staged theta pinch is currently under construction at the University of Washington. 

It was proposed by the LASL group to connect two conventional linear theta pinches of length Zy with semi-circular racetrack ends, of major radius R. In this way, it was hoped that the energy loss in the ends would correspond to transverse" losses, assumed to be anomalous, rather than "parallel." The confinement time then becomes 2... 

The suggestion of using cusps on the end of long plasma columns is an old one which was tried experimentally in the early days of theta pinch research. While in principle cusps are at least as leaky as strong simple mirrors (M >> 1), a 3 = 1 cusp (i.e., with the interior field-free) has the overriding virtue of being fully mhd stable. 

The use of high M simple mirrors at the ends of a high density, theta-pinch-like column does not appear useful because of the instability of such devices. However, the use of sophisticated doublemirror electrostatic traps, which forms the basis for the tandem mirror program, is very promising. This approach, which developed from the "Q-enhancement program" for simple mirrors, has historically not been considered as a "long linear system," and is discussed elsewhere in this workshop. 

A variety of configurations has been considered,including spheromaks, field-reversed simple mirrors, relativistic ring systems, and field reversed theta pinches. Of these, the latter may be considered a direct descendant of the long linear systems approach indeed, experiments on FR0P date back to the 1960 s. In this method, a quasi-steady bias field is first established in the plasma tube. 

The question of stability is crucial to any fusion scheme. The elongated reversed-field theta-pinch is observed to be stable for some time after formation but eventually succumbs to a rotational instability this is thought to be due to the plasma gaining angular momentum to compensate for the angular momentum carried away by escaping ions, and is therefore directly associated with plasma loss [22],... 

This equilibrium concentration of plutonium, = 10% can be reached for 5-10 years, when the neutron flux is sufficient. D. P. Feoktistov /2/ showed that cylindrical — whit L > / — theta-pinch-type thermonuclear systems are suitable for this purposes. 

The theta-pinch with long cusp ends (Fig. 1) /3/ is considered a magnetic trap. Progress in experimental and theoretical studies makes it possible to achieve this concept. Let us discuss the main problem of this trap. 

Early experiments have illucidated some of the macroscopic characteristics of CT s. In the magnetized coaxial plasma experiments, the possibility of formation by this approach was demonstrated and grossly stable plasma rings were obtained which lasted for many Alfven wave transit times. CT s studied using theta-pinches were, in some cases, found to tear into separate rings, to coalesce, to contract axially towards an equilibrium state, and to develop m = 2 type instability associated with plasma rotation. 

THETA PINCH COIL 0UABJ2 106E Sr—COID PUSMA... 

Fig. 3. Formation of a reversed-field theta pinch. THE ASTRON...

There has been a recent increase in interest in the CT in the United States. This interest stems from the successful demonstration of toroidal confinement in Tokamaks and FRC s formed with theta-pinches, and from a renewed desire to investigate confinement configurations with simplified reactor consequences. In this section I will summarize experimental studies in the United States under the broad categories, CT s... 

Table 1, FRC, Reversed-Bias Theta-Pinch Experiments...

The PS-1 device20 shown in Fig. 9 (paramagnetic ppheromak, University of Maryland), uses a reverse bias theta-pinch to form the basic poloidal-field configuration. Toroidal field is introduced, after establishing the reverse bias field and before firing the main theta-pinch coil, by a Z-pinch discharge (ipeak " 0 kA,... 

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