Laser Mégajoule irradiation uniformity for direct drive

Canaud, B.; Fortin, X.; Dague, N.; Bocher, J. L.

doi:10.1063/1.1504102

Cited by 27 publications

(19 citation statements)

References 7 publications

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“…They almost correspond to the optimum parameters for a total number of beams larger than one thousand. The calculations assume that each bundle acts as one láser beam with associated reduced errors given by: api = a (1), which is the extensión of the one developed in references [20,21]. In this equation, the non-uniformity is a combination of the intrinsic non-uniformity <Tg plus a second term which accounts for the beam imperfections 1/2 and scales as 1 / N t g t .…”

Section: Bundlesmentioning

confidence: 99%

“…of the láser intensity over a sphere of radius T-Q (J is the average intensity and the integral covers the whole sphere surface) [17][18][19][20][21][22][23], The intrinsic non-uniformity ao, which is a characteristic of each facility, has been calculated neglecting any láser imperfection as e.g. beam-to-beam power imbalance (api) and pointing error (aPE).…”

Section: Illumination Non-uniformitymentioning

confidence: 99%

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Stochastic homogenization of the laser intensity to improve the irradiation uniformity of capsules directly driven by thousands laser beams

Temporal

Canaud

2011

Eur. Phys. J. D

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Abstract. Illumination uniformity of a spherical capsule directly driven by láser beams has been assessed numerically. Láser facilities characterized by ND = 12, 20, 24, 32, 48 and 60 directions of irradiation with associated a single láser beam or a bundle of NB láser beams have been considered. The láser beam intensity profile is assumed super-Gaussian and the calculations take into account beam imperfections as power imbalance and pointing errors. The optimum láser intensity profile, which minimizes the root-meansquare deviation of the capsule illumination, depends on the valúes of the beam imperfections. Assuming that the NB beams are statistically independents is found that they provide a stochastic homogenization of the láser intensity associated to the whole bundle, reducing the errors associated to the whole bundle by the factor 1/N B , which in turn improves the illumination uniformity of the capsule. Moreover, it is found that the uniformity of the irradiation is almost the same for all facilities and only depends on the total number of láser beams Not = ND X NB •

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Section: Bundlesmentioning

confidence: 99%

Section: Illumination Non-uniformitymentioning

confidence: 99%

Stochastic homogenization of the laser intensity to improve the irradiation uniformity of capsules directly driven by thousands laser beams

Temporal

Canaud

2011

Eur. Phys. J. D

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“…The corresponding beam placement (a three-cone-like bunch distribution with equatorial planar quasi-symmetry) and the optimized beam pattern eliminate odd modes and create dominant modes 6 and 8. Using the same assumptions as in [38], we consider axially symmetric beams with m-super-…”

Section: Target Designs and Focal Shapementioning

confidence: 99%

High-gain direct-drive target design for the Laser Mégajoule

et al. 2004

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In the context of the French Laser-Mégajoule fusion-research programme, a direct-drive target design is developed. It is based on the use of a CH-foam ablator filled with cryogenic deuterium-tritium. One-dimensional optimization leads to a potential gain of 60 with a 1.5 MJ laser. The hydrodynamic stability of the implosion is investigated at the ablation front and the hot-spot surface by means of modelling and two-dimensional simulations. The effect of irradiation non-uniformities on low-mode (time-dependent) implosion asymmetries is studied by two-dimensional hydrodynamics simulations with three-dimensional laser-light raytracing. The effect of beam focal shapes on hot spot low-mode asymmetries is also addressed.

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“…In the LMJ facility, the laser beams are grouped in quads; thus the power imbalance benefits from a statistical factor which reduces it to σ PI = 5% (quad-to-quad). The illumination non-uniformity, evaluated taking into account these beam uncertainties, is usually measured as an average value (σ ) estimated over a large number of calculations [72][73][74][75][76][77] . In these calculations, each of the three parameters (laser power, laser pointing, and target position) varies randomly and follows a Gaussian distribution centred to their nominal values and characterized by the corresponding standard deviation σ PI , σ PE , or σ TP .…”

Section: Illumination Non-uniformitymentioning

confidence: 99%

Irradiation uniformity at the Laser MegaJoule facility in the context of the shock ignition scheme

Temporal

Canaud

Garbett

et al. 2014

High Pow Laser Sci Eng

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The use of the Laser MegaJoule facility within the shock ignition scheme has been considered. In the first part of the study, one-dimensional hydrodynamic calculations were performed for an inertial confinement fusion capsule in the context of the shock ignition scheme providing the energy gain and an estimation of the increase of the peak power due to the reduction of the photon penetration expected during the high-intensity spike pulse. In the second part, we considered a Laser MegaJoule configuration consisting of 176 laser beams that have been grouped providing two different irradiation schemes. In this configuration the maximum available energy and power are 1.3 MJ and 440 TW. Optimization of the laser-capsule parameters that minimize the irradiation non-uniformity during the first few ns of the foot pulse has been performed. The calculations take into account the specific elliptical laser intensity profile provided at the Laser MegaJoule and the expected beam uncertainties. A significant improvement of the illumination uniformity provided by the polar direct drive technique has been demonstrated. Three-dimensional hydrodynamic calculations have been performed in order to analyse the magnitude of the azimuthal component of the irradiation that is neglected in twodimensional hydrodynamic simulations.

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Laser Mégajoule irradiation uniformity for direct drive

Cited by 27 publications

References 7 publications

Stochastic homogenization of the laser intensity to improve the irradiation uniformity of capsules directly driven by thousands laser beams

Stochastic homogenization of the laser intensity to improve the irradiation uniformity of capsules directly driven by thousands laser beams

High-gain direct-drive target design for the Laser Mégajoule

Irradiation uniformity at the Laser MegaJoule facility in the context of the shock ignition scheme

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