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1.
Phys Rev E ; 102(5-1): 053216, 2020 Nov.
Article in English | MEDLINE | ID: mdl-33327156

ABSTRACT

Using an analytical model and computer simulation, we show that the wakefield driven by an ultrashort laser pulse in high-density plasma periodically reverses its polarity due to the carrier-envelope phase shift of the driver. The wakefield polarity reversal occurs on spatial scales shorter than the typical length considered for electron acceleration with the laser-wakefield mechanism. Consequently, the energies of accelerated electrons are significantly affected. The results obtained are important for the laser-wakefield acceleration under the conditions relevant to present-day high-repetition-rate laser systems.

2.
Phys Rev Lett ; 124(8): 084802, 2020 Feb 28.
Article in English | MEDLINE | ID: mdl-32167312

ABSTRACT

Acceleration of particles from the interaction of ultraintense laser pulses up to 5×10^{21} W cm^{-2} with thin foils is investigated experimentally. The electron beam parameters varied with decreasing spot size, not just laser intensity, resulting in reduced temperatures and divergence. In particular, the temperature saturated due to insufficient acceleration length in the tightly focused spot. These dependencies affected the sheath-accelerated protons, which showed poorer spot-size scaling than widely used scaling laws. It is therefore shown that maximizing laser intensity by using very small foci has reducing returns for some applications.

3.
Phys Rev Lett ; 122(25): 254801, 2019 Jun 28.
Article in English | MEDLINE | ID: mdl-31347867

ABSTRACT

As an alternative to Compton backscattering and bremsstrahlung, the process of colliding high-energy electron beams with strong laser fields can more efficiently provide both a cleaner and brighter source of photons in the multi-GeV range for fundamental studies in nuclear and quark-gluon physics. In order to favor the emission of high-energy quanta and minimize their decay into electron-positron pairs, the fields must not only be sufficiently strong, but also well localized. We here examine these aspects and develop the concept of a laser-particle collider tailored for high-energy photon generation. We show that the use of multiple colliding laser pulses with 0.4 PW of total power is capable of converting more than 18% of multi-GeV electrons passing through the high-field region into photons, each of which carries more than half of the electron initial energy.

4.
Sci Rep ; 8(1): 2938, 2018 02 13.
Article in English | MEDLINE | ID: mdl-29440772

ABSTRACT

Detections of the pulse durations and arrival timings of relativistic electron beams are important issues in accelerator physics. Electro-optic diagnostics on the Coulomb fields of electron beams have the advantages of single shot and non-destructive characteristics. We present a study of introducing the electro-optic spatial decoding technique to laser wakefield acceleration. By placing an electro-optic crystal very close to a gas target, we discovered that the Coulomb field of the electron beam possessed a spherical wavefront and was inconsistent with the previously widely used model. The field structure was demonstrated by experimental measurement, analytic calculations and simulations. A temporal mapping relationship with generality was derived in a geometry where the signals had spherical wavefronts. This study could be helpful for the applications of electro-optic diagnostics in laser plasma acceleration experiments.

5.
Sci Rep ; 7(1): 17968, 2017 12 21.
Article in English | MEDLINE | ID: mdl-29269841

ABSTRACT

Burst Intensification by Singularity Emitting Radiation (BISER) is proposed. Singularities in multi-stream flows of emitting media cause constructive interference of emitted travelling waves, forming extremely localized sources of bright coherent emission. Here we for the first time demonstrate this extreme localization of BISER by direct observation of nano-scale coherent x-ray sources in a laser plasma. The energy emitted into the spectral range from 60 to 100 eV is up to ~100 nJ, corresponding to ~1010 photons. Simulations reveal that these sources emit trains of attosecond x-ray pulses. Our findings establish a new class of bright laboratory sources of electromagnetic radiation. Furthermore, being applicable to travelling waves of any nature (e.g. electromagnetic, gravitational or acoustic), BISER provides a novel framework for creating new emitters and for interpreting observations in many fields of science.

6.
Rev Sci Instrum ; 85(2): 02B904, 2014 Feb.
Article in English | MEDLINE | ID: mdl-24593609

ABSTRACT

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the <10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ∼10(21) W cm(-2), the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M).


Subject(s)
Aluminum , Heavy Ions , Lasers , Particle Accelerators/instrumentation
7.
Phys Rev Lett ; 108(13): 135004, 2012 Mar 30.
Article in English | MEDLINE | ID: mdl-22540709

ABSTRACT

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multiterawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving µJ/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.

8.
Phys Rev Lett ; 103(16): 165002, 2009 Oct 16.
Article in English | MEDLINE | ID: mdl-19905702

ABSTRACT

An approach for accelerating ions, with the use of a cluster-gas target and an ultrashort pulse laser of 150-mJ energy and 40-fs duration, is presented. Ions with energy 10-20 MeV per nucleon having a small divergence (full angle) of 3.4 degrees are generated in the forward direction, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell simulation that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas.

9.
Phys Rev Lett ; 103(19): 194803, 2009 Nov 06.
Article in English | MEDLINE | ID: mdl-20365929

ABSTRACT

A high stability electron bunch is generated by laser wakefield acceleration with the help of a colliding laser pulse. The wakefield is generated by a laser pulse; the second laser pulse collides with the first pulse at 180 degrees and at 135 degrees realizing optical injection of an electron bunch. The electron bunch has high stability and high reproducibility compared with single pulse electron generation. In the case of 180 degrees collision, special measures have been taken to prevent damage. In the case of 135 degrees collision, since the second pulse is countercrossing, it cannot damage the laser system.

10.
Phys Rev Lett ; 103(21): 215003, 2009 Nov 20.
Article in English | MEDLINE | ID: mdl-20366045

ABSTRACT

An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

11.
Phys Rev Lett ; 103(23): 235003, 2009 Dec 04.
Article in English | MEDLINE | ID: mdl-20366154

ABSTRACT

Laser light reflection by a relativistically moving electron density modulation (flying mirror) in a wake wave generated in a plasma by a high intensity laser pulse is investigated experimentally. A counterpropagating laser pulse is reflected and upshifted in frequency with a multiplication factor of 37-66, corresponding to the extreme ultraviolet wavelength. The demonstrated flying mirror reflectivity (from 3 x 10(-6) to 2 x 10(-5), and from 1.3 x 10(-4) to 0.6 x 10(-3), for the photon number and pulse energy, respectively) is close to the theoretical estimate for the parameters of the experiment.

12.
Phys Rev Lett ; 100(14): 145001, 2008 Apr 11.
Article in English | MEDLINE | ID: mdl-18518041

ABSTRACT

The laser-driven acceleration of high quality proton beams from a double-layer target, comprised of a high-Z ion layer and a thin disk of hydrogen, is investigated with three-dimensional particle-in-cell simulations for an obliquely incident laser pulse. The proton beam energy reaches its maximum at a certain incidence angle, where it can be much greater than the energy at normal incidence. The proton beam propagates at some angle with respect to the target surface normal and with some tilt around the target surface, as determined by the proton energy and the incidence angle.

13.
Phys Rev Lett ; 100(4): 045004, 2008 Feb 01.
Article in English | MEDLINE | ID: mdl-18352290

ABSTRACT

We observed the increase of the conversion efficiency from laser energy to Kalpha x-ray energy (eta(K)) produced by a 60 fs frequency doubled high-contrast laser pulse focused on a Cu foil, compared to the case of the fundamental laser pulse. eta(K) shows a strong dependence on the nonlinearly modified rising edge of the laser pulse. It reaches a maximum for a 100 fs negatively modified pulse. The hot electron efficient heating leads to the enhancement of eta(K). This demonstrates that high-contrast lasers are an effective tool for optimizing eta(K), via increasing the hot electrons by vacuum heating.

14.
Phys Rev Lett ; 99(13): 135001, 2007 Sep 28.
Article in English | MEDLINE | ID: mdl-17930598

ABSTRACT

In a plasma wake wave generated by a high power laser, modulations of the electron density take the shape of paraboloidal dense shells, moving almost at the speed of light. A counterpropagating laser pulse is partially reflected from the shells, acting as relativistic flying mirrors, producing a time-compressed frequency-multiplied pulse due to the double Doppler effect. The counterpropagating laser pulse reflection from the plasma wake wave accompanied by its frequency multiplication (with a factor from 50 to 114) was detected in our experiment.

15.
Phys Rev E Stat Nonlin Soft Matter Phys ; 71(1 Pt 2): 015403, 2005 Jan.
Article in English | MEDLINE | ID: mdl-15697651

ABSTRACT

We study experimentally the interaction of the shortest at present (23-fs) , relativistically intense (20-TW), tightly focused laser pulses with underdense plasma. MeV electrons constitute a two-temperature distribution due to different plasma wave-breaking processes at a plasma density of 10(20) cm(-3). These two groups of electrons are shown numerically to constitute bunches with very distinctive time durations.

16.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(6 Pt 2): 066408, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15244746

ABSTRACT

Interaction of an ultraintense, a(0) >>1, laser pulse with an underdense Ar plasma is analyzed via a two-dimensional particle-in-cell simulation which self-consistently includes optical-field ionization. In spite of rapid growth of ion charge Z and, hence, electron density at the laser front, relativistic self-focusing is shown to persist owing to a reduction of the expected plasma defocusing resulting from the weak radial dependence of the ion charge on laser intensity (even for Z/gamma>1 where gamma is the electron relativistic factor).

17.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(3 Pt 2): 035401, 2004 Mar.
Article in English | MEDLINE | ID: mdl-15089350

ABSTRACT

The self-injection of plasma electrons which have been accelerated to relativistic energies by a laser pulse moving with a group velocity less than the speed of light with I lambda(2)>5 x 10(19) W microm(2)/cm(2) is found via particle-in-cell simulation to be efficient for laser wake-field acceleration. When the matching condition a(0)> or =(2(1/4)omega/omega(pl))(2/3) is met, the self-injection, along with wave breaking, dominates monoenergetic electron acceleration yielding up to 100 MeV energies by a 100 TW, 20 fs laser pulse. In contrast to the injection due to wave-breaking processes, self-injection allows suppression of production of a Maxwell distribution of accelerated particles and the extraction of a beam-quality bunch of energetic electrons.

18.
Phys Rev Lett ; 88(18): 185002, 2002 May 06.
Article in English | MEDLINE | ID: mdl-12005689

ABSTRACT

A strong effect of radiation damping on the interaction of an ultraintense laser pulse with an overdense plasma slab is found and studied via a relativistic particle-in-cell simulation including ionization. Hot electrons generated by the irradiation of a laser pulse with a radiance of I lambda(2)>10(22) W microm(2)/cm(2) and duration of 20 fs can convert more than 35% of the laser energy to radiation. This incoherent x-ray emission lasts for only the pulse duration and can be intense. The radiation efficiency is shown to increase nonlinearly with laser intensity. Similar to cyclotron radiation, the radiation damping may restrain the maximal energy of relativistic electrons in ultraintense-laser-produced plasmas.

19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 64(6 Pt 2): 066403, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11736278

ABSTRACT

The laser wake field generated by two colliding laser beams has been studied numerically. The wake field amplitude is enhanced by a counterpropagating long pulse laser, which has an appropriate frequency difference, and becomes an order of magnitude larger than that of the standard wake field. The field amplitude increases in proportion to the pumping laser intensities until it saturates under the wave breaking limit. The details of the enhanced wake field have been examined at the saturated state.

20.
Fukuoka Igaku Zasshi ; 92(9): 334-9, 2001 Sep.
Article in Japanese | MEDLINE | ID: mdl-11680976

ABSTRACT

The clinical significance of angiogenesis was investigated in Borrmann type IV gastric cancer. Tumors with high microvessel density (MVD) often metastasized to the liver and lymph nodes. A significant correlation was recognized between macrophage infiltration and MVD. However, MVD was not a prognostic factor. Peritoneal dissemination was a prognostic factor in Borrmann type IV gastric cancer. Thus, angiogenesis plays an important role in the metastasis, but not prognosis in Borrmann type IV gastric cancer.


Subject(s)
Macrophages/pathology , Neovascularization, Pathologic , Stomach Neoplasms/blood supply , Aged , Antigens, CD/analysis , Antigens, Differentiation, Myelomonocytic/analysis , Biomarkers/analysis , Endothelial Growth Factors/analysis , Female , Humans , Lymphokines/analysis , Male , Middle Aged , Peritoneal Neoplasms/pathology , Peritoneal Neoplasms/secondary , Platelet Endothelial Cell Adhesion Molecule-1/analysis , Prognosis , Stomach Neoplasms/pathology , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth Factors
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