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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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

The laser control of the muon g -2 experiment at Fermilab

Here, we present that the Muon g-2 Experiment at Fermilab is expected to start data taking in 2017. It will measure the muon anomalous magnetic moment, a μ = (g μ -2)/2 to an unprecedented precision: the goal is 0.14 parts per million (ppm). The new experiment will require upgrades of detectors, electronics and data acquisition equipment to handle the much higher data volumes and slightly higher instantaneous rates. In particular, it will require a continuous monitoring and state-of-art calibration of the detectors, whose response may vary on both the millisecond and hour long timescale. The calibration system is composed of six laser sources and a light distribution system will provide short light pulses directly into each crystal (54) of the 24 calorimeters which measure energy and arrival time of the decay positrons. A Laser Control board will manage the interface between the experiment and the laser source, allowing the generation of light pulses according to specific needs including detector calibration, study of detector performance in running conditions, evaluation of DAQ performance. Here we present and discuss the main features of the Laser Control board.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Optical emission of a plasma from low-density targets irradiated with coherence-controllable laser radiation

The results of experiments on the interaction of nanosecond laser radiation with low-density volume-structured targets of different density and thickness are reported. The targets were irradiated by laser radiation with controllable coherence. The primary objective was to investigate the effect of target parameters on the characteristics of radiation scattered by the plasma. The spectral characteristics of the radiation scattered by the plasma in the backward direction and in the direction of laser beam propagation were obtained. Also the radiation scattering patterns were recorded. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Benefits from developments in the field of Decommissioning for Fukushima Daiichi fuel debris retrieval: Remote-Controlled Laser Cutting Process - 17110

Among the numerous challenges towards the decommissioning of Fukushima Dai-ichi reactors, removing fuel debris is certainly one of the tougher ones, requiring several technical developments. One of them, related to laser cutting of fuel debris is being developed by a French consortium 'ONET Technologies, CEA and IRSN'. Remote controlled laser cutting was implemented for the first time in a real decommissioning workshop in 2015, in UP1 reprocessing plant. In addition to laser cutting development in air and underwater, key aspects of fuel debris cutting of representative of corium debris simulants was performed to test the quantities of aerosols, gas and dusts released during the debris laser cutting. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Quantum memory node based on a semiconductor double quantum dot in a laser-controlled optical resonator

The concept of a quantum node consisting of a memory qubit and a frequency convertor is proposed and analysed. The memory qubit is presented by a semiconductor four-level double quantum dot (DQD) placed in an optical microresonator (MR). The DQD contains an electron in the quantised part of the conduction band and the MR can be populated by a certain number of photons. The DQD and MR states are controlled be applying the laser and electrostatic fields. The difference between the telecommunication frequency of the photon (transport qubit) supplied to the system through a waveguide and the frequency of the electronic transition in the DQD is compensated for using an auxiliary element, i.e. a frequency convertor based on a single quantum dot (QD). This design allows the electron – photon state of the hybrid system to be controlled by an appropriate variation of the field parameters and the switching between resonance and nonresonance DQD and MR interaction regimes. As an example, a GaAs DQD placed in a microdisk MR is studied. A numerical technique for modelling an optical spectrum of a microdisk MR with an additional layer (AL) deposited on its surface is developed. Using this technique, the effect of the AL on the MR eigenmode properties is investigated and the possibility of tuning its frequency to the QD electronic transition frequency by depositing an AL on the disk surface is demonstrated. (quantum memory)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Laboratory tests of laser control of electron beams for future colliders

Laser-driven Compton backscattering (CBS) has been proposed as method for controlling the intensity of colliding bunches in the FCC-ee so as to avoid the flip-flop instability caused by intensity asymmetry in colliding bunches. Laser-based collimation has also been proposed as an indestructible collimator for high-intensity electron beams. We have initiated a laboratory-based test program of these concepts with the E344 experiment at FACET-II. In this paper, we describe simulations of laser–beam interactions at FACET-II and the relevant scaling for FCC-ee. We also describe the experimental setup and diagnostics that will be used to make the measurements at FACET-II.

accelerator physics↗
DOE OSTI2026

Laboratory Tests of Laser Control of Electron Beams for Future Colliders

Laser-driven Compton backscattering (CBS) has been proposed as method for controlling the intensity of colliding bunches in the FCC-ee so as to avoid the flip-flop instability caused by intensity asymmetry in colliding bunches. Laser-based collimation has also been proposed as an indestructible collimator for high-intensity electron beams. We have initiated a laboratory-based test program of these concepts with the E344 experiment at FACET-II. In this paper, we describe simulations of laser-beam interactions at FACET-II and the relevant scaling for FCC-ee. We also describe the experimental setup and diagnostics that will be used to make the measurements at FACET-II.

Accelerator Physics (physics.acc-ph)↗
DOE OSTI2018

IR Laser Control of the Clustering of CF{sub 3}Br Molecules during the Gas-Dynamic Expansion of a CF{sub 3}Br/Ar Mixture: Bromine Isotope Selectivity

The infrared (IR) laser radiation control of the clustering of CF3Br molecules during the gas-dynamic expansion of a CF{sub 3}Br/Ar mixture at the exit from a nozzle is investigated. Prominence is given to studying the possibility of bromine-isotope-selective suppression of the clustering of CF{sub 3}Br molecules due to their resonance vibrational excitation in the gas-dynamic expansion zone near the nozzle. A continuous CO{sub 2} laser is used in experiments to excite molecules and clusters in a beam, and a quadrupole mass spectrometer is used to detect them. The experimental setup and the experimental technique are described. The dependences of the efficiency of molecule clustering suppression on the exciting laser radiation parameters, the gas parameters (composition, pressure) above the nozzle, and the distance from the nozzle exit section to a molecule irradiation zone are obtained. Bromine-isotope-selective suppression of molecule clustering is shown to occur at the exit from the nozzle due to the resonance vibrational excitation of gas-dynamically cooled CF{sub 3}Br molecules. When CF{sub 3}Br/Ar mixtures are used at pressure ratios p(CF{sub 3}Br): p(Ar) = 1: 10 and 1: 30, the enrichment of a cluster beam by bromine isotopes are K{sub enr}({sup 81}Br) ≈ 1.18 ± 0.09 and 1.12 ± 0.07 during the 9R(30) laser line (1084.635 cm{sup –1}) irradiation of a jet. The clustering suppression selectivity is α ≈ 1.18 when the mixture at the pressure ratio p(CF{sub 3}Br): p(Ar) = 1: 10 is used. These results suggest that the proposed method can selectively control the clustering of the molecules containing the heavy element isotopes that have a small isotope shift in IR absorption spectra (OsO{sub 4}, WF{sub 6}, UF{sub 6}).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Laser-Controlled Torsions: Four-Dimensional Theory and the Validity of Reduced Dimensionality Models

A multitude of possible applications along with unique coherence, chirality, and symmetry properties makes the control of molecular torsion with moderately strong, nonresonant laser pulses a fascinating subject. A description of combined rotation and torsion requires at least four angular degrees of freedom, which is challenging for the majority of systems. Lower-dimensional models have been proposed but also questioned. Here, we develop a four-dimensional model for the coupled rotational-torsional motions of molecules consisting of two identical moieties. By comparing four-dimensional calculations with a two-dimensional model, we define conditions under which the lower-dimensional model is valid. In particular, we point to the crucial role of coordinate dependence of the polarizability tensor. Our results do not agree with those of previous four-dimensional calculations but support the conclusions of recent experiments.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Pre-Ionization Controlled Laser Plasma Formation for Ignition Applications

The presented research explored new physics and ignition schemes based on laser induced plasmas that are fundamentally distinct from past laser ignition research focused on single laser pulses. Specifically, we consider the use of multiple laser pulses where the first pulse provides pre-ionization allowing controlled absorption of the second pulse. In this way, we can form tailored laser plasmas in terms of their ionization fraction, gas temperature (e.g. to achieve elevated temperature of ~2000 K ideally suited for an ignition source), reduced energy loss to shock waves and radiation, and large kernel size (e.g. length ~1-10 cm). The proposed research included both experimental and modeling efforts, at Colorado State University, Princeton University and University of Tennessee, towards the basic science of the new laser plasma approach with emphasis on tailoring the plasmas to practical propulsion systems. Experimental results (CSU) show that the UV beam produces a pre-ionized volume which assists in breakdown of the NIR beam, leading to reduction in NIR breakdown threshold by factor of >2. Numerical modeling is performed to examine the ionization and breakdown of both beams. The main theoretical and computational parts of the work were done at Princeton University. The modeled breakdown threshold of the NIR, including assist by pre-ionization, is in reasonable agreement with the experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Pre-Ionization Controlled Laser Plasma Formation for Ignition Applications (Final Scientific/Technical Report)

This report consists of three grand funded papers. Abstracts for each follow. 1) In this work, we present experimental and modeling studies of air pre-ionization using ultraviolet (UV) laser pulses and its effect on laser breakdown of an overlapped near-infrared (NIR) pulse. Experimental studies are conducted with a 266 nm beam (fourth harmonic of Nd:YAG) for UV pre-ionization and an overlapped 1064 nm NIR beam (fundamental of Nd:YAG), both having pulse duration of 10 ns. Results show that the UV beam produces a pre-ionized volume which assists in breakdown of the NIR beam, leading to reduction in NIR breakdown threshold by factor of >2. Numerical modeling is performed to examine the ionization and breakdown of both beams. The modeled breakdown threshold of the NIR, including assist by pre-ionization, is in reasonable agreement with the experimental results. 2) The present contribution compares the energy absorption, optical emission, temperature, and fluid dynamics of ultraviolet (UV) λ = 266 nm and near infrared (NIR) λ = 1064 nm nanosecond laser induced plasmas in ambient air. For UV pulses at the conditions studied, energy absorption by the plasmas increases relatively gradually with laser pulse energy starting at delivered energy of E~8 mJ. Corresponding measurements of plasma luminosity show that the absorption of UV radiation does not necessarily result in visible plasma emission. For the NIR induced plasmas, the energy absorption profile is far more abrupt and begins at ~55 mJ. In contrast with UV, the absorption of NIR radiation is always accompanied by intense optical emission. The temperatures of both types of plasma have been measured with Rayleigh scattering thermometry (at times after the Thomson signal sufficiently diminishes). The UV plasmas can attain a wider range of temperatures, including lower temperatures, depending on the pulse energy (e.g., T ~400–2000K for E ~7–35 mJ at Δt = 10 μs after the pulse) while the NIR plasmas show only hotter temperatures (e.g., T ~ 12 000 K for E = 75 mJ at Δt = 10 μs after the pulse) as is consistent with the literature. Differences in the fluid dynamics for UV versus NIR pulses are shown with Schlieren imaging. In this work, the contrast in the UV and NIR plasma threshold behavior is attributed to differing roles of avalanche ionization and multiphoton ionization as is also illustrated by a simple numerical model. 3) The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We perform a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution of the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.

Mechanical engineering↗
DOE OSTI2017

Laser control over the ultrafast Coulomb explosion of N 2 2 + after Auger decay: A quantum-dynamics investigation

By theoretical calculation, we show the possibility to control and partially suppress the Coulomb explosion of N 2 molecules after core-level photoionization by an x-ray laser and subsequent Auger decay. This is achieved by means of a femtosecond infrared laser pulse interacting with the N 2 2 + dication produced by the x-ray pulse. Suppression of molecular fragmentation requires few-femtosecond IR pulses interacting with the system either during or shortly after the arrival of the x-ray pulse. The IR pulse suppresses fragmentation mostly by optically coupling the electronic routes to ultrafast molecular dissociation with electronic channels able to support long-lived vibrational resonances. The effect is strongly dependent on the orientation of the molecule with respect to the polarization axis of the IR field. These calculations are motivated by x-ray pump–IR probe experiments performed at an x-ray free-electron laser [J. M. Glownia et al. , Opt. Express 18 , 17620 (2010) ], where only enhancement of N 2 2 + fragmentation as a function of the pump-probe delay time was reported. The opposite effect reported here becomes apparent when the various electronic channels are considered separately. In practice, this corresponds to a coincident measurement of the energy of the ejected Auger electron

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Laser-controlled optical transconductance varistor system

An optical transconductance varistor system having a modulated radiation source configured to provide modulated stimulus, a wavelength converter operably connected to the modulated radiation source to produce a modulated stimulus having a predetermined wavelength, and a wide bandgap semiconductor photoconductive material in contact between two electrodes. The photoconductive material is operably coupled, such as by a beam transport module, to receive the modulated stimulus having the predetermined wavelength to control a current flowing through the photoconductive material when a voltage potential is present across the electrodes.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Spatiotemporal control of laser intensity

The controlled coupling of a laser to a plasma has the potential to address grand scientific challenges including reaching the Schwinger limit, developing compact free electron lasers, extending linear colliders to TeV energies, and generating novel light sources for probing electron dynamics within molecules. Currently, many such applications have limited flexibility and poor control over the laser focal volume. Here we present an advanced focusing scheme called a “flying focus” where a chromatic focusing system combined with chirped laser pulses enables a small–diameter laser focus to propagate nearly 100 times its Rayleigh length, while decoupling the speed at which the peak intensity moves from its group velocity. This unprecedented spatiotemporal control over the laser focal volume allows the laser focus to co- or counter–propagate along its axis at any velocity. Experiments validating the concept measured subluminal (-0.09c) to superluminal (39c) focal spot velocities generating a nearly constant peak intensity over 4.5 mm.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

High precision control of laser energy for laser–matter interaction studies

Precise, highly reproducible control of the laser energy is required for high confidence laser–matter interaction research such as in dynamic compression science and high energy density physics. The energy must be adjustable without affecting the pulse shape (time varying intensity) or beam smoothness. We have developed a convenient two-stage energy tuning method for a nominal 100 J, 351 nm (UV) laser. The energy is adjusted in 10 J (10%) increments by operating the laser at full energy and inserting a beam splitter in the laser output. As the splitter is located after the final frequency tripling optics, the UV pulse shape is unchanged. The energy is varied by substituting a splitter of different reflectivity. For finer 3 J (3%) increments, the infrared pulse is attenuated inside the laser before the final amplifier. This requires modest tuning to preserve the pulse shape. The demonstrated variation in shot-to-shot reproducibility is less than +/–2.5 J (5% of the full energy), irrespective of the laser output energy. These approaches can be adapted to most ~100 J class lasers. We describe these techniques and show two examples where they have elucidated the underlying physics in laser shock compression experiments. One used only the beam splitters to establish the pressure for melting in iron. The other combined both techniques to finely increment the peak stress (~2 GPa steps) in germanium to precisely determine the onset and completion of melting—including the melting kinetics. Furthermore, these unambiguous results would not be possible without the developments described here.

47 OTHER INSTRUMENTATION↗