Protons and carbon ions acceleration in the target-normal-sheath-acceleration regime using low-contrast fs laser and metal-graphene targets

2019 ◽  
Vol 60 (1) ◽  
pp. e201900076
Author(s):  
Lorenzo Torrisi ◽  
Mariapompea Cutroneo ◽  
Alfio Torrisi
Keyword(s):  
Carbon Ions ◽  
Low Contrast ◽  
Fs Laser

scholarly journals Optimization of laser acceleration of protons from mixed structure nanotarget

2015 ◽  
Vol 33 (2) ◽  
pp. 339-346 ◽  
Author(s):  
Saeed Mirzanejhad ◽  
Farshad Sohbatzadeh ◽  
Atefeh Joulaei ◽  
Javad Babaei ◽  
Khadijeh Shahabei
Keyword(s):  
Laser Pulses ◽  
Analytical Models ◽  
Ion Acceleration ◽  
Carbon Ions ◽  
Simulation Code ◽  
Particle In Cell ◽  
Target Composition ◽  
Cell Simulation ◽  
Fs Laser ◽  
20 Nm

AbstractIn this study, ion acceleration from thin planar diamond-like carbon (DLC) and polystyrene (PS) foils irradiated by ultraintense (a0 = 200) and ultrashort (15 fs) laser pulses is investigated numerically. The effects of target composition and thickness on the acceleration of protons and carbon ions are reported by 1D3V particle-in-cell simulation code and compared with the analytical models of ion acceleration. In the analytical formalism, the acceleration criterion of ions with different charge-to-mass ratio (q/m) is obtained. This criterion is related to the potential difference through the electrostatic shock distortion and its velocity. According to this result, charged particles with large q/m ratio have a good chance to accelerate in front of the electrostatic shock field. It is shown that mono-energetic proton bunch with energies >1.5 GeV is produced by 20 nm DLC foil supported by 10 nm hydrogen layer. Finally nanometer PS foil is examined and 2.33 Gev protons with ~1.5% energy spread are obtained for 50 nm thickness.

Exploring Coronal Structures with SOHO

2000 ◽  
Vol 179 ◽  
pp. 403-406
Author(s):  
M. Karovska ◽  
B. Wood ◽  
J. Chen ◽  
J. Cook ◽  
R. Howard
Keyword(s):  
Solar Corona ◽  
Image Enhancement ◽  
Coronal Mass Ejections ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Low Contrast ◽  
Contrast Structures ◽  
Scale Structures ◽  
Small Scale Structures ◽  
Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

XUV Absorption Spectra of Carbon Ions

1988 ◽  
Vol 102 ◽  
pp. 71-73
Author(s):  
E. Jannitti ◽  
P. Nicolosi ◽  
G. Tondello
Keyword(s):  
Absorption Spectra ◽  
Cross Section ◽  
Theoretical Calculations ◽  
Photoionization Cross Section ◽  
Carbon Ions

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.

One Million Direct Magnification Microscopy

1971 ◽  
Vol 29 ◽  
pp. 166-167
Author(s):  
J. A. Hugo ◽  
V. A. Phillips
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Illumination Level ◽  
Level Of Detail ◽  
Photographic Emulsion ◽  
Low Contrast ◽  
Fluorescent Screen ◽  
Resolution Electron ◽  
Lattice Images ◽  
Electron Microscopes

A continuing problem in high resolution electron microscopy is that the level of detail visible to the microscopist while he is taking a picture is inferior to that obtainable by the microscope, readily readable on a photographic emulsion and visible in an enlargement made from the plate. Line resolutions, of 2Å or better are now achievable with top of the line 100kv microscopes. Taking the resolution of the human eye as 0.2mm, this indicates a need for a direct viewing magnification of at least one million. However, 0.2mm refers to optimum viewing conditions in daylight or the equivalent, and certainly does not apply to a (colored) image of low contrast and illumination level viewed on a fluorescent screen through a glass window by the dark-adapted eye. Experience indicates that an additional factor of 5 to 10 magnification is needed in order to view lattice images with line spacings of 2 to 4Å. Fortunately this is provided by the normal viewing telescope supplied with most electron microscopes.

Field Emission SEM Equipped With Noise Compensator

1973 ◽  
Vol 31 ◽  
pp. 302-303
Author(s):  
S. Saito ◽  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Field Emission ◽  
Low Contrast ◽  
Probe Current ◽  
High Resolution Images ◽  
Scanning Electron

Field emission scanning electron microscope (FESEM) features extremely high resolution images, and offers many valuable information. But, for a specimen which gives low contrast images, lateral stripes appear in images. These stripes are resulted from signal fluctuations caused by probe current noises. In order to obtain good images without stripes, the fluctuations should be less than 1%, especially for low contrast images. For this purpose, the authors realized a noise compensator, and applied this to the FESEM.Fig. 1 shows an outline of FESEM equipped with a noise compensator. Two apertures are provided gust under the field emission gun.

Analysis of 3-d molecular distribution with the digital imaging microscope

1988 ◽  
Vol 46 ◽  
pp. 40-41
Author(s):  
W.A. Carrington ◽  
F.S. Fay ◽  
K.E. Fogarty ◽  
L. Lifshitz
Keyword(s):  
Image Restoration ◽  
Digital Imaging ◽  
Fluorescent Dyes ◽  
Optical Axis ◽  
Computer Hardware ◽  
Computer Algorithms ◽  
Low Contrast ◽  
Specific Proteins ◽  
Effective Use ◽  
Single Living Cells

Advances in digital imaging microscopy and in the synthesis of fluorescent dyes allow the determination of 3D distribution of specific proteins, ions, GNA or DNA in single living cells. Effective use of this technology requires a combination of optical and computer hardware and software for image restoration, feature extraction and computer graphics.The digital imaging microscope consists of a conventional epifluorescence microscope with computer controlled focus, excitation and emission wavelength and duration of excitation. Images are recorded with a cooled (-80°C) CCD. 3D images are obtained as a series of optical sections at .25 - .5 μm intervals.A conventional microscope has substantial blurring along its optical axis. Out of focus contributions to a single optical section cause low contrast and flare; details are poorly resolved along the optical axis. We have developed new computer algorithms for reversing these distortions. These image restoration techniques and scanning confocal microscopes yield significantly better images; the results from the two are comparable.

Resistance Monitor and Control for Vacuum Evaporation of Metals and Carbon

1976 ◽  
Vol 34 ◽  
pp. 572-573
Author(s):  
Russell L. Steere ◽  
Eric F. Erbe ◽  
J. Michael Moseley
Keyword(s):  
Electronic Device ◽  
Point Sources ◽  
High Contrast ◽  
Variable Resistor ◽  
Quality Of Results ◽  
Low Contrast ◽  
Evaporation Source ◽  
And Control ◽  
At Will

We have designed and built an electronic device which compares the resistance of a defined area of vacuum evaporated material with a variable resistor. When the two resistances are matched, the device automatically disconnects the primary side of the substrate transformer and stops further evaporation.This approach to controlled evaporation in conjunction with the modified guns and evaporation source permits reliably reproducible multiple Pt shadow films from a single Pt wrapped carbon point source. The reproducibility from consecutive C point sources is also reliable. Furthermore, the device we have developed permits us to select a predetermined resistance so that low contrast high-resolution shadows, heavy high contrast shadows, or any grade in between can be selected at will. The reproducibility and quality of results are demonstrated in Figures 1-4 which represent evaporations at various settings of the variable resistor.

“High Resolution High Voltage Electron Microscopy”

1968 ◽  
Vol 26 ◽  
pp. 326-327
Author(s):  
Benjamin M. Siegel
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Voltage ◽  
Full Potential ◽  
Contrast Imaging ◽  
High Voltage Electron Microscopy ◽  
Low Contrast ◽  
Voltage Electron ◽  
Critical Areas ◽  
High Voltage Electron

The potential advantages of high voltage electron microscopy for extending the limits of resolution and contrast in imaging low contrast objects, such as biomolecular specimens, is very great. The results of computations will be presented showing that at accelerating voltages of 500-1000 kV it should be possible to achieve spacial resolutions of 1 to 1.5 Å and using phase contrast imaging achieve adequate image contrast to observe single atoms of low atomic number.The practical problems associated with the design and utilization of the high voltage instrument are, optimistically, within the range of competence of the state of the art. However, there are some extremely important and critical areas to be systematically investigated before we have achieved this competence. The basic electron optics of the column required is well understood, but before the full potential of an instrument capable of resolutions of better than 1.5 Å are realized some very careful development work will be required. Of great importance for the actual achievement of high resolution with a high voltage electron microscope is the fundamental limitation set by the characteristics of the high voltage electron beam that can be obtained from the accelerator column.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

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