An investigation of the L-shell x-ray conversion efficiency for laser-irradiated tin foils

We have used the ShenguangⅡlaser in third harmonic(351 nm)to investigate the emission of L-shell radiation in the 3.3–4.4 ke V range generated using thin foils of Sn coated onto a parylene substrate with irradiation of order 1015 W cm-2 and nanosecond pulse duration.In our experiment,we have concentrated on assessing the emission on the non-laser irradiated side as this allows an experimental geometry relevant to experiments on photo-ionised plasmas where a secondary target must be placed close to the source,to achieve x-ray fluxes appropriate to astrophysical objects.Overall L-shell conversion efficiencies are estimated to be of order 1%,with little dependence on Sn thickness between 400 and 800 nm.

Innovative Education and Training in high power laser plasmas(PowerLaPs) for plasma physics, high power laser-matter interactions and high energy density physics-theory and experiments

The Erasmus Plus programme’Innovative Education and Training in high power laser plasmas’,otherwise known as PowerLaPs,is described.The PowerLaPs programme employs an innovative paradigm in that it is a multi-centre programme where teaching takes place in five separate institutes with a range of different aims and styles of delivery.The ’in class’ time is limited to four weeks a year,and the programme spans two years.PowerLaPs aims to train students from across Europe in theoretical,applied and laboratory skills relevant to the pursuit of research in laserplasma interaction physics and inertial confinement fusion(ICF).Lectures are intermingled with laboratory sessions and continuous assessment activities.The programme,which is led by workers from the Technological Educational Institute(TEI)of Crete,and supported by co-workers from the Queen’s University Belfast,the University of Bordeaux,the Czech Technical-University in Prague,Ecole Polytechnique,the University of Ioannina,the University of Salamanca and the University of York,has just completed its first year.Thus far three Learning Teaching Training(LTT)activities have been held,at the Queen’s University Belfast,the University of Bordeaux and the Centre for Plasma Physics and Lasers(CPPL)of TEI Crete.The last of these was a two-week long Intensive Programme(IP),while the activities at the other two universities were each five days in length.Thus far work has concentrated upon training in both theoretical and experimental work in plasma physics,high power laser-matter interactions and high energy density physics.The nature of the programme will be described in detail and some metrics relating to the activities carried out to date will be presented.

Innovative education and training in high power laser plasmas(PowerLaPs) for plasma physics, high power laser matter interactions and high energy density physics: experimental diagnostics and simulations

The second and final year of the Erasmus Plus programme’Innovative Education and Training in high power laser plasmas’,otherwise known as PowerLaPs,is described.The PowerLaPs programme employs an innovative paradigm in that it is a multi-centre programme,where teaching takes place in five separate institutes with a range of different aims and styles of delivery.The’in-class’time is limited to 4 weeks a year,and the programme spans 2 years.PowerLaPs aims to train students from across Europe in theoretical,applied and laboratory skills relevant to the pursuit of research in laser plasma interaction physics and inertial confinement fusion.Lectures are intermingled with laboratory sessions and continuous assessment activities.The programme,which is led by workers from the Hellenic Mediterranean University and supported by co-workers from the Queen’s University Belfast,the University of Bordeaux,the Czech Technical University in Prague,Ecole Polytechnique,the University of Ioannina,the University of Salamanca and the University of York,has just finished its second and final year.Six Learning Teaching Training activities have been held at the Queen’s University Belfast,the University of Bordeaux,the Czech Technical University,the University of Salamanca and the Institute of Plasma Physics and Lasers of the Hellenic Mediterranean University.The last of these institutes hosted two 2-week-long Intensive Programmes,while the activities at the other four universities were each 5 days in length.In addition,a’Multiplier Event’was held at the University of Ioannina,which will be briefly described.In this second year,the work has concentrated on training in both experimental diagnostics and simulation techniques appropriate to the study of plasma physics,high power laser matter interactions and high energy density physics.The nature of the programme will be described in detail,and some metrics relating to the activities carried out will be presented.In particular,this paper will focus on the overall assessment of the programme.

Role of magnetic field evolution on filamentary structure formation in intense laser–foil interactions

Filamentary structures can form within the beam of protons accelerated during the interaction of an intense laser pulse with an ultrathin foil target. Such behaviour is shown to be dependent upon the formation time of quasi-static magnetic field structures throughout the target volume and the extent of the rear surface proton expansion over the same period.This is observed via both numerical and experimental investigations. By controlling the intensity profile of the laser drive,via the use of two temporally separated pulses, both the initial rear surface proton expansion and magnetic field formation time can be varied, resulting in modification to the degree of filamentary structure present within the laser-driven proton beam.

Bremsstrahlung emission from high power laser interactions with constrained targets for industrial radiography

Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.

A history of high-power laser research and development in the United Kingdom

The first demonstration of laser action in ruby was made in 1960 by T.H.Maiman of Hughes Research Laboratories,USA.Many laboratories worldwide began the search for lasers using different materials,operating at different wavelengths.In the UK,academia,industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications.This historical review looks at the contribution the UK has made to the advancement of the technology,the development of systems and components and their exploitation over the last 60 years.

Proton probing of laser-driven EM pulses travelling inhelical coils

The ultrafast charge dynamics following the interaction of an ultra-intense laser pulse with a foil target leads to the launch of an ultra-short, intense electromagnetic(EM) pulse along a wire connected to the target. Due to the strong electric field(of the order of GV m^(-1)) associated to such laser-driven EM pulses, these can be exploited in a travelling-wave helical geometry for controlling and optimizing the parameters of laser accelerated proton beams. The propagation of the EM pulse along a helical path was studied by employing a proton probing technique. The pulse-carrying coil was probed along two orthogonal directions, transverse and parallel to the coil axis. The temporal profile of the pulse obtained from the transverse probing of the coil is in agreement with the previous measurements obtained in a planar geometry. The data obtained from the longitudinal probing of the coil shows a clear evidence of an energy dependent reduction of the proton beam divergence, which underpins the mechanism behind selective guiding of laser-driven ions by the helical coil targets.

Influence of laser polarization on collective electron dynamics in ultraintense laser-foil interactions

The collective response of electrons in an ultrathin foil target irradiated by an ultraintense(~6×10^(20)W cm^(-2)) laser pulse is investigated experimentally and via 3D particle-in-cell simulations. It is shown that if the target is sufficiently thin that the laser induces significant radiation pressure, but not thin enough to become relativistically transparent to the laser light, the resulting relativistic electron beam is elliptical, with the major axis of the ellipse directed along the laser polarization axis. When the target thickness is decreased such that it becomes relativistically transparent early in the interaction with the laser pulse, diffraction of the transmitted laser light occurs through a so called ‘relativistic plasma aperture', inducing structure in the spatial-intensity profile of the beam of energetic electrons. It is shown that the electron beam profile can be modified by variation of the target thickness and degree of ellipticity in the laser polarization.