NBT-1M design report

The high magnetic field machine called NBT-1M is constructed to obtain the experimental scaling law of plasma confinement, hot electron annulus and so on. The design of NBT-1M is conducted by many valuable informations and experimental results which were obtained in NBT-1, EBT-1/S devices. According to the required plasma density n of about 1012/cc, the frequency of an applicable microwave source is selected. The NBT-1M employs 8.5 GH sub(z) (75 kW, cw), 18 GH sub(z) (45 kW, cw) or 28 GH sub(z) (or 35 GH sub(z)) (200 kW gyrotron) depending on the experimental phase 1, 2 and 3. According to the microwave frequency, the magnetic field strength is determined, and the maximum field strength is 1.0 T at the axis of midplane and 2.4 T at mirror throat. The mirror ratio is 2.4. The plasma radius and the confinement time are determined by the requirement of confinement physics. The characteristics of bumpy torus magnetic field, the wedge coil configuration, the design parameters of NBT-1M, the efficient use of microwave power, and the results of numerical studies of the magnetic field and particle orbits in NBT-1M are described in detail in this report. (Kato, T.)