The generation of extremely bright coherent X-ray pulses in the femtosecond and attosecond regime is currently one of the most exciting frontiers of physics-allowing, for the first time, measurements ...with unprecedented temporal resolution. Harmonics from laser-solid target interactions have been identified as a means of achieving fields as high as the Schwinger limit (E=1.3×1016 V m−1) and as a highly promising route to high-efficiency attosecond (10−18 s) pulses owing to their intrinsically phase-locked nature. The key steps to attain these goals are achieving high conversion efficiencies and a slow decay of harmonic efficiency to high orders by driving harmonic production to the relativistic limit. Here we present the first experimental demonstration of high harmonic generation in the relativistic limit, obtained on the Vulcan Petawatt laser. High conversion efficiencies (η>10−6 per harmonic) and bright emission (>1022 photons s−1 mm−2 mrad−2 (0.1% bandwidth)) are observed at wavelengths <4 nm (the `water-window' region of particular interest for bio-microscopy).
Abstract
We have developed a non-destructive technique to observe Li in an electrode and metallic Li deposition on an anode using muonic x-rays. With high intent negative muon beam at J-PARC, we have ...attempted operando measurements of Li and metallic Li deposition in LIBs for the first time. Both increase and decrease of Li in a cathode during charging and discharging processes were observed. We also observed significant increase of muonic x-rays of Li with cycles, which may correspond to the degradation of charge capacity with the cycles.
Abstract
Negative muon elemental analysis, which can measure depth-wise elemental composition from 100 nm to several centimeters with a depth resolution of order
µ
m, is a revolutionary technology ...that enables the nondestructive analysis of materials. In recent years, this technique has begun to apply to understand historical cultural heritage. We have studied the Japanese archaeological heritage to provide new insights into Japanese archaeological research. Here, we report the progress on development of intense (high speed) negative muon X-ray measurement system at KEK Muon Science Laboratory (MSL) in the Japan Proton Accelerator Research Complex (J-PARC). For this purpose, the efficiency of detectors (wide energy range and high resolution) were improved by preparing a high-purity multi-arrayed germanium semiconductor detectors (HP Ge) to detect one photon or less per muon pulse available in J-PARC. In addition, by increasing the number of detectors and suppressing the noise sources, we have succeeded to enhance the detection efficiency by about 10 times compared to conventional systems.
Present status of J-PARC MUSE Shimomura, K; Koda, A; Pant, A D ...
Journal of physics. Conference series,
03/2023, Letnik:
2462, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
At J-PARC MUSE, since the
µ
SR2017 conference and up to FY2022, there have been several new developments at the facility, including the completion of a new experimental area S2 at the ...surface muon beamline S-line and the first muon beam extraction to the H1 area in the H-line, mainly to carry out high-statistics fundamental physics experiments. Several new studies are also underway, such as applying negative muon non-destructive elemental analysis to the analysis of samples returned from the asteroid Ryugu in the D2 area of the D-line. This paper reports on the latest status of MUSE.
It is demonstrated experimentally and by numerical simulations that the presence of a long-pulse-laser-created back plasma on the target backside can focus the relativistic electrons produced by ...shortpulse laser interaction with the front of a solid target. Comparing this to that without the back plasma, the number density of the fast electrons is increased by one order of magnitude, and their divergence angle is reduced fivefold. The effect is attributed to the absence of the backside sheath electric field and the collimation effect of the megagauss self-generated baroclinic magnetic field there. Such an acceleration scheme can be useful to applications requiring high-energy and chargedensity electron bunches, such as fast ignition in inertial fusion.
To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high precision x-ray spectroscopy of the 5g-4f and 5f- 4d transitions (BSQED contribution of 2.4 and ...5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the 5g_{9/2}- 4f_{7/2} transition energy to be 6297.08±0.04(stat)±0.13(syst) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.
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.
Spectrally-peaked proton beams of high charge ( , , nC ) have been observed from the interaction of an intense laser ( W cm−2) with ultrathin CH foils, as measured by spectrally-resolved full beam ...profiles. These beams are reproducibly generated for foil thicknesses 5-100 nm, and exhibit narrowing divergence with decreasing target thickness down to for 5 nm. Simulations demonstrate that the narrow energy spread feature is a result of buffered acceleration of protons. The radiation pressure at the front of the target results in asymmetric sheath fields which permeate throughout the target, causing preferential forward acceleration. Due to their higher charge-to-mass ratio, the protons outrun a carbon plasma driven in the relativistic transparency regime.
To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a ...fluence of 0.5 J/cm
2
. The temporal evolution of the ablation plume was investigated in vacuum and helium environments. In vacuum, the flow velocity perpendicular to the sample surface was determined to be 2.7 km/s for neutral atoms and 4.0 km/s for singly charged atoms. These velocities are about 20 % lower than those of cerium measured under similar conditions. From the evolution of the plume in helium, we found that an observation time of 3–5 μs and an observation height of about 2.5 mm are most suited for obtaining higher sensitivity. Observation times less than 3 μs were unsuitable for precise isotope analysis since the spectral modifications arising from the Doppler splitting effect are different between the two uranium isotopes. Using the established conditions, we evaluated the calibration curve linearity, limit of detection, and precision for three samples having different abundances of
235
U.
Modern high-power lasers can generate extreme states of matter that are relevant to astrophysics, equation-of-state studies and fusion energy research. Laser-driven implosions of spherical polymer ...shells have, for example, achieved an increase in density of 1,000 times relative to the solid state. These densities are large enough to enable controlled fusion, but to achieve energy gain a small volume of compressed fuel (known as the 'spark') must be heated to temperatures of about 108 K (corresponding to thermal energies in excess of 10 keV). In the conventional approach to controlled fusion, the spark is both produced and heated by accurately timed shock waves, but this process requires both precise implosion symmetry and a very large drive energy. In principle, these requirements can be significantly relaxed by performing the compression and fast heating separately; however, this 'fast ignitor' approach also suffers drawbacks, such as propagation losses and deflection of the ultra-intense laser pulse by the plasma surrounding the compressed fuel. Here we employ a new compression geometry that eliminates these problems; we combine production of compressed matter in a laser-driven implosion with picosecond-fast heating by a laser pulse timed to coincide with the peak compression. Our approach therefore permits efficient compression and heating to be carried out simultaneously, providing a route to efficient fusion energy production.
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