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1.
Nat Commun ; 15(1): 4037, 2024 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-38740793

RESUMO

Laser-driven plasma accelerators provide tabletop sources of relativistic electron bunches and femtosecond x-ray pulses, but usually require petawatt-class solid-state-laser pulses of wavelength λL ~ 1 µm. Longer-λL lasers can potentially accelerate higher-quality bunches, since they require less power to drive larger wakes in less dense plasma. Here, we report on a self-injecting plasma accelerator driven by a long-wave-infrared laser: a chirped-pulse-amplified CO2 laser (λL ≈ 10 µm). Through optical scattering experiments, we observed wakes that 4-ps CO2 pulses with < 1/2 terawatt (TW) peak power drove in hydrogen plasma of electron density down to 4 × 1017 cm-3 (1/100 atmospheric density) via a self-modulation (SM) instability. Shorter, more powerful CO2 pulses drove wakes in plasma down to 3 × 1016 cm-3 that captured and accelerated plasma electrons to relativistic energy. Collimated quasi-monoenergetic features in the electron output marked the onset of a transition from SM to bubble-regime acceleration, portending future higher-quality accelerators driven by yet shorter, more powerful pulses.

2.
Sci Rep ; 9(1): 532, 2019 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-30679471

RESUMO

The generation of X-rays and γ-rays based on synchrotron radiation from free electrons, emitted in magnet arrays such as undulators, forms the basis of much of modern X-ray science. This approach has the drawback of requiring very high energy, up to the multi-GeV-scale, electron beams, to obtain the required photon energy. Due to the limit in accelerating gradients in conventional particle accelerators, reaching high energy typically demands use of instruments exceeding 100's of meters in length. Compact, less costly, monochromatic X-ray sources based on very high field acceleration and very short period undulators, however, may enable diverse, paradigm-changing X-ray applications ranging from novel X-ray therapy techniques to active interrogation of sensitive materials, by making them accessible in energy reach, cost and size. Such compactness and enhanced energy reach may be obtained by an all-optical approach, which employs a laser-driven high gradient accelerator based on inverse free electron laser (IFEL), followed by a collision point for inverse Compton scattering (ICS), a scheme where a laser is used to provide undulator fields. We present an experimental proof-of-principle of this approach, where a TW-class CO2 laser pulse is split in two, with half used to accelerate a high quality electron beam up to 84 MeV through the IFEL interaction, and the other half acts as an electromagnetic undulator to generate up to 13 keV X-rays via ICS. These results demonstrate the feasibility of this scheme, which can be joined with other techniques such as laser recirculation to yield very compact photon sources, with both high peak and average brilliance, and with energies extending from the keV to MeV scale. Further, use of the IFEL acceleration with the ICS interaction produces a train of high intensity X-ray pulses, thus enabling a unique tool synchronized with a laser pulse for ultra-fast strobe, pump-probe experimental scenarios.

3.
Phys Rev Lett ; 120(16): 164801, 2018 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-29756951

RESUMO

Photonic structures operating in the terahertz (THz) spectral region enable the essential characteristics of confinement, modal control, and electric field shielding for very high gradient accelerators based on wakefields in dielectrics. We report here an experimental investigation of THz wakefield modes in a three-dimensional photonic woodpile structure. Selective control in exciting or suppressing of wakefield modes with a nonzero transverse wave vector is demonstrated by using drive beams of varying transverse ellipticity. Additionally, we show that the wakefield spectrum is insensitive to the offset position of strongly elliptical beams. These results are consistent with analytic theory and three-dimensional simulations and illustrate a key advantage of wakefield systems with Cartesian symmetry: the suppression of transverse wakes by elliptical beams.

4.
Phys Rev Lett ; 120(11): 114802, 2018 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-29601767

RESUMO

We present results of an experiment showing the first successful demonstration of a cascaded microbunching scheme. Two modulator-chicane prebunchers arranged in series and a high power mid-IR laser seed are used to modulate a 52 MeV electron beam into a train of sharp microbunches phase locked to the external drive laser. This configuration is shown to greatly improve matching of the beam into the small longitudinal phase space acceptance of short-wavelength accelerators. We demonstrate trapping of nearly all (96%) of the electrons in a strongly tapered inverse free-electron laser accelerator, with an order-of-magnitude reduction in injection losses compared to the classical single-buncher scheme. These results represent a critical advance in laser-based longitudinal phase space manipulations and find application in high gradient advanced acceleration as well as in high peak and average power coherent radiation sources.

5.
Phys Rev Lett ; 118(5): 054802, 2017 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-28211719

RESUMO

Temporal pulse tailoring of charged-particle beams is essential to optimize efficiency in collinear wakefield acceleration schemes. In this Letter, we demonstrate a novel phase space manipulation method that employs a beam wakefield interaction in a dielectric structure, followed by bunch compression in a permanent magnet chicane, to longitudinally tailor the pulse shape of an electron beam. This compact, passive, approach was used to generate a nearly linearly ramped current profile in a relativistic electron beam experiment carried out at the Brookhaven National Laboratory Accelerator Test Facility. Here, we report on these experimental results including beam and wakefield diagnostics and pulse profile reconstruction techniques.

6.
Phys Rev Lett ; 117(17): 174801, 2016 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-27824445

RESUMO

We present results of an experiment where, using a 200 GW CO_{2} laser seed, a 65 MeV electron beam was decelerated down to 35 MeV in a 54-cm-long strongly tapered helical magnetic undulator, extracting over 30% of the initial electron beam energy to coherent radiation. These results, supported by simulations of the radiation field evolution, demonstrate unparalleled electro-optical conversion efficiencies for a relativistic beam in an undulator field and represent an important step in the development of high peak and average power coherent radiation sources.

7.
Nat Commun ; 5: 4928, 2014 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-25222026

RESUMO

Compact, table-top sized accelerators are key to improving access to high-quality beams for use in industry, medicine and academic research. Among laser-based accelerating schemes, the inverse free-electron laser (IFEL) enjoys unique advantages. By using an undulator magnetic field in combination with a laser, GeV m(-1) gradients may be sustained over metre-scale distances using laser intensities several orders of magnitude less than those used in laser wake-field accelerators. Here we show for the first time the capture and high-gradient acceleration of monoenergetic electron beams from a helical IFEL. Using a modest intensity (~10(13) W cm(-2)) laser pulse and strongly tapered 0.5 m long undulator, we demonstrate >100 MV m(-1) accelerating gradient, >50 MeV energy gain and excellent output beam quality. Our results pave the way towards compact, tunable GeV IFEL accelerators for applications such as driving soft X-ray free-electron lasers and producing γ-rays by inverse Compton scattering.

8.
Phys Rev Lett ; 112(4): 045001, 2014 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-24580460

RESUMO

We demonstrate experimentally that a relativistic electron bunch shaped with a sharp rising edge drives plasma wakefields with one to seven periods along the bunch as the plasma density is increased. The plasma density is varied in the 10(15)-10(17) cm(-3) range. The wakefields generation is observed after the plasma as a periodic modulation of the correlated energy spectrum of the incoming bunch. We choose a low bunch charge of 50 pC for optimum visibility of the modulation at all plasma densities. The longitudinal wakefields creating the modulation are in the MV/m range and are indirect evidence of the generation of transverse wakefields that can seed the self-modulation instability, although the instability does not grow significantly over the short plasma length (2 cm). We show that the seeding provides a phase reference for the wakefields, a necessary condition for the deterministic external injection of a witness bunch in an accelerator. This electron work supports the concept of similar experiments in the future, e.g., SMI experiments using long bunches of relativistic protons.

9.
Phys Rev Lett ; 113(26): 264801, 2014 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-25615344

RESUMO

We report experimental measurements of narrow-band, single-mode excitation, and drive beam energy modulation, in a dielectric wakefield accelerating structure with planar geometry and Bragg-reflector boundaries. A short, relativistic electron beam (∼1 ps) with moderate charge (∼100 pC) is used to drive the wakefields in the structure. The fundamental mode of the structure is reinforced by constructive interference in the alternating dielectric layers at the boundary, and is characterized by the spectral analysis of the emitted coherent Cherenkov radiation signal. Data analysis shows a narrow-band peak at 210 GHz corresponding to the fundamental mode of the structure. Simulations in both 2D and 3D provide insight into the propagating fields and reproduction of the electron beams dynamics observables and emitted radiation characteristics.

10.
Phys Rev Lett ; 111(13): 134802, 2013 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-24116784

RESUMO

A strong energy modulation in an electron bunch passing through a dielectric-lined waveguide was recently demonstrated in Antipov et al., Phys. Rev. Lett. 108, 144801 (2012). In this Letter, we demonstrate a successful conversion of this energy modulation into a beam density modulation, and the formation of a series of microbunches with a subpicosecond periodicity by means of magnetic optics (chicane). A strong coherent transition radiation signal produced by the microbunches is obtained and the tunability of its carrier frequency in the 0.68-0.9 THz range by regulating the energy chirp in the incoming electron bunch is demonstrated using infrared interferometry. A tabletop, compact, tunable, and narrowband source of intense THz radiation based on this technology is proposed.

11.
Phys Rev Lett ; 109(18): 185007, 2012 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-23215291

RESUMO

Current filamentation instability is observed and studied in a laboratory environment with a 60 MeV electron beam and a plasma capillary discharge. Multiple filaments are observed and imaged transversely at the plasma exit with optical transition radiation. By varying the plasma density the transition between single and multiple filaments is found to be k(p)σ(r)~2.2. Scaling of the transverse filament size with the plasma skin depth is predicted in theory and observed over a range of plasma densities. Lowering the bunch charge, and thus the bunch density, suppresses the instability.

12.
Phys Rev Lett ; 108(24): 244801, 2012 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-23004279

RESUMO

We report first evidence of wakefield acceleration of a relativistic electron beam in a dielectric-lined slab-symmetric structure. The high energy tail of a ∼60 MeV electron beam was accelerated by ∼150 keV in a 2 cm-long, slab-symmetric SiO2 waveguide, with the acceleration or deceleration clearly visible due to the use of a beam with a bifurcated longitudinal distribution that serves to approximate a driver-witness beam pair. This split-bunch distribution is verified by longitudinal reconstruction analysis of the emitted coherent transition radiation. The dielectric waveguide structure is further characterized by spectral analysis of the emitted coherent Cherenkov radiation at THz frequencies, from a single electron bunch, and from a relativistic bunch train with spacing selectively tuned to the second longitudinal mode (TM02). Start-to-end simulation results reproduce aspects of the electron beam bifurcation dynamics, emitted THz radiation properties, and the observation of acceleration in the dielectric-lined, slab-symmetric waveguide.

13.
Phys Rev Lett ; 108(14): 144801, 2012 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-22540797

RESUMO

We report the observation of a strong wakefield induced energy modulation in an energy-chirped electron bunch passing through a dielectric-lined waveguide. This modulation can be effectively converted into a spatial modulation forming microbunches with a periodicity of 0.5-1 ps and, hence, capable of driving coherent terahertz radiation. The experimental results agree well with theoretical predictions.

14.
Nano Lett ; 9(1): 332-7, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19105652

RESUMO

Mechanically exfoliated graphene mounted on a SiO2/Si substrate was subjected to HF/H(2)O etching or irradiation by energetic protons. In both cases gas was released from the SiO2 and accumulated at the graphene/SiO2 interface resulting in the formation of "bubbles" in the graphene sheet. Formation of these "bubbles" demonstrates the robust nature of single layer graphene membranes, which are capable of containing mesoscopic volumes of gas. In addition, effective mass transport at the graphene/SiO2 interface has been observed.


Assuntos
Cristalização/métodos , Grafite/química , Membranas Artificiais , Microscopia Eletrônica de Varredura/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Gases/química , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
15.
Phys Rev Lett ; 101(5): 054801, 2008 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-18764397

RESUMO

We demonstrate that trains of subpicosecond electron microbunches, with subpicosecond spacing, can be produced by placing a mask in a region of the beam line where the beam transverse size is dominated by the correlated energy spread. We show that the number, length, and spacing of the microbunches can be controlled through the parameters of the beam and the mask. Such microbunch trains can be further compressed and accelerated and have applications to free electron lasers and plasma wakefield accelerators.

16.
Philos Trans A Math Phys Eng Sci ; 364(1840): 611-22, 2006 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-16483952

RESUMO

The staged electron laser acceleration (STELLA) experiment demonstrated staging between two laser-driven devices, high trapping efficiency of microbunches within the accelerating field and narrow energy spread during laser acceleration. These are important for practical laser-driven accelerators. STELLA used inverse free electron lasers, which were chosen primarily for convenience. Nevertheless, the STELLA approach can be applied to other laser acceleration methods, in particular, laser-driven plasma accelerators. STELLA is now conducting experiments on laser wakefield acceleration (LWFA). Two novel LWFA approaches are being investigated. In the first one, called pseudo-resonant LWFA, a laser pulse enters a low-density plasma where nonlinear laser/plasma interactions cause the laser pulse shape to steepen, thereby creating strong wakefields. A witness e-beam pulse probes the wakefields. The second one, called seeded self-modulated LWFA, involves sending a seed e-beam pulse into the plasma to initiate wakefield formation. These wakefields are amplified by a laser pulse following shortly after the seed pulse. A second e-beam pulse (witness) follows the seed pulse to probe the wakefields. These LWFA experiments will also be the first ones driven by a CO(2) laser beam.

17.
Phys Rev Lett ; 92(5): 054801, 2004 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-14995313

RESUMO

Laser-driven electron accelerators (laser linacs) offer the potential for enabling much more economical and compact devices. However, the development of practical and efficient laser linacs requires accelerating a large ensemble of electrons together ("trapping") while keeping their energy spread small. This has never been realized before for any laser acceleration system. We present here the first demonstration of high-trapping efficiency and narrow energy spread via laser acceleration. Trapping efficiencies of up to 80% and energy spreads down to 0.36% (1 sigma) were demonstrated.

18.
Phys Rev Lett ; 91(1): 014802, 2003 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-12906544

RESUMO

We describe our studies of the generation of plasma wake fields by a relativistic electron bunch and of phasing between the longitudinal and transverse fields in the wake. The leading edge of the electron bunch excites a high-amplitude plasma wake inside the overdense plasma column, and the acceleration and focusing wake fields are probed by the bunch tail. By monitoring the dependence of the acceleration upon the plasma's density, we approached the beam-matching condition and achieved an energy gain of 0.6 MeV over the 17 mm plasma length, corresponding to an average acceleration gradient of 35 MeV/m. Wake-induced modulation in energy and angular divergence of the electron bunch are mapped within a wide range of plasma density. We confirm a theoretical prediction about the phase offset between the accelerating and focusing components of plasma wake.

19.
J Comp Physiol B ; 173(4): 319-25, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12664090

RESUMO

The hemocyanin of the European spiny lobster Palinurus elephas (synonym: Palinurus vulgaris) is a hexamer composed by four closely related but distinct subunits. We have obtained the full cDNA sequences of all four subunits, which cover 2275-2298 bp and encode for native polypeptides of 656 and 657 amino acids. The P. elephas hemocyanin subunits belong to the alpha-type of crustacean hemocyanins, whereas beta- and gamma-subunits are absent in this species. An unusual high ratio of non-synonymous versus synonymous nucleotide substitutions was observed, suggesting positive selection among subunits. Assuming a constant evolution rate, the P. elephas hemocyanin subunits emerged from a single hemocyanin gene around 25 million years ago. The alpha-type hemocyanins of P. elephas and the American spiny lobster Panulirus interruptus split around 100 million years ago. This is about five times older than the assumed divergence time of the species and suggests that the genera may have split with the formation of the Atlantic Ocean. The application of the Bayesian method for phylogenetic inference allows for the first time a solid reconstruction of the evolution of the decapod hemocyanins, showing that the beta-subunit types diverged first and that the crustacean pseudo-hemocyanins are associated with the gamma-type subunits.


Assuntos
Evolução Molecular , Hemocianinas/genética , Palinuridae/genética , Sequência de Aminoácidos/genética , Animais , Teorema de Bayes , DNA Complementar/genética , Masculino , Dados de Sequência Molecular , Filogenia , Isoformas de Proteínas/genética , Homologia de Sequência de Aminoácidos
20.
Mol Biol Evol ; 18(8): 1566-73, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11470848

RESUMO

Hemocyanins are copper-containing respiratory proteins of the Arthropoda that have so far been thoroughly investigated only in the Chelicerata and the Crustacea but have remained unstudied until now in the Myriapoda. Here we report the first sequence of a myriapod hemocyanin. The hemocyanin of Spirostreptus sp. (Diplopoda: Spirostreptidae) is composed of two distinct subunits that are arranged in a 6 x 6 native molecule. The cloned hemocyanin subunit cDNA codes of for a polypeptide of 653 amino acids (75.5 kDa) that includes a signal peptide of 18 amino acids. The sequence closely resembles that of the chelicerate hemocyanins. Molecular phylogenetic analyses reject with high statistical confidence the integrity of the Tracheata (i.e., Myriapoda + Insecta) but give conflicting results on the position of the myriapod hemocyanin. While distance matrix and maximum-likelihood methods support a basal position of the Spirostreptus hemocyanin with respect to the other hemocyanins, parsimony analysis suggests a sister group relationship with the chelicerate hemocyanins. The latter topology is also supported by a unique shared deletion of an alpha-helix. A common ancestry of Myriapoda and Chelicerata should be seriously considered.


Assuntos
Artrópodes/genética , Hemocianinas/genética , Filogenia , Sequência de Aminoácidos , Animais , Artrópodes/classificação , Clonagem Molecular , DNA Complementar/química , DNA Complementar/genética , Evolução Molecular , Hemocianinas/química , Dados de Sequência Molecular , Alinhamento de Sequência , Análise de Sequência de DNA , Análise de Sequência de Proteína , Homologia de Sequência de Aminoácidos
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