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Articles 31 - 60 of 64
Full-Text Articles in Physical Sciences and Mathematics
Observation Of Laser Satellites In A Plasma Produced By A Femtosecond Laser Pulse, S.A. Pikuz, Anatoly Maksimchuk, Donald Umstadter, M. Nantel, I. Yu. Skobelev, A. Ya. Faenov, A. Osterheld
Observation Of Laser Satellites In A Plasma Produced By A Femtosecond Laser Pulse, S.A. Pikuz, Anatoly Maksimchuk, Donald Umstadter, M. Nantel, I. Yu. Skobelev, A. Ya. Faenov, A. Osterheld
Donald P. Umstadter
Laser satellites are detected in the emission spectra of magnesium and aluminum plasmas produced by femtosecond laser pulses. This is made possible by the realization of picosecond time resolution in a highluminosity x-ray spectrograph with a spherically curved mica crystal. The temporal characteristics of these newly recorded spectral lines show unequivocally that they are formed as a result of nonlinear processes.
Laser Injection Of Ultrashort Electron Pulses Into Wakefield Plasma Waves, Donald P. Umstadter, J.K. Kim, E. Dodd
Laser Injection Of Ultrashort Electron Pulses Into Wakefield Plasma Waves, Donald P. Umstadter, J.K. Kim, E. Dodd
Donald P. Umstadter
A novel laser-plasma-based source of relativistic electrons is described. It involves a combination of orthogonally directed laser beams, which are focused in a plasma. One beam excites a wakefield electron plasma wave. Another locally alters the trajectory of some of the electrons in such a way that they can be accelerated and trapped by the wave. With currently available table-top terawatt lasers, a single ultrashort-duration electron bunch can be accelerated to multi-MeV energies in a fraction of a millimeter, with femtosecond synchronization between the light pulse, the electron bunch, and the plasma wave. Both analytical and numerical-simulation results are presented.
Mechanism And Control Of High-Intensity-Laser-Driven Proton Acceleration, T. Lin, K. Flippo, M. Rever, Anatoly Maksimchuk, Donald P. Umstadter
Mechanism And Control Of High-Intensity-Laser-Driven Proton Acceleration, T. Lin, K. Flippo, M. Rever, Anatoly Maksimchuk, Donald P. Umstadter
Donald P. Umstadter
We discuss the optimization and control of laser-driven proton beams. Specifically, we report on the dependence of high-intensity laser accelerated proton beams on the material properties of various thin-film targets. Evidence of star-like filaments and beam hollowing (predicted from the electrothermal instability theory) is observed on Radiochromic Film (RCF) and CR-39 nuclear track detectors. The proton beam spatial profile is found to depend on initial target conductivity and target thickness. For resistive target materials, these structured profiles are explained by the inhibition of current, due to the lack of a return current. The conductors, however, can support large propagating currents …
Temporal Contrast In Ti:Sapphire Lasers: Characterization And Control, Marc Nantel, Jiro Itatani, An-Chun Tien, Jerome Faure, Daniel Kaplan, Marcel Bouvier, Takashi Buma, Paul Van Rompay, John Nees, Peter P. Pronko, Donald P. Umstadter, Gerald A. Mourou
Temporal Contrast In Ti:Sapphire Lasers: Characterization And Control, Marc Nantel, Jiro Itatani, An-Chun Tien, Jerome Faure, Daniel Kaplan, Marcel Bouvier, Takashi Buma, Paul Van Rompay, John Nees, Peter P. Pronko, Donald P. Umstadter, Gerald A. Mourou
Donald P. Umstadter
As ultrafast lasers achieve ever higher focused intensities on target, the problem of ensuring a clean laser-solid interaction becomes more pressing. In this paper, we give concrete examples of the deleterious effects of low-contrast interactions, and address the problem of subpicosecond laser intensity contrast ratio on both characterization and control fronts. We present the new technique of high-dynamic-range plasma-shuttered streak camera contrast measurement, as well as two efficient and relatively inexpensive ways of improving the contrast of short pulse lasers without sacrificing on the output energy: a double-pass Pockels cell (PC), and clean high-energy-pulse seeding of the regenerative amplifier.
Femtosecond Free-Electron Laser By Chirped Pulse Amplification, L.H. Yu, E. Johnson, D. Li, Donald P. Umstadter
Femtosecond Free-Electron Laser By Chirped Pulse Amplification, L.H. Yu, E. Johnson, D. Li, Donald P. Umstadter
Donald P. Umstadter
In this work we combine elements of chirped pulse amplification techniques, now familiar in solid-state lasers, with an amplifier based upon a seeded free-electron laser (FEL). The resulting device would produce amplified pulses of unprecedented brevity at wavelengths shorter than can be currently obtained by any tunable laser system. We use a subharmonically seeded FEL to illustrate the concept. Radiation from a Ti:sapphire laser is frequency tripled and stretched optically to provide a coherent seed pulse for the FEL. When coupled to an electron beam inside a magnetic wiggler, the seed radiation introduces an additional energy modulation on the electron …
The Coupling Of Stimulated Raman And Brillouin Scattering In A Plasma, Donald P. Umstadter, W.B. Mori, C. Joshi
The Coupling Of Stimulated Raman And Brillouin Scattering In A Plasma, Donald P. Umstadter, W.B. Mori, C. Joshi
Donald P. Umstadter
The observation of an anti-Stokes satellite in the spectrum of light backscattered from a CO2 laser plasma is reported. Its origin is found to be Thomson scattering of the incident light from a counterpropagating mode-coupled plasma wave. The parent electron and ion waves in the mode-coupling process were driven by stimulated Raman and Brillouin backscattering. The parent and daughter plasma waves were detected by ruby laser Thomson scattering. A computer simulation modeling the experiment shows further cascading of the Stokes backscattered light to lower frequencies, apparently a result of its rescattering from another, higher phase velocity, counterpropagating coupled mode. Comparisons …
Relativistic Nonlinear Optics, Phillip F. Schewe, Ben Stein, Donald P. Umstadter
Relativistic Nonlinear Optics, Phillip F. Schewe, Ben Stein, Donald P. Umstadter
Donald P. Umstadter
Laser light is a convenient way of transporting both electric and magnetic fields. When an electron encounters light, however, it is usually the electric field that does the talking; the magnetic part of light is less influential since its effect on the electron is proportional to the electron's speed as a fraction of the speed of light (c). In new experiments at the University of Michigan this is all changed since the intensity of the laser light used is so great (a terawatt of power, compared to a milliwatt for a laser in a CD player) that the electrons in …
Laser-Triggered Ion Acceleration And Table Top Isotope Production, K. Nemoto, Anatoly Maksimchuk, Sudeep Banerjee, K. Flippo, G. Mourou, Donald P. Umstadter, B. Yu. Bychenkov
Laser-Triggered Ion Acceleration And Table Top Isotope Production, K. Nemoto, Anatoly Maksimchuk, Sudeep Banerjee, K. Flippo, G. Mourou, Donald P. Umstadter, B. Yu. Bychenkov
Donald P. Umstadter
We have observed deuterons accelerated to energies of about 2 MeV in the interaction of relativistically intense 10 TW, 400 fs laser pulse with a thin layer of deuterated polystyrene deposited on Mylar film. These high-energy deuterons were directed to the boron sample, where they produced ~105 atoms of positron active isotope 11C from the reaction 10B(d,n)11C. The activation results suggest that deuterons were accelerated from the front surface of the target.
Acceleration Of Electrons In A Self-Modulated Laser Wakefield, Shouyuan Chen, M. Krishnan, Anatoly Maksimchuk, Donald P. Umstadter
Acceleration Of Electrons In A Self-Modulated Laser Wakefield, Shouyuan Chen, M. Krishnan, Anatoly Maksimchuk, Donald P. Umstadter
Donald P. Umstadter
Acceleration of electrons in a self-modulated laser-wakefield is investigated. The generated electron beam is oberved to have a multi-component beam profile and its energy distribution undergoes discrete transitions as the conditions are varied. These features can be explained by simple simulations of electron propagation in a 3-D plasma wave.
Control Of Bright Picosecond X-Ray Emission From Intense Subpicosecond Laser-Plasma Interactions, J. Workman, Anatoly Maksimchuk, X. Liu, U. Ellenberger, J.S. Coe, C.-Y. Chien, Donald P. Umstadter
Control Of Bright Picosecond X-Ray Emission From Intense Subpicosecond Laser-Plasma Interactions, J. Workman, Anatoly Maksimchuk, X. Liu, U. Ellenberger, J.S. Coe, C.-Y. Chien, Donald P. Umstadter
Donald P. Umstadter
Using temporally and spectrally resolved diagnostics, we show that the pulse duration of laser-produced soft x rays emitted from solid targets can be controlled, permitting a reduction to as short as a few picoseconds. To enable this control, only a single parameter must be adjusted, namely, the intensity of the high-contrast ultrashort laser pulse (400 fs). These results are found to be in qualitative agreement with a simple model of radiation from a collisionally dominated atomic system.
Laser Acceleration Of Protons From Thin Film Targets, K. Flippo, Sudeep Banerjee, V. Yu. Bychenkov, S. Gu, Anatoly Maksimchuk, G. Mourou, K. Nemoto, Donald P. Umstadter
Laser Acceleration Of Protons From Thin Film Targets, K. Flippo, Sudeep Banerjee, V. Yu. Bychenkov, S. Gu, Anatoly Maksimchuk, G. Mourou, K. Nemoto, Donald P. Umstadter
Donald P. Umstadter
A collimated beam of fast protons, with energies as high as 10 MeV and total number of 109, confined in a cone angle of 40°±10° has been observed when a 10 TW laser with frequencies either ω0 (corresponding to 1 μm) or 2ω0 was focused to an intensity of a few times 1018 W/cm2 on the surface of a thin film target. The protons, which originate from impurities on the front side of the target, are accelerated over a region extending into the target and exit out the backside in a direction normal to the target surface. Acceleration field gradients …
Observation Of Steepening In Electron Plasma Waves Driven By Stimulated Raman Backscattering, Donald Umstadter, R. Williams, C. Clayton, C. Joshi
Observation Of Steepening In Electron Plasma Waves Driven By Stimulated Raman Backscattering, Donald Umstadter, R. Williams, C. Clayton, C. Joshi
Donald P. Umstadter
Harmonics of plasma waves excited by CO2-laser–induced stimulated Raman scattering have been observed by frequency- and wave-number-resolved ruby Thomson scattering. Measurements of their relative amplitudes agreed with predictions of nonlinear warm-plasma wave-steepening theory up to the maximum observed amplitude of the fundamental component, ñ1/n0=16%.
Interactions Of Ultrashort, Ultrahigh Intensity Laser Pulses With Underdense Plasmas, Xiaofang Wang, Wei Yu, Sterling Backus, Margaret Murnane, Henry Kapteyn, Donald P. Umstadter
Interactions Of Ultrashort, Ultrahigh Intensity Laser Pulses With Underdense Plasmas, Xiaofang Wang, Wei Yu, Sterling Backus, Margaret Murnane, Henry Kapteyn, Donald P. Umstadter
Donald P. Umstadter
The interactions of ultraintense laser pulses with underdense plasmas are studied in a new regime in which the longitudinal spatial extent of the pulse duration is close to both the laser focal spot size and the plasma wavelength.
Dense And Relativistic Plasmas Produced By Compact High-Intensity Lasers, Donald Umstadter, Shouyuan Chen, G. Ma, Anatoly Maksimchuk, G. Mourou, M. Nantel, S. Pikuz, G. Sarkisov, R. Wagner
Dense And Relativistic Plasmas Produced By Compact High-Intensity Lasers, Donald Umstadter, Shouyuan Chen, G. Ma, Anatoly Maksimchuk, G. Mourou, M. Nantel, S. Pikuz, G. Sarkisov, R. Wagner
Donald P. Umstadter
High-intensity lasers interacting with plasmas are used to study processes in the laboratory that would otherwise only occur in astrophysics. These include relativistic plasmas, electron acceleration in ultrahigh Ðeld-gradient wake Ðelds, pressure ionization and continuum lowering in strongly coupled plasmas, and X-ray line emission via Raman scattering.
Optical Deflection And Temporal Characterization Of An Ultrafast Laser-Produced Electron Beam, Sudeep Banerjee, Scott Sepke, Rahul Shah, Anthony Valenzuela, Anatoly Maksimchuk, Donald P. Umstadter
Optical Deflection And Temporal Characterization Of An Ultrafast Laser-Produced Electron Beam, Sudeep Banerjee, Scott Sepke, Rahul Shah, Anthony Valenzuela, Anatoly Maksimchuk, Donald P. Umstadter
Donald P. Umstadter
The interaction of a laser-produced electron beam with an ultraintense laser pulse in free space is studied. We show that the optical pulse with a0=0.5 imparts momentum to the electron beam, causing it to deflect along the laser propagation direction. The observed 3-degree angular deflection is found to be independent of polarization and in good agreement with a theoretical model for the interaction of free electrons with a tightly focused Gaussian pulse, but only when longitudinal fields are taken into account. This technique is used to temporally characterize a subpicosecond laser-wakefield-driven electron bunch. Applications to electron-beam conditioning are also discussed.
Experimental Observation Of Nonlinear Thomson Scattering, Szu-Yuan Chen, Anatoly Maksimchuk, Donald Umstadter
Experimental Observation Of Nonlinear Thomson Scattering, Szu-Yuan Chen, Anatoly Maksimchuk, Donald Umstadter
Donald P. Umstadter
A century ago, J. J. Thomson showed that the scattering of low-intensity light by electrons was a linear process (i.e., the scattered light frequency was identical to that of the incident light) and that light’s magnetic field played no role. To- day, with the recent invention of ultra-high-peak- power lasers it is now possible to create a sufficient photon density to study Thomson scattering in the relativistic regime. With increasing light intensity, electrons quiver during the scattering process with increasing velocity, approaching the speed of light when the laser intensity approaches 1018 W/cm2. In this limit, the …
Forward Ion Acceleration In Thin Films Driven By A High-Intensity Laser, Anatoly Maksimchuk, S. Gu, K. Flippo, Donald P. Umstadter, V. Yu. Bychenkov
Forward Ion Acceleration In Thin Films Driven By A High-Intensity Laser, Anatoly Maksimchuk, S. Gu, K. Flippo, Donald P. Umstadter, V. Yu. Bychenkov
Donald P. Umstadter
A collimated beam of fast protons, with energies as high as 1.5 MeV and total number of ≳109, confined in a cone angle of 40°±10° is observed when a high-intensity high-contrast subpicosecond laser pulse is focused onto a thin foil target. The protons, which appear to originate from impurities on the front side of the target, are accelerated over a region extending into the target and exit out the back side in a direction normal to the target surface. Acceleration field gradients ∼10 GeV/cm are inferred. The maximum proton energy can be explained by the charge-separation electrostatic-field acceleration due to …
Pulse Radiolysis Of Liquid Water Using Picosecond Electron Pulses Produced By A Table-Top Terawatt Laser System, Ned Saleh, Kirk Flippo, Koshichi Nemoto, Donald P. Umstadter, Robert A. Crowell, Charles D. Jonah, Alexander D. Trifunac
Pulse Radiolysis Of Liquid Water Using Picosecond Electron Pulses Produced By A Table-Top Terawatt Laser System, Ned Saleh, Kirk Flippo, Koshichi Nemoto, Donald P. Umstadter, Robert A. Crowell, Charles D. Jonah, Alexander D. Trifunac
Donald P. Umstadter
A laser based electron generator is shown, for the first time, to produce sufficient charge to conduct time resolved investigations of radiation induced chemical events. Electron pulses generated by focussing terawatt laser pulses into a supersonic helium gas jet are used to ionize liquid water. The decay of the hydrated electrons produced by the ionizing electron pulses is monitored with 0.3 µs time resolution. Hydrated electron concentrations as high as 22 µM were generated. The results show that terawatt lasers offer both an alternative to linear accelerators and a means to achieve subpicosecond time resolution for pulse radiolysis studies.
Cold Relativistic Wavebreaking, J.K. Kim, Donald P. Umstadter
Cold Relativistic Wavebreaking, J.K. Kim, Donald P. Umstadter
Donald P. Umstadter
The two-dimensional wave-breaking of relativistic plasma waves driven by a ultrashort high-power lasers, is described within a framework of cold 2-D fluid theory. It is shown that the transverse nonlinearity of the plasma wave results in temporally increasing transverse plasma oscillation in the wake of the laser pulse, inevitably inducing wave-breaking below the 1-D threshold. A condition for wavebreaking is obtained and evaluated. A preformed density channel is found to partially cancel the effect and increase the length of wakefield that survives before wavebreaking occurs.
Ultrashort Ultraviolet Free-Electron Lasers, Donald Umstadter, L. H. Yu, E. Johnson, D. Li
Ultrashort Ultraviolet Free-Electron Lasers, Donald Umstadter, L. H. Yu, E. Johnson, D. Li
Donald P. Umstadter
In this work we combine elements of chirped pulse amplification (CPA) techniques, now familiar in solid-state lasers, with an amplifier based upon a seeded free-electron laser (FEL), The resulting device would produce amplified pulses of unprecedented brevity at wavelengths shorter than can be currently obtained by any tunable laser system. We use a subharmonically seeded FEL to illustrate the concept. Radiation from a Ti:sapphire laser is frequency-tripled and stretched optically to provide a coherent seed pulse for the FEL. When coupled to an electron beam inside a magnetic wiggler, the seed radiation introduces an additional energy modulation on the electron …
Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter
Donald P. Umstadter
Clayton et al. Respond: The authors of the Comment are quite correct when they point out that the ruby-laser scattering system used in our study can only respond to beat-excited density fluctuations with ky = k2, where the CO2 (ruby) beam propagates in the z (y) direction.
Laser Based Synchrotron Radiation, Kim Ta Phuoc, Frederic Burgy, Jean-Philippe Rousseau, Victor Malka, Antoine Rousse, Rahul Shah, Donald P. Umstadter, Alexander Puhkov, Sergei Kiselev
Laser Based Synchrotron Radiation, Kim Ta Phuoc, Frederic Burgy, Jean-Philippe Rousseau, Victor Malka, Antoine Rousse, Rahul Shah, Donald P. Umstadter, Alexander Puhkov, Sergei Kiselev
Donald P. Umstadter
Beams of x rays in the kiloelectronvolt energy range have been produced from laser-matter interaction. Here, energetic electrons are accelerated by a laser wakefield, and experience betatron oscillations in an ion channel formed in the wake of the intense femtosecond laser pulse. Experiments using a 50 TW laser (30 fs duration) are described, as well as comparisons with numerical simulations. These results pave the way of a new generation of radiation in the x-ray spectral range, with a high collimation and an ultrafast pulse duration, produced by the use of compact laser system.
Electron Acceleration And The Propagation Of Ultrashort High-Intensity Laser Pulses In Plasmas, Xiaofang Wang, Mohan Krishnan, Ned Saleh, Haiwen Wang, Donald P. Umstadter
Electron Acceleration And The Propagation Of Ultrashort High-Intensity Laser Pulses In Plasmas, Xiaofang Wang, Mohan Krishnan, Ned Saleh, Haiwen Wang, Donald P. Umstadter
Donald P. Umstadter
Reported are interactions of high-intensity laser pulses ( λ = 810 nm and l≤3×1018 W/cm2) with plasmas in a new parameter regime, in which the pulse duration ( τ = 29 fs) corresponds to 0.6–2.6 plasma periods. Relativistic filamentation is observed to cause laser-beam breakup and scattering of the beam out of the vacuum propagation angle. A beam of megaelectronvolt electrons with divergence angle as small as 1° is generated in the forward direction, which is correlated to the growth of the relativistic filamentation. Raman scattering, however, is found to be much less than previous long-pulse results.
Tabletop Accelerators Are Brighter And Faster, Phil Schewe, Ben Stein, Donald P. Umstadter
Tabletop Accelerators Are Brighter And Faster, Phil Schewe, Ben Stein, Donald P. Umstadter
Donald P. Umstadter
At last week's APS plasma physics meeting, Donald Umstadter of the University of Michigan's Center for Ultrafast Optical Science (734-764-2284, dpu@umich.edu) reported on advances at his lab and elsewhere in tabletop laser accelerators, devices that use light to accelerate beams of electrons and protons to energies of a million volts in distances of only microns. This acceleration rate or "gradient" is up to a thousand times larger than in conventional accelerators because the tabletop laser light can now exert pressures of gigabars, the highest ever achieved, and approaching the pressure of light near the Sun. Not only that, but Umstadter's …
Phase Dependence Of Thomson Scattering In An Ultraintense Laser Field, Fei He, Y. Y. Lau, Donald P. Umstadter, Trevor Strickler
Phase Dependence Of Thomson Scattering In An Ultraintense Laser Field, Fei He, Y. Y. Lau, Donald P. Umstadter, Trevor Strickler
Donald P. Umstadter
The Thomson scattering spectra of an electron by an ultraintense laser field are computed. It is found that the electron orbit, and therefore its nonlinear Thomson scattering spectra, depend critically on the amplitude of the ultraintense laser field and on the phase at which the electron sees the laser electric field. Contrary to some customary notions, the Thomson scattering spectra, in general, do not occur at integer multiples of the laser frequency and the maximum frequency is proportional to the first instead of the third power of the electric field strength for the case of an ultraintense laser. The implications …
Self-Focusing, Channel Formation, And High-Energy Ion Generation In Interaction Of An Intense Short Laser Pulse With A He Jet, G.S. Sarkisov, B. Yu. Bychenkov, V.N. Novikov, V.T. Tikhonchuk, Anatoly Maksimchuk, Shouyuan Chen, R. Wagner, G. Mourou, Donald Umstadter
Self-Focusing, Channel Formation, And High-Energy Ion Generation In Interaction Of An Intense Short Laser Pulse With A He Jet, G.S. Sarkisov, B. Yu. Bychenkov, V.N. Novikov, V.T. Tikhonchuk, Anatoly Maksimchuk, Shouyuan Chen, R. Wagner, G. Mourou, Donald Umstadter
Donald P. Umstadter
Using interferometry, we investigate the dynamics of interaction of a relativistically intense 4-TW, 400-fs laser pulse with a He gas jet. We observe a stable plasma channel 1 mm long and less than 30 μm in diameter, with a radial gradient of electron density ∼5×1022 cm-4 and with an on-axis electron density approximately ten times less than its maximum value of 8×1019 cm-3. A high radial velocity of the surrounding gas ionization of ∼3.8×108 cm/s has been observed after the channel formation, and it is attributed to the fast ions expelled from the laser channel and propagating radially outward. We …
Thomson Scattering And Ponderomotive Intermodulation Within Standing Laser Beat Waves In Plasma, Scott Sepke, Y.Y. Lau, James Paul Holloway, Donald P. Umstadter
Thomson Scattering And Ponderomotive Intermodulation Within Standing Laser Beat Waves In Plasma, Scott Sepke, Y.Y. Lau, James Paul Holloway, Donald P. Umstadter
Donald P. Umstadter
Electrons in a standing electromagnetic wave—an optical lattice—tend to oscillate due to the quiver and ponderomotive potentials. For sufficiently intense laser fields (lλ2≤5×1017 W cm-2 µm2) and in plasmas with sufficiently low electron densities (n≤1018 cm-3), these oscillations can occur faster than the plasma can respond. This paper shows that these oscillations result in Thomson scattering of light at both the laser and ponderomotive bounce frequencies and their harmonics as well as at mixtures of these frequencies. We term this mixing ponderomotive intermodulation. Here, the case of counterpropagating laser beams creating a one-dimensional (1D) optical lattice is analyzed. The near-equilibrium …
Evolution Of A Plasma Waveguide Created During Relativistic-Ponderomotive Self-Channeling Of An Intense Laser Pulse, Shouyuan Chen, G.S. Sarkisov, Anatoly Maksimchuk, R. Wagner, Donald P. Umstadter
Evolution Of A Plasma Waveguide Created During Relativistic-Ponderomotive Self-Channeling Of An Intense Laser Pulse, Shouyuan Chen, G.S. Sarkisov, Anatoly Maksimchuk, R. Wagner, Donald P. Umstadter
Donald P. Umstadter
An on-axis plasma density depression channel was observed during and after the passage of a relativistically and ponderomotively self-guided laser pulse through a plasma. Optical interferometry was used to produce time-resolved plasma density distributions, revealing the formation of a plasma waveguide. These results were complemented by the guiding of a collinear trailing pulse.
Application Of A Picosecond Soft X-Ray Source To Time-Resolved Plasma Dynamics, J. Workman, M. Nantel, Anatoly Maksimchuk, Donald P. Umstadter
Application Of A Picosecond Soft X-Ray Source To Time-Resolved Plasma Dynamics, J. Workman, M. Nantel, Anatoly Maksimchuk, Donald P. Umstadter
Donald P. Umstadter
We demonstrate the application of an ultrashort x-ray source as an external probe to measure plasma dynamics. The plasma is generated by a 100-fs Ti: sapphire laser focused onto thin metallic films. Time-resolved spectroscopy of the gold x-ray probe transmission through a perturbed 1000 Å aluminum film reveals redshifts of the L-shell photoabsorption edge. We show that the dynamic behavior of this shift is consistent with the relaxation of the aluminum following the compression generated by a shock wave traveling through the film. An analytic plasma model, with comparison to a numerical hydrodynamics model, indicates compression up to 1.4 times …
Fast Ignitor Concept With Light Ions, V. Yu. Bychenkov, W. Rozmus, Anatoly Maksimchuk, Donald Umstadter, C.E. Capjack
Fast Ignitor Concept With Light Ions, V. Yu. Bychenkov, W. Rozmus, Anatoly Maksimchuk, Donald Umstadter, C.E. Capjack
Donald P. Umstadter
A short-laser-pulse driven ion flux is examined as a fast ignitor candidate for inertial confinement fusion. Ion ranges in a hot precompressed fuel are studied. The ion energy and the corresponding intensity of a short laser pulse are estimated for the optimum ion range and ion energy density flux. It is shown that a lightion beam triggered by a few-hundreds-kJ laser at intensities of ~1021W/cm2 is relevant to the fast ignitor scenario.