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Antici, P., Albertazzi, B., Audebert, P., Buffechoux, S., Hannachi, F., d'Humieres, E., et al. (2012). Measuring hot electron distributions in intense laser interaction with dense matter. New Journal Of Physics, 14, 063023.
Abstract: Retrieving the characteristics of hot electrons produced in the interaction between solid targets and ultra-intense (I > 10(18) W cm(-2)) laser pulses is essential for achieving progress in our understanding of the interaction physics, which is key for optimizing numerous downstream applications. Until now, various methods have been used, direct or indirect, but no correlation and no assessment of their respective merits were performed. Here we compare results retrieved from four different diagnostics, direct or indirect, as well as local or non-local, i.e. spectrometry of electrons, spectrometry of the protons accelerated by the electrons and optical probing of these beams expanding into vacuum from the targets. We show that measurements obtained locally at the target rear surface are consistent with those far away from the target and that one can use the diagnostics of the co-moving proton beams to retrieve information about electrons.
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Antoniadis, I., Baessler, S., Bertolami, O., Dubbers, D., Meyerovich, A., Nesvizhevsky, V., et al. (2011). Workshop GRANIT-2010, 14-19 February 2010, Les Houches, France. Comptes Rendus Physique, 12(8), 703–706.
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Arnoux, G., Devaux, S., Alves, D., Balboa, I., Balorin, C., Balshaw, N., et al. (2012). A protection system for the JET ITER-like wall based on imaging diagnostics. Review Of Scientific Instruments, 83(10), 10D727.
Abstract: The new JET ITER-like wall (made of beryllium and tungsten) is more fragile than the former carbon fiber composite wall and requires active protection to prevent excessive heat loads on the plasma facing components (PFC). Analog CCD cameras operating in the near infrared wavelength are used to measure surface temperature of the PFCs. Region of interest (ROI) analysis is performed in real time and the maximum temperature measured in each ROI is sent to the vessel thermal map. The protection of the ITER-like wall system started in October 2011 and has already successfully led to a safe landing of the plasma when hot spots were observed on the Be main chamber PFCs. Divertor protection is more of a challenge due to dust deposits that often generate false hot spots. In this contribution we describe the camera, data capture and real time processing systems. We discuss the calibration strategy for the temperature measurements with cross validation with thermal IR cameras and bi-color pyrometers. Most importantly, we demonstrate that a protection system based on CCD cameras can work and show examples of hot spot detections that stop the plasma pulse. The limits of such a design and the associated constraints on the operations are also presented.
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Ayub, M. K., Ali, S., & Mendonca, J. T. (2011). Phonons with orbital angular momentum. Physics Of Plasmas, 18(10).
Abstract: Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma. (C) 2011 American Institute of Physics. [doi:10.1063/1.3655429]
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B. Goncalves, J. S., B. Carvalho, A.P. Rodrigues, M. Correia, A. Batista, J. Vega, M. Ruiz, J.M. (2011). ITER prototype fast plant system controller. Fus. Eng. and Design, 86(6-8 Part 1), 556–560.
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