Andrew J. Lancaster

National Physical Laboratory | NPL

A current focus of the international metrology community is the digitalisation of documents, certificates and services in response to initiatives underway throughout industry and to the requirement to follow the principles of data being Findable, Accessible, Interoperable, and Reusable. We propose the key elements of a digital framework for the SI...

Spectral interferometry is becoming a popular method of performing dimensional measurements, e.g. of surfaces, but such devices require pre-calibration of their spectrometers to achieve traceability. The use of a spectral lamp and imaging spectrometer to perform inherently traceable distance measurements using spectral interferometry, without the n...

Accurate knowledge of the charged particle bunch longitudinal (time) profile is important in the context of wakefield accelerators, Compton Light sources, x-ray SASE FELs and THz radiation sources. However, it is still a challenge to obtain this information for subpicosecond long bunches and microbunched beams with the required femtosecond (fs) res...

The design of a compact Fabry-Pérot interferometer (FPi) and results of the experimental studies carried out using the device are presented. Our FPi uses freestanding wire-grid polarizers (WGPs) as beamsplitters and is suitable for use at terahertz (THz) frequencies. The FPi was studied at the LUCX facility, KEK, Japan, and an 8 MeV linear electron...

High average current, transportable energy recovery linacs (ERLs) can be very attractive tools for a number of applications including next generation high-luminosity, compact light sources. Conventional ERLs are based on an electron beam circulating through the same set of rf cavity cells. This leads to an accumulation of high-order modes inside th...

Micro-bunched particle beams are used for a wide range of research including wakefield-based particle acceleration and tunable sources of radiation. In all applications, accurate and non-destructive monitoring of the bunch-to-bunch separation is required. With the development of femtosecond lasers, the generation of micro-bunched beams directly fro...

To make the light sources compact and energy efficient, an energy recovery Superconducting RF LINAC can be used. We suggest a dual-axis, asymmetric cavity instead of conventional single axis, symmetric cavity configurations to generate average electron beam currents above 1 A, while still avoiding development of the beam breakup instability (BBU)....

The main objective of the project is to build a high resolution time-profile monitor for femtosecond electron beams, based on the spectral analysis of coherent Smith-Purcell radiation (cSPr). The monitor will be capable of determining the electron bunch time profile non-destructively and on a shot-by-shot basis. The results of recent experimental a...

It is proposed to use the polarization of coherent Smith-Purcell radiation (cSPr) to distinguish between the cSPr signal and background radiation in a single-shot longitudinal bunch profile monitor. A preliminary measurement of the polarization has been carried out using a 1 mm periodic metallic grating installed at the 8 MeV electron accelerator L...

We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement inter...

In December 2000, the Cassini fly-by near Jupiter delivered high-resolution images of Jupiter’s clouds over the entire planet in a band between 50°N and 50°S. Three daily-averaged two-dimensional velocity snapshots extracted from these images are used to perform spectral analysis of jovian atmospheric macroturbulence. A similar analysis is also per...

The Cassini spacecraft flew by Jupiter in December 2000, returning hundreds of images near closest approach [1]. We have been analysing the images spanning four Jupiter rotation periods at closest approach using automated cloud tracking software to obtain horizontal velocity fields. Our method has some advantages over other methods used for this pu...