From Storage Rings to Free Electron Lasers for Hard X-Rays
Explore the source record for details and available documents.
Nuhn, H.↗
SEARCH · Engineering Papers
Results for “HARD LASER”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Evolution of residual stress, free volume, and hardness in the laser shock peened Ti-based metallic glass
Laser shock peening (LSP) with different cycles was performed on the Ti-based bulk metallic glasses (BMGs). The sub-surface residual stress of the LSPed specimens was measured by high-energy X-ray diffraction (HEXRD) and the near-surface residual stress was measured by scanning electron microscope/focused ion beam (SEM/FIB) instrument. The sub-surface residual stress in the LSP impact direction (about-170MPa) is much lower than that perpendicular to the impact direction (about -350 MPa), exhibiting anisotropy. The depth of the compressive stress zone increases from 400 mu m to 500 mu m with increasing LSP cycles. The highest near-surface residual stress is about -750 MPa. LSP caused the free volume to increase and the maximum increase appeared after the first LSP process. Compared with the hardness (567 +/- 7 HV) of the as-cast BMG, the hardness (590 +/- 9 HV) on the shocked surface shows a hardening effect due to the hardening mechanism of compressive residual stress; and the hardness (420 +/- 9 HV) on the longitudinal section shows a softening effect due to the softening mechanism of free volume.
bulk metallic glasses↗
A single-shot transmissive spectrometer for hard x-ray free electron lasers
We report hard x-ray single-shot spectral measurements of the Linac Coherent Light Source. The spectrometer is based on a 10 {mu}m thick cylindrically bent Si single crystal operating in the symmetric Bragg geometry to provide dispersion and high transmission simultaneously. It covers a spectral range >1% using the Si(111) reflection. Using the Si(333) reflection, it reaches a resolving power of better than 42 000 and transmits >83% of the incident flux at 8.3 keV. The high resolution enabled the observation of individual spectral spikes characteristic of a self-amplified spontaneous emission x-ray free electron laser source. Potential applications of the device are discussed.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Pulse energy measurement at the hard x-ray laser in Japan
The pulse energies of a free electron laser have accurately been measured in the hard x-ray spectral range. In the photon energy regime from 4.4 keV to 16.8 keV, pulse energies up to 100 {mu}J were obtained at the hard x-ray laser facility SACLA (SPring-8 Angstrom Compact free-electron LAser). Two independent methods, using a cryogenic radiometer and a gas monitor detector, were applied and agreement within 3.3% was achieved. Based on our validated pulse energy measurement, a SACLA online monitor detector could be calibrated for all future experiments.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Microstructure, precipitates and hardness of selectively laser melted AlSi10Mg alloy before and after heat treatment
Highlights: • Microstructural characterization of SLM AlSi10Mg alloy and comparison with cast and powder AlSi10Mg • Effect of solution heat treatment and aging on the hardness change of SLM AlSi10Mg alloy • Evolution of strengthening precipitates and Fe-rich intermetallics in SLM AlSi10Mg during heat treatment - Abstract: The microstructure and precipitates within selectively laser melted (SLM) AlSi10Mg alloys in the as-built state and after T6 heat treatment were examined and correlated to the hardness evolution. The as-built alloy exhibited columnar patterns perpendicular to the build-direction and fish-scale pattern along the build-direction originating from the melt pool. The microstructure consisted of fine Al cells and eutectic structure with up to 4 μm in size. Tiny needle-like Si particles with highly faulted structure were identified within the Al cells and formed semi-coherent interface with the matrix. Nanoscale Si particles and π-Al{sub 8}Si{sub 6}Mg{sub 3}Fe phase were observed to segregate along the cell and grain boundary. Solution heat treatment (SHT) at 520 °C resulted in the dissolution of Al cellular microstructure. Precipitation and coarsening of the Si particles occurred, while the aspect ratio of Si particles remained nearly constant. The π-Al{sub 8}Si{sub 6}Mg{sub 3}Fe phase decomposed into plate-shaped β-Al{sub 5}SiFe. The artificial aging (AA) at 160 °C did not alter the microstructure but led to the formation of metastable Mg{sub 2}Si precipitates. The GP zones and β″ were identified through transmission electron microscopy after AA of 6 h, and β″ existed up to AA of 24 h. The hardness decreased after SHT due to the coarsening of the microstructure and reduced solid solution hardening. Hardness reached maximum magnitude after AA of 6–10 h due to the precipitation hardening, and remained relatively unchanged up to AA of 24 h. Microstructure and/or hardness of gas atomized powders and bulk cast AlSi10Mg alloys were also examined as references.
36 MATERIALS SCIENCE↗
Double-pulse speckle contrast correlations with near Fourier transform limited free-electron laser light using hard X-ray split-and-delay
Abstract The ability to deliver two coherent X-ray pulses with precise time-delays ranging from a few femtoseconds to nanoseconds enables critical capabilities of probing ultra-fast phenomena in condensed matter systems at X-ray free electron laser (FEL) sources. Recent progress made in the hard X-ray split-and-delay optics developments now brings a very promising prospect for resolving atomic-scale motions that were not accessible by previous time-resolved techniques. Here, we report on characterizing the spatial and temporal coherence properties of the hard X-ray FEL beam after propagating through split-and-delay optics. Speckle contrast analysis of small-angle scattering measurements from nanoparticles reveals well-preserved transverse coherence of the beam. Measuring intensity fluctuations from successive X-ray pulses also reveals that only single or double temporal modes remain in the transmitted beam, corresponding to nearly Fourier transform limited pulses.
42 ENGINEERING↗
Effect of heat treatment on microstructural evolution and hardness homogeneity in laser powder bed fusion of alloy 718
The thermal history developed in laser powder bed fusion (LPBF) processes has been shown to be complex resulting in equally complex microstructures and mechanical properties. Microscopic observations and Vickers micro-hardness mapping measurements were carried out on diff ;erent section planes of LPBF alloy 718 cuboids. Three-dimensional finite element analysis was used to simulate thermal history and to predict the residual stress distribution in the as-built material. Computational thermodynamics was used to predict the micro-segregation and nucleation driving force of various phases in the bulk and in segregated regions. Varied heat-treatments such as simulated hot isostatic pressing, and double aging were applied. Their influence on the microstructure, microsegregation, precipitate formation, and micro-hardness variations of LPBF alloy 718 were investigated. Hardness map results showed heterogeneous micro-hardness on the xy- and xz-planes of the as-built parts where the bottom plane and center regions had larger hardness of ~315 HV 0.5 while the top plane and contours showed hardness of ~300 HV 0.5 . It was found that the aging treatment increased the overall hardness of the as-built condition from ~310 HV 0.5 to 470 HV 0.5 but also increased the hardness gradient throughout the coupon. After simulated hot isostatic pressing process (i.e., without applied pressure) at 1020 °C for 4 h followed by water quench (HIPWQ), the hardness gradient and hardness was minimized (~210 HV 0.5 ) as the microstructure transitioned from heterogeneous columnar grains in the as-built condition to more uniform recrystallized grains. A double aging treatment was applied to enhance hardness from ~210 HV 0.5 to ~440 HV 0.5 . Finally, HIPWQ followed by double aging produced a homogeneous microstructure and more uniform hardness map with enhanced mechanical properties in LPBF alloy 718 coupons.
36 MATERIALS SCIENCE↗
Platform development towards ultra-intense laser-based simultaneous hard X-ray and MeV neutron multimodal radiography
Explore the source record for details and available documents.
Physics - Plasma physics , Lasers, Physics↗
Following the Birth of a Nanoplasma Produced by an Ultrashort Hard-X-Ray Laser in Xenon Clusters
Not Available
Kumagai, Yoshiaki↗
Toward a Single Mode Free Electron Laser for Coherent Hard X-Ray Experiments
Abstract Not Provided
Instrumentation,INST, MATSCI, ACCPHY↗
Low-Charge, Hard X-Ray Free Electron Laser Driven with an X-Band Injector and Accelerator
After the successful operation of the Free Electron Laser in Hamburg (FLASH) and the Linac Coherent Light Source (LCLS), soft and hard x-ray free electron lasers (FELs) are being built, designed, or proposed at many accelerator laboratories. Acceleration employing lower frequency rf cavities, ranging from L-band to C-band, is usually adopted in these designs. In the first stage bunch compression, higher-frequency harmonic rf system is employed to linearize the beam's longitudinal phase space, which is nonlinearly chirped during the lower frequency rf acceleration process. In this paper, a hard x-ray FEL design using an all X-band accelerator at 11.424 GHz (from photocathode rf gun to linac end) is presented, without the assistance of any harmonic rf linearization. It achieves LCLS-like performance at low charge using X-band linac drivers, which is more versatile, efficient, and compact than ones using S-band or C-band rf technology. It employs initially 42 microns long (rms), low-charge (10 pC) electron bunches from an X-band photoinjector. An overall bunch compression ratio of roughly 100 times is proposed in a two stage bunch compressor system. The start-to-end macroparticle 3D simulation employing several computer codes is presented in this paper, where space charge, wakefields, and incoherent and coherent synchrotron radiation effects are included. Employing an undulator with a short period of 1.5 cm, a Genesis FEL simulation shows successful lasing at a wavelength of 0.15 nm with a pulse length of 2 fs and a power saturation length as short as 20 meters, which is equivalent to LCLS low-charge mode. Its overall length of both accelerators and undulators is 180 meters (much shorter than the effective LCLS overall length of 1230 meters, including an accelerator length of 1100 meters and an undulator length of 130 meters), which makes it possible to be built in places where only limited space is available.
43 PARTICLE ACCELERATORS↗
Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel
The variation of the C concentration in proeutectoid ferrite (α{sub PF}) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (T{sub m}) of α{sub PF} to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of α{sub PF}. The C concentration in α{sub PF} at T{sub m} in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of α{sub PF} with isothermal holding time at 775 °C in S20C steel revealed C enrichment in α{sub PF} at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in α{sub PF} during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring α{sub PF} as well as pearlitic ferrite. The supersaturated C concentration in α{sub PF} is reduced during the long-range diffusive transformation of α{sub PF} to γ. However, some of the excess C atoms still remain in α{sub PF} until α{sub PF} starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ.
36 MATERIALS SCIENCE↗
Resonant X-ray emission spectroscopy from broadband stochastic pulses at an X-ray free electron laser
Abstract Hard X-ray spectroscopy is an element specific probe of electronic state, but signals are weak and require intense light to study low concentration samples. Free electron laser facilities offer the highest intensity X-rays of any available light source. The light produced at such facilities is stochastic, with spikey, broadband spectra that change drastically from shot to shot. Here, using aqueous ferrocyanide, we show that the resonant X-ray emission (RXES) spectrum can be inferred by correlating for each shot the fluorescence intensity from the sample with spectra of the fluctuating, self-amplified spontaneous emission (SASE) source. We obtain resolved narrow and chemically rich information in core-to-valence transitions of the pre-edge region at the Fe K-edge. Our approach avoids monochromatization, provides higher photon flux to the sample, and allows non-resonant signals like elastic scattering to be simultaneously recorded. The spectra obtained match well with spectra measured using a monochromator. We also show that inaccurate measurements of the stochastic light spectra reduce the measurement efficiency of our approach.
Fuller, Franklin D. (ORCID:0000000237737087)↗
High-resolution single-shot spectral monitoring of hard x-ray free-electron laser radiation
We have developed an on-line spectrometer for hard x-ray free-electron laser (XFEL) radiation based on a nanostructured diamond diffraction grating and a bent crystal analyzer. Our method provides high spectral resolution, interferes negligibly with the XFEL beam, and can withstand the intense hard x-ray pulses at high repetition rates of >100 Hz. The spectrometer is capable of providing shot-to-shot spectral information for the normalization of data obtained in scientific experiments and optimization of the accelerator operation parameters. We have demonstrated these capabilities of the setup at the Linac Coherent Light Source, in self-amplified spontaneous emission mode at full energy of >1 mJ with a 120 Hz repetition rate, obtaining a resolving power of Ε/δΕ > 3 × 10 4 . In conclusion, the device was also used to monitor the effects of pulse duration down to 8 fs by analysis of the spectral spike width.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Microstructural evolution and hardness response in the laser beam welded joints of pure titanium during recrystallization and grain growth
Highlights: • The LABs and high local misorientations indicate the existence of plastic strains in the as-welded HAZ and FZ. • During heat treatment the recrystallization occurs in the HAZs, decreasing plastic strains, but it doesn't appear in the FZs. • The coarse and unstrained grains gradually replace the fine and strained ones in the HAZs during recrystallization. • The decrease of plastic strains in the HAZs during recrystallization causes the descent of average hardness values based on the strain strengthening. - Abstract: Microstructural evolution and hardness response in the laser beam welded joints of pure titanium during recrystallization and grain growth were investigated by means of electron backscatter diffraction and hardness measurement. The low-angle boundaries (LABs) and high local misorientations, in the as-welded heat affected zone (HAZ) and fusion zone (FZ), indicate the existence of plastic strains caused by the plastic strains due to the thermal stress and the non-equilibrium phase transformations. The recrystallization occurs in the HAZs during heat treatment, but the grain growth after recrystallization does not appear under the heat treatment conditions. Moreover as a result of the slightly high impurity contents in the as-welded FZ, no distinct recrystallization is found in the FZs in this work. During recrystallization in the HAZs, the coarse and unstrained grains with equiaxed shape and smooth boundary gradually consume the fine and strained ones with irregular shape and serrate boundary. Meanwhile, the LABs disappear and the low local misorientations replace the high ones in the modified grains. The recrystallization during heat treatment causes the decrease of plastic strains in the HAZs, which reflects on the descent of average hardness values based on the strain strengthening.
36 MATERIALS SCIENCE↗
Single Shot Coherence Properties of the Free-Electron Laser SACLA in the Hard X-ray Regime
We measured the coherence properties of the free-electron laser SACLA on a single shot basis at an X-ray energy of 8 keV. By analysing small-angle X-ray scattering speckle patterns from colloidal dispersions we found a degree of transverse coherence of $β_t$ = 0.79 ± 0.09. Taking detector properties into account, we developed a simulation model in oder to determine the degree of coherence from intensity histograms. Finally we calculated a coherence time of $τ_c$ = 0.1 fs and a pulse duration of 5.2 fs which corresponds with previous predictions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Relative Defect Density Measurements of Laser Shock Peened 316L Stainless Steel Using Positron Annihilation Spectroscopy
The surface of an annealed 316L stainless steel coupon was laser shock peened and Vickers hardness measurements were subsequently taken of its surface. This Vickers hardness data was compared with measurements taken using the technique of positron annihilation Doppler broadening spectroscopy. When compared, a correlation was found between the Vickers hardness data measurements and those made using Doppler broadening spectroscopy. Although materials with a high defect density can cause the S-parameter measurements to saturate, variations in the Sparameter measurements suggest that through further research the Doppler broadening technique could be used as a viable alternative to measuring a material's hardness. In turn, this technique, could be useful in industrial settings where surface hardness and surface defects are used to predict lifetime of components.
36 MATERIALS SCIENCE↗
Evidence for phonon hardening in laser-excited gold using x-ray diffraction at a hard x-ray free electron laser
Studies of laser-heated materials on femtosecond timescales have shown that the interatomic potential can be perturbed at sufficiently high laser intensities. For gold, it has been postulated to undergo a strong stiffening leading to an increase of the phonon energies, known as phonon hardening. Despite efforts to investigate this behavior, only measurements at low absorbed energy density have been performed, for which the interpretation of the experimental data remains ambiguous. By using in situ single-shot x-ray diffraction at a hard x-ray free-electron laser, the evolution of diffraction line intensities of laser-excited Au to a higher energy density provides evidence for phonon hardening.
36 MATERIALS SCIENCE↗