Non-Destructive High-Resolution X-ray Diffraction for Cultural Heritage

许多不同的分析技术通常应用于文物的科学分析，以阐明其物质特性。每种技术在返回的信息类型、复杂性和费用、样品制备要求以及对不同类型的物质对象的适用性方面都有其优点和缺点。虽然x射线荧光（XRF）在提供元素信息方面非常有用，并且傅里叶变换红外光谱和拉曼光谱等技术可以产生相信息，但只有x射线衍射（XRD）才能确定和明确地识别晶体相。尽管如此，XRD在考古测量中的使用相对零星，并且仅在小生境领域中使用，主要是因为样品制备要求。该项目旨在为文化遗产和考古文物的考古分析带来非破坏性XRD技术的令人兴奋的进展。申请人开发的创新XRD方法可以在完全不需要样品制备的情况下实现高分辨率的XRD分析。20年前，对文物进行取样被认为是标准做法，但随着手持XRF等非破坏性技术的发展，博物馆和其他藏品的策展人不太愿意允许进行侵入性检查。保持文物的物理完整性现在被认为是至关重要的。对于某些类别的文物，破坏性取样是目前确定其来源的唯一现实方法。石制人工制品就是一个主要的例子。西方博物馆的许多石制品都来自艺术市场，许多人对其真实性表示怀疑。鉴定石质人工制品最有效的方法是详细描述矿物组成，以确定地质来源，但目前几乎总是需要破坏性取样来达到这一目的。第二个主要应用领域是鉴定美术绘画和绘画对象（如木乃伊肖像和印度微缩画）中的颜料。虽然拉曼光谱可以成功地识别相当大比例的颜料，但仍然有一个重要的数字，该方法是无效的。颜料具有独特的衍射模式指纹图谱，XRD研究基本上可以为所有颜料提供关键信息。对石制文物、绘画和彩绘文物的研究将成为拟议项目的主要重点。目前，这种创新的XRD技术需要同步加速器设备来实现。申请者将在美国国家标准与技术研究所使用尖端的高分辨率x射线探测器（超导过渡边缘传感器阵列）在原理验证实验中演示该方法。这项工作将支持该技术最终从同步加速器过渡到实验室和博物馆。另一个目的是研究基于相同底层技术但分辨率低得多的手持式XRD仪器原型的考古测量能力。先前使用这种原型装置的工作强烈表明，金属遗产物体的分析是一个特别有前途的领域。避免了从高价值和稀有物体中提取样品的需要是一个非常显著的优势，适用于其他研究领域。其中包括古生物学和陨石研究，以及通过样本返回任务带回地球的行星物质。

Many different analytical techniques are commonly applied in the scientific analysis of heritage objects in order to elucidate their material properties. Each technique has advantages and disadvantages in terms of the type of information returned, complexity and expense, sample preparation requirements and applicability to different types of material objects. While X-ray fluorescence (XRF) is very useful in providing elemental information, and techniques such as Fourier-transform infrared spectroscopy and Raman spectroscopy can yield phase information, only X-ray diffraction (XRD) allows the definitive and unambiguous identification of crystallographic phases. Despite this, the use of XRD in archaeometry has been relatively sporadic and of utility only in niche areas, largely because of sample preparation requirements. This project aims to bring exciting advances in non-destructive XRD techniques to the archaeometric analysis of cultural heritage and archaeological artefacts. The innovative XRD methods developed by the applicants enable high resolution XRD analysis of objects with no sample preparation requirement at all. While twenty years ago sampling of artefacts was considered standard practice, the growth of non-destructive techniques such as handheld XRF have made curators at museums and other collections very much less willing to allow invasive procedures. Maintaining the physical integrity of heritage artefacts is now considered to be of paramount importance. There are certain classes of heritage objects for which destructive sampling is currently the only realistic approach to determining provenance. Stone artefacts are a primary example. Many stone objects in Western Museums are from the art market and doubts have been expressed about the authenticity of many. The most effective method of provenancing stone artefacts is the detailed characterisation of the mineralogical composition in order to identify the geological source, but destructive sampling is nearly always currently required for this purpose. A second major application area is the identification of pigments in fine art paintings and on painted objects such as mummy portraits and Indian miniatures. Although Raman spectroscopy can successfully identify a significant proportion of pigments, there remain an important number for which the method is ineffective. Pigments have unique diffraction pattern fingerprints and XRD studies can provide the critical information for essentially all pigments. The study of stone artefacts and of paintings and painted artefacts will form a major focus of the proposed project. Currently, this innovative XRD technique requires synchrotron facilities for implementation. The applicants will demonstrate the method using cutting-edge high-resolution X-ray detectors (superconducting transition-edge sensor arrays) at the National Institute of Standards and Technology in the US in proof-of-principle experiments. This work will support the eventual transition of the technique away from synchrotrons and into the laboratory and museum. An additional aim is to investigate the archaeometric capability of a prototype handheld XRD instrument, based on the same underlying technique but having much lower resolution. Previous work with this prototype device strongly suggests that the analysis of metallic heritage objects is an especially promising area. The avoidance of the need to extract samples from high-value and rare objects is a highly-significant advantage and is applicable in other research areas. These include palaeontology and the study of meteorites and planetary materials brought to Earth by sample-return missions.