- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Proton acceleration via the TNSA mechanism using a smoothed laser focus
摘要： In this work, we present the results of an experiment aiming at proton acceleration using a focus with a homogeneous intensity distribution, called smoothed focus. To achieve this goal, we implemented a phase plate before the pre-amplifier of the Petawatt High-Energy Laser for Heavy Ion EXperiments laser facility. The phase plate was used for the first time at a high-power short-pulse laser. Demonstrating a low divergent ion beam was the main goal of this work. Numerical simulations using the particle-in-cell code Extendable PIC Open Collaboration estimated a 2–5 times reduction in the angular divergence of the proton beam using a phase plate due to a smoother sheath at the rear side of the target. However, the reduction in the angular divergence was not sensible according to the experimental data. A positive point is that the spectrum of protons that are generated with the smoothed beam is shifted toward lower energies, provided that the laser absorption is kept in check, compared to the Gaussian proton spectrum. Moreover, the number of protons that are generated with the smoothed beam is higher than the ones generated with the Gaussian beam.
关键词： smoothed laser focus,proton acceleration,phase plate,TNSA mechanism,PHELIX laser facility
更新于2025-09-23 15:19:57
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Implementation of a phase plate for the generation of homogeneous focal-spot intensity distributions at the high-energy short-pulse laser facility PHELIX
摘要： We propose and demonstrate the use of random phase plates (RPPs) for high-energy sub-picosecond lasers. Contrarily to previous work related to nanosecond lasers, an RPP poses technical challenges with ultrashort-pulse lasers. Here, we implement the RPP near the beginning of the ampli?er and image-relay it throughout the laser ampli?er. With this, we obtain a uniform intensity distribution in the focus over an area 1600 times the diffraction limit. This method shows no signi?cant drawbacks for the laser and it has been implemented at the PHELIX laser facility where it is now available for users.
关键词： high-power laser,phase plate,short-pulse laser,beam shaping
更新于2025-09-12 10:27:22
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Laser phase plate for transmission electron microscopy
摘要： Transmission electron microscopy (TEM) of rapidly frozen biological specimens, or cryo-EM, would benefit from the development of a phase plate for in-focus phase contrast imaging. Several types of phase plates have been investigated, but rapid electrostatic charging of all such devices has hindered these efforts. Here, we demonstrate electron phase manipulation with a high-intensity continuous-wave laser beam, and use it as a phase plate for TEM. We demonstrate the laser phase plate by imaging an amorphous carbon film. The laser phase plate provides a stable and tunable phase shift without electrostatic charging or unwanted electron scattering. These results suggest the possibility for dose-efficient imaging of unstained biological macromolecules and cells.
关键词： cryo-EM,laser,Transmission electron microscopy,biological specimens,phase plate
更新于2025-09-12 10:27:22
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Charging of electron beam irradiated amorphous carbon thin films at liquid nitrogen temperature
摘要： We studied the charging behavior of an amorphous carbon thin film kept at liquid-nitrogen temperature under focused electron-beam irradiation. Negative charging of the thin film is observed. The charging is attributed to a local change in the work function of the thin film induced by electron-stimulated desorption similar to the working principle of the hole free phase plate in its Volta potential implementation at elevated temperature. The negative bias of the irradiated film arises from the electron beam induced desorption of water molecules from the carbon film surface. The lack of positive charging, which is expected for non-conductive materials, is explained by a sufficient electrical conductivity of the carbon thin film even at liquid-nitrogen temperature as proven by multi-probe scanning tunneling microscopy and spectroscopy measurements.
关键词： Thin film,Radiation damage,Phase plate,Electron-beam induced charging,Hole free phase plate,Transmission electron microscope,Volta phase plate
更新于2025-09-10 09:29:36