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非常高亮度的电子加速器辐射源，我将首先研究在等离子尾流场加速器中产生的单个10 GeV光束，作为“典型”驱动光束。这种简单的设置将提供“干净”，相对简单的物理，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尾流场加速器配置中使用两个10 GeV束（驱动束和见证束），加速场为~10 GeV/m，然后是无尾流等离子体源。比较这两种情况，我们预计在无尾等离子体中，由于光束能量恒定（注意：在两种情况下，驱动光束都会损失能量），见证束的辐射光谱会更窄。如果可能的话，等离子体密度将逐渐降低，以观察从高Ku到低（~1）Ku的转变。接下来，我将重复上面的两束过程，但使用由FACET-II光束线实验区域附近的计划光注入器提供的100 MeV低发射度见证光束。这种结构将为弯曲晶体探测器系统提供低x射线能量下的强低Ku信号。最后，我将尝试产生并观察非常高亮度的x射线，从一个超亮的，等离子体注入光束在无醒等离子体。这部分的进展还将取决于等离子体注入程序的进展，例如特洛伊木马，以及等离子体源的开发，它必须提供从等离子体注入区域（宽等离子体柱，高密度）到无迹等离子体区域（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).