Achievement of robust high-efficiency 1 MW oscillation in the hard-self-excitation region by a 170GHz continuous-wave gyrotron
Achievement of robust high-efficiency 1 MW oscillation in the hard-self-excitation region by a 170GHz continuous-wave gyrotron
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DOI：
10.1038/nphys599
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发表时间：
2007-06-01
期刊：
影响因子：
19.6
通讯作者：
Kajiwara, Ken
中科院分区：
文献类型：
--
作者：
Sakamoto, Keishi;Kasugai, Atsushi;Kajiwara, Ken
回旋管是相干微波辐射的高功率源(1)。它们的振荡机制是回旋共振脉泽效应，在回旋共振脉泽效应中，适度相对论磁化电子束的一小部分转动动能被转换为电磁能量。回旋管发展最活跃的领域是它们可能用于将磁约束聚变等离子体加热到热核引燃点。这项工作的一个主要障碍是，在高功率毫米波工作期间(2-9)，相互竞争的模式和模式转换严重降低了回旋管的稳定性和效率(10-13)。在这里，我们证明了这些问题可以通过在振荡过程中主动控制电子束参数来克服。在此过程中，我们成功地演示了170 GHz回旋管的稳健稳态工作，在硬自激区产生了1 mW的连续输出功率，其效率达到了前所未有的55%以上。此外，我们发现，由于非线性效应，先前预期将与主工作模式竞争并对主工作模式产生不利影响的相邻共振模实际上并未危及主工作模式，而是帮助了该模式。这一结果改善了在未来的实验聚变反应堆(如ITER14-19)中使用这些设备进行加热和不稳定性控制的前景。
Gyrotrons are a high-power source of coherent microwave radiation(1). Their oscillation mechanism is a cyclotron-resonance maser effect, in which a fraction of the rotational kinetic energy of a mildly relativistic magnetized electron beam is converted into electromagnetic energy. The most active area of gyrotron development is their potential use for heating magnetically confined fusion plasmas to the point of thermonuclear ignition. A major obstacle to this endeavour is that during high-power millimetre-wave operation(2-9) competing modes and mode shifts seriously degrade a gyrotron's stability and efficiency(10-13). Here, we show that these problems can be overcome by active control of the electron-beam parameters during the oscillation. In doing so, we successfully demonstrate the robust steady-state operation of a 170 GHz gyrotron producing a continuous 1 MW output power with an unprecedented efficiency of over 55% in a hard-self-excitation region. Moreover, we find that an adjacent resonant mode previously expected to compete with and adversely affect the principal operating mode does not in fact jeopardize but rather helps this mode as a result of nonlinear effects. The result improves the outlook for using these devices for heating and instability control in future experimental fusion reactors, such as ITER14-19.