Stage 1 - P1 2017
The project implementation schedule
Phase no. 11
Responsible: Dr. T. DASCALU
Title: "Ultraintense Airy-Bessel laser beams for high power THz generation"
Abstract: Broadband and high power THz radiation sources are divided into two categories: laser based sources and particle-accelerator based sources. Regardless the generation methods, (laser beam filamentation or optical rectification), the intensity profile of the laser beam used to generate high energy THz pulses is Gaussian type. Maximum THz pulse energy achieved by focusing a Gaussian type laser beam is limited by the multifilament phenomenon and by the plasma distribution. Alternative ways to increase THz pulse energy seems to be given by using other intensity laser beam profiles like Airy and Bessel type.
In this study ray tracing simulations were done in order to achieve Airy and Bessel type laser beams. Also a theoretical model for THz radiation generation through optical rectification in lithium niobate nonlinear crystal was developed. Experimentally results regarding Bessel type laser beam were consistent with theoretical modeling.
Phase no. 12
Responsible: Dr. C. DIPLASU
Title: "Developing, testing and calibrating diagnostic systems for particle acceleration experiments in laser-plasma interaction"
Abstract: The interaction of high power laser (PW) with any kind of target creates extreme conditions of matter existence, ultra-dens plasma, in which relativistic waves develop. The main result is the acceleration of electrons and then protons or ions, to energies comparable to those obtained in classical accelerators, but on much smaller distances (millimetre order).
In this context, specific diagnostic methods of accelerated particle beams (electrons, protons) in laser-plasma interaction have been implemented (constructed and tested). In the practical accomplishment of the experimental diagnostic devices, the configuration of the PW laser system and the CETAL interaction chamber was taken into account.
Phase no. 13
Responsible: Dr. G. DINESCU
Title: "Diagnostics of plasmas used for mentenance of optical components and assessment of the morphological and compositional modifications induced on intentionally contaminated test surfaces"
Abstract: In order to highlight the effects produced by radiofrequency plasmas generated at low pressure on contaminated surfaces, thin films of a-C:H were deposited on silicon as model for the contaminant layers. The surfaces covered with a-C:H were exposed to the radiofrequency plasmas generated in argon. The experiments focused on testing the cleaning efficiency of two different plasma sources: a plasma source with central powered electrode and a plasma source with outer annular electrodes.
Ellipsometry, profilometry and AFM measurements were performed on surfaces covered with a-C:H before and after their exposure to plasma. The measurements proved that the surfaces are getting cleaned upon the plasma exposure, the roughness decreased, and the reflectivity increased. We obtained cleaning rate between 5.3*10-1 nm/min and 1.46 nm/min in case of using plasma source with central powered electrode and between 0 and 2.16 nm/min for plasma source with outer circular electrodes.
Phase no. 14
Responsible: Dr. M. GANCIU
Title: "Study and characterization of the electromagnetic pulses generated by ultrahigh intensity lasers; identification of new screening methods and new applications. "
Abstract: The interaction between very high-power lasers and solid targets can be used to generate and accelerate charged particles. Typical for such interaction, is the generation of electromagnetic pulses (EMPs), within a very broad frequency range, from tens of MHz up to tens of GHz. The mechanisms responsible for creating such gigantic EMPs are not very well known or explained yet, as they are associated with ultra-intense electronic currents within very short time periods (ps-ns), or to the electrical charging of the targets and of their holders, for voltages of tens to hundreds of kV, corresponding to the expansion of ultra-relativistic electrons at temperatures corresponding to energies in the MeV – tens of MeV range. This phase of research reports on the realization and implementation of an experimental model for a generator of electromagnetic pulses (EMPs) used for testing and calibration, for typical rise time values of hundreds of picoseconds and voltage amplitudes in the kV range. The generator was mounted inside the interaction chamber, in place of the solid targets. Adapted antennas have been designed and tested, aimed at detecting the EMPs. Measurements were performed with respect to the spectral composition of the generated pulses, as our main concern lies in characterizing a critical issue, which is typical for very high power lasers, related to the propagation of electromagnetic pulses through the beam line. We are also interested in investigating if the spectrum of EMPs contains components that are higher than the critical frequency of the laser beam line. Solutions were identified to minimize the effect of EMPs.