10 research outputs found
Heterodyne measurement of sidebands and frequency combs: a derivation
A mathematical description of heterodyne measurement of an optical frequency
comb is presented. It is shown that for a signal beam containing many frequency
teeth, the amplitude and phase of each tooth can be determined from the
beatnote generated when the signal is interfered with a local oscillator with
known offset frequency
Single-Shot Electron Diffraction using a Cold Atom Electron Source
Cold atom electron sources are a promising alternative to traditional
photocathode sources for use in ultrafast electron diffraction due to greatly
reduced electron temperature at creation, and the potential for a corresponding
increase in brightness. Here we demonstrate single-shot, nanosecond electron
diffraction from monocrystalline gold using cold electron bunches generated in
a cold atom electron source. The diffraction patterns have sufficient signal to
allow registration of multiple single-shot images, generating an averaged image
with significantly higher signal-to-noise ratio than obtained with unregistered
averaging. Reflection high-energy electron diffraction (RHEED) was also
demonstrated, showing that cold atom electron sources may be useful in
resolving nanosecond dynamics of nanometre scale near-surface structures.Comment: This is an author-created, un-copyedited version of an article
published in Journal of Physics B: Atomic, Molecular and Optical Physics. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from it. The Version of Record is
available online at http://dx.doi.org/10.1088/0953-4075/48/21/21400
The effect of bean origin and temperature on grinding roasted coffee
Coffee is prepared by the extraction of a complex array of organic molecules from the roasted bean, which has been ground into fine particulates. The extraction depends on temperature, water chemistry and also the accessible surface area of the coffee. Here we investigate whether variations in the production processes of single origin coffee beans affects the particle size distribution upon grinding. We find that the particle size distribution is independent of the bean origin and processing method. Furthermore, we elucidate the influence of bean temperature on particle size distribution, concluding that grinding cold results in a narrower particle size distribution, and reduced mean particle size. We anticipate these results will influence the production of coffee industrially, as well as contribute to how we store and use coffee daily
Modelling sea level surges in the Firth of Clyde, a fjordic embayment in south-west Scotland
Time-resolved brightness measurements by streaking
Brightness is a key figure of merit for charged particle beams, and time-resolved brightness measurements can elucidate the processes involved in beam creation and manipulation. Here we report on a simple, robust, and widely applicable method for the measurement of beam brightness with temporal resolution by streaking one-dimensional pepperpots, and demonstrate the technique to characterize electron bunches produced from a cold-atom electron source. We demonstrate brightness measurements with 145 ps temporal resolution and a minimum resolvable emittance of 40 nm rad. This technique provides an efficient method of exploring source parameters and will prove useful for examining the efficacy of techniques to counter space-charge expansion, a critical hurdle to achieving single-shot imaging of atomic scale targets