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.
A Neutron/Gamma-ray combined inspection system for hidden special nuclear materials (SNMs) in cargo containers has been developed under a program of Japan Science and Technology Agency in Japan. This ...inspection system consists of an active neutron-detection system for fast screening and a laser Compton backscattering gamma-ray source in coupling with nuclear resonance fluorescence (NRF) method for precise inspection. The inertial electrostatic confinement fusion device has been adopted as a neutron source and two neutron-detection methods, delayed neutron noise analysis method and high-energy neutron-detection method, have been developed to realize the fast screening system. The prototype system has been constructed and tested in the Reactor Research Institute, Kyoto University. For the generation of the laser Compton backscattering gamma-ray beam, a race track microtron accelerator has been used to reduce the size of the system. For the NRF measurement, an array of LaBr 3 (Ce) scintillation detectors has been adopted to realize a low-cost detection system. The prototype of the gamma-ray system has been demonstrated in the Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology. By using numerical simulations based on the data taken from these prototype systems and the inspection-flow, the system designed by this program can detect 1 kg of highly enriched 235 U (HEU) hidden in an empty 20-ft container within several minutes.
Optical parametric chirped-pulse amplification (OPCPA) operation with low gain by seeding with high-energy, clean pulses is shown to significantly improve the contrast to better than 10(-10) to ...10(-11) in a high-intensity Ti:sapphire laser system that is based on chirped-pulse amplification. In addition to the high-contrast broadband, high-energy output from the final amplifier is achieved with a flat-topped spatial profile of filling factor near 77%. This is the result of pump beam spatial profile homogenization with diffractive optical elements. Final pulse energies exceed 30 J, indicating capability for reaching peak powers in excess of 500 TW.
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.
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.
We have observed simultaneously both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a 5-μm thick titanium target. In order to control the proton ...acceleration and THz radiation, we have changed the duration of the amplified spontaneous emission (ASE) preceding the main pulse generated by the high-intensity Ti:sapphire laser. A fast proton beam with the maximal energy of ∼ 490 keV has been realized by reducing the duration of the ASE. Simultaneously, an intense emission of THz radiation is observed for various ASE durations. We propose the antenna mechanism for the THz radiation, according to which the fast electrons moving along the target surface emit the low-frequency electromagnetic wave.
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.
Magnetic spectrometer Grand Raiden Fujiwara, M; Akimune, H; Daito, I ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
1999, Volume:
422, Issue:
1
Journal Article
Peer reviewed
A high-resolution magnetic spectrometer called “Grand Raiden” is operated at the RCNP ring cyclotron facility in Osaka for nuclear physics studies at intermediate energies. This magnetic spectrometer ...has excellent ion-optical properties. In the design of the spectrometer, the second-order dispersion matching condition has been taken into account, and almost all the aberration terms such as
(x|θ
3),
(x|θφ
2),
(x|θ
2δ)
and (
x|
θδ
2) in a third-order matrix calculation are optimized. A large magnetic rigidity of the spectrometer (
K
=
1400
MeV) gives a great advantage to measure the charge-exchange (
3He, t) reactions at 450
MeV. The ability of the high-resolution measurement has been demonstrated. Various coincidence measurements are performed to study the nuclear structures of highly excited states through decay properties of nuclear levels following nuclear reactions at intermediate energies.
The Nuclear Physics oriented pillar of the pan-European Extreme Light Infrastructure (ELI-NP) will host an ultra-bright, energy tunable, and quasi-monochromatic gamma-ray beam system in the range of ...0.2-19.5 MeV produced by laser-Compton backscattering technique. The applied research program envisioned at ELI-NP targets to use nuclear resonance fluorescence (NRF) and computed tomography to provide new opportunities for industry and society. High sensitivity NRF-based investigations can be successfully applied to safeguard applications and management of radioactive wastes as well as to uncharted fields like cultural heritage and medical imaging. Gamma-ray radioscopy and computed tomography performed at ELI-NP has the potential to achieve high resolution in industrial-sized objects provided the detection challenges introduced by the unique characteristics of the gamma beam are overcome. Here we discuss the foreseen industrial applications that will benefit from the high quality and unique characteristics of ELI-NP gamma beam and the challenges they present. We present the experimental setups proposed to be implemented for this goal, discuss their performance based on analytical calculations and numerical Monte-Carlo simulations, and comment about constrains imposed by the limitation of current scintillator detectors. Several gamma-beam monitoring devices based on scintillator detectors will also be discussed.
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