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Full-Text Articles in Physical Sciences and Mathematics
Erratum: ‘‘Phase Dependence Of Thomson Scattering In An Ultraintense Laser Field’’ Phys. Plasmas 9, 4325 [2002], Fei He, Y. Y. Lau, Donald P. Umstadter, Trevor Strickler
Erratum: ‘‘Phase Dependence Of Thomson Scattering In An Ultraintense Laser Field’’ Phys. Plasmas 9, 4325 [2002], Fei He, Y. Y. Lau, Donald P. Umstadter, Trevor Strickler
Donald P. Umstadter
The conclusions of this paper on the frequency scaling of the peak intensity of Thomson scattering of an electron that is initially at rest are restricted to the backscatter direction of the laser. All data were obtained only for the backscatter direction. In the forward direction of the laser, there is no frequency upshift. At an oblique angle that depends on the normalized laser field amplitude, ω/ω0 ~ O(a3) for large a, where ω0 is the laser frequency and a is the normalized laser electric field amplitude. Also, in Fig. 3, a = 10.
Electron Injection By Dephasing Electrons With Laser Fields, E. Dodd, J.K. Kim, Donald P. Umstadter
Electron Injection By Dephasing Electrons With Laser Fields, E. Dodd, J.K. Kim, Donald P. Umstadter
Donald P. Umstadter
The authors seek to review injection concepts for plasma based acceleration. It is shown that regardless of injection mechanism, resultant beams will be similar due to wave structure. Also, most schemes employ the same basic processes, namely the dephasing of electrons by laser fields, and can thus be analyzed with similar approaches.
Coherent Control Of Stimulated Raman Scattering Using Chirped Laser Pulses, Evan S. Dodd, Donald P. Umstadter
Coherent Control Of Stimulated Raman Scattering Using Chirped Laser Pulses, Evan S. Dodd, Donald P. Umstadter
Donald P. Umstadter
A novel method for the control of stimulated Raman scattering and hot electron production in short-pulse laser-plasma interactions is proposed. It relies on the use of a linear frequency chirp in nonbandwidth limited pulses. Theoretical calculations show that a 12% bandwidth will eliminate Raman forward scattering for a plasma density that is 1% of the critical density. The predicted changes to the growth rate are confirmed in two-dimensional particle-in-cell simulations. Relevance to areas of current research is also discussed.
Observation Of The Plasma Channel Dynamics And Coulomb Explosion In The Interaction Of A High-Intensity Laser Pulse With A He Gas Jet, G.S. Sarkisov, V. Yu. Bychenkov, V.T. Tikhonchuk, Anatoly Maksimchuk, Shouyuan Chen, R. Wagner, G. Mourou, Donald P. Umstadter
Observation Of The Plasma Channel Dynamics And Coulomb Explosion In The Interaction Of A High-Intensity Laser Pulse With A He Gas Jet, G.S. Sarkisov, V. Yu. Bychenkov, V.T. Tikhonchuk, Anatoly Maksimchuk, Shouyuan Chen, R. Wagner, G. Mourou, Donald P. Umstadter
Donald P. Umstadter
We report the first interferometric observations of the dynamics of electron–ion cavitation of relativistically self-focused intense 4 TW, 400 fs laser pulse in a He gas jet. The electron density in a channel 1 mm long and 30 mm in diameter drops by a factor of approximately 10 from the maximum value of ~8x1019 cm23. A high radial velocity of the plasma expansion, ~3.8x108 cm/s, corresponding to an ion energy of about 300 keV, is observed. The total energy of fast ions is estimated to be 6% of the laser pulse energy. The high-velocity radial plasma expulsion is explained by …
Status Of The Lilac Experiment, N. Saleh, P. Han, C. Keppel, P. Gueye, V Yanovsky, Donald P. Umstadter
Status Of The Lilac Experiment, N. Saleh, P. Han, C. Keppel, P. Gueye, V Yanovsky, Donald P. Umstadter
Donald P. Umstadter
We present the status of the LILAC experiment [1], including results on the propagation of 30-fs duration laser pulses in plasmas of the requisite density, and measurements of the dark current [2]. We also discuss the status of a laser upgrade, an electron beam line and plans for the future.
Relativistic Laser–Plasma Interactions, Donald Umstadter
Relativistic Laser–Plasma Interactions, Donald Umstadter
Donald P. Umstadter
By focusing petawatt peak power laser light to intensities up to 1021 Wcm−2, highly relativistic plasmas can now be studied. The force exerted by light pulses with this extreme intensity has been used to accelerate beams of electrons and protons to energies of a million volts in distances of only microns. This acceleration gradient is a thousand times greater than in radio-frequency-based accelerators. Such novel compact laser-based radiation sources have been demonstrated to have parameters that are useful for research in medicine, physics and engineering. They might also someday be used to ignite controlled thermonuclear fusion. Ultrashort …
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 …
Nonlinear Plasma Waves Resonantly Driven By Optimized Laser Pulse Trains, Donald Umstadter, E. Esarey, J. Kim
Nonlinear Plasma Waves Resonantly Driven By Optimized Laser Pulse Trains, Donald Umstadter, E. Esarey, J. Kim
Donald P. Umstadter
A method for generating large-amplitude plasma waves, which utilizes an optimized train of independently adjustable, intense laser pulses, is discussed and analyzed. Both the pulse widths and interpulse spacings are optimally determined such that resonance is maintained and the plasma wave amplitude is maximized. By mitigating the effects of both phase and resonant detuning, and by reducing laser-plasma instabilities, the use of appropriately tailored multiple laser pulses is a highly advantageous technique for accelerating electrons. Practical methods of producing the required pulse trains are suggested.
Submillimeter-Resolution Radiography Of Shielded Structures With Laser-Accelerated Electron Beams, Viswanathan Ramanathan, Sudeep Banerjee, Nathan Powers, Nathaniel Cunningham, Nathan A. Chandler-Smith, Kun Zhao, Kevin Brown, Donald Umstadter, Shaun Clarke, Sara Pozzi, James Beene, Randy Vane, David Schultz
Submillimeter-Resolution Radiography Of Shielded Structures With Laser-Accelerated Electron Beams, Viswanathan Ramanathan, Sudeep Banerjee, Nathan Powers, Nathaniel Cunningham, Nathan A. Chandler-Smith, Kun Zhao, Kevin Brown, Donald Umstadter, Shaun Clarke, Sara Pozzi, James Beene, Randy Vane, David Schultz
Donald P. Umstadter
We investigate the use of energetic electron beams for high-resolution radiography of flaws embedded in thick solid objects. A bright, monoenergetic electron beam (with energy >100 MeV) was generated by the process of laser-wakefield acceleration through the interaction of 50-TW, 30-fs laser pulses with a supersonic helium jet. The high energy, low divergence, and small source size of these beams make them ideal for high-resolution radiographic studies of cracks or voids embedded in dense materials that are placed at a large distance from the source. We report radiographic imaging of steel with submillimeter resolution.
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 …
Competition Between Ponderomotive And Thermal Forces In Short-Scale-Length Laser Plasmas, X. Liu, Donald Umstadter
Competition Between Ponderomotive And Thermal Forces In Short-Scale-Length Laser Plasmas, X. Liu, Donald Umstadter
Donald P. Umstadter
Interactions of intense 400-fs laser pulses with a solid target are studied with time-integrated and time-resolved measurements. The latter are accomplished by means of a pump and probe experiment, in which the motion of the critical surface is measured with 250-fs resolution. It is found that when the average electron quiver energy (mvos2/2) becomes comparable to the electron thermal energy (kTe), the ponderomotive force of the high-intensity laser significantly reduces the thermal expansion of a laser plasma. This study is performed in an interesting regime not easily accessible with longer pulse lasers, in which the electron density scale length during …
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.
X-Ray Radiation From Nonlinear Thomson Scattering Of An Intense Femtosecond Laser On Relativistic Electrons In A Helium Plasma, K. Ta Phuoc, A. Rousse, M. Pittman, J.P. Rousseau, V. Malka, S. Fritzler, Donald Umstadter, D. Hulin
X-Ray Radiation From Nonlinear Thomson Scattering Of An Intense Femtosecond Laser On Relativistic Electrons In A Helium Plasma, K. Ta Phuoc, A. Rousse, M. Pittman, J.P. Rousseau, V. Malka, S. Fritzler, Donald Umstadter, D. Hulin
Donald P. Umstadter
We have generated x-ray radiation from the nonlinear Thomson scattering of a 30 fs/1.5 J laser beam on plasma electrons. A collimated x-ray radiation with a broad continuous spectrum peaked at 0.15 keV with a significant tail up to 2 keV has been observed. These characteristics are found to depend strongly on the laser strength parameter a0. This radiative process is dominant for a0 greater than unity at which point the relativistic scattering of the laser light originates from MeV energy electrons inside the plasma.
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 …