This work is focused on experiments showing enhancements in power extraction efficiency and spectral control of a W-band Free Electron Laser oscillator (FELo) using ramping of the electron beam energy. The FELo operates at 1.4 MeV with electron beam currents of 1–2 A with pulse duration 10–20 $\mathrm{\mu }$s. Changing the beam energy post-laser-saturation of the initially unbunched continuous electron beam changes the phase-space oscillation trajectory between the beam energy and trapping ponderomotive wave. This enables very significant increases in output power with just 2% changes in beam energy, cases of 39%, and 100% are presented. Unlike in previous work a variable delay has been introduced between the start of the electron beam and the ramp in electron beam energy such that the effect can be observed unambiguously despite significant system jitter from shot-to-shot. In addition to increasing radiative efficiency, where desirable this could be used to rapidly modulate the power without a need to modify parameters such as the beam current or resonator out-coupling. This effect is shown to pull the locked longitudinal modes up or down depending on the direction of the ramp allowing fine frequency control and influence over mode-competition and mode-hops. To complement the experiments simulations were run to map the full range of beam-energy-ramping against resonator out-coupling and beam current for the experimental system.

这项工作的重点是实验，这些实验显示了利用电子束能量的倾斜增强了W波段自由电子激光振荡器（FELo）的功率提取效率和频谱控制的能力。FELo在1.4 MeV下工作，电子束电流为1–2 A，脉冲持续时间为10–20$\mathrm{\mu }$s。改变最初未成束的连续电子束的激光饱和后的束能量，会改变束能量与俘获的致动力波之间的相空间振荡轨迹。光束能量仅发生2％的变化，就可以实现输出功率的显着增加，出现的情况分别为39％和100％。与以前的工作不同，在电子束的开始与电子束能量的斜率之间引入了可变的延迟，因此尽管每次发射之间系统抖动很大，但仍可以清楚地观察到这种影响。除了提高辐射效率外，在需要的情况下，还可将其用于快速调制功率，而无需修改诸如射束电流或谐振器输出耦合之类的参数。已显示出这种效果可根据斜坡的方向向上或向下拉动锁定的纵向模式，从而实现精细的频率控制并影响模式竞争和模式跳跃。为了补充实验，进行了仿真，以针对实验系统映射整个范围的束能量斜率与谐振器输出耦合和束电流的关系。