431 research outputs found
Two-Pulse Ionization Injection into Quasi-Linear Laser Wakefields
We describe a scheme for controlling electron injection into the quasi-linear
wakefield driven by a guided drive pulse via ionization of a dopant species by
a collinear injection laser pulse with a short Rayleigh range. The scheme is
analyzed by particle in cell simulations which show controlled injection and
acceleration of electrons to an energy of 370 MeV, a relative energy spread of
2%, and a normalized transverse emittance of 3.0 {\mu}m.
This is an arXiv version of the original APS paper. It should be cited as N.
Bourgeois, J. Cowley, and S. M. Hooker, Phys. Rev. Lett. 111, 155004 (2013).
APS link here: http://link.aps.org/doi/10.1103/PhysRevLett.111.155004Comment: 5 pages, 4 figure
Quasi-phase-matching of high-order-harmonic generation using multimode polarization beating
The generalization of quasi-phase-matching using polarization beating and of
multimode quasi-phase-matching (MMQPM) for the generation of high-order
harmonics is explored, and a method for achieving polarization beating is
proposed. If two (and in principle more) modes of a waveguide are excited,
modulation of the intensity, phase, and/or polarization of the guided radiation
will be achieved. By appropriately matching the period of this modulation to
the coherence length, quasi-phase-matching of high-order-harmonic radiation
generated by the guided wave can occur. We show that it is possible to achieve
efficiencies with multimode quasi-phase-matching greater than the ideal square
wave modulation. We present a Fourier treatment of QPM and use this to show
that phase modulation, rather than amplitude modulation, plays the dominant
role in the case of MMQPM. The experimental parameters and optimal conditions
for this scheme are explored
Complete spatial characterization of an optical wavefront using a variable-separation pinhole pair
We present a technique for measuring the transverse spatial properties of an
optical wavefront. Intensity and phase profiles are recovered by analysis of a
series of interference patterns produced by the combination of a scanning
X-shaped slit and a static horizontal slit; the spatial coherence may be found
from the same data. We demonstrate the technique by characterizing high
harmonic radiation generated in a gas cell, however the method could be
extended to a wide variety of light sources.Comment: 4 pages, 3 figures, 1 tabl
Deliberately Personal: The politics of tobacco control in NSW
In this paper we examine some of the main features of public discourse concerning tobacco control, analysing parliamentary debate in New South Wales between 1980 and 2003. We ask both how deeply tobacco industry discursive frames (eg, the ‘right to smoke’) penetrated and organized parliamentary discourse and identify what kinds of ideas were mobilized to justify tobacco control despite government reluctance to intervene. We find that the overall evolution of tobacco control policy was shaped by legislators’ commitment to the ideals of deliberative democracy. We argue firstly that parliamentary debate on tobacco control was conducted in highly moralised language that effectively excluded the tobacco industry’s arguments. Secondly, we show that this discourse was constructed and validated through the extensive use of personal anecdote and references, through which MPs sought to reflect public opinion and engage in authentic deliberation. Finally we argue that MPs positioned this concern for authentic deliberation as part of the debate on tobacco itself, associating tobacco control with ideal government
Learning, becoming, being: The Journey from student teacher to full teacher registration.
This research aims to investigate the journey of student teachers as they complete their programme of study and begin their careers in the teaching profession. There is little documented evidence of what, if any, impact an initial teacher education programme can have on teachers as they move through the profession – from student to newly qualified teacher to fully certificated teacher. This project will explore this relationship and how graduates call on the knowledge acquired in their initial teacher education qualification to inform their practice as teachers. The Teaching Council of Aotearoa New Zealand is currently undertaking a project examining Future Focussed Initial Teacher Education this project will complement this work as well as the Ministry of Education's Draft Strategic Plan for Early Learning. The aims of both of these pieces of work are to provide quality learning outcomes for all children and effective teaching strategies. This project will explore these aims and the relationship between an initial teacher education programme.
The research is a longitudinal study with three phases. The first phase investigated graduates perceptions of preparedness to teach and as they enter the workforce how their field-based initial teacher education training has contributed to this. The next two phases will follow the newly qualified teachers as the transverse the induction and mentoring towards full certification. In these two phases of this research the participants will become teacher researchers.
This presentation reports on the findings of the first phase which included a survey and semi-structured interview
Traversing the journey from student teacher to full teacher certification
This research aims to investigate the journey of student teachers as they complete their program of study and begin their careers in the teaching profession. There is little documented evidence of what, if any, impact an initial teacher education program can have on teachers as they move through the profession – from student to newly qualified teacher to fully certificated teacher. This project will explore this relationship and how graduates call on the knowledge acquired in their initial teacher education qualification to inform their practice as teachers. The Teaching Council of Aotearoa New Zealand is currently undertaking a project examining Future Focussed Initial Teacher Education this project will complement this work as well as the Ministry of Education's Draft Strategic Plan for Early Learning. The aims of both of these pieces of work are to provide quality learning outcomes for all children and effective teaching strategies. This project will explore these aims and the relationship between an initial teacher education program.
Abstracts—Day 1: Wednesday, July 3rd ● 33
The research is a longitudinal study with three phases. The first phase investigated graduates perceptions of preparedness to teach and as they enter the workforce how their field-based initial teacher education training has contributed to this. The next two phases will follow the newly qualified teachers as the transverse the induction and mentoring towards full certification. In these two phases of this research the participants will become teacher researchers
Combined visible and near-infrared OPA for wavelength scaling experiments in strong-field physics
We report the operation of an optical parametric amplifier (OPA) capable of
producing gigawatt peak-power laser pulses with tunable wavelength in either
the visible or near-infrared spectrum. The OPA has two distinct operation modes
(i) generation of >350 uJ, sub 100 fs pulses, tunable between 1250 - 1550 nm;
(ii) generation of >190 uJ, sub 150 fs pulses tunable between 490 - 530 nm. We
have recorded high-order harmonic spectra over a wide range of driving
wavelengths. This flexible source of femtosecond pulses presents a useful tool
for exploring the wavelength-dependence of strong-field phenomena, in both the
multi-photon and tunnel ionization regimes.Comment: 14 pages, 9 figures, This paper was published in Proceedings of SPIE
10088, Nonlinear Frequency Generation and Conversion: Materials and Devices
XVI, doi 10.1117/12.225077
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