Neutral beam injection (NBI) is one of the auxiliary power systems considered for the EU DEMO pulsed plasma (‘DEMO1’). In this paper, we discuss the characteristics of optimized NBI in terms of the DEMO1 requirements, relating physics and engineering contexts in a novel parameter range compared to current NBI systems and in a larger plasma volume than ITER. Different injection options are investigated to account for various concepts discussed in the literature. The investigation is carried out using a wide range of sensitivity studies by means of the METIS 0.5D transport code and ASCOT Monte Carlo simulations of injected neutral-beam particles. This investigation has generated a series of recommendations for the NBI design, contributing to the system optimization process. We show how tangential injection aimed at the plasma core, with an energy 800 keV, is recommended to maintain high fusion power performance and fulfill the requirements for bulk heating. Compliance with engineering constraints on the NBI design, e.g., the least interference with breeding blanket modules or compatibility with solutions for the beamline components, imposes some restrictions when discussing the beam geometry. The minimum density at which an NBI can be safely operated without harmful shine-through losses is investigated for different injection energies and compared to the ITER case. The NBI operational window for DEMO is shown to be significantly extended to transient, low-density phases, also highlighting the importance of NBI systems designed for modular energy and power output. NBI can therefore sustain the plasma during a considerable portion of the transient phases, i.e., the current ramp-up and ramp-down phases. The final decision on the DEMO heating mix will be made on the basis of system operability and performance: the optimized NBI is shown to be a suitable and effective option for the EU DEMO inductive scenario.

中性束注入 (NBI) 是考虑用于 EU DEMO 脉冲等离子体 ('DEMO1') 的辅助电源系统之一。在本文中，我们讨论了优化 NBI 在 DEMO1 要求方面的特性，与当前 NBI 系统相比，在新的参数范围内以及在比 ITER 更大的等离子体体积中，将物理和工程背景相关联。研究了不同的注射选项以解释文献中讨论的各种概念。通过 METIS 0.5D 传输代码和注入中性束粒子的 ASCOT 蒙特卡罗模拟，使用广泛的灵敏度研究进行了调查。本次调查为 NBI 设计提出了一系列建议，有助于系统优化过程。我们展示了切向注入如何针对等离子体核心，具有能量建议使用 800 keV，以保持高聚变功率性能并满足整体加热的要求。遵守对 NBI 设计的工程限制，例如，对育种毯模块的干扰最小或与光束线组件的解决方案的兼容性，在讨论光束几何形状时会施加一些限制。针对不同的注入能量研究了 NBI 可以安全运行而没有有害透光损失的最小密度，并与 ITER 情况进行了比较。DEMO 的 NBI 操作窗口被证明可以显着扩展到瞬态、低密度阶段，这也凸显了为模块化能量和功率输出设计的 NBI 系统的重要性。因此，NBI 可以在相当大部分的瞬态阶段期间维持等离子体，即，当前的上升和下降阶段。DEMO 加热组合的最终决定将根据系统可操作性和性能做出：优化的 NBI 被证明是适用于欧盟 DEMO 感应场景的合适且有效的选择。