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

https://www.clf.stfc.ac.uk/Pages/2014-15.aspx

Full-coherent free electron laser seeded by 13th- and 15th-order harmonics of near-infrared femtosecond laser pulses

Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Togashi, Tadashi*; Fukami, Kenji*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164006_1 - 164006_6, 2013/08

https://doi.org/10.1088/0953-4075/46/16/164006

By introducing 13th- (61.7 nm) and 15th-order harmonics (53.4 nm) of femtosecond laser pulses at 800 nm into an undulator of SCSS (SPring-8 Compact SASE Source) test accelerator at RIKEN, these harmonic pulses were amplified by a factor of more than 10 with a high contrast ratio through the interaction between accelerated electron bunches and the harmonic pulses. From numerical simulations of the amplification processes of high-order harmonic pulses in the undulator, optimum conditions of the electron bunch duration interacting with the high-order harmonic pulses were investigated for generating full-coherent and intense pulses in the extreme ultraviolet wavelength region.

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

https://doi.org/10.1063/1.4737558

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.

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

https://doi.org/10.1103/PhysRevLett.108.135004

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 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.

Development of a sub-MeV X-ray source via Compton backscattering

Kawase, Keigo; Kando, Masaki; Hayakawa, Takehito; Daito, Izuru; Kondo, Shuji; Homma, Takayuki; Kameshima, Takashi*; Kotaki, Hideyuki; Chen, L. M.*; Fukuda, Yuji; et al.

Nuclear Instruments and Methods in Physics Research A, 637(1, Suppl.), p.S141 - S144, 2011/05

https://doi.org/10.1016/j.nima.2010.02.042

We report the present status of the sub-MeV X-ray generation via Compton backscattering by using 150-MeV electron beam and the Nd:YAG laser. In particular, we show the result of the X-ray generation experiment and of the laser pulse compression for increasing the X-ray flux.

Extreme ultraviolet free electron laser seeded with high-order harmonic of Ti:sapphore laser

Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Okino, Tomoya*; Yamanouchi, Kaoru*; et al.

Optics Express (Internet), 19(1), p.317 - 324, 2011/01

https://doi.org/10.1364/OE.19.000317

The 13th harmonic of a Ti:sapphire (Ti:S) laser in the plateau region was injected as a seeding source to a 250-MeV free-electron-laser (FEL) amplifier. When the amplification conditions were fulfilled, strong enhancement of the radiation intensity by a factor of 650 was observed. The random and uncontrollable spikes, which appeared in the spectra of the Self-Amplified Spontaneous Emission (SASE) based FEL radiation without the seeding source, were found to be suppressed drastically to form to a narrow-band, single peak profile at 61.2 nm. The properties of the seeded FEL radiation were well reproduced by numerical simulations. We discuss the future precept of the seeded FEL scheme to the shorter wavelength region.

Method of observing the spot where full-power counter-propagating laser pulses collide in plasma media

Kawase, Keigo; Kando, Masaki; Pirozhkov, A. S.; Homma, Takayuki; Kameshima, Takashi*; Daito, Izuru; Hayashi, Yukio; Kotaki, Hideyuki; Fukuda, Yuji; Esirkepov, T. Z.; et al.

Applied Physics Express, 3, p.016101_1 - 016101_3, 2010/01

https://doi.org/10.1143/APEX.3.016101

A new observation method of providing a precise collision of two full-power counter-propagating laser pulses is proposed and demonstrated. The method is a combination of top-view imaging, side-view shadowgram, extra-ultraviolet (XUV) spectrograph, and returning pulse monitoring. This allows us to align two counter-propagating laser pulses at their colliding point in a real situation (full power laser operation in plasma). The achieved spatial resolution of the monitor in the plasma is 1.35 with the precision level of alignment better than 15 even when there is plasma present.

Electron optical injection with head-on and countercrossing colliding laser pulses

Kotaki, Hideyuki; Daito, Izuru; Kando, Masaki; Hayashi, Yukio; Kawase, Keigo; Kameshima, Takashi*; Fukuda, Yuji; Homma, Takayuki; Ma, J.*; Chen, L. M.*; et al.

Physical Review Letters, 103(19), p.194803_1 - 194803_4, 2009/11

https://doi.org/10.1103/PhysRevLett.103.194803

Energy increase in multi-MeV ion acceleration in the interaction of a short pulse laser with a cluster-gas target

Fukuda, Yuji; Faenov, A. Y.; Tampo, Motonobu; Pikuz, T. A.*; Nakamura, Tatsufumi; Kando, Masaki; Hayashi, Yukio; Yogo, Akifumi; Sakaki, Hironao; Kameshima, Takashi*; et al.

Physical Review Letters, 103(16), p.165002_1 - 165002_4, 2009/10

https://doi.org/10.1103/PhysRevLett.103.165002

A new approach for accelerating ions, based on the use of a cluster-gas target and a compact ultrashort pulse laser, is presented. It is shown that ions with energy 10-20 MeV per nucleon having a small divergence (full angle) of 3.4 are generated, corresponding to an approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell code 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 near-critical density plasmas.

Experimental studies of the high and low frequency electromagnetic radiation produced from nonlinear laser-plasma interactions

Kando, Masaki; Pirozhkov, A. S.; Fukuda, Yuji; Esirkepov, T. Z.; Daito, Izuru; Kawase, Keigo; Ma, J. L.*; Chen, L. M.*; Hayashi, Yukio; Mori, Michiaki; et al.

European Physical Journal D, 55(2), p.465 - 474, 2009/09

https://doi.org/10.1140/epjd/e2009-00246-x

Nonlinear interaction of intense laser beams with plasma causes a number of different regimes of generation of high energy particle beams and of strong radiation with the emitted photon energy from the X-ray to THz frequency range. The review of the first proof-of-principle experiment and the latest progress on the flying mirror is presented. A low frequency EM radiation emission has also been observed in our experiments. The interpretation invokes the relativistic electromagnetic solitons. The solitons are formed in an underdense plasma in the process of the laser pulse frequency downshift. They store a portion of EM wave energy with the polarization inherited from the laser and emit it at the plasma-vacuum interface in a form of the low frequency EM bursts. We present the results of the polarization-resolved measurements.