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 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 laser plasma 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 Hellenic Mediterranean University, and supported by co-workers from Queens 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 (LTT) activities have been held, at the Queens University Belfast, the University of Bordeaux, the Czech Technical University, the University of Salamanca, and the Institute of Plasma Physics and Lasers (CPPL) of the Hellenic Mediterranean University. The last of these institute hosted two two-week long Intensive Programmes (IPs), whilst the activities at the other four universities were each five days in length. In addition to this a "Multiplier Event" was held at the University of Ioannina, which will be briefly described. In this second year the work has concentrated upon 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 upon the overall assessment of the programme

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 laser-plasma 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

Methodologies of dynamic nanoscopic material characterization using acoustic sources generated by ultrashort laser pulses

The rapid development of nanotechnology during the recent years demands the development of new material characterization techniques at the microscopic level. In this thesis the development of dynamic nanoscopic characterization of materials is presented, based on acoustic sources generated by ultrashort laser pulses. The acoustic waves are generated in thin-film metal transducers that convert the laser pulse energy into elastic waves. For the generation of such acoustical sources both nanosecond and femtosecond laser pulses are used. Dynamic, whole-field interferometric techniques are developed, having appropriate spatial and temporal resolution, in order to monitor the generated surface micro-mechanical deformations as they expand outwards the irradiated region. The capabilities of the developed methodologies are demonstrated in the study of simple layered metal/glass systems, in the thermoelastic, melting and ablation regimes. These methodologies are also applied in simple layered structures with artificially induced surface defects. In this case, the influence of the duration of the exciting laser pulses on the coupling depth of the Rayleigh surface waves is studied, and microscale reflection and interference of these waves is recorded. Furthermore, the applicability of these methodologies is demonstrated for the case of composite layered systems, incorporating poly-methyl-methacrylate and epoxy resin substrates. Last, but not least, the experimental findings are used for the development and validation of a finite element analysis model that simulates the multiphysics problem.Με την ραγδαία ανάπτυξη της νανοτεχνολογίας κατά τα τελευταία χρόνια, γίνεται ολοένα και πιο επιτακτική η ανάγκη ανάπτυξης νέων τεχνικών χαρακτηρισμού υλικών σε μικροσκοπικό επίπεδο. Στην διατριβή αυτή αναπτύσσονται μεθοδολογίες δυναμικού νανοσκοπικού χαρακτηρισμού υλικών με ακουστικές πηγές παραγόμενες από υπερβραχείς παλμούς laser. Η παραγωγή των ακουστικών κυμάτων γίνεται σε λεπτό μεταλλικό επιφανειακό στρώμα που έχει το ρόλο του μετατροπέα της φωτεινής ενέργειας του laser σε ελαστικά κύματα. Για την δημιουργία των ακουστικών πηγών χρησιμοποιήθηκαν τόσο nanosecond όσο και femtosecond παλμοί laser. Για την δυναμική παρακολούθηση των δημιουργούμενων ακουστικών κυμάτων αναπτύσσονται συμβολομετρικές πειραματικές τεχνικές χωρο-χρονικής απεικόνισης ολικού πεδίου, με κατάλληλη χωρική και χρονική διακριτική ικανότητα, ώστε να είναι δυνατή η απεικόνιση επιφανειακών μικρο-μηχανικών παραμορφώσεων κατά την εξάπλωση των κυμάτων αυτών. Οι δυνατότητες των μεθοδολογιών αξιολογήθηκαν σε απλά διαστρωματωμένα υλικά μετάλλου/γυαλιού, τόσο στην θερμοελαστική περιοχή και την περιοχή τήξης, όσο και στην περιοχή φωτοαποδόμησης. Εφαρμόστηκαν επίσης σε απλά διαστρωματωμένα υλικά με τεχνητά δημιουργούμενες επιφανειακές ατέλειες. Σε αυτά μελετήθηκε η επίδραση της χρονικής διάρκειας των παλμών laser διέγερσης στο βάθος σύζευξης των Rayleigh επιφανειακών κυμάτων, και καταγράφηκαν μικρο-κυματικά φαινόμενα ανάκλασης και συμβολής. Έπειτα επιδείχθηκε η εφαρμογή των παραπάνω μεθοδολογιών σε σύνθετα διαστρωματωμένα υλικά, που περιέχουν πολυμεθυλμεθακρυλικά υποστρώματα και υποστρώματα εποξικής ρητίνης. Τέλος, τα πειραματικά αποτελέσματα αποτέλεσαν τη βάση για την ανάπτυξη και επαλήθευση μοντέλου πεπερασμένων στοιχείων προσομοίωσης της πολύ-φυσικής του φαινομένου

The Effect of Geometry on the Acoustic Radiation of Plasma Filaments in Air

International audienceLaser-generated plasma filaments in ambient air generate acoustic pulses with characteristic emission directivity and frequency spectra. This work studies the effect of the geometrical characteristics of the plasma channel on the generated acoustic radiation. For this purpose, a model based on the classical line source is adopted, which deploys the correlation between light and sound following laser breakdown to predict the acoustic radiation of filaments in air. Through the model, the acoustic directivity and frequency spectra of plasma filaments with different lengths and plasma density distributions are studied. Preliminary results from acoustic measurements of the filament’s sound radiation are presented in the frequency domain. Finally, a complete model based on the wave equation with a heat source is outlined, which allows for the estimation of the filament’s acoustic radiation in the time and frequency domain at any point in space. Preliminary results from a computational simulation of a scaled model of a plasma channel are also shown, indicating that such a model can predict the directivity and spectral characteristics of filament sound sources

Vibrational Analysis of a Splash Cymbal by Experimental Measurements and Parametric CAD-FEM Simulations

The present study encompasses a thorough analysis of the vibrations in a splash musical cymbal. The analysis is performed using a hybrid methodology that combines experimental measurements with parametric computer-aided design and finite element method simulations. Experimental measurements, including electronic speckle pattern interferometry, and impulse response measurements are conducted. The interferometric measurements are used as a reference for the evaluation of finite element method modal analysis results. The modal damping ratio is calculated via the impulse response measurements and is adopted by the corresponding simulations. Two different approximations are employed for the computer-aided design and finite element method models: one using three-point arcs and the other using lines to describe the non-smooth curvature introduced during manufacturing finishing procedures. The numerical models employing the latter approximation exhibit better agreement with experimental results. The numerical results demonstrate that the cymbal geometrical characteristics, such as the non-smooth curvature and thickness, greatly affect the vibrational behavior of the percussion instrument. These results are of valuable importance for the development of vibroacoustic numerical models that will accurately simulate the sound synthesis of cymbals

Downscaled Finite Element Modeling of Metal Targets for Surface Roughness Level under Pulsed Laser Irradiation

A three-dimensional, thermal-structural finite element model, originally developed for the study of laser–solid interactions and the generation and propagation of surface acoustic waves in the macroscopic level, was downscaled for the investigation of the surface roughness influence on pulsed laser–solid interactions. The dimensions of the computational domain were reduced to include the laser-heated area of interest. The initially flat surface was progressively downscaled to model the spatial roughness profile characteristics with increasing geometrical accuracy. Since we focused on the plastic and melting regimes, where structural changes occur in the submicrometer scale, the proposed downscaling approach allowed for their accurate positioning. Additionally, the multiscale simulation results were discussed in relation to experimental findings based on white light interferometry. The combination of this multiscale modeling approach with the experimental methodology presented in this study provides a multilevel scientific tool for an in-depth analysis of the influence of heat parameters on the surface roughness of solid materials and can be further extended to various laser–solid interaction applications

Coherent XUV Multispectral Diffraction Imaging in the Microscale

The rapid growth of nanotechnology has increased the need for fast nanoscale imaging. X-ray free electron laser (XFEL) facilities currently provide such coherent sources of directional and high-brilliance X-ray radiation. These facilities require large financial investments for development, maintenance, and manpower, and thus, only a few exist worldwide. In this article, we present an automated table-top system for XUV coherent diffraction imaging supporting the capabilities for multispectral microscopy at high repetition rates, based on laser high harmonic generation from gases. This prototype system aims towards the development of an industrial table-top system of ultrafast soft X-ray multi-spectral microscopy imaging for nanostructured materials with enormous potential and a broad range of applications in current nanotechnologies. The coherent XUV radiation is generated in a semi-infinite gas cell via the high harmonic generation of the near-infrared femtosecond laser pulses. The XUV spectral selection is performed by specially designed multilayer XUV mirrors that do not affect the XUV phase front and pulse duration

Coherent XUV Multispectral Diffraction Imaging in the Microscale

The rapid growth of nanotechnology has increased the need for fast nanoscale imaging. X-ray free electron laser (XFEL) facilities currently provide such coherent sources of directional and high-brilliance X-ray radiation. These facilities require large financial investments for development, maintenance, and manpower, and thus, only a few exist worldwide. In this article, we present an automated table-top system for XUV coherent diffraction imaging supporting the capabilities for multispectral microscopy at high repetition rates, based on laser high harmonic generation from gases. This prototype system aims towards the development of an industrial table-top system of ultrafast soft X-ray multi-spectral microscopy imaging for nanostructured materials with enormous potential and a broad range of applications in current nanotechnologies. The coherent XUV radiation is generated in a semi-infinite gas cell via the high harmonic generation of the near-infrared femtosecond laser pulses. The XUV spectral selection is performed by specially designed multilayer XUV mirrors that do not affect the XUV phase front and pulse duration

An Integrated Method for the Vibroacoustic Evaluation of a Carbon Fiber Bouzouki

An integrated method, which combines Electronic Speckle Pattern Interferometry, impulse response measurements, finite element method simulations, and psychoacoustic tests, is proposed to evaluate the vibroacoustic behavior of a carbon fiber bouzouki. Three of the carbon fiber instruments are manufactured, and one is qualified via interferometric experimental measurements with reference to a traditional wooden bouzouki, which was evaluated for its sound and playability by the proposed method. Psychoacoustic tests were used to evaluate the sound and playability of the newly qualified carbon fiber bouzouki, which was further modeled by the finite element method and simulated. The simulation results agreed well with the experimental measurements. Furthermore, finite element simulation results of the qualified carbon fiber bouzouki were demonstrated with reference to the traditional wooden bouzouki experimental results, providing new findings crucial for the optimization of the manufacturing and the vibroacoustic behavior of the carbon fiber instrument. The proposed integrated method can be applied to a variety of carbon fiber stringed musical instruments