Ambient Pressure Mass Spectrometry at the Sub Micron Scale

本计画旨在发展一种新的常压质谱成像系统。它将使用加速到MeV势能的离子束-速度为光速的5%或更低。束将使用一组四极磁透镜聚焦到小于1微米的尺寸，并将通过100纳米厚的氮化硅窗口进入空气中，在空气中它将能够在停止前行进0.5- 1.0厘米。放置在该离子束前面的样品将通过离子与系统中的电子的相互作用（电子能量损失）而被溅射（侵蚀）。先前在真空中的实验已经证明，如果样品是分子材料，则可以从表面提取大的（~ 45 kDa）分子种类，并且可以在飞行时间质谱仪中检测这些分子种类以确定它们的分子质量。同时被移除的碎片给出了关于溅射分子的键合排列的指示，并可用于确定可能的分子排列。束本身可以使用静电场进行光栅扫描，以便可以确定材料表面的微米尺度的分子图。当离子进入材料表面时，它们的移动速度足够快，以至于它们也会导致它们所经过的原子外壳中的电子被激发，并在放松时发出特征X射线。这些X射线也可以收集和分析使用一种技术称为粒子诱导X射线发射（PIXE）这将是世界上第一台能够在空气中以亚微米尺度成像的扫描质谱仪。这种设备的应用范围从法医学到生物医学，包括地质学和环境学，以及帮助了解艺术和考古学的起源和制造。仍然存在。在项目期间，将鼓励这些应用。

This proposal aims to develop a new ambient pressure mass spectrometry imaging system. It will use a beam of ions accelerated to MeV potential energy - velocities of the order of 5% the speed of light or less. The beam will be focussed using a set of quadrapole magnetic lenses to less than a micron in size and will be passed out of the vacuum system through a 100nm thick silicon nitride window into air where it will be able to travel between 0.5-1.0cm before stopping. A sample placed in front of this beam of ions will be sputtered (eroded) by the interaction of the ions with the electrons in the system (electronic energy loss). Previous experiments in vacuum have demonstrated that if the sample is a molecular material it is possible to extract large (~45kDa) molecular species from the surface and that these can be detected in a Time of Flight mass spectrometer to determine their molecular mass. Fragments that are removed at the same time give indications about the bonding arrangements of the molecules sputtered and can be used to determine the probable molecular arrangement.The beam itself can be raster scanned using an electrostatic field so that a molecular map of the surface of the material can be determined at the micron scale. The ions as they enter the surface of the material are moving fast enough that they will also cause electrons in the outer shells of the atoms that they pass to become exited and in relaxing back will give out a characteristic X-ray. These X-rays can also be collected and analysed using a technique known as Partical Induced X-ray Emmision (PIXE) to give trace element maps as well.This will be the worlds first scanning mass spectrometer capable of imaging at the sub micron scale in air.Applications for this equipment range from forensics to biomedicine taking in geology and the environment as well as helping to understand the origins and manufacture of art and archeological remains. These applications will be encouraged over the period of the project.