En-route to the fission-fusion reaction mechanism: a status update on laser-driven heavy ion acceleration

The fission-fusion reaction mechanism was proposed in order to generate extremely neutron-rich nuclei close to the waiting point N = 126 of the rapid neutron capture nucleosynthesis process (r-process). The production of such isotopes and the measurement of their nuclear properties would fundamentally help to increase the understanding of the nucleosynthesis of the heaviest elements in the universe. Major prerequisite for the realization of this new reaction scheme is the development of laser-based acceleration of ultra-dense heavy ion bunches in the mass range of A = 200 and above. In this paper, we review the status of laser-driven heavy ion acceleration in the light of the fission-fusion reaction mechanism. We present results from our latest experiment on heavy ion acceleration, including a new milestone with laser-accelerated heavy ion energies exceeding 5 MeV/u

Surface Coverage Issues When Using Eddy Current Arrays

Over the past few years, the need for improved flaw detection sensitivity has motivated the development of imaging techniques for eddy current testing [1]. The imaging approach has a major advantage over more traditional eddy current detection methods as image processing routines may be applied to the eddy current images to enhance flaw detection capability. Smaller probes are also being developed to further improve the resolution and sensitivity of flaw detection. The use of smaller probes, however, requires shorter data acquisition sampling intervals. This forces a tradeoff between inspection resolution and inspection speed. The need for simultaneous improvement in both inspection resolution and speed has stimulated an interest in eddy current arrays. As a result, a powerful new eddy current array inspection technology is emerging

Two Approaches to Solving the Inversion Problem for Eddy Current NDE

The eddy current NDE inversion problem is to determine flaw parameters from eddy current sensor impedance changes. Two approaches to solving this problem are discussed for geometries with two components of eddy current. The first is to use the Finite Element Method of numerical analysis to compute the sensor impedance change for each flaw parameter value. The second approach is to combine the Finite Element Method with an analytical scattering technique. These two approaches are applied to the problem of an infinitely long coil surrounding an infinitely long conducting bar with an infinitely long surface crack. The calculated impedance changes show good agreement with known analytical and experimental results

In Solidarity

This edition of Next Page is a departure from our usual question and answer format with a featured campus reader. Instead, we asked speakers who participated in the College’s recent Student Solidarity Rally (March 1, 2017) to recommend readings that might further our understanding of the topics on which they spoke

Proton acceleration by irradiation of isolated spheres with an intense laser pulse

We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2-3 x 10(20) W cm(-2). With a laser focal spot size of 10 mu m full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 mu m. Maximum proton energies of similar to 25 MeV are achieved for targets matching the focal spot size of 10 mu m in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. They make use of well-defined targets and point out pathways for future applications and experiments.DFG via the Cluster of Excellence Munich-Centre for Advanced Photonics (MAP) Transregio SFB TR18NNSA DE-NA0002008Super-MUC pr48meIvo CermakCGC Instruments in design and realization of the Paul trap systemIMPRS-APSLMUexcellent Junior Research FundDAAD|ToIFEEuropean Union's Horizon research and innovation programme 633053Physic

Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging

Radiographic imaging with x-rays and protons is an omnipresent tool in basic research and applications in industry, material science and medical diagnostics. The information contained in both modalities can often be valuable in principle, but difficult to access simultaneously. Laser-driven solid-density plasma-sources deliver both kinds of radiation, but mostly single modalities have been explored for applications. Their potential for bi-modal radiographic imaging has never been fully realized, due to problems in generating appropriate sources and separating image modalities. Here, we report on the generation of proton and x-ray micro-sources in laser-plasma interactions of the focused Texas Petawatt laser with solid-density, micrometer-sized tungsten needles. We apply them for bi-modal radiographic imaging of biological and technological objects in a single laser shot. Thereby, advantages of laser-driven sources could be enriched beyond their small footprint by embracing their additional unique properties, including the spectral bandwidth, small source size and multi-mode emission. Here the authors show a synchronized single-shot bi-modal x-ray and proton source based on laser-generated plasma. This source can be useful for radiographic and tomographic imaging

Cardiovascular and Behavioral Response to Auditory Stimuli in Boys With Fragile X Syndrome

Objective The aim of this study was to determine whether young boys with fragile X syndrome (FXS) exhibit abnormal physiological or behavioral responses to a moderately intense auditory stimulus, as heightened sensory reactivity is believed to contribute to problem behaviors in this population. Methods We examined the physiological basis, via heart activity, of auditory startle in young boys with FXS (n = 22) compared with typically developing controls (n = 27). Associations with mental age, behavioral reactivity, and chronological age were examined. Results Results suggest that older boys with FXS display increased cardiac reactivity to auditory input than younger boys with FXS that distinguishes them from typically developing controls. Higher mental age was associated with decreased latency to react. Conclusions Results contribute to increased understanding of the pathology in sensory processing in boys with FXS, which can inform refinement of the phenotype in young children with FXS and aid in the development of efficacious psychopharmacological and/or behavioral interventions