Using Silica Aerogel to Characterize Hypervelocity Shrapnel Produced in High Power Laser Experiments

Tobin, Michael T.; Andrew, J.B.; Haupt, David K.; Mann, Karen; Poco, J.F.; Satcher, Joe H.; Curran, D. R.; Tokheim, R. E.; Eder, David C.

doi:10.1016/j.ijimpeng.2003.10.018

Cited by 17 publications

(11 citation statements)

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“…Similarly the laser energy emerging from the beam splitter E meas is given by E meas = P(1-R) 2 T P E foc Where P was the throughput of the beam splitter and the efficiency of the beam collection by the calorimeter. The calorimeter measurement was cross-calibrated with the VULCAN laser energy diagnostic to check linearity, scatter and reproducibility.…”

Section: E Foc = a E Vulcanmentioning

confidence: 99%

“…This is caused by debris forming a coating or shrapnel causing physical damage to surfaces e.g. impact craters or thermally induced cracking [2]. For operational and cost reasons it is desirable to protect focussing optics against debris and more importantly shrapnel with thin debris shields [or "pellicles"] since the focussing optics are large, expensive and have long delivery times.…”

Section: Introductionmentioning

confidence: 99%

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Transmission and laser damage studies of fused silica and PMMA debris shields with picosecond light pulses

et al. 2005

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Progress in building high-energy, short pulse laser systems with peak powers in the 100 to 1000 TW regime and applying them to plasma physics experiments has highlighted the need for debris mitigation solutions compatible with high intensity pulses [1]. Mitigation schemes ideally need to protect focusing optics for a number of laser pulses at reasonable cost without degrading beam quality. In this paper we describe preliminary experiments performed at the VULCAN laser facility to address some of these issues. The short pulse beam was passed through a thin optical shield at intensities up to 4 x 10 12 W/cm 2 . The transmission of the shield was measured as a function of intensity along with the near and far field beam quality. Transmission losses occurred at the highest intensities used and these were related to the start of laser damage of the shield. The morphology of the damage features on the surface and in the bulk material was studied by a combination of white light interferometry as well as optical and scanning electron microscopy.

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Section: E Foc = a E Vulcanmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transmission and laser damage studies of fused silica and PMMA debris shields with picosecond light pulses

et al. 2005

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“…Moreover, ejecta created by HVI may remain in orbit and collide with other man-made space structures [3]. Similarly, the various instruments of the Laser MégaJoule (LMJ) experiment chamber can be hit by a variety of shrapnel and debris originating from the target assembly [4,5].…”

Section: Introductionmentioning

confidence: 99%

Dynamic cratering of graphite: Experimental results and simulations

Seisson

Hebert

Bertron

et al. 2014

International Journal of Impact Engineering

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. b s t r a c tThe cratering process in brittle materials under hypervelocity impact (HVI) is of major relevance for debris shielding in spacecraft or high-power laser applications. Amongst other materials, carbon is of particular interest since it is widely used as elementary component in composite materials. In this paper we study a porous polycrystalline graphite under HVI and laser impact, both leading to strong debris ejection and cratering. First, we report new experimental data for normal impacts at 4100 and 4200 m s À1 of a 500-mm-diameter steel sphere on a thick sample of graphite. In a second step, dynamic loadings have been performed with a high-power nanosecond laser facility. High-resolution X-ray tomographies and observations with a scanning electron microscope have been performed in order to visualize the crater shape and the subsurface cracks. These two post-mortem diagnostics also provide evidence that, in the case of HVI tests, the fragmented steel sphere was buried into the graphite target below the crater surface. The current study aims to propose an interpretation of the results, including projectile trapping. In spite of their efficiency to capture overall trends in crater size and shape, semi-empirical scaling laws do not usually predict these phenomena. Hence, to offer better insight into the processes leading to this observation, the need for a computational damage model is argued. After discussing energy partitioning in order to identify the dominant physical mechanisms occurring in our experiments, we propose a simple damage model for porous and brittle materials. Compaction and fracture phenomena are included in the model. A failure criterion relying on Weibull theory is used to relate material tensile strength to deformation rate and damage. These constitutive relations have been implemented in an Eulerian hydrocode in order to compute numerical simulations and confront them with experiments. In this paper, we propose a simple fitting procedure of the unknown Weibull parameters based on HVI results. Good agreement is found with experimental observations of crater shapes and dimensions, as well as debris velocity. The projectile inclusion below the crater is also reproduced by the model and a mechanism is proposed for the trapping process. At least two sets of Weibull parameters can be used to match the results. Finally, we show that laser experiment simulations may discriminate in favor of one set of parameters.

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“…Debris and shrapnel have been measured in the context of damage to and survival of debris shields in facilities such as NIF [13,22], Omega [23], and Pharos at NRL [13]. The debris also damage the diagnostics thus drastically reducing the signal-to-noise ratio and the ability to extract precise, useable information.…”

Section: Introductionmentioning

confidence: 99%

Advantages of a soft protective layer for good signal-to-noise ratio proton radiographs in high debris environments

Galloudec

Cobble

Nelson

et al. 2011

High Energy Density Physics

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Proton radiography is a very powerful diagnostic but in some high debris environments it may be challenging to get a good signal-to-noise ratio radiograph to gain insights into the electric and magnetic field topology, and thus the basic physics. Such environments are produced for example on z-pinches and also on lasers such as the National Ignition Facility. We demonstrate here the feasibility of clean, very high signal-to-noise ratio proton radiographs in extremely hostile environments.2

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Using Silica Aerogel to Characterize Hypervelocity Shrapnel Produced in High Power Laser Experiments

Cited by 17 publications

References 0 publications

Transmission and laser damage studies of fused silica and PMMA debris shields with picosecond light pulses

Transmission and laser damage studies of fused silica and PMMA debris shields with picosecond light pulses

Dynamic cratering of graphite: Experimental results and simulations

Advantages of a soft protective layer for good signal-to-noise ratio proton radiographs in high debris environments

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