Dealing with LMJ final optics damage: post-processing and models

Lacombe, Chloé; Hallo, Guillaume; Sozet, Martin; Fourtillan, Pauline; Díaz, Roberto Ruiz; Vermersch, Sébastien; Néauport, Jérôme

doi:10.1117/12.2571074

Cited by 4 publications

(8 citation statements)

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“…To extend the operation lifetime of these optics, two methods have been developed to stop the damage growth. (i) The socalled local laser blocker that consists in locally reducing the beam fluence under the growth threshold [3], [4]. In order not to impact the total beam energy for the experiments, this technique is limited to about ten beam blockers per optic at the location of the damage sites.…”

Section: Introductionmentioning

confidence: 99%

LMJ 2023 facility status

Denis

Néauport²,

Blanchot³

et al. 2023

High Power Lasers for Fusion Research VII

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The Laser Megajoule facility, developed by the CEA is based on 176 Nd:glass laser beams focused on a micro-target positioned inside a 10-meter diameter spherical chamber. The facility will deliver a total energy of 1.4MJ of UV light at 0.35 µm and a maximum power of 400 TW. A specific pétawatt beam, PETAL, offers a combination of a very high intensity beam, synchronized with the nanosecond beams of the LMJ. This combination allows expanding the LMJ experimental field in the High Energy Density Physics (HEDP) domain.Since September 2021, a major project milestone has been achieved with the commissioning of the half LMJ (88 beams are fully operational with 10 heating bundles of 8 beams and a specific bundle for plasma diagnostics purpose). The installation and the commissioning of new laser bundles and new plasma diagnostics around the target chamber are continuing, simultaneously to the realization of plasma experiments.Another project milestone has been achieved at the end of 2021, with a dedicated laser experiment in the facility to explore the Power-Energy Diagram.

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Section: Introductionmentioning

confidence: 99%

LMJ 2023 facility status

Denis

Néauport²,

Blanchot³

et al. 2023

High Power Lasers for Fusion Research VII

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“…Thus, observation systems have been developed to track laser damage sites without removing fused silica components after each laser shot. NIF, SG-III and LMJ facilities use similar observation systems that are called Final Optics Damage Inspection (FODI) [20,21] for NIF and SG-III, and Chamber Center Diagnostic Module (or MDCC) for LMJ [22]. FODI and MDCC were both designed to image each UV final optics from the center of the experiment chamber after each laser shot.…”

Section: Introductionmentioning

confidence: 99%

“…FODI and MDCC were both designed to image each UV final optics from the center of the experiment chamber after each laser shot. These optics are illuminated through the edge of the component [20,22,21] resulting in dark-field pictures on which damage sites are visible as bright spots.…”

Section: Introductionmentioning

confidence: 99%

“…Monitoring and predicting laser damage growth by processing dark field images of optical components acquired by different diagnostics is a challenge for high energy laser facilities [21,22]. During the last fifteen years, NIF has developed algorithms, such as the so-called Local Area Signal-To-Noise Ratio (LASNR) procedure [23], to detect potential laser damage sites as soon as they initiate on the last optical components.…”

Section: Introductionmentioning

confidence: 99%

“…Machine learning techniques and decision trees were used to automatically spot and track these sites with a small amount of false alarms [24,21] for diameters greater than 50 µm. Detection of laser damage sites at LMJ is also based on the LASNR algorithm [22]. This method allows for a basic non-destructive control of vacuum windows after each shot.…”

Section: Introductionmentioning

confidence: 99%

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Detection and tracking of laser damage sites on fused silica components by digital image correlation

Hallo

Lacombe

Néauport

et al. 2021

Optics and Lasers in Engineering

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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Estimating and monitoring laser-induced damage size on glass windows with a deep-learning-based pipeline

SOLTANE¹,

Hallo

Lacombe

et al. 2022

J. Opt. Soc. Am. A

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Laser-induced damage is a major issue in high power laser facilities such as the Laser MégaJoule (LMJ) and National Ignition Facility (NIF) since they lower the efficiency of optical components and may even require their replacement. This problem occurs mainly in the final stages of the laser beamlines and in particular in the glass windows through which laser beams enter the central vacuum chamber. Monitoring such damage sites in high energy laser facilities is, therefore, of major importance. However, the automatic monitoring of damage sites is challenging due to the small size of damage sites and to the low-resolution images provided by the onsite camera used to monitor their occurrence. A systematic approach based on a deep learning computer vision pipeline is introduced to estimate the dimensions of damage sites of the glass windows of the LMJ facility. The ability of the pipeline to specialize in the estimation of damage sites of a size less than the repair threshold is demonstrated by showing its higher efficiency than classical machine learning approaches in the specific case of damage site images. In addition, its performances on three datasets are evaluated to show both robustness and accuracy.

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Dealing with LMJ final optics damage: post-processing and models

Cited by 4 publications

References 1 publication

LMJ 2023 facility status

LMJ 2023 facility status

Detection and tracking of laser damage sites on fused silica components by digital image correlation

Estimating and monitoring laser-induced damage size on glass windows with a deep-learning-based pipeline

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