A more ambitious tokamak for technology tests has been proposed by a team at General Atomics in San Diego, California [24]. This machine is shown in Fig. 9.32. Note that this depicts only one side of the torus; the major axis is at

the left edge of the diagram. The dominant feature is the huge copper toroidal field coil surrounding machine. It will produce a field of 6 T (60,000 G). As seen by the size of the human figure compared to that in Fig. 8.23, FDF is actually smaller than JET. Yet the machine produces 250 MW of fusion power and can run continuously for two weeks at a time. The neutron flux is the required 1-2 MW/m2, and the fluence is 3-6 MW-years/m2 over a life of ten years.

Though FDF is much smaller than ITER, it can produce the neutrons for tech­nological testing because it does not reach ignition. It runs steadily at Q=5, where Q is the fusion power divided by the power input to the plasma. For ignition Q > 10 is necessary, and that is much more difficult. Nonetheless, FDF needs all the features of advanced tokamaks: high bootstrap current, internal transport barriers, radiofre­quency current drive, and so forth. Remote handling will be developed, with replacement components lowered from the top, where the upper part of the toroidal field coil can be removed. Initially, blanket modules will be tested. Then, after a 2-year shutdown, a full solid ceramic blanket will be installed and tested. In the third stage, after another 2-year shutdown, a Pb-Li blanket will be installed. Only a machine with a full blanket can test such quantities as thermal stress, nuclear waste and disposal, radiation damage, and material lifetimes.

With full blankets, FDF as currently designed can demonstrate a closed fuel cycle, breeding as much tritium as it uses, reaching a TBR of 1.2. In fact, if operated at 400 MW of fusion power, it could actually breed tritium at the rate of 1 kg per year to be stored for use in DEMO. This is a very ambitious goal. In this sense, FDF is comparable to ITER in what it will accomplish. ITER will push superconducting technology, test alpha particle effects, and aim for ignition, but FDF will tackle the harder problems of technology with a smaller machine. FDF will not be cheap at perhaps one-third the cost of ITER; but since it will be a direct replacement for DIII-D, much of the expertise is already in place; and, importantly, the politics of an international project can be avoided. After the cancelation of TFTR, the USA needs to regain its position at the forefront of fusion research.