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Psychometrics is the science of psychological measurement. For an intelligence test to be considered valid, it must be evaluated using the principles and methods of psychometrics. In this chapter we introduce basic psychometric techniques such as factor analysis and review the evolution of psychometric theories of intelligence, with emphasis on the Cattell-Horn-Carroll theory of cognitive abilities.
The process of high energy electron acceleration along the surface of grating targets (GTs) that were irradiated by a relativistic, high-contrast laser pulse at an intensity
was studied. Our experimental results demonstrate that for a GT with a periodicity twice the laser wavelength, the surface electron flux is more intense for a laser incidence angle that is larger compared to the resonance angle predicted by the linear model. An electron beam with a peak charge of
, for electrons with energies
, was measured. Numerical simulations carried out with parameters similar to the experimental conditions also show an enhanced electron flux at higher incidence angles depending on the preplasma scale length. A theoretical model that includes ponderomotive effects with more realistic initial preplasma conditions suggests that the laser-driven intensity and preformed plasma scale length are important for the acceleration process. The predictions closely match the experimental and computational results.
The generation of high-order harmonics in ultraviolet spectral range by targets of periodic modulation interacting with relativistic, high contrast laser pulse (Iλ2 = 1020 W/cm2 · μm2) was investigated experimentally and numerically. The spectral intensity of the 2nd- and 3rd-order harmonic emission from grating of different periodicities (250, 410, and 480 nm) is presented. The enhancement of the 3rd harmonic order compared with 2nd was observed for a grating of 480 nm periodicity. The experimental results indicate the role of the grating periodicity on the emission efficiency of different higher order harmonics in the UV spectral range. The higher order harmonics are emitted at the grating surface separated from the specular reflection of the laser pulse, due of the interference effects. In addition, 2D numerical PIC simulations demonstrate a complex angular distribution of the higher harmonics (HH) spectral intensity and confirm the strong dependence of the HH efficiency of a specific order on the grating periodicity, as observed experimentally. These special features of the high harmonic emission by periodically modulated targets open the route toward the control of HH spectral composition and of the emission efficiency of the lower order harmonics.
With the latest configuration, the Ti:Sa laser system ARCTURUS (Düsseldorf University, Germany) operates with a double-chirped pulse amplification (CPA) architecture delivering pulses with an energy of 7 J before compression in each of the two high-power beams. By the implementation of a plasma mirror system, the intrinsic laser contrast is enhanced up to
on a time scale of hundreds of picoseconds, before the main peak. The laser system has been used in various configurations for advanced experiments and different studies have been carried out employing the high-power laser beams as a single, high-intensity interaction beam (
), in dual- and multi-beam configurations or in a pump–probe arrangement.
Grommet insertion is a common surgical procedure in children. Long waiting times for grommet insertion are not unusual. This project aimed to streamline the process by introducing a pathway for audiologists to directly schedule children meeting National Institute for Health and Care Excellence Clinical Guideline 60 (‘CG60’) for grommet insertion.
Method and results
A period from June to November 2014 was retrospectively audited. Mean duration between the first audiology appointment and grommet insertion was 294.5 days (median = 310 days). Implementing the direct-listing pathway reduced the duration between first audiology appointment and grommet insertion (mean = 232 days; median = 231 days). There has been a reduction in the time between the first audiology appointment and surgery (mean difference of 62.5 days; p = 0.024), and a reduction in the time between second audiology appointment and surgery (28 days; p = 0.009).
Direct-listing pathways for grommet insertion can reduce waiting times and expedite surgery. Implementation involves a simple alteration of current practice, adhering to National Institute for Health and Care Excellence Clinical Guideline 60. The ultimate decision regarding surgery still rests with ENT specialists.
Many transitional wall-bounded shear flows are characterised by the coexistence in state space of laminar and turbulent regimes. Probing the edge boundary between the two attractors has led in the last decade to the numerical discovery of new (unstable) solutions to the incompressible Navier–Stokes equations. However, the iterative bisection method used to compute edge states can become prohibitively costly for large systems. Here we suggest a simple feedback control strategy to stabilise edge states, hence accelerating their numerical identification by several orders of magnitude. The method is illustrated for several configurations of cylindrical pipe flow. Travelling waves solutions are identified as edge states, and can be isolated rapidly in only one short numerical run. A new branch of solutions is also identified. When the edge state is a periodic orbit or chaotic state, the feedback control does not converge precisely to solutions of the uncontrolled system, but nevertheless brings the dynamics very close to the original edge manifold in a single run. We discuss the opportunities offered by the speed and simplicity of this new method to probe the structure of both state space and parameter space.
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
) 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.
Based on the analysis of data from the numerous dedicated experiments on plasma disruptions in the TEXTOR tokamak the mechanisms of the formation of runaway electron (RE) beams and their losses are proposed. The plasma disruption is caused by a strong stochastic magnetic field formed due to nonlinearly excited low-mode-number magneto-hydro-dynamics (MHD) modes. It is hypothesized that the RE beam is formed in the central plasma region confined by an intact magnetic surface due to the acceleration of electrons by the inductive toroidal electric field. In the case of plasmas with the safety factor
the most stable RE beams are formed by the outermost intact magnetic surface located between the magnetic surface
and the closest low-order rational surface
. The thermal quench (TQ) time caused by the fast electron transport in a stochastic magnetic field is calculated using the collisional transport model. The current quench (CQ) stage is due to the particle transport in a stochastic magnetic field. The RE beam current is modelled as a sum of a toroidally symmetric part and a small-amplitude helical current with a predominant
component. The REs are lost due to two effects: (i) by outward drift of electrons in a toroidal electric field until they touch the wall and (ii) by the formation of a stochastic layer of REs at the beam edge. Such a stochastic layer for high-energy REs is formed in the presence of the
MHD mode. It has a mixed topological structure with a stochastic region open to the wall. The effect of external resonant magnetic perturbations on RE loss is discussed. A possible cause of the sudden MHD signals accompanied by RE bursts is explained by the redistribution of runaway current during the resonant interaction of high-energetic electron orbits with the
Proton radiography using laser-driven sources has been developed as a diagnostic since the beginning of the decade, and applied successfully to a range of experimental situations. Multi-MeV protons driven from thin foils via the Target Normal Sheath Acceleration mechanism, offer, under optimal conditions, the possibility of probing laser-plasma interactions, and detecting electric and magnetic fields as well as plasma density gradients with ~ps temporal resolution and ~ 5–10 µm spatial resolution. In view of these advantages, the use of proton radiography as a diagnostic in experiments of relevance to Inertial Confinement Fusion is currently considered in the main fusion laboratories. This paper will discuss recent advances in the application of laser-driven radiography to experiments of relevance to Inertial Confinement Fusion. In particular we will discuss radiography of hohlraum and gasbag targets following the interaction of intense ns pulses. These experiments were carried out at the HELEN laser facility at AWE (UK), and proved the suitability of this diagnostic for studying, with unprecedented detail, laser-plasma interaction mechanisms of high relevance to Inertial Confinement Fusion. Non-linear solitary structures of relevance to space physics, namely phase space electron holes, have also been highlighted by the measurements. These measurements are discussed and compared to existing models.
In-field critical current Ic variations, detected using a short sample, angular Ic(77K, H=5.2kOe, Angle) measurement on the ends of a 20 m coated conductor tape fabricated by the MOD / RABiTS process, are shown to be variations in the Ic(H) anisotropy that exist on subcentimeter length scales. A Ic(75 K, H, Angle) study was performed on segments cut from the tape where the power law exponent of the field dependence, α, Ic ∼H−α was calculated for Ic(H, Angle) data. Two extrema behaviors, anisotropic and isotropic, were identified. The isotropic material is shown to outperform the anisotropic material for a wide range of fields and angles at T=26 K.
The use of laser-accelerated protons as a particle probe for the detection of electric fields in plasmas has led in recent years to a wealth of novel information regarding the ultrafast plasma dynamics following high intensity laser-matter interactions. The high spatial quality and short duration of these beams have been essential to this purpose. We will discuss some of the most recent results obtained with this diagnostic at the Rutherford Appleton Laboratory (UK) and at LULI - Ecole Polytechnique (France), also applied to conditions of interest to conventional Inertial Confinement Fusion. In particular, the technique has been used to measure electric fields responsible for proton acceleration from solid targets irradiated with ps pulses, magnetic fields formed by ns pulse irradiation of solid targets, and electric fields associated with the ponderomotive channelling of ps laser pulses in under-dense plasmas.
The interaction of high-intensity laser pulses with matter releases
instantaneously ultra-large currents of highly energetic electrons,
leading to the generation of highly-transient, large-amplitude electric
and magnetic fields. We report results of recent experiments in which such
charge dynamics have been studied by using proton probing techniques able
to provide maps of the electrostatic fields with high spatial and temporal
resolution. The dynamics of ponderomotive channeling in underdense plasmas
have been studied in this way, as also the processes of Debye sheath
formation and MeV ion front expansion at the rear of laser-irradiated thin
metallic foils. Laser-driven impulsive fields at the surface of solid
targets can be applied for energy-selective ion beam focusing.
We present a novel technique for focusing and energy selection of
high-current, MeV proton/ion beams. This method employs a hollow
micro-cylinder that is irradiated at the outer wall by a high intensity,
ultra-short laser pulse. The relativistic electrons produced are injected
through the cylinder's wall, spread evenly on the inner wall surface
of the cylinder, and initiate a hot plasma expansion. A transient radial
electric field (107–1010 V/m) is
associated with the expansion. The transient electrostatic field induces
the focusing and the selection of a narrow band component out of the
broadband poly-energetic energy spectrum of the protons generated from a
separate laser irradiated thin foil target that are directed axially
through the cylinder. The energy selection is tunable by changing the
timing of the two laser pulses. Computer simulations carried out for
similar parameters as used in the experiments explain the working of the
Due to their particular properties (low emittance, short duration, and
large number density), the beams of multi-MeV protons generated during the
interaction of ultraintense (I > 1019 W/cm2)
short pulses with thin solid targets are suited for use as a particle
probe in laser-plasma experiments. When traversing a sample, the proton
density distribution is, in general, affected by collisional stopping,
scattering and deflections via electromagnetic fields, and each of these
effects can be used for diagnostic purposes. In particular, in the limit
of very thin targets, the proton beams represent a valuable diagnostic
tool for the detection of quasi-static electromagnetic fields. The proton
imaging and deflectometry techniques employ these beams, in a
point-projection imaging scheme, as an easily synchronizable diagnostic
tool in laser- plasma interactions, with high temporal and spatial
resolution. By providing diagnostic access to electro-magnetic field
distributions in dense plasmas, this novel diagnostics opens up to
investigation a whole new range of unexplored phenomena. Several transient
processes were investigated employing this technique, via the detection of
the associated electric fields. Examples provided in this paper include
the detection of pressure-gradient electric field in extended plasmas, and
the study of the electrostatic fields associated to the emission of MeV
proton beams in high-intensity laser-foil interactions.
A study employing macro- and micro-sedimentological techniques was conducted at three sites with recently deglaciated sediments in the proglacial area of Brúarjökull, a surge-type outlet glacier of the Vatnajökull ice cap, Iceland. Tills at these sites were likely deposited and deformed during the 1963/64 surge. At the height of the last surge, these sediments were beneath 90-120 m of ice, and associated basal shear stresses would have been 24-32 kPa. Tills associated with the surge at these sites formed by a combination of subglacial sediment deformation and lodgement and are thus regarded as ‘hybrid tills’. The tills show evidence of both ductile and brittle deformation. Discontinuous clay lenses within the tills, indicating local ice-bed decoupling and sliding, imply that subglacial water pressures were spatially and temporally variable during the surge. The thickness of the subglacial deforming-till layer was 50-90 cm.
Over current stabilization of YBa2Cu30x (YBCO) coated conductor high temperature superconductor tape is required in most applications. The conductor must carry currents in excess of the critical current, Ic, without damage during over current events. Conductor damage is the result of joule heating and excessive temperature rise in regions with low Ic. We have developed and applied a measurement technique using a locally applied magnetic field with a high spatial gradient to define a small area over which the Ic is depressed. By measuring the voltage and temperature as a function of current, power dissipation and temperature rise were determined. Unstabilized conductors experienced thermal runaway and are easily damaged. Copper stabilizers applied by electroplating decreased dramatically the temperature rise and increased the level of power dissipation compared with the unstabilized conductor.
In this paper, we report the first results of dosimetric analysis of
broad-spectrum, multi-MeV laser accelerated proton beams obtained
during experiments at the Rutherford Appleton Laboratory using the
Chirped Pulse beam of the Vulcan laser. The spectra are retrieved by a
numerical analysis that allows the reconstruction of the energetic
profile of the proton beam from data obtained using radiochromic