Towards Zeptosecond-Scale Pulses from X-Ray Free-Electron Lasers

The short wavelength and high peak power of the present generation of free-electron lasers (FELs) opens the possibility of ultra-short pulses even surpassing the present (tens to hundreds of attoseconds) capabilities of other light sources - but only if x-ray FELs can be made to generate pulses consisting of just a few optical cycles. For hard x-ray operation (~0.1nm), this corresponds to durations of approximately a single attosecond, and below into the zeptosecond scale. This talk will describe a novel method to generate trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL facilities by using a relatively short 'afterburner'. Such pulses would enhance research opportunity in atomic dynamics and push capability towards the investigation of electronic-nuclear and nuclear dynamics. The corresponding multi-colour spectral output, with a bandwidth envelope increased by up to two orders of magnitudes over SASE, also has potential applications.Comment: Submitted to 35th International Free Electron Laser Conference, New York, 201

A preliminary report on work conducted in 1985 to evaluate Plantago ovata as a potential crop in the Ord River irrigation area

This paper reports on the first year of a 3 year programme aimed at developing P. ovata as a crop in the Ord River Irrigation Area (O.R.I.A.) of Kimberley region of Western Australia. The data from one year of trials indicate that Plantago ovata is highly suited to mechanisation and the Ord River Irrigation Area (ORIA). Machine harvested yields of up to 1.2 t/ha off 0.12 ha were achieved (after cleaning). The maximum hand harvested yield was 2.1 t/ha, 60 per cent higher than any other published value. Cununurra clays proved the best soil type for growth of the crop and this corresponds with an underutilised, developed resource of 14,000 ha

A Review of Frailty Syndrome and Its Physical, Cognitive and Emotional Domains in the Elderly

Peer reviewedPublisher PD

Search for the BcB_{c} meson in hadronic Z decays

Out of 3.1 million hadronic Z decays collected by the ALEPH detector between 1991 and 1994 a sample of approximately 600 J/Psi candidates decaying into e+e- or mu+mu- are selected. From these events, a search for the Bc meson decaying into the channels (J/psi pi+), (J/psi e+ nu) and (J/psi mu+ nu) is performed. This search results in the observation of 0, 1 and 1 candidate in each of these channels respectively, with 0.32, 0.17 and 0.13 background event expected. This allows the following 90 \% confidence level upper limits to be derived: G ( Z->Bc X)/G ( Z->q q) Br (Bc->J\psi pi+) Bc X)/G ( Z->q q) Br (Bc->J\psi l nu ) < 7 10**-5

A wide bandwidth free-electron laser with mode locking using current modulation

A new scheme for mode locking a free-electron laser (FEL) amplifier is proposed based on electron beam current modulation. It is found that certain properties of the original concept (Thompson and McNeil 2008 Phys. Rev. Lett. 100 203901), based on the energy modulation of electrons, are improved, including the spectral brightness of the source and the purity of the series of short pulses. Numerical comparisons are made between the new and old schemes and between a mode-locked FEL and a self-amplified spontaneous emission FEL. Illustrative examples using a hypothetical mode-locked FEL amplifier are provided. The ability to generate intense coherent radiation with a large bandwidth is demonstrated

PACE: Pattern Accurate Computationally Efficient Bootstrapping for Timely Discovery of Cyber-Security Concepts

Public disclosure of important security information, such as knowledge of vulnerabilities or exploits, often occurs in blogs, tweets, mailing lists, and other online sources months before proper classification into structured databases. In order to facilitate timely discovery of such knowledge, we propose a novel semi-supervised learning algorithm, PACE, for identifying and classifying relevant entities in text sources. The main contribution of this paper is an enhancement of the traditional bootstrapping method for entity extraction by employing a time-memory trade-off that simultaneously circumvents a costly corpus search while strengthening pattern nomination, which should increase accuracy. An implementation in the cyber-security domain is discussed as well as challenges to Natural Language Processing imposed by the security domain.Comment: 6 pages, 3 figures, ieeeTran conference. International Conference on Machine Learning and Applications 201

Start-to-end modelling of a mode-locked optical klystron free electron laser amplifier

A free electron laser (FEL) in a mode-locked optical klystron (MLOK) configuration is modelled using start-to-end simulations that simulate realistic electron beam acceleration and transport before input into a full three-dimensional FEL simulation code. These simulations demonstrate that the MLOK scheme is compatible with the present generation of radiofrequency accelerator designs. A train of few-optical cycle pulses is predicted with peak powers similar to those of the equivalent conventional FEL amplifier. The role of electron beam energy modulation in these results is explained and the limitations of some simulation codes discussed. It is shown how seeding the FEL interaction using a High Harmonic seed laser can improve the coherence properties of the output