Browsing by Subject "laser"
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Item Acceleration Of Protons To Above 6 MeV Using H2O >Snow> Nanowire Targets(2012-11) Pomerantz, I.; Schleifer, E.; Nahum, E.; Eisenmann, S.; Botton, M.; Gordon, D.; Sprangel, P.; Zigler, A.; Pomerantz, I.A scheme is presented for using H2O >snow> nanowire targets for the generation of fast protons. This novel method may relax the requirements for very high laser intensities, thus reducing the size and cost of laser based ion acceleration system.Item Analysis of Flow Additives in Laser-Based Powder Bed Fusion of Polymers: Implications for Flow Behavior, Processing, Temperature Profile, and Part Characteristics(University of Texas at Austin, 2023) Cholewa, S.; Jacksch, A.; Drummer, D.Powder bed fusion of polymers requires the use of flow additives to ensure adequate flowability of the feedstock material. However, information regarding flow additives and their load is limited, as is an understanding of their impact on processing conditions. This study investigates the flow behavior using static and dynamic measurements under process conditions, focusing on the influence of flow additives. Subsequently, processing studies are conducted using thermography to analyze the laser-material interaction. The characteristics of parts produced from Polypropylene and Polyamide 12 systems are also examined. The findings of this research enhance the understanding of the impact of flow additives on the processing conditions of laser-based powder bed fusion of polymers, potentially leading to optimized process parameters and improved part quality and mechanical properties.Item Characterization of deuterium clusters mixed with helium gas for an application in beam-target-fusion experiments(2014-12) Bang, W.; Quevedo, H. J.; Bernstein, A. C.; Dyer, G.; Ihn, Y. S.; Cortez, J.; Aymond, F.; Gaul, E.; Donovan, M. E.; Barbui, M.; Bonasera, A.; Natowitz, J. B.; Albright, B. J.; Fernandez, J. C.; Ditmire, T.; Quevedo, H. J.; Bernstein, A. C.; Dyer, G.; Ihn, Y. S.; Cortez, J.; Aymond, F.; Gaul, E.; Donovan, M. E.; Ditmire, T.We measured the average deuterium cluster size within a mixture of deuterium clusters and helium gas by detecting Rayleigh scattering signals. The average cluster size from the gas mixture was comparable to that from a pure deuterium gas when the total backing pressure and temperature of the gas mixture were the same as those of the pure deuterium gas. According to these measurements, the average size of deuterium clusters depends on the total pressure and not the partial pressure of deuterium in the gas mixture. To characterize the cluster source size further, a Faraday cup was used to measure the average kinetic energy of the ions resulting from Coulomb explosion of deuterium clusters upon irradiation by an intense ultrashort pulse. The deuterium ions indeed acquired a similar amount of energy from the mixture target, corroborating our measurements of the average cluster size. As the addition of helium atoms did not reduce the resulting ion kinetic energies, the reported results confirm the utility of using a known cluster source for beam-target-fusion experiments by introducing a secondary target gas.Item Commissioning of a Metal Vapor Laser for the Illumination of High Speed Motion Pictures(IEEE, 1993-01) Wehrlen, D.J.; Sarin, S.An effort to produce high-speed (20000 frames/s) motion pictures for the purpose of projectile analysis using a pulse-mode copper vapor laser as the sole illumination source was conducted. A single-shaft rotating prism camera was successfully synchronized with a 20-W continuous average power, copper vapor laser. Initial work performed on this task was focused on laser commissioning, which consisted of laser cavity purging, laser tuning, and optical component selection. Additional work reported includes laser bench setup, fiber-optic delivery of laser light, laser/camera synchronization, and film selectionItem DETERMINATION OF INPUT LASER ENERGY FOR MELTING POWDER LAYERS OF VARIOUS THICKNESSES IN HIGH-SPEED PBF-LB/P USING NEARINFRARED LASER AND ABSORBENT(University of Texas at Austin, 2023) Yamauchi, Yuki; Kigure, Takashi; Niino, ToshikiThe rate of production of PBF-LB/P can be increased by increasing the layer thickness. However, this reduces the part resolution in the stacking direction. To obtain both a high rate of production and high part resolution, layer thickness adjustment in accordance with part geometry can be effective. Optimizing the input laser energy with respect to the layer thickness ensures sufficient melting and part strength. According to previous studies, the use of a nearinfrared laser and absorbent can increase penetration depth or depth of fusion. However, the optical properties of the powder bed can vary significantly depending on the layer thickness, and, therefore, the input energy that actually contributes to melting also changes with layer thickness. This study proposes a method for determining the input laser energy for various layer thickness without trial and error by estimating the amount of energy required to melt the powder layer while accounting for the optical properties of the bed.Item Fabrication of Parts Containing Small Features using Stereolithography(1996) Partanen, Jouni P.The StereoLithography (SL) process has benefited from many advances in the last four to five years. These include new resins with reduced shrinkage and curl distortion, enhanced software, and improved scanning techniques. One can produce highly accurate parts for most dimensions within a few mils of the design value as shown in numerous accuracy and benchmarking studies. SLA systems use a laser beam focused to a spot size of 200 -250 ~m. This limits the range of applications where SL can provide accurate models to parts which do not contain very small features i. e. wall thickness values less than about 300 ~m. Industries that manufacture products involving components with small features include electronics and medical. In this presentation we describe an extension of the SL technology to applications involving small features. This capability is achieved by reducing the laser focal spot size in an SLA-250 to 75 ~m. The technological principle behind the spot size reduction is described in the presentation, together with process issues and applications ofthe technology.Item Formation Of Optical Bullets In Laser-Driven Plasma Bubble Accelerators(2010-11) Dong, P.; Reed, S. A.; Yi, S. A.; Kalmykov, S.; Shvets, G.; Matlis, N. H.; McGuffey, C.; Bulanov, S. S.; Chvykov, V.; Kalintchenko, G.; Krushelnick, K.; Maksimchuk, A.; Matsuoka, T.; Thomas, A. G. R.; Yanovsky, V.; Downer, M. C.; Dong, P.; Reed, S. A.; Downer, M. C.Electron density bubbles generated in plasma of density n(e) similar to 10(19)/cm(3) are shown to reshape copropagating probe pulses into optical >bullets.> The bullets, reconstructed by frequency-domain interferometric techniques, are used to visualize bubble formation independently of relativistic electron generation.Item Frequency Domain Tomography Of Evolving Laser-Plasma Accelerator Structures(2009-11) Dong, P.; Reed, S.; Kalmykov, S.; Shvets, G.; Downer, M.; Dong, Peng; Reed, Stephen; Kalmykov, Serguei; Shvets, Gennady; Downer, MikeFrequency Domain Holography (FDH), a technique for visualizing quasistatic objects propagating near the speed of light, has produced >snapshots> of laser wakefields,(1) but they are averaged over structural variations that occur during propagation through the plasma medium. Here we explore via simulations a generalization of FDH --- that we call Frequency Domain Tomography (FDT) --- that can potentially record a time sequence of quasistatic snapshots, like the frames of a movie, of the wake structure as it propagates through the plasma. FDT utilizes a several probe-reference pulse pairs that propagate obliquely to the drive pulse and wakefield, along with tomographic reconstruction algorithms similar to those used in medical CAT scans.Item Frequency-Domain Streak Camera And Tomography For Ultrafast Imaging Of Evolving And Channeled Plasma Accelerator Structures(2010-11) Li, Z. Y.; Zgadzaj, R.; Wang, X. M.; Reed, S.; Dong, P.; Downer, M. C.; Li, Zhengyan; Zgadzaj, Rafal; Wang, Xiaoming; Reed, Stephen; Dong, Peng; Downer, Michael C.We demonstrate a prototype Frequency Domain Streak Camera (FDSC) that can capture the picosecond time evolution of the plasma accelerator structure in a single shot. In our prototype Frequency-Domain Streak Camera, a probe pulse propagates obliquely to a sub-picosecond pump pulse that creates an evolving nonlinear index >bubble> in fused silica glass, supplementing a conventional Frequency Domain Holographic (FDH) probe-reference pair that co-propagates with the >bubble>. Frequency Domain Tomography (FDT) generalizes Frequency-Domain Streak Camera by probing the >bubble> from multiple angles and reconstructing its morphology and evolution using algorithms similar to those used in medical CAT scans. Multiplexing methods (Temporal Multiplexing and Angular Multiplexing) improve data storage and processing capability, demonstrating a compact Frequency Domain Tomography system with a single spectrometer.Item High Intensity Femtosecond Xuv Pulse Interactions With Atomic Clusters(2009-09) Hoffmann, K.; Murphy, B.; Keto, J.; Ditmire, T.; Hoffmann,K.; Murphy, B.; Keto, J.; Ditmire, T.The interactions of large xenon clusters irradiated by intense, femtosecond extreme-ultraviolet pulses at a wavelength of 38 nm have been studied. Using high harmonic generation from a 35 fs near-infrared terawatt laser, clusters have been irradiated by XUV pulses of 10(11) W/cm(2) intensity. Charge states up to Xe(8+) are observed, states well above that produced by single atom illumination, indicating that plasma continuum lowering is important. Furthermore the kinetic energy distribution of the exploding ions is consistent with a quasineutral hydrodynamic expansion, rather than a Coulomb explosion.Item Roughness Parameters for Classification of As-Built and Laser Post-Processed Additive Manufactured Surfaces(University of Texas at Austin, 2019) Richter, B.; Blanke, N.; Werner, C.; Vollertsen, F.; Pfefferkorn, F.E.One of the challenges facing the industrial adoption of additively manufactured parts is the surface roughness on the as-built part. The surface roughness of parts is frequently characterized by metrics specified by international standards organizations. However, these standards list many surface metrics that can make it unclear which to use to best describe the surface. In this work, the ability of the various surface metrics to successfully classify the as-built and post-processed surfaces is studied using linear classification models. Laser polishing via remelting and manual grinding are the post-processing techniques used to smooth the as-built surface. The ability of the linear classifier to successfully categorize the various surfaces is demonstrated, and the various surface metrics are ranked according to the strength of their individual ability to classify the surfaces. This work promotes the method as a potential way to autonomously classify as-built and laser polished surfaces.Item Summary Report Of Working Group 8: Laser Technology For Laser-Plasma Accelerators(2012-06) Gaul, E.; Toth, C.; Gaul, Erhard; Tóth, CsabaLaser Technology has long been the limiting and the enabling step for laser plasma accelerators. The work presented here addressed the current and near future laser technology relevant to particle acceleration as well as laser technology challenges for future accelerator facilities. Many laser facilities are operating or will be operating shortly at high intensity, high peak power, and with good beam parameters.Item Ultrafast Radial Transport In A Micron-Scale Aluminum Plasma Excited At Relativistic Intensity(2004-06) Bowes, B. T.; Downer, M. C.; Langhoff, H.; Wilcox, M.; Hou, B.; Nees, J.; Mourou, G.; Bowes, B. T.; Downer, M. C.; Langhoff, H.; Wilcox, M.; Hou, B.; Nees, J.; Mourou, G.Using femtosecond microscopy, we observe a thermal/ionization front expand radially at similar to10(8)cm/s from a lambda(2)-size spot of an aluminum target excited at >10(18)W/cm(2). Numerical modeling shows transport is predominantly radiative and may be initially nonlocal.