Betatron Radiation from Underdense Plasma

等离子体加速器为产生高质量的短脉冲电子束提供了独特的机会，这是产生高质量辐射的理想基础。为了启用一种新型的超高亮度倍他管辐射源，我将首先研究在等离子体尾波场加速器中产生的单个10GeV束流，作为一种典型的驱动束流。这一简单的设置将提供“干净的”、相对简单的物理学，可以与模拟和模型进行比较，并用于校准所有设备和探测器。在单束调试之后，我将在典型的等离子体尾波场加速器配置中使用两个10GeV束流(驱动和见证)，加速场为~10GeV/m，然后是无尾迹等离子体源。将两者进行比较，我们预计在无尾迹等离子体中，由于光束能量恒定(注：驱动光束在两种情况下都会损失能量)，见证束团的辐射光谱会变得不那么宽广。如果可能，等离子体密度将逐渐降低，以观察从高到低(~1)Ku的转变。接下来，我将重复上面的两束程序，但使用计划中的光注入器在小平面-II光束线实验区附近提供的100 MeV低发射度见证束流。这种配置将在低X射线能量下为弯曲晶体探测器系统提供强的低Ku信号。最后，我将尝试在无尾迹的等离子体中产生和观察超亮等离子体注入光束产生的非常高亮度的X射线强子辐射。这一部分的进展还将取决于等离子体注入程序(如特洛伊木马)以及等离子体源开发方面的进展，等离子体源开发必须提供从等离子体注入区域(宽等离子体柱，高密度)到无尾流等离子体区域(窄等离子体柱，可能较低密度)的无缝过渡。

Plasma accelerators provide unique opportunities for the generation of high quality, short-pulse electrons beams which are an ideal basis for high quality radiation generation. To commission a new type of very high brightness betatron radiation source, I will first study a single 10 GeV beam generated in a plasma wakefield accelerator, as a 'typical' drive beam. This simple setup will provide "clean", relatively simple physics that can be compared to simulations and models and used to calibrate all devices and detectors. Following single-bunch commissioning, I will then use two 10 GeV bunches (drive and witness) in a typical plasma wakefield accelerator configuration with accelerating fields of ~10 GeV/m, followed by the wakeless plasma source. Comparing the two, we expect to see a less broad radiation spectrum from the witness bunch in the wakeless plasma, due to the constant beam energy (note: the drive beam loses energy in both cases). The plasma density will then be progressively lowered to observe the transition from high to low (~1) Ku, if possible. Next, I will repeat the two-bunch procedure above, but using the 100 MeV, low emittance witness beam provided by the planned photo injector near the experimental area of the FACET-II beamline. This configuration would provide a strong low Ku signal at low X-ray energy for the bent crystal detector system. Finally, I will attempt to generate and observe very high brightness X-ray betatron radiation from an ultra-bright, plasma-injected beam in a wakeless plasma. Progress in this part will depend also on progress in e.g. plasma injection programs, such as Trojan Horse, as well as plasma source development, which must provide a seamless transition from the plasma injection region (wide plasma column, high density) to the wakeless plasma region (narrow plasma column, possibly lower density).