A5082082749- Laser-Plasma Interactions and Diagnostics
- Chromatin Remodeling and Cancer
- Laser-Matter Interactions and Applications
- Renin-Angiotensin System Studies
- Laser-induced spectroscopy and plasma
- Mechanisms of cancer metastasis
- Advanced X-ray Imaging Techniques
- Cancer Mechanisms and Therapy
- Nuclear Physics and Applications
- Magnetic properties of thin films
- High-pressure geophysics and materials
- Peptidase Inhibition and Analysis
- Laser Material Processing Techniques
- Laser Design and Applications
- Ocular and Laser Science Research
- Magnetic Properties and Applications
- Experimental Learning in Engineering
- Mass Spectrometry Techniques and Applications
- Innovative Teaching Methods
- Spectroscopy and Laser Applications
- Spectroscopy and Quantum Chemical Studies
- Problem and Project Based Learning
- Orbital Angular Momentum in Optics
- Atomic and Molecular Physics
- Advanced Optical Sensing Technologies
Brigham Young University
2004-2024
Centre for Cancer Biology
2023
University of Nebraska–Lincoln
2003-2016
KLA (United States)
2015
Netherlands Institute for Radio Astronomy
2008
We report the generation of MeV x rays using an undulator and accelerator that are both driven by same 100-terawatt laser system. The pulse driving scattering independently optimized to generate a high energy electron beam ($>200\text{ }\text{ }\mathrm{MeV}$) maximize output x-ray brightness. total photon number was measured be $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{7}$, source size $5\text{ }\ensuremath{\mu}\mathrm{m}$, divergence angle $\ensuremath{\sim}10\text{...
We report results on highly oriented, face-centered tetragonal ordered CoPt and FePt thin films grown nonepitaxially by directly depositing thermally oxidized Si substrates subsequent annealing. By controlling the thickness, composition, annealing conditions, and/or a proper underlayer, nearly perfect (001)-oriented can be obtained. Magnetic measurements reveal large perpendicular anisotropy for such films.
A method of preparing nonepitaxially grown, highly textured L10 FePt thin films is described. nearly perfect (001) texture was obtained by direct deposition on Corning 7059 glass substrates and subsequent rapid thermal annealing. The ordering orientation the L10-phase grains were controlled initial as-deposited film structure, also annealing process. Magnetic measurements reveal large perpendicular anisotropy for these films. processes used nonepitaxial growth ordered are much more...
A multilayered deposition structure was developed for fabricating FePt:B2O3 films. We successfully obtained nanostructured films with FePt grains aligned perpendicular to film plane by postannealing the as-deposited multilayers at 550 °C 30 min. It found that development of (001) texture depends strongly on total thickness, initial B2O3 layer and Fe concentration. Nearly perfect orientation FePt-ordered can be in small large slightly higher Our results show highly oriented ordered fct phase...
We report the results of experiments on laser-wakefield acceleration in a novel two-stage gas target with independently adjustable density and atomic-composition profiles. were able to tailor these profiles way that led separation processes electron injection permitted independent control both. This resulted generation stable, quasimonoenergetic beams central energy tunable 50--300 MeV range. For first time, we are beam charge spread over entire tunability
Stable operation of a laser-plasma accelerator near the threshold for electron self-injection in blowout regime has been demonstrated with 25--60 TW, 30 fs laser pulses focused into 3--4 millimeter length gas jet. Nearly Gaussian shape and high nanosecond contrast pulse appear to be critically important controllable, tunable generation 250--430 MeV bunches low-energy spread, $\ensuremath{\sim}10\text{ }\text{ }\mathrm{pC}$ charge, few-mrad divergence pointing stability, vanishingly small...
In this paper, we present results on a scalable high-energy electron source based laser wakefield acceleration. The accelerator using 30–80 TW, 30 fs pulses, operates in the blowout regime, and produces high-quality, quasi-monoenergetic beams range 100–800 MeV. These have angular divergence of 1–4 mrad, 5%–25% energy spread, with resulting brightness 1011 electrons mm−2 MeV−1 mrad−2. beam parameters can be tuned by varying plasma conditions. use high-quality pulse appropriate target...
Ten-millijoule 35-femtosecond laser pulses interact with a cell of helium or neon that extends from focusing lens to an exit foil near the focus. High harmonic orders in range 50 100 are investigated as function focal position relative foil. An aperture placed front increases brightness observed harmonics by more than order magnitude. Counter-propagating light is used directly probe where high generated within In neon, last few millimeters before foil, limited absorption. helium, produced...
Fourier-transform-limited light pulses were obtained at the laser-plasma interaction point of a 100-TW peak-power laser in vacuum. The spectral-phase distortion induced by dispersion mismatching between stretcher, compressor, and dispersive materials was fully compensated for means an adaptive closed-loop. coherent temporal contrast on sub-picosecond time scale two orders magnitude higher than that without control. This novel phase control capability enabled experimental study dependence...
We report results of an experimental study laser-wakefield acceleration electrons, using a staged device based on double-jet gas target that enables independent injection and stages. This novel scheme is shown to produce stable, quasi-monoenergetic, tunable electron beams. show optimal accelerator performance achieved by systematic variation five critical parameters. For the stage, we amount trapped charge controlled density, composition, laser power. density length jet are found determine...
We investigate the use of energetic electron beams for high-resolution radiography flaws embedded in thick solid objects. A bright, monoenergetic beam (with energy $>100\text{ }\text{ }\mathrm{MeV}$) was generated by process laser-wakefield acceleration through interaction 50-TW, 30-fs laser pulses with a supersonic helium jet. The high energy, low divergence, and small source size these make them ideal radiographic studies cracks or voids dense materials that are placed at large distance...
A repetitive petawatt-class Ti:sapphire laser system operating with high spatial and temporal beam quality is demonstrated. Maximum pulse energy of 30 J obtained via five multi-pass amplification stages. Closed-loop feedback control systems in the domains are used to yield Fourier-transform-limited duration (33.7 fs), diffraction-limited focal spot sizes (with several different tight focusing optics). The parameters have been fully characterized at high-power, monitored real-time, ensure...
We investigate the spatial evolution of a laser pulse used to generate high-order harmonics (orders ranging from 45 91) in semi-infinite helium-filled gas cell. The 5 mJ, 30 fs pulses experience elongated focusing with two distinct waists when focused f/125 optics 80 Torr helium. Extended phase matching for generation occurs region between double foci laser, where beam changes diverging converging.
We report on direct measurements of self-guiding 800 nm, 30 fs, 5 mJ laser pulses used to generate high-order harmonics in 80 torr helium. track the spatial evolution as they propagate several centimeters near focus under conditions suitable for harmonic generation. The is observed focus, diverge, and refocus. This behavior accompanied by a flattop beam profile. Both these features are absent when focused vacuum. also 4 nm spectral blue shift center contrast with no at wider radii.
Magnetization reversal and intergranular interactions have been studied in composite CoxPt100−x:C thin films using several magnetic characterization techniques. The interactions, as determined by ΔM curves, were strongly dependent on the ratio of Co Pt concentration. For with high content, exchange coupling was predominant, while dipolar exhibited film equiatomic concentration Pt. Magnetic interaction directly observed force microscopy. There is a strong correlation between value length...
This paper outlines the feasibility of replacing a midterm assessment with student-created digital media project. We examine benefits peer review process for pedagogy, effectiveness student-generated media, and self-evaluations as replacement traditional forms assessment. conclude that this innovative teaching model is both effective timely more college courses are being taught digitally and/or asynchronously.
Undergraduate students on track for medical school are often required to take general physics lab courses. Many of these carry an attitude obligation into courses which can make it challenging instructors engage in course material. We address the question: How does engaging with medically based models introductory labs affect pre-med undergraduate perceptions modeling process and their science? redesigned electricity magnetism course, where approximately 70% undergraduates reported plans...
We are studying the use of 0.1–1.0 GeV laser‐accelerated electron beams as active interrogation probes for long‐standoff radiography or nuclear activation concealed special material. Use in this energy range is largely unexplored, but such could provide notable advantages over lower‐energy and x‐rays. High‐energy electrons exhibit large penetration through air solids, low beam divergence both direct secondary Bremsstrahlung present laboratory measurements activation, using high‐power Diodes...
An adaptive spectral-phase control method is demonstrated for laser wakefield acceleration of electrons. Phase capability was implemented to experimentally study the dependence on spectral phase intense light.
Quasi monoenergetic and tunable x-ray beams are reported by inverse-Compton scattering from laser wakefield accelerated electrons. The high peak brightness, ultrashort duration, small size of the source make it uniquely suitable for many applications.
A bright, narrow band MeV γ-ray source-ray source based on Thomson scattering using a laser-driven electron accelerator has been developed. We discuss the application of this for selective activation in regions high particle (neutron or gamma) production, with minimal absorption intervening materials.