K. I. Thomassen

Millimeter wave tokamak heating and current drive with a high power free electron laser

The author discusses the design of an experimental facility for investigating electron cyclotron heating and current drive in tokamaks with microwave generation by a free electron laser. The tokamak to be used is the Alcator C.

A technology demonstration facility

A facility for generating engineering data on the nuclear technologies needed to build an engineering test reactor (ETR) is described here. The facility, based on a tandem mirror operating in the Kelley mode, could be used to produce a high neutron flux (1.4 MW/m2) on an 8-m2 test area for testing fusion blankets. Runs of more than 100 h, with an average availability of 30%, would produce a fluence of 5 mW/yr/m2 and give the necessary experience for successful operation of an ETR.

High-flux source of fusion neutrons for material and component testing

The inner part of a fusion reactor will have to operate at very high neutron loads. In steady-state reactors the minimum fluence before the scheduled replacement of the reactor core should be at least l0-15 Mw.yr/m 2 . A more frequent replacement of the core is hardly compatible with economic constraints. A most recent summary of the discussions of these issues is presented in Ref. [l]. If and when times come to build a commercial fusion reactor, the availability of information on the behavior of materials and components at such fluences will become mandatory for making a final decision. This makes it necessary an early development and construction of a neutron source for fusion material and component testing. In this paper, we present information on one very attractive concept of such a source: a source based on a so called Gas Dynamic Trap. This neutron source was proposed in the mid 1980s (Ref. [2]; see also a survey [3] with discussion of the early stage of the project). Since then, gradual accumulation of the relevant experimental information on a modest-scale experimental facility GDT at Novosibirsk, together with a continuing design activity, have made initial theoretical considerations much more credible. We believe that such a source can be built within 4 or 5 years. Of course, one should remember that there is a chance for developing steady-state reactors with a liquid (and therefore continuously renewable) first wall [4], which would also serve as a tritium breeder. In this case, the need in the neutron testing will become less pressing. However, it is not clear yet that the concept of the flowing wall will be compatible with all types of steady-state reactors. It seems therefore prudent to be prepared to the need of a quick construction of a neutron source. It should also be mentioned that there exist projects of the accelerator-based neutron sources (e.g., [5]). However, they generally have two major disadvantages: a wrong neutron spectrum, with a considerable excess of high-energy neutrons, and smaller test volume. In addition their development requires considerable investments into non-fusion-related technologies, whereas the work on plasma-type sources would certainly boost technology of fusion energy. Broad discussion of these issues can be found in Refs. [3, 6, 7].

An FEL-Based Microwave System for Fusion

This paper describes designs for 280-GHz and 560-GHz microwave sources based on free electron lasers (FELs). These 10-MW units are based on technology developed over the last 5 years. A first demonstration of high-average-power microwave production with an FEL system is expected in the Microwave Tokamak Experiment (MTX) facility. This paper gives details on the design and construction of that 250-GHz, 2-MW system and discusses specific applications for the Compact Ignition Tokamak (CIT).

The Tokamak Physics Experiment

The mission of the Tokamak Physics Experiment (TPX) [Nevins et al., Plasma Physics and Controlled Nuclear Fusion, Wurzburg (International Atomic Energy Agency, Vienna, 1992), Vol. 3, p. 279] is to develop the scientific basis for an economically competitive and continuously operating tokamak fusion power source. This complements the primary mission of the International Thermonuclear Experimental Reactor (ITER) [ITER Document Ser. No. 18 (International Atomic Energy Agency, Vienna, 1991)], the demonstration of ignition and long‐pulse burn, and the integration of nuclear technologies. The TPX program is focused on making the demonstration power plant that follows ITER as compact and attractive as possible, and on permitting ITER to achieve its ultimate goal of steady‐state operation. This mission of TPX requires the development of steady‐state regimes with high beta, good confinement, and a high fraction of a self‐driven bootstrap current. These regimes must be compatible with plasma stability, strong heat‐...

A programmatic framework for the Tokamak Physics Experiment (TPX)

Significant advances have been made in the confinement of reactor-grade plasmas, so that we are now preparing for experiments at the “power breakeven” level in the JET and TFTR experiments. In ITER we will extend the performance of tokamaks into the burning plasma regime, develop the technology of fusion reactors, and produce over a gigawatt of fusion power. Besides taking these crucial steps toward the technical feasibility of fusion, we must also take steps to ensure its economic acceptability. The broad requirements for economically attractive tokamak reactors based on physics advancements have been set forth in a number of studies. An advanced physics data base is emerging from a physics program of concept improvement using existing tokamaks around the world. This concept improvements program is emerging as the primary focus of the U.S. domestic tokamak program, and a key element of that program is the proposed Tokamak Physics Experiment (TPX). With TPX we can develop the scientific data base for compact, continuously-operating fusion reactors, using advanced steady-state control techniques to improve plasma performance. We can develop operating techniques needed to ensure the success of ITER and provide first-time experience with several key fusion reactor technologies. This paper explains the relationships of TPX to the current U.S. fusion physics program, to the ITER program, and to the development of an attractive tokamak demonstration plant for this next stage in the fusion program.

Electron cyclotron wave sources and applications for fusion

Advances in magnetic fusion research have come as often from the use of new technologies as from the invention of ideas and discovery of phenomena that are then applied to new experiments. The technologies needed for plasma production, heating, confinement, and control have largely been developed and are a major factor in the success of our current experiments. These include high vacuum techniques, normal and superconducting magnets, particle beams, pellet fueling devices, and rf sources in the ion cylotron and lower hybrid range of frequencies. One area where development is especially required, and where the potential impact on fusion research is large, is that of electron cyclotron wave (ECW) sources in the 100–600 GHz range. This journal issue is devoted to methods for ECW generation and transmission, and to applications including heating, current drive, profile shaping, and instability control. To help focus these articles the requirements(1) for a system to heat the Compact Ignition Tokamak (CIT) were used to define the necessary technology. Somewhat lower frequencies, but similar power, is anticipated(2) for the International Thermonuclear Experimental Reactor (ITER), and for future large devices of that class, should they use ECW sources in them.

Cold fusion: What do we know? what do we think?

SummaryConsidering the experiments which have been listed as convincing in Fig. 1, two groups have provided evidence for the existence of an unidentified small heat source. The low level of heat that is produced in the Texas A&M and Stanford work, can most plausibly be explained by a chemical explanation. The absence of helium and neutrons is consistent with this explanation, however, the high tritium level observed by Texas A&M is not.In the dry cell tests two groups present good evidence for an unidentified small neutron source. The best guess for an explanation may be hot fusion cascade. In our opinion, there is really no convincing case yet for nuclear fusion, certainly not of any practical value, but there seems to be a real effect and it has to yet be identified.There are far more groups with good equipment who found no effect at all. There may be some possible reasons for that, but there is certainly no clear reason for it. We think that the evidence suggests that more work is appropriate. We think that funding should be commensurate with the understanding of this phenomenon and of its possible usefulness.

The Spheromak Path to Fusion

Options for a spheromak fusion-energy reactor are described and provide examples of the attractive opportunities which this magnetic configuration offers. However, the ability of the spheromak to confine plasma energy has not yet been demonstrated. The physics issues, including confinement in the presence of current drive by a magnetic dynamo driven by helicity injection, are summarized. These are being studied in the Sustained Spheromak Physics Experiment at LLNL.

Nuclear electric propulsion development and qualification facilities

This paper summarizes the findings of a Tri‐Agency panel; consisting of members from the National Aeronautics and Space Administration (NASA), U.S. Department of Energy (DOE), and U.S. Department of Defense (DOD); charged with reviewing the status and availability of facilities to test components and subsystems for megawatt‐class nuclear electric propulsion (NEP) systems. The facilities required to support development of NEP are available in NASA centers, DOE laboratories, and industry. However, several key facilities require significant and near‐term modification in order to perform the testing required to meet a 2014 launch date. For the higher powered Mars cargo and piloted missions, the priority established for facility preparation is: (1 thruster developmental testing facility, (2 thruster lifetime testing facility, (3 dynamic energy conversion development and demonstration facility, and (4 advanced reactor testing facility (if required to demonstrate an advanced multiwatt power system). Facilities t...