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High-repetition-rate (${\geqslant}$ kHz) targets and optics from liquid microjets for high-intensity laser–plasma interactions
- Part of
- K. M. George, J. T. Morrison, S. Feister, G. K. Ngirmang, J. R. Smith, A. J. Klim, J. Snyder, D. Austin, W. Erbsen, K. D. Frische, J. Nees, C. Orban, E. A. Chowdhury, W. M. Roquemore
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- Journal:
- High Power Laser Science and Engineering / Volume 7 / 2019
- Published online by Cambridge University Press:
- 15 August 2019, e50
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- Article
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High-intensity laser–plasma interactions produce a wide array of energetic particles and beams with promising applications. Unfortunately, the high repetition rate and high average power requirements for many applications are not satisfied by the lasers, optics, targets, and diagnostics currently employed. Here, we aim to address the need for high-repetition-rate targets and optics through the use of liquids. A novel nozzle assembly is used to generate high-velocity, laminar-flowing liquid microjets which are compatible with a low-vacuum environment, generate little to no debris, and exhibit precise positional and dimensional tolerances. Jets, droplets, submicron-thick sheets, and other exotic configurations are characterized with pump–probe shadowgraphy to evaluate their use as targets. To demonstrate a high-repetition-rate, consumable, liquid optical element, we present a plasma mirror created by a submicron-thick liquid sheet. This plasma mirror provides etalon-like anti-reflection properties in the low field of 0.1% and high reflectivity as a plasma, 69%, at a repetition rate of 1 kHz. Practical considerations of fluid compatibility, in-vacuum operation, and estimates of maximum repetition rate are addressed. The targets and optics presented here demonstrate a potential technique for enabling the operation of laser–plasma interactions at high repetition rates.
8 - Combustion
- M. Samimy, Ohio State University, K. S. Breuer, Brown University, Rhode Island, L. G. Leal, University of California, Santa Barbara, P. H. Steen, Cornell University, New York
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- Book:
- A Gallery of Fluid Motion
- Published online:
- 25 January 2010
- Print publication:
- 12 January 2004, pp 81-87
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Summary
Interaction of 2D wake and jet plume
Burner setup. A propane-air turbulent premixed flame is stabilized on a 30 mm Bunsen-type burner by an annular pilot. The equivalence ratio is 0.68. The flame height is about 85 mm. The mean velocity of the unburned mixture is 2.36 m/sec. Turbulence is given to the mixture by a perforated plate. The turbulence rms fluctuations at the burner exit is 0.15 m/sec. The Taylor and the Kolmogorov microscales are 1.81 and 0.22 mm, respectively, and the Reynolds number based on the Taylor microscale is 17.4.
Photographic setup. This schlieren photograph was taken by a Canon-F1 camera with a 300 mm telephoto lens of f=5.6. Two 200 mm schlieren mirrors with the focal length of 2000 mm were used for the Z-light path arrangement. The vertical knife edge is mounted at the focal point of one mirror. The light source was a xenon stroboscope with a condenser lens and a pinhole. The maximum light power is 8 J (170 1x-sec). The flash duration time is typically 15 μsec. The flash timing was synchronized with the camera shutter. The film used was the Neopan SS (ASA 100) and was developed by Fujidol.
Interpretation. With a moderate or weak turbulence of the unburned mixture, the instantaneous turbulent premixed flame zone consists of a continuous wrinkled laminar flame front. The wrinkle size seems to be irrelevant to the turbulence scale. Along the unburned mixture flow, the amplitude of wrinkles increases from bottom to top. We think that the hydrodynamic instability plays an important role in the flame wrinkling.
1 - Jets and mixing layers
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- By M. M. Koochesfahani, P. E. Dimotakis, M. Gharib, P. Derango, E. Villermaux, H. Rehab, E. J. Hopfinger, D. E. Parekh, W. C. Reynolds, M. G. Mungal, T. Loiseleux, J.-M. Chomaz, T. F. Fric, A. Roshko, S. P. Gogineni, M. M. Whitaker, L. P. Goss, W. M. Roquemore, S. Wernz, H. F. Fasel, S. Gogineni, C. Shih, A. Krothapalli
- M. Samimy, Ohio State University, K. S. Breuer, Brown University, Rhode Island, L. G. Leal, University of California, Santa Barbara, P. H. Steen, Cornell University, New York
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- Book:
- A Gallery of Fluid Motion
- Published online:
- 25 January 2010
- Print publication:
- 12 January 2004, pp 1-10
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Summary
Laser-induced fluorescence (LIF) diagnostics and highspeed, real-time digital image acquisition techniques are combined to map the composition field in a water mixing layer. A fluorescent dye, which is premixed with the lowspeed freestream fluid and dilutes by mixing with the highspeed fluid, is used to monitor the relative concentration of high-speed to low-speed fluid in the layer.
The three digital LIF pictures shown here were obtained by imaging the laser-induced fluorescence originating from a collimated argon ion laser beam, extending across the transverse dimension of the shear layer, onto a 512–element linear photodiode array. Each picture represents 384 contiguous scans, each at 400 points across the layer, for a total of 153 600 point measurements of concentration. The vertical axis maps onto 40 mm of the transverse coordinate of the shear layer, and the horizontal axis is time increasing from right to left for a total flow real time of 307 msec. The pseudocolor assignment is linear in the mixture fraction (ξ) and is arranged as follows: red-unmixed fluid from the low-speed stream (ξ=0); blue-unmixed fluid from the high-speed stream (ξ=1); and the rest of the spectrum corresponds to intermediate compositions.
Figures 1 and 2, a single vortex and pairing vortices, respectively, show the composition field before the mixing transition. The Reynolds number based on the local visual thickness of the layer and the velocity difference across the layer is Re=1750 with U2/U1=0.46 and U1=13 cm/sec. Note the large excess of high-speed stream fluid in the cores of the structures.
9 - Instability
- M. Samimy, Ohio State University, K. S. Breuer, Brown University, Rhode Island, L. G. Leal, University of California, Santa Barbara, P. H. Steen, Cornell University, New York
-
- Book:
- A Gallery of Fluid Motion
- Published online:
- 25 January 2010
- Print publication:
- 12 January 2004, pp 88-96
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- Export citation
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Summary
These photographs show the vortex structures that result from the interaction of vortices that are shed from a 2D bluff body and those shed from a slot jet. The slot jet (3 mm x 150 mm) is located in the center of the rectangular face of the bluff body (15 mm x 240 mm). The photographs are positioned so that the velocity of the slot jet increases from left to right. In the first three photographs starting from the left, the velocity of the jet is smaller than the velocity of the flow around the bluff-body. In the fourth picture, the shear layer velocities of the jet and bluff body are nearly equal and a wavy structure is observed. At higher velocities, as noted by the 5th and 6th photographs, the vortex structures from the jet dominate the flow field. This is noted by the change in the direction of rotation of the vortices.
The flow is visualized by the Reactive Mie Scattering (RMS) technique in which Mie scattering is observed from micron size TiO2 particles that are formed by the spontaneous reaction of TiCl4 vapor in the slot jet air with the water in the annulus air. The technique has been shown to be more effective than smoke because it highlights the streamlines where molecular mixing is taking place. The photographs were taken in the 15ns firing of a YAG laser used to form the light sheet.
For an averaged air jet velocity of 18.5 cm/s, the alternating vortex structures shed from the 2D bluff body are evident after about 5 bluff-body widths downstream. As the jet velocity increases, the wake from the bluff body is significantly modified.