David Howell

ATF extraction line laser-wire system

The ATF extraction line laser-wire (LW) aims to achieve a micron-scale laser spot size and to verify that micron- scale beam profile measurements can be performed at the International linear collider beam delivery system. Recent upgrades to the LW system are presented together with recent results including the first use of the LW as a beam diagnostic tool.

Beam Profile Measurements and Simulations of the Petra Laser-Wire

The Laser-wire will be an essential diagnostic tool at the International Linear Collider. It uses a finely focussed laser beam to measure the transverse profile of electron bunches by detecting the Compton-scattered photons (or degraded electrons) downstream of where the laser beam intersects the electron beam. Such a system has been installed at the PETRA storage ring at DESY, which uses a piezo-driven mirror to scan the laser-light across the electron beam. Latest results of experimental data taking are presented and compared to detailed simulations using the Geant4 based program BDSIM.

Identifying eighteenth century pigments at the Bodleian library using in situ Raman spectroscopy, XRF and hyperspectral imaging.

There are multiple challenges in analysing pigments in historic watercolour paintings on paper, and typically non-invasive, in situ methods are required. Recent developments in portable analytical instrumentation have made this more accessible to heritage institutions, but many commercial systems are not optimised for the specific requirements of manuscripts and works on paper. This paper describes the successful use of Raman spectroscopy, X-ray fluorescence spectroscopy (XRF) and hyperspectral imaging to identify and map watercolour pigments used by the eighteenth century botanical illustrator, Ferdinand Bauer, and demystify the unusual colour code system found in his sketches. The value, delicate nature and large size of these paintings necessitated the use of using in situ, non-contact methods of analysis. A portable, bespoke Raman spectrometer specifically designed for analysing pigments from works on paper was used together with a bespoke portable Fibre optic reflectance spectrometer, portable X-Ray Fluorescence spectrometer and a hyperspectral imaging sensor. The results demonstrate that although there is a significant compromise between achieving good Raman spectroscopic results from artists’ pigments and using sufficiently low laser power densities so as not to cause damage to the pigments, good results could be obtained with this portable system, particularly when combined with XRF, fibre optic reflectance spectroscopy (FORS) and hyperspectral imaging. Eight pigments were identified unequivocally from 125 watercolour paintings analysed, suggesting that Bauer used a more traditional and more limited palette than previously considered, and that his palette changed significantly in his later paintings. Similar pigments identified by the authors on colour chart that was discovered in 1999 in Madrid and attributed to Bauer, add weight to the attribution of this chart to Bauer. The data provides a much deeper insight into Bauer’s colour annotations, and how he was able to achieve such an impressive degree of colour fidelity in his work.

Hyperspectral analysis of cultural heritage artifacts: pigment material diversity in the Gough Map of Britain

The Gough Map, one of the earliest surviving maps of Britain, was created and extensively revised over the 15th century. In 2015, the map was imaged using a hyperspectral imaging system while in the collection at the Bodleian Library, Oxford University. The goal of the collection of the hyperspectral image (HSI) of the Gough Map was to address questions such as enhancement of faded text for reading and analysis of the pigments used during its creation and revision. In particular, pigment analysis of the Gough Map will help historians understand the material diversity of its composition and potentially the timeline of, and methods used in, the creation and revision of the map. Multiple analysis methods are presented to analyze a particular pigment in the Gough Map with an emphasis on understanding the within-material diversity, i.e., the number and spatial layout of distinct red pigments. One approach for understanding the number of distinct materials in a scene (i.e., endmember selection and dimensionality estimation) is the Gram matrix approach. Here, this method is used to study the within-material differences of pigments in the map with common visual color. The application is a pigment analysis tool that extracts visually common pixels (here, the red pigments) from the Gough Map and estimates the material diversity of the pixels. Results show that the Gough Map is composed of at least five kinds of dominant red pigments with a particular spatial pattern. This research provides a useful tool for historical geographers and cartographic historians to analyze the material diversity of HSI of cultural heritage artifacts.

Proposal of the Next Incarnation of Accelerator Test Facility at KEK for the International Linear Collider

To reach design luminosity, the International Linear Collider (ILC) must be able to create and reliably maintain nanometer size beams. The ATF damping ring is the unique facility where ILC emittances are possible. In this paper we present and evaluate the proposal to create a final focus facility at the ATF which, using compact final focus optics and an ILC-like bunch train, would be capable of achieving 37 nm beam size. Such a facility would enable the development of beam diagnostics and tuning methods, as well as the training of young accelerator physicists.

Revealing the Past: How Science Is Unlocking Cartographic Secrets

Although advanced imaging and analytical techniques have long been available, it is only over the last 3–5 years that they have been more generally applied to serious study of library materials. This has been driven by incredible advances in technology which allow for non-invasive, non-sampling, non-contact methods to be designed specifically with the curators’ concerns for the safety of the material in mind. At the same time the curators’ increasing awareness of what is possible has increased the demand for such services.

Jonathan Ashley-Smith: mentor, role model, inspiration

Jonathan Ashley-Smith has been such a prominent player in the field of conservation that he has had an impact on many people’s careers. He has certainly been an inspiration for this author who presents a personal overview of the many ways in which Ashley-Smith helped steer my path. My first meeting with Jonathan was terrifying; a tall man with long hair, an earring and wearing motorcycle leathers, but at the same time holding one of the most senior posts in the UK conservation profession. Almost exactly 10 years my senior, Jonathan was appointed as Head of Conservation at the Victoria and Albert Museum (V&A) at a relatively young age of 31, and on my first meeting him he had already been in post for seven years. As a very junior conservator, just beginning in textile conservation at Hampton Court Palace, I felt it was a bit like meeting an almost godlike figure, although he certainly wasn’t the besuited managerial-type I expected. In fact, throughout his entire career Jonathan has broken the mould both in his thoughts and actions and it is this free-thinking approach that has made him so influential in conservation, both in the UK and beyond. Dedicated to the profession and its people, Jonathan was Head of Conservation at the V&A for 27 years (1977–2004) and has subsequently taken on many varied educational and advisory roles in the profession. Despite appearances, both Jonathan and I are quite introverted so it took us awhile to get to know each other. Eventuallywe found that we had a number of shared interests: beer, scepticism of acceptedwisdom, humour and a sense of the absurd! I would regularly travel into London and meet up with him, usually in a pub near the V&A, and catch up on what was going on in our different fields. Jonathan is a scientist by training and his PhD is in Chemistry and as I was developing a conservation laboratory at Hampton Court Palace his advice and support back thenwere invaluable. Jonathanwas a specialist in metallurgy and took an interest in my early attempts to evaluate cleaning methods for metal threads using scanning electron microscopy. Actually, his main support was in encouraging the art of ‘doing science’ in general and enabling collaboration with the V&A’s science group and helping with the work of the V&A’s textile conservators. And with the Hampton Court Palace laboratory having someone of Jonathan’s stature encouraging me to develop my repertoire of analytical techniques certainly helped in putting the case for more investment and funding, so much so that the laboratory was eventually equipped to offer High Performance LiquidChromatography (HPLC), size exclusion chromatography (SEC), tensile strength testing, polarised light microscopy and infrared spectroscopy. By 1983 the conservation world had seen the publication of a series of three books, Science for Conservators, edited by Jonathan. The volumes, 1. Materials for Conservation, 2. Cleaning and 3. Adhesives and Coatings, gave an excellent introduction to the science required by practising conservators. As the Scientific Editor it was Jonathan who pulled together an excellent team of authors and advisors to produce the volumes, and this also indicated the direction that he was heading in, towards implementing the better education of conservators. As such, Jonathan was one of the instigators of the Royal College of Art (RCA) and V&A conservation course, which I had Journal of the Institute of Conservation, 2018 Vol. 41, No. 1, 85–89, https://doi.org/10.1080/19455224.2017.1417013

There’s more to reflectance spectroscopy than lux.

Fibre-optic reflectance spectroscopy is widely used as a tool for the analysis of coloured materials such as pigments and paints. We describe a new design for a FORS probe which is held some 5cm away from the sample surface and interrogates a spot of 2mm diameter, offering a significant advantage over existing methods. The spectrometer employs an illuminance of 1250lux, equivalent to 0.5mWcm−2 averaged across the visible spectrum. The spectral measurements take less than a second ensuring that the risk of sample photodegradation is minimal. Under these conditions there is no detectable temperature rise of the illuminated area. Increasing the illuminance above 25mWcm−2, a light level significantly higher than that required for our measurements, gave rise to significant localised temperature rises in model manuscripts. This demonstrates the need for caution when using this technique for the analysis of precious heritage items.

Pigment diversity estimation for hyperspectral images of the Selden map of China

The Selden Map of China, an early 17th century wall map of East Asia was rediscovered in 2008. Recently, the map was imaged using a VNIR hyperspectral imaging system while in the collection at the Bodleian Library, Oxford University. The goal of the collection of the hyperspectral image (HSI) of the Selden Map was to help historians understand the material diversity of its composition and potentially the methods used in the creation of the map. The Selden map has been named one of the ”Treasures of the Bodleian” and it poses many questions such as the diversity of pigments used to create the map. In this research, we extract visually common pixels (here, the green pigments) from the Selden Map and estimate the material diversity of the green pixels. Previous pigment analysis on the HSI of the Gough Map1, 2 used an endmember based approach, the Gram Matrix technique,3, 4 to understand the number of distinct materials in a scene and then used spectral angle mapper (SAM) to classify all the pigments. Here, we use the same Gram Matrix technique, but due to the complexity of the Selden Map data, instead of using SAM, we use two spectral unmixing techniques, NNLS (nonnegative linear least squares)5 and FUMI (functions of multiple instances)6 to determine the weights of all the endmembers for each data point to study the within-material diversity. Results show that the Selden Map is composed of at least 6 kinds of dominant green pigments with a particular spatial pattern. This research provides a useful tool for historical geographers and cartographic historians to analyze the material diversity of HSI of cultural heritage artifacts.

A pigment analysis tool for hyperspectral images of cultural heritage artifacts

The Gough Map, in the collection at the Bodleian Library, Oxford University, is one of the earliest surviving maps of Britain. Previous research deemed that it was likely created over the 15th century and afterwards it was extensively revised more than once. In 2015, the Gough Map was imaged using a hyperspectral imaging system at the Bodleian Library. The collection of the hyperspectral image (HSI) data was aimed at faded text enhancement for reading and pigment analysis for the material diversity of its composition and potentially the timeline of its creation. In this research, we introduce several methods to analyze the green pigments in the Gough Map, especially the number and spatial distribution of distinct green pigments. One approach, called the Gram Matrix, has been used to estimate the material diversity in a scene (i.e., endmember selection and dimensionality estimation). Here, we use the Gram Matrix technique to study the within-material differences of pigments in the Gough map with common visual color. We develop a pigment analysis tool that extracts visually common pixels, green pigments in this case, from the Gough Map and estimates its material diversity. It reveals that the Gough Map consists of at least six kinds of dominant green pigments. Both historical geographers and cartographic historians will benefit from this work to analyze the pigment diversity using HSI of cultural heritage artifacts.