Experimental results from TMX-U. [Tandem Mirror Experiment-Update]

This paper presents the recent results from the Tandem Mirror Experiment-Update(TMX-U). Many of these results can be divided into two major areas: (1) axial confinement and plasma potential, and (2) radial transport and total confinement (i.e., particle balance). Among the key observations to be discussed are the following: When the ion-confining potential theta/sub ic/ is small, theta/sub ic//T/sub i/ approx. 1 to 2, the axial confinement time scales as the theoretical Pastukhov time. Deep thermal barriers (theta/sub b/ approx. 0.7 kV, theta/sub b//T/sub e/ approx. 6 to 7) have been measured, but there is no strong correlation between ion-confining potential and the thermal-barrier depth. By installing a calibrated H/sub ..cap alpha../ emission diagnostic to measure the ionization current, we have quantified particle balance between the ionization source current and the four plasma current channels: (1) axial losses, (2) nonambipolar radial losses, (3) ambipolar radial losses, and (4) density changes. All current channels are directly measured except for the ambipolar current, which is inferred from the particle balance equation. TMX-U operation above 1 to 3 x 10/sup 12/ cm/sup -3/ is dominated by current channel (1) and below 1 x 10/sup 12/ cm/sup -3/ by one or more of the remaining three channels. Central-cell particle buildup has been observed for one or two e-foldings and, within the radial core, found consistent with particle balance

Axial power loss along open field lines

Studies are underway to evaluate the linear mirror geometry as a candidate for a high-fluence, neutron irradiation facility. This steady-state, low-Q design is currently perceived to comprise a two-component plasma driven by neutral beams with mirror confinement of the hot ions and with no electrostatic axial reduction in the warm ion end losses. Warm-ion fueling and end-wall power density will require substantial cold plasma exterior to the mirror cell and neutral gas near the end wall. In this paper, we evaluate to what extent the loss power parallel to the axial magnetic field along open field lines is a function of the escaping plasma and end-wall parameters. By allowing the source power to depend directly on the plasma density and electron temperature, several new conclusions may be pertinent to closed field-line geometries with open field-line divertors

TMX-U diagnostic system

Using data from the TMX-U diagnostic system, the production of sloshing ions has already been verified and the formation of electron thermal barriers is presently being investigated on the Tandem Mirror Experiment-Upgrade (TMX-U) at Lawrence Livermore National Laboratory. The TMX-U diagnostics are made up of the earlier TMX complement of diagnostics that determine confinement, microstability, and low-frequency stability, plus diagnostic instrumentation that measures electron parameters associated with mirror-confined electrons. This paper describes the three subsystems within the TMX-U diagnostic system: (1) the diagnostic facility (shot leader console, data cable system, and diagnostic timing system); (2) the individual diagnostic instruments that measure plasma and machine parameters; and (3) the data-acquisition and -analysis computer

The need for a fusion technology information program

In providing an adequate energy technology for the future, which new programs should be considered by the Department of Energy national laboratories to ensure that the US remains in the forefront of international science and technology is an important question. This paper suggests that the urgency for energy independence demands an active communication program that would increase awareness of energy as a critical national issue and would present fusion, with its benefits and risks, as one of the long-term alternative energy sources