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Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; et al.

RAL-TR-2015-025, P. 22, 2015/00

Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; et al.

New Journal of Physics (Internet), 16(9), p.093003_1 - 093003_30, 2014/09

 Times Cited Count:22 Percentile:20.08(Physics, Multidisciplinary)

Journal Articles

Instrumentation for diagnostics and control of laser-accelerated proton (ion) beams

Bolton, P.; Borghesi, M.*; Brenner, C.*; Carroll, D. C.*; De Martinis, C.*; Fiorini, F.*; Flacco, A.*; Floquet, V.*; Fuchs, J.*; Gallegos, P.*; et al.

Physica Medica; European Journal of Medical Physics, 30(3), p.255 - 270, 2014/05

 Times Cited Count:44 Percentile:14(Radiology, Nuclear Medicine & Medical Imaging)

Journal Articles

Relativistic high harmonic generation in gas jet targets

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

AIP Conference Proceedings 1465, p.167 - 171, 2012/07

 Times Cited Count:1 Percentile:48.59

Journal Articles

High-order harmonics from bow wave caustics driven by a high-intensity laser

Esirkepov, T. Z.; Pirozhkov, A. S.; Kando, Masaki; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

AIP Conference Proceedings 1465, p.172 - 180, 2012/07

 Times Cited Count:0 Percentile:100

The bow wave induced mechanism of high-order harmonics generation was discovered using simulations and catastrophe theory. This mechanism feasibility was successfully demonstrated in 3D and 2D PIC simulations. The mechanism and the simulations explained high-order harmonics in the XUV spectral region seen in recent experiments with terawatt lasers. Development of new XUV light and X-ray source based on the high-order harmonics generation mechanism is proposed.

Journal Articles

Soft-X-ray harmonic comb from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

Physical Review Letters, 108(13), p.135004_1 - 135004_5, 2012/03

 Times Cited Count:59 Percentile:8.18(Physics, Multidisciplinary)

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multi-terawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving $$mu$$J/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.

Journal Articles

Coherent X-ray generation in relativistic laser - gas jet interactions

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Koga, J. K.; Kiriyama, Hiromitsu; et al.

Proceedings of SPIE, Vol.8140, p.81400A_1 - 81400A_16, 2011/10

Oral presentation

Observation of high-order harmonics produced by relativistic laser-plasma interaction

Kando, Masaki; Pirozhkov, A. S.; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.*; Kawachi, Tetsuya; Sagisaka, Akito; et al.

no journal, , 

When we focus laser pulses to the relativistic intensities (10$$^{18}$$ W/cm$$^2$$) in helium plasma, modulated spectra in the ultraviolet region (80- 300 eV) are observed in the forward direction. Some spectra contain odd and even high harmonics of the nearly fundamental frequency of the laser, continuum frequencies, and modulated structures. When we use a higher peak power laser (50-170 TW, 50fs), these spectral features are reproduced almost 100% probability. Also these spectra are observed when the laser polarization is changed to circular. The mechanism observed in our experiment is different from usual high-harmonics from gas targets, betatron radiation of electrons in wakefield, or nonlinear Thomson scattering due to above experimental conditions and results. We propose a theoretical model that electron density cusps formed by intense laser pulses radiate coherently. The validity of the model is confirmed with computer simulations.

Oral presentation

New coherent X-ray source based on relativistic high harmonic generation in gas jet targets

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; et al.

no journal, , 

We experimentally demonstrate new regime of high-order harmonic generation by relativistic-irradiance lasers in gas jet targets. With 9 TW laser, the harmonics reach the "water window" spectral region. Using 120 TW laser, we demonstrate the photon number scalability, with the energy of 40 $$mu$$J/sr per harmonic at 120 eV. We introduce a new mechanism of high-order harmonic generation based on the relativistic plasma phenomena and catastrophe theory. The mechanism is illustrated with high-resolution 2D and 3D PIC simulations. We discuss the potential applicability of the new coherent X-ray source for bioimaging.

Oral presentation

High-order harmonic generation in gas jet targets in the relativistic laser-plasma interaction regime

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.

no journal, , 

We experimentally demonstrate a new regime of high-order harmonic generation by relativistic-irradiance lasers in gas jet targets. Bright harmonics with both the odd and even orders are generated in the forward direction by either linearly or circularly polarized pulses, while the base harmonic frequency is downshifted. With a 9 TW laser, the harmonics reach the "water window" spectral region. Using a 120 TW laser, we demonstrate the photon number scalability up to 40 uJ/sr per harmonic at 120 eV. We introduce a new harmonic generation mechanism based on the relativistic plasma phenomena and catastrophe theory.

Oral presentation

High-order harmonic generation in gas jet targets by relativistic irradiance lasers

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Hayashi, Yukio; Kotaki, Hideyuki; et al.

no journal, , 

We have recently discovered a new high-order harmonic generation mechanism based on relativistic-irradiance ($$>10^{18}$$ W/cm$$^2$$) femtosecond lasers interacting with gas jet targets. The comb-like spectra consisting of even and odd orders are generated in the forward direction by either linearly or circularly polarized pulses. In experiments with the 9 TW J-KAREN laser, the spectra extended up to the photon energy of 360 eV, within the "water window" spectral range. We demonstrated the photon number scalability with laser power, reaching $$3times10^{12}$$ photons/sr within the 120$$pm$$0.5 nm spectral region at 120 TW with Astra Gemini laser. In this paper we describe the results concerning angular distribution, new data obtained with J-KAREN laser, and the generation mechanism in more details.

Oral presentation

High-order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Ya.*; Pikuz, T.; Hayashi, Yukio; Kotaki, Hideyuki; Ragozin, E. N.*; Koga, J. K.; Kiriyama, Hiromitsu; et al.

no journal, , 

We discovered a new high-order harmonic generation regime based on relativistic-irradiance ($$>$$ 10$$^{18}$$W/cm$$^{2}$$) femtosecond lasers interacting with gas jet targets using J-KAREN laser in JAEA and Astra Gemini laser in the CLF, RAL. The comb-like spectra, consisting of several hundred even and odd harmonic orders, are generated by either linearly or circularly polarized pulses. We introduced the new harmonic generation mechanism, where the harmonics are collectively emitted by oscillating electron spikes formed at the joint of the boundaries of a cavity and bow wave created by the relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by 2D and 3D PIC simulations. We describe recent results including the angular distribution, new experimental data obtained with the J-KAREN laser, and the generation mechanism in more details.

Oral presentation

High-order harmonics from gas jet targets with multi-TW lasers at intensities $$>$$ 10$$^{18}$$ W/cm$$^2$$

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Ya.*; Pikuz, T.; Hayashi, Yukio; Kotaki, Hideyuki; Ragozin, E. N.*; Koga, J. K.; Kiriyama, Hiromitsu; et al.

no journal, , 

We discovered a new high-order harmonic generation regime in the interaction of multi-TW relativistic-irradiance femtosecond lasers with gas jet targets. The spectra consisting of hundreds of even and odd harmonic orders are generated by either linearly or circularly polarized pulses. We proposed a new harmonic generation mechanism, where the harmonics are collectively emitted by oscillating electron spikes, whose sharpness and stability are explained by catastrophe theory.

13 (Records 1-13 displayed on this page)
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