Fibre-Based Fast T-ray Tomography

这个项目的目的是演示太赫兹断层成像，以毫秒的图像帧速率运行。我们建议设计、建立和表征一个快速的多通道无运动部件的THz层析成像系统，利用一种新的基于高功率激光二极管驱动的短脉冲光纤激光器的THz源。光纤激光器的输出将结合在一起，通过差频产生太赫兹辐射。从所提出的源发出的太赫兹辐射的特性允许使用廉价的热释电探测器阵列。大量的太赫兹测量通道将被实现为一个并行的、可重新配置的数据采集和处理电子系统。太赫兹断层成像的速度和便利性将通过以下方面的新解决方案实现：光纤激光器；太赫兹光学序列(差频产生、光束调节、探测器几何结构)；信号采集和处理；图像重建方法。该技术还将为快速台式太赫兹层析成像在科学和工程领域的广泛应用开辟道路。我们提出了一个演示实验，将使用这种新型的太赫兹层析成像系统来绘制高压火焰中主要物质的浓度和温度场分布。由于烟尘颗粒的散射，这些火焰对通常的红外分析技术是不透明的，但申请者已经证明，这些火焰对太赫兹辐射是透明的。此外，这些火焰中的许多物种在太赫兹区域表现出吸收共振。因此，太赫兹断层成像有望成为研究高压火焰的唯一方法。这对我们理解燃烧过程具有重要的意义，例如，有可能提高效率和减少温室气体排放的航空发动机。在存在碳烟的高压火焰情况下，我们将至少展示以下性能：图像帧采集周期lt；1ms；空间分辨率为D2/的主要物种横截面分布图；水分子的温度分布图(T~1000K)。该项目是RCUK资助的太赫兹基础技术工作的直接成果，结合了断层摄影术(曼彻斯特)、太赫兹技术(利兹)和新型激光光源(南安普顿)方面的成熟专业知识。目前正在进行的基础技术太赫兹工作和该项目之间的协同作用将使我们能够在现实条件下识别火焰中化学物种的光谱行为，并指明用于温度测绘的最佳谱线选择。该项目是迈向太赫兹断层成像的关键一步，用于对混合气体系统和各种其他物体进行成像，预计将对太赫兹技术的未来实用性和可负担性产生重大影响。

The aim of this project is to demonstrate THz tomography, operating at millisecond image frame rates. We propose to design, build and characterise a fast multi-channel THz tomography system without moving parts, utilising a new THz source based on short-pulse fibre lasers driven by high-power laser-diodes. The output of the fibre lasers will be combined to produce THz emission by difference-frequency generation. The character of the THz emission from the proposed source allows inexpensive pyroelectric detector arrays to be used. A large number of THz measurement channels will be realised as a parallel and re-configurable data acquisition and processing electronic system. The breakthrough in speed and facility of THz tomography will be achieved via novel solutions in: fibre lasers; THz optical train (difference-frequency generation, beam conditioning, detector geometry); signal acquisition and processing; methods for image reconstruction. The proposed technology will also open the way to fast benchtop THz tomographs with applications in a wide area of science and engineering.We propose a demonstrator experiment which will employ this novel THz tomography system to map major species' concentrations and temperature field distributions in high-pressure flames. These flames are opaque to the usual IR analysis techniques because of scattering from the soot particles, but have been shown by the applicants to be transparent to THz radiation. In addition, many of the species in these flames exhibit absorption resonances in the THz region. THz tomography therefore promises to be the only way to study high pressure flames. This has important implications in our understanding of the combustion processes in, for example, aero engines with the possibility of improving efficiency and reducing emissions of greenhouse gases. We'll demonstrate at least the following performance in the case of high-pressure flames in the presence of soot: image frame acquisition period <1ms; maps of the cross-sectional distribution of major species with spatial resolution (in area) of D2/64; maps of distribution of temperature (T~1000K) of water molecules. This project is a direct consequence of the THz Basic Technology work funded by RCUK and combines established expertise in tomography (Manchester), THz technology (Leeds) and novel laser sources (Southampton). The synergy between the currently running Basic Technology THz work and this project will allow the identification of the spectral behaviour of the chemical species in the flame under realistic conditions and indicate the best choice of spectral lines for temperature mapping. The project is a crucial step towards THz tomography for imaging of gas mixture systems and a variety of other objects, with expected strong impact on the future utility and affordability of the THz technology.