Description
The compact tokamak, characterized by a smaller volume and higher plasma pressure compared to ITER, has been studied as a candidate for a future Korean burning reactor. These characteristics are expected to enable reactor construction with reduced cost and shorter development time. Many of these features can be realized through the application of high-temperature superconductors and the integration of optimized heating and current drive systems based on advanced technological selections. This study focuses on the neutral beam system, which serves as the main heating and current drive in the compact tokamak. A combination of a major radius of approximately 3.5 m and a plasma density of $2\times 10^{20}m^{−3}$ indicates that a 400 keV neutral beam is appropriate for achieving a balance between on- and off-axis power deposition. This beam energy is high enough for efficient current drive while remaining below the critical slowing-down energy of beam ions, allowing balanced ion and electron heating with superior ion heating, which is favorable for burn control. In addition, the reactor requires a high electricity-to-beam conversion efficiency to demonstrate net electricity production, irrespective of cost considerations. A high beam density is also required to minimize the occupation of the blanket region. These constraints lead to the design of a positive ion–based neutral beam system employing non-conventional neutralization and energy recovery schemes. Preliminary analysis indicates that 400 keV is the maximum beam energy achievable with positive ions. This paper discusses the engineering issues associated with the proposed neutral beam system and feasible options for their resolution, with a view toward the early demonstration of net electricity production through a compact tokamak.