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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

Quasi-monochromatic pencil beam of laser-driven protons generated using a conical cavity target holder

Nishiuchi, Mamiko; Pirozhkov, A. S.; Sakaki, Hironao; Ogura, Koichi; Esirkepov, T. Z.; Tanimoto, Tsuyoshi; Kanasaki, Masato; Yogo, Akifumi; Hori, Toshihiko; Sagisaka, Akito; et al.

Physics of Plasmas, 19(3), p.030706_1 - 030706_4, 2012/03

 Times Cited Count:6 Percentile:68(Physics, Fluids & Plasmas)

A 7 MeV proton beam collimated to 16 mrad containing more than $$10^6$$ particles is experimentally demonstrated by focusing a 2J, 60 fs pulse of a Ti:sapphire laser onto targets of different materials and thicknesses placed in a millimeter scale conical holder. The electric potential induced on the target holder by laser-driven electrons accelerates and dynamically controls a portion of a divergent quasi-thermal proton beam originated from the target, producing a quasi-monoenergetic "pencil" beam.

Journal Articles

The Progress in the laser-driven proton acceleration experiment at JAEA with table-top Ti:Sappire laser system

Nishiuchi, Mamiko; Ogura, Koichi; Pirozhkov, A. S.; Tanimoto, Tsuyoshi; Yogo, Akifumi; Sakaki, Hironao; Hori, Toshihiko; Fukuda, Yuji; Kanasaki, Masato; Sagisaka, Akito; et al.

Proceedings of SPIE Europe Optics + Optoelectronics 2011, Vol.8079, 7 Pages, 2011/04

 Times Cited Count:0 Percentile:100

Because of the peculiar characteristics of the laser-driven proton beam, many potential applications are proposed including establishing compact medical accelerator for the cancer therapy. For our final destination to establish the compact laser-driven proton accelerator, the experiments are performed to investigate proton and ion acceleration from thin foil targets, using a high contrast, ultra-short laser pulse from the J-KAREN laser at the Japan Atomic Energy Agency. The P-polarized laser pulse with the parameters of 800 nm, 40 fs, 4J, and with extremely high ASE contrast of 10$$^{11}$$ is focused onto the thin-foil targets with variable materials and thicknesses ranging from 100 um to sub-um. The achieved peak intensity is $$>$$ 10$$^{20}$$ Wcm$$^{-2}$$. The maximum proton energy is reached to 14 MeV. The number of $$sim$$ 10 MeV protons is enough to carry 2 Gy dose onto the skin of the mouse within 10min with 10 Hz operation. This enables us to carry out in-vivo test instead of in-vitro test.

Oral presentation

Laser-accelerated high energy proton beam generation with the high contrast Ti:Sap laser at JAEA

Nishiuchi, Mamiko; Yogo, Akifumi; Ogura, Koichi; Mori, Michiaki; Sagisaka, Akito; Pirozhkov, A. S.; Orimo, Satoshi; Tampo, Motonobu; Kiriyama, Hiromitsu; Shimomura, Takuya; et al.

no journal, , 

no abstracts in English

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

Highly collimated Quasi-monochromatic laser-driven proton beam generation by target holder having conical cavity

Nishiuchi, Mamiko; Pirozhkov, A. S.; Sakaki, Hironao; Ogura, Koichi; Esirkepov, T. Z.; Tanimoto, Tsuyoshi; Yogo, Akifumi; Hori, Toshihiko; Sagisaka, Akito; Fukuda, Yuji; et al.

no journal, , 

We have successfully accelerate quasi-mono-energetic collimated 7MeV proton beam bt the interaction between the 2J 60fs Ti Sappire laser pulses with the thin-foil target on the target holder with conical cavity. The focusing and energy selection is by the E-field induced along the surface of the conical cavity by the point charge brought away by the escape electrons.

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.

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