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94 results on '"Acef, Ouali"'

2. Frequency tripled 1542 nm telecom laser diode stabilized to iodine hyperfine line in the 10-15 range

Author

Philippe, Charles, Tragat, Rodolphe Le, Holleville, David, Lours, Michel, Minh-Pham, Tuam, Hrabina, Jan, Burck, Frederic Du, Wolf, Peter, and Acef, Ouali

Subjects
Physics - Atomic Physics, Physics - Instrumentation and Detectors, Physics - Optics
Abstract

We report on telecom laser frequency stabilization to narrow iodine hyperfine line in the green range of the optical domain, after a frequency tripling process using two nonlinear PPLN crystals. We have generated up to 300 mW optical power in the green (P3w), from 800 mW of infrared power (Pw). This result corresponds to an optical conversion efficiency eta= P3w/Pw ~ 36 %. To our knowledge, this is the best value ever demonstrated for a CW frequency tripling process. We have used a narrow linewidth iodine hyperfine line (component a1 of the 127I2 R 35 (44-0) line) to stabilize the IR laser yielding to frequency stability of 4.8x10-14 t-1/2 with a minimum of 6x10-15 reached after 50 s of integration time. The whole optical setup is very compact and mostly optically fibered. This approach opens the way for efficient and elegant architecture development for space applications as one of several potential uses., Comment: in 30th European Frequency and Time Forum (EFTF'2016), 4th - 7th April 2016, York, United Kingdom

Published
2016

3. Optical phase locking of two infrared CW lasers separated by 100 THz

Author

Chiodo, Nicola, Du-Burck, Frédéric, Hrabina, Jan, Lours, Michel, Chea, Erick, and Acef, Ouali

Subjects
Physics - Optics
Abstract

We report on phase-locking of two continuous wave infrared laser sources separated by 100 THz emitting around 1029 nm and 1544 nm respectively. Our approach uses three independent harmonic generation processes of the IR laser frequencies in periodically poled MgO: LiNbO3 crystals to generate second and third harmonic of that two IR sources. The beat note between the two independent green radiations generated around 515 nm is used to phase-lock one IR laser to the other, with tunable radio frequency offset. In this way, the whole setup operates as a mini frequency comb (MFC) emitting four intense optical radiations (1544 nm, 1029 nm, 772 nm and 515 nm), with output powers at least 3 orders of magnitude higher than the available power from each mode emitted by femtosecond lasers.

Published
2014
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4. CW frequency doubling of 1029 nm radiation Using single pass bulk and waveguide PPLN crystals

Author

Chiodo, Nicola, Burck, Frédéric Du, Hrabina, Jan, Candela, Yves, Wallerand, Jean-Pierre, and Acef, Ouali

Subjects
Physics - Optics
Abstract

Following various works on second harmonic process using periodically poled Lithium Niobate crystals (PPLN), we report on the performances comparison between commercial bulk and waveguide crystals at 1029 nm. We use a continuous wave (CW) amplified Yb doped single fibre laser delivering up to 500mW in single mode regime. In case of bulk crystal we generate 4 mW using 400 mW IR power. The use of waveguide crystal leads to an increase of the harmonic power up to 33mW with input IR power limited to 200mW. Nevertheless, this impressive efficiency was affected by the long term degradation of the non-linear waveguide crystal.

Published
2013
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5. Lasers for coherent optical satellite links with large dynamics

Author

Chiodo, Nicola, Djerroud, Khelifa, Acef, Ouali, Clairon, Andre, and Wolf, Peter

Subjects
Physics - Optics
Abstract

We present the experimental realization of a laser system for ground to satellite optical Doppler ranging at the atmospheric turbulence limit. Such a system needs to display good frequency stability (a few parts in 10^{-14}) whilst allowing large and well controlled frequency sweeps of +/- 12 GHz at rates exceeding 100 MHz/s. Furthermore it needs to be sufficiently compact and robust for transportation to different astronomical observation sites where it is to be interfaced with satellite ranging telescopes. We demonstrate that our system fulfills those requirements and should therefore allow operation of ground to low Earth orbit satellite coherent optical links limited only by atmospheric turbulence.

Published
2013
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6. Experimental study of radiative shocks at PALS facility

Author

Stehlé, Chantal, González, Matthias, Kozlova, Michaela, Rus, Bedrich, Mocek, Tomas, Acef, Ouali, Colombier, Jean-Philippe, Lanz, Thierry, Champion, Norbert, Jakubczak, Krzysztof, Polan, Jiri, Barroso, Patrice, Bauduin, Daniel, Audit, Edouard, Dostal, Jan, and Stupka, Michal

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics
Abstract

We report on the investigation of strong radiative shocks generated with the high energy, sub-nanosecond iodine laser at PALS. These shock waves are characterized by a developed radiative precursor and their dynamics is analyzed over long time scales (~50 ns), approaching a quasi-stationary limit. We present the first preliminary results on the rear side XUV spectroscopy. These studies are relevant to the understanding of the spectroscopic signatures of accretion shocks in Classical T Tauri Stars., Comment: 21 pages, 1 table, 7 figures

Published
2010
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7. A coherent optical link through the turbulent atmosphere

Author

Djerroud, Khelifa, Acef, Ouali, Clairon, Andre, Lemonde, Pierre, Man, Catherine N., Samain, Etienne, and Wolf, Peter

Subjects
Physics - Optics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We describe the realization of a 5 km free space coherent optical link through the turbulent atmosphere between a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results for applications, with particular emphasis on optical Doppler ranging to satellites and long distance frequency transfer., Comment: version 2, modified following comments from colleagues and reviewers

Published
2009
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9. Absolute Frequency Measurement of the 1S-3S Transition in Hydrogen

Author

Hagel, Gaëtan, Battesti, Rémy, Schwob, Catherine, Nez, Francois, Julien, Lucile, Biraben, Francois, Acef, Ouali, Zondy, Jean-Jacques, Clairon, André, Beig, R., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Lipowsky, R., editor, Löhneysen, H. v., editor, Ojima, I., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Karshenboim, Savely G., editor, Bassani, F., editor, Pavone, F.S., editor, Inguscio, M., editor, and Hänsch, T.W., editor

Published
2001
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11. New probing techniques of radiative shocks

Author

Stehlé, Chantal, Kozlová, Michaela, Larour, Jean, Nejdl, Jaroslav, Champion, Norbert, Barroso, Patrice, Suzuki-Vidal, Francisco, Acef, Ouali, Delattre, Pierre-Alexandre, Dostál, Jan, Krus, Miroslav, and Chièze, Jean-Pierre

Published
2012
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12. Towards the development of a compact-monolithic optical assembly for Telecom laser frequency stabilization for LISA ground tests and other applications

Author

Acef, Ouali, primary, Mehlman, Alexis, additional, Holleville, David, additional, Lours, Michel, additional, Le Targat, Rodolphe, additional, Wolf, Peter, additional, Lehec, Henri, additional, Bize, Sébastien, additional, Acef, Ouali, additional, Boutin, Aurelien, additional, LePage, Karine, additional, Fulop, Ludovic, additional, Oudda, Laure, additional, and Lévèque, Thomas, additional

Published
2021
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17. 1.5 µm - optical frequency standard iodine stabilized in the 10-15 range for space-mission applications

Author

Philippe, Charles, Le Targat, Rodolphe, Holleville, David, Lours, Michel, Wolf, Peter, Lévèque, Thomas, Le Goff, Roland, Acef, Ouali, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), and SODERN

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience; We report on the development of an optical frequency standard (OFS) operating in the C-Telecom band, stabilized in the 10-15 range, using Doppler-free spectroscopy of iodine hyperfine line around 514 nm. To bridge the frequency gap between infrared (IR) and green domains, we operate an efficient frequency tripling process of the IR laser diode, with two cascaded nonlinear Lithium Niobate crystals. We have implemented an original optical arrangement which allows a high efficiency optical power conversion (P  P), yielding to 300 mW at 514 nm. The generated green optical power is 20 times higher than the optical level required for the frequency stabilization purpose. We have demonstrated a residual frequency instability of 4.8 x 10-14 τ-1/2 with a minimum value of 6 x 10-15 conferred to a butterfly laser diode emitting at 1542 nm. A novel demonstrator-fully fibered iodine stabilized laser system is under development to match several space missions requirements

Published
2017

19. Experimental study of counter propagating radiative shocks

Author

Singh, Raj Laxmi, Stehlé, Chantal, Suzuki-Vidal, Francisco, Kozlová, Michaela, Larour, Jean, Chaulagain, Uddhab, Clayson, Thomas, Nejdl, Jaroslav, Krus, Miroslav, Dostál, Jan, Dudzak, R., Barroso, Patrice, Acef, Ouali, Cotelo, M., Rodriguez, R., Gil, J. M., Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

International audience; S 04 Atelier général PNPS Radiative shocks are present at different stages of stellar evolution, for instance in the stellar infancy when matter is accreted from the stellar disk to the photosphere of the young star and is also ejected in the form of stellar jets, up to the final stages as supernovae and the interaction of their remnants with the interstellar medium. Such shocks are strongly influenced by the radiation through its coupling with hydrodynamics. Thus their topology and dynamics are quite complex. Generating such hypersonic shocks in the laboratory, with controlled conditions, is thus an adequate tool to study the influence of radiation and to compare them with numerical simulations. So far, such laboratory astrophysics studies are performed on large-scale laser facilities, addressing hydrodynamic radiative shocks, in Xenon with very high velocity (50 - 150 km/s) and moderate pressure (0.1 - 1 bar). These experiments advance the understanding of the effect of radiation on the different shock components (radiative precursors, shock collapse, walls heating etc.). In continuation of these laboratory experiments, we recently performed experiments at PALS laser facility to study a fairly new topic focusing on the interaction of two counter propagating shocks. The objective is to understand the influence of one radiative precursor onto another, to achieve higher temperature in the compressed medium. In the astrophysical context, aforementioned studies are relevant for instance, collision of supernovae remnants and more indirectly the interaction of supernovae remnants with dense molecular clouds and the impact of accretion flows on a stellar atmosphere. The experiments have been able to launch shocks with different shock speeds (~30-55 km/s and 10-25 km/s), in varying gases (Ar, Xe) and pressures (~0.1-0.3 bar). Optical interferometry allowed us to estimate several physical parameters such as shock speed and electron density in the precursor, XUV spectroscopy allowed to give information about the shock temperature. We will present some preliminary results together with numerical simulations.

Published
2016

20. Experimental study of the collision of two laser-driven radiative shocks at the PALS laser

Author

Singh, Raj Laxmi, Stehlé, Chantal, Suzuki-Vidal, Francisco, Larour, Jean, Chaulagain, Uddhab, Clayson, Thomas, Nejdl, Jaroslav, Krus, Miroslav, Kozlová, Michaela, Dostál, Jan, Acef, Ouali, Barroso, Patrice, Cotelo, M., Velarde, P., Rodriguez Perez, R., Gil, J. M., Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph]
Abstract

International audience; Radiative shocks are present in various astrophysical contexts and can be proxy of fundamental accretion processes, for instance X-ray signatures from accretion shocks can be related to the rate of mass accretion onto forming stars. Thus the study of hypersonic shocks (Mach number >> 1) in the laboratory Under controlled conditions is of primary interest in order to study the influence of radiation, and to compare with numerical simulations. In the past decade, several experiments on radiative shocks have been performed on various large-scale laser facilities, demonstrating the formation of shocks in Xenon with velocities ~50 - 150 km/s in background gas pressures ~0.1 - 1 bar (Bouquet et al. 2004, Gonzalez et. al. 2006, Reighard et. al. 2007, Stehlé et al. 2010, Doss et al. 2011, Drake et al. 2011, Dizière et al. 2012, Stehlé et al. 2012, Chaulagain et al. 2015). Many advances have been achieved in understanding the effect of radiation on the different shock components (radiative precursor, shock collapse, wall heating etc.), however, these studies were focused solely on the case of a single radiative shock. We have recently conducted experiments at the PALS laser facility, looking at the collision between two counter streaming radiative shocks. Besides providing a new experimental platform, these experiments aimed at studying how one radiative precursor is influenced by the presence of another. The experiments launched shocks with different shock speeds (~30-55 km/s and 10-25 km/s), at a range of different pressures (~0.1-0.3 bar), and with different gases (Ar, Xe). Optical interferometry allowed us to estimate several physical parameters such as shock speed and electron density in the precursor, whereas the use of time and spatially resolved optical spectroscopy led to a number of spectral signatures. We will present preliminary results together with numerical simulations.

Published
2016

21. La mesure du temps aujourd'hui

Author

de Clercq, Emeric, Zanon-Willette, Thomas, Acef, Ouali, Henry, Florence, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Références micro-ondes et échelles de temps, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), and Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]
Abstract

National audience; This is a short review of the state of the art of the measurement of time in the metrology laboratories. After a brief recall of the successive definitions of the second, now defined on an atomic transition of the caesium atom, we present today atomic clocks: the Cs beam clock, still the workhorse of time metrology, and the Cs fountain clock based on cold atoms, which revolutionized the field. A promising new generation based on higher frequency transitions is coming, the optical clocks, the strontium clock is given as an example. Afterwards a few methods of clock comparison and clock signal dissemination are addressed.

Published
2016

22. A COMPACT FREQUENCY STABILIZED TELECOM LASER DIODE FOR SPACE APPLICATIONS

Author

Philippe, Charles, Holleville, David, Le Targat, Rodolphe, Wolf, Peter, Lévèque, Thomas, Le Goff, Roland, Martaud, Emmanuelle, Acef, Ouali, Henry, Florence, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), and SODERN

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience; We report on a Telecom laser diode (LD) frequency stabilization to a narrow iodine hyperfine line in the green range, after frequency tripling process using fibered nonlinear waveguide PPLN crystals. We have generated up to 300 mW optical power in the green range (~514 nm) from 800 mW of infrared power (~1542 nm), corresponding to a nonlinear conversion efficiency  = P3/P ~ 36%. Less than 10 mW of the generated green power are used for Doppler-free spectroscopy of 127I2 molecular iodine, and therefore- for the frequency stabilization purpose. The frequency tripling optical setup is very compact (< 5 l), fully fibered, and could operate over the full C-band of the Telecom range (1530 nm 1565 nm). Several thousands of hyperfine iodine lines may thus be interrogated in the 510 nm 521 nm range. We build up an optical bench used at first in free space configuration, using the well-known modulation transfer spectroscopy technique (MTS), in order to test the potential of this new frequency standard based on the couple 1.5 µm laser / iodine molecule. We have already demonstrated a preliminary frequency stability of 4.8 x 10-14  -1/2 with a minimum value of 6 x 10-15 reached after 50 s of integration time, conferred to a laser diode operating at 1542.1 nm. We focus now our efforts to expand the frequency stability to a longer integration time in order to meet requirements of many space experiments, such earth gravity missions, inters satellites links or space to ground communications. Furthermore, we investigate the potential of a new approach based on frequency modulation technique (FM), associated to a 3rd harmonic detection of iodine lines to increase the compactness of the optical setup.

Published
2016

23. Molecular laser stabilization for LISA

Author

Acef, Ouali, primary, Jeannin, Olivier, primary, Prat, Pierre, primary, Plagnol, Eric, primary, Berthon, Jacques, primary, Turazza, Oscar, primary, Halloin, Hubert, primary, Argence, Berengere, primary, de Vismes, Eden, primary, Brillet, Alain, primary, and Mondin, Linda, primary

Published
2017
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24. Iodine Absorption Cells Purity Testing

Author

Hrabina, Jan, primary, Zucco, Massimo, additional, Philippe, Charles, additional, Pham, Tuan, additional, Holá, Miroslava, additional, Acef, Ouali, additional, Lazar, Josef, additional, and Číp, Ondřej, additional

Published
2017
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25. IODINE-FREQUENCY STABILIZED TELECOM LASER DIODE AT 515 NM

Author

Philippe, Charles, Du Burck, Frédéric, Acef, Ouali, Minh-Pham, Tuam, Hrabina, Jan, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Métrologie des fréquences optiques, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Lasers (LPL), Université Paris 13 (UP13)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Institute of Scientific Instruments of the ASCR (ISI), and Henry, Florence

Subjects
[PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience

Published
2015

26. Iodine absorption cells quality evaluation methods

Author

Hrabina, Jan, additional, Zucco, Massimo, additional, Holá, Miroslava, additional, Šarbort, Martin, additional, Acef, Ouali, additional, Du-Burck, Frédéric, additional, Lazar, Josef, additional, and Číp, Ondřej, additional

Published
2016
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27. MOLECULAR LASER STABILIZATION FOR LISA.

Author

Halloin, Hubert, Acef, Ouali, Argence, Bérengère, Jeannin, Olivier, Prat, Pierre, Turazza, Oscar, de Vismes, Eden, Auger, Gérard, Plagnol, Eric, Brillet, Alain, Mondin, Linda, and Berthon, Jacques

Published
2017
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29. Radiative shocks at PALS: latest results and future prospects

Author

Stehlé, Chantal, Chaulagain, Uddhab, De Sà, Lionel, Ibgui, Laurent, Ciardi, Andrea, Larour, Jean, Kozlová, Michaela, Nejdl, Jaroslav, Suzuki-Vidal, Francisco, Barroso, Patrice, Velarde, P., Rodriguez Perez, R., Gil, J. M., Espinosa, G., Acef, Ouali, Laboratoire de Physique des Plasmas (LPP), Université Paris-Saclay-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École polytechnique (X)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institute of Physics [Prague], Czech Academy of Sciences [Prague] (CAS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Instituto de Fusión Nuclear, Universidad Politécnica de Madrid (UPM), University of Coimbra, Dept Physic, University of Coimbra [Portugal] (UC), and Universidad Nacional Autónoma de México (UNAM)

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph]
Abstract

International audience; affiche P53 Being able to produce and diagnose radiative shocks under controlled laboratory conditions is a key aspect to understand their role in astrophysical processes such as accretion in stellar formation. The ongoing study of radiative shocks using high-power lasers has significantly advanced our understanding on the physics of these complex flows. In particular, experiments at the Prague Asterix Laser System (PALS) have demonstrated the formation of radiative shocks in Xenon with a characteristic velocity of 50-60 km/s. Latest results on the generation on radiative shocks at PALS demonstrate the feasibility of fielding novel probing techniques such as time-resolved imaging using an X-ray laser at 21.2 nm, allowing to probe simultaneously the high-density shock-front together with the lower-density radiative precursor in front of the shock. These results will be compared with 2-D radiative-hydrodynamic simulations using the code ARWEN. Future experimental campaigns will focus on spectroscopic measurements of the different shock regions together with new experimental configurations such as the interaction of counter-streaming radiative shocks. These prospects will be presented and discussed from both experimental and simulation point of view. This work is supported by french ANR STARSHOCK (grant 08-BLAN-0263-07), Programme National de Physique Stellaire" (PNPS) of CNRS/INSU, France, Observatoire de Paris and labex Plas@Par ( ANR-11-IDEX-0004-02 )

Published
2014

30. Structure of a laser-driven radiative shock

Author

Chaulagain, Uddhab, Stehle, Chantal, Larour, Jean, Kozlová, Michaela, Suzuki-Vidal, Francisco, Barroso, Patrice, Cotelo, M., Velarde, P., Rodriguez, R., Gil, J. M., Ciardi, Andrea, Acef, Ouali, Nejdl, Jaroslav, de Sá, Lionel, Singh, Raj Laxmi, Ibgui, Laurent, Champion, Norbert, Laboratoire de Physique des Plasmas (LPP), Université Paris-Saclay-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École polytechnique (X)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Dynamique des milieux interstellaires et plasmas stellaires, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Molécules dans l'Univers, Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institute of Physics of ASCR, Na Slovance 2, 182 21 Prague 8, Czech Republic, Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, (CCM), Imperial College London, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Instituto de Fusión Nuclear, Universidad Politécnica de Madrid, Departamento de Fisica, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain, Systèmes de Référence Temps Espace (SYRTE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and Henry, Florence

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics::Galaxy Astrophysics
Abstract

International audience; Radiative shocks are ubiquitous in stellar environments and are characterized by high temperature plasma emitting a considerable fraction of their energy as radiation. The physical structure of these shocks is complex and experimental benchmarks are needed to provide a deeper understanding of the physics at play. In addition, experiments provide unique data for testing radiation hydrodynamics codes which, in turn, are used to model astrophysical phenomena. Radiative shocks have been studied on various high-energy laser facilities for more than a decade, highlighting the importance of radiation on the plasma dynamics. Particularly the PALS facility has focused in producing radiative shocks with typical velocities of ∼50–60 km s−1 in xenon at a fraction of a bar. In addition PALS has the unique capability of producing the most powerful XUV laser available today (21.2 nm (58.4 eV), 0.15 ns), opening the door to new diagnostics of dense plasmas. Here we present results of XUV imaging of the precursor and post-shock structure of radiative shocks generated in xenon in this facility, together with time-and-space resolved measurements of the XUV self-emission using fast diode. The experimental results are interpreted with the help of 2D ARWEN radiative hydrodynamics simulations and state-of-the art monochromatic opacities.

Published
2014

31. Iodine absorption cells quality measurements

Author

Hrabina, Jan, primary, Sarbort, Martin, additional, Hola, Miroslava, additional, Cip, Ondrej, additional, Lazar, Josef, additional, Zucco, Massimo, additional, Acef, Ouali, additional, and Du-Burck, Frederic, additional

Published
2016
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32. New insights on the physics of radiative shocks

Author

Chaulagain, Uddhab, Stehlé, Chantal, Larour, Jean, Koszlova, Michaela, Suzuki-Vidal, Francisco, Acef, Ouali, Dostál, Jan, Krus, Miroslav, Barroso, Patrice, Reix, Florent, Jagourel, Pascal, Ciardi, Andrea, Référent-HAL, LPP, Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Astrophysics::High Energy Astrophysical Phenomena, [PHYS.PHYS.PHYS-PLASM-PH] Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Astrophysics::Galaxy Astrophysics
Abstract

International audience; Shock waves play a significant role in several astrophysical phenomena. Among them, Radiative shocks are strong shocks, in which the shock front is heated to very high temperature and thus emit an important radiation flux. The interesting feature of the radiative shocks is that their structure is strongly influenced by the coupling between hydrodynamics and radiation. They occur in astrophysical system in the different stages of the stellar evolution, for instance during the accretion processes in the stellar infancy, and are studied in high-energy density laboratory experiments using kJ class lasers. Such laser facilities enable to drive shocks in which the radiative flux may prevail hydrodynamic mechanism of energy transfer. Typical irradiances of 10**14 W.cm-2, allows to produce radiative shocks in high atomic gas medium at low pressure, where the important radiation generated by the shocked plasma leads to the formation of an ionizing wave, also call radiative precursor, in the cold upstream xenon. I will present new experimental results realized on the PALS laser installation aiming at improving the present knowledge of these complex flows. The greatest attention is paid to the application of to new diagnostics, namely, the instantaneous imaging of the whole shock structure using an auxiliary laser at 21.2 nm and a time-and-space resolved plasma self-emission using fast diodes. This work is supported by french ANR STARSHOCK (grant 08-BLAN-0263-07) and by Laserlab-Europe II programme.

Published
2013

34. Spectral properties of iodine cells for laser standards

Author

Hrabina, Jan, additional, Šarbort, Martin, additional, Acef, Ouali, additional, Du Burck, Frédéric, additional, Chiodo, Nicola, additional, Chea, Erick, additional, Holá, Miroslava, additional, Číp, Ondřej, additional, and Lazar, Josef, additional

Published
2014
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40. Experimental study of radiative shocks at PALS facility

Author

Stehlé, Chantal, primary, González, Matthias, additional, Kozlova, Michaela, additional, Rus, Bedrich, additional, Mocek, Tomas, additional, Acef, Ouali, additional, Colombier, Jean Philippe, additional, Lanz, Thierry, additional, Champion, Norbert, additional, Jakubczak, Krzysztof, additional, Polan, Jiri, additional, Barroso, Patrice, additional, Bauduin, Daniel, additional, Audit, Edouard, additional, Dostal, Jan, additional, and Stupka, Michal, additional

Published
2010
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44. Astrophysical radiative shocks: From modeling to laboratory experiments

Author

GONZÁLEZ, MATTHIAS, primary, STEHLÉ, CHANTAL, additional, AUDIT, EDOUARD, additional, BUSQUET, MICHEL, additional, RUS, BEDRICH, additional, THAIS, FRÉDÉRIC, additional, ACEF, OUALI, additional, BARROSO, PATRICE, additional, BAR-SHALOM, ABRAHAM, additional, BAUDUIN, DANIEL, additional, KOZLOVÀ, MICHAELA, additional, LERY, THIBAUT, additional, MADOURI, ALI, additional, MOCEK, TOMAS, additional, and POLAN, JIRI, additional

Published
2006
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50. Metrology of hydrogen atom: Determination of the Rydberg constant and Lamb shifts.

Author

Hagel, Gae´tan, Schwob, Catherine, Jozefowski, Leszek, de Beauvoir, Be´atrice, Hilico, Laurent, Acef, Ouali, Nez, Franc¸ois, Julien, Lucile, Clairon, Andre´, and Biraben, Franc¸ois

Subjects
HYDROGEN, MEASUREMENT
Abstract

We present the optical frequency measurements of the 2S-8S/D and 2S-12D twophoton transitions in hydrogen and deuterium. From an analysis taking into account these results and the very accurate measurements of the 1S-2S transition, we show that the optical frequency measurements have superseded the microwave determination of the 2S Lamb shift and we deduce optimized values for the Rydberg constant and for the 1S and 2S Lamb shifts. We report also the recent developpement of our 1S-3S experiment. [ABSTRACT FROM AUTHOR]

Published
2001

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