FRC Helimac Design Information (updated 9/23/99)

The two accompanying sketches show our concept for a helimak.

There are 16 TF coils with four turns per coil and 11.7 kA current. which produce a toroidal field of 0.1 T. The TF pulse is limited to 100 s for uncooled coils or to 150 s for water cooled coils. The ultimate limit on the pulse length is the 60 MJ output capacity of the motor generator. The temperature rise in the uncooled coils is less than 1 degree per shot (perhaps significantly less). There is no temperature rise in the cooled coils in a discharge cycle. The TF feeds are on the right side of the machine in concept drawing 1. The feeds include a toroidal turn to cancel the effective one toroidal turn in the TF coil set.

The VF coils are shown in the poloidal cross section of concept drawing 2. There are three coils producing a field of a few hundred gauss.

We expect to be able to use the existing TEXT-VF or divertor power supplies to power the TF coils. The latter would require rewiring to the large motor generator.

The vacuum vessel is also shown in the cross section of concept drawing 2. The dimensions are shown there. In concept figure 1, the flanges are shown. These flanges are wire-sealed ovals, and are large enough to allow manned access. They are the same as the TEXT coils to allow use of existing technology.

The main purpose of this concept was to provide assurance that we can site the machine in the unused end of the main FRC lab and to assure that we could use existing power supplies. Both of these have been accomplished and the results are positive.

The concept can now provide a starting point for optimization of the magnetic field (including error fields due to feeds), for design of biasing plates, for design of diagnostics, and for design of a vacuum system.

FIGURE 1

Figure 3. Coil Construction

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Figure 4. - Vacuum Vessel