Phase-Space Evolution of a Trapped Electron Beam

1973 ◽  
Vol 30 (3) ◽  
pp. 75-77 ◽  
Author(s):  
K. W. Gentle ◽  
J. Lohr
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Trapped Electron

scholarly journals Double layers in the downward current region of the aurora

2003 ◽  
Vol 10 (1/2) ◽  
pp. 45-52 ◽  
Author(s):  
R. E. Ergun ◽  
L. Andersson ◽  
C. W. Carlson ◽  
D. L. Newman ◽  
M. V. Goldman
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Phase Space ◽  
Electric Field ◽  
Electric Fields ◽  
Double Layers ◽  
Parallel Electric Field ◽  
Electrostatic Waves ◽  
Current Region ◽  
Decisive Evidence

Abstract. Direct observations of magnetic-field-aligned (parallel) electric fields in the downward current region of the aurora provide decisive evidence of naturally occurring double layers. We report measurements of parallel electric fields, electron fluxes and ion fluxes related to double layers that are responsible for particle acceleration. The observations suggest that parallel electric fields organize into a structure of three distinct, narrowly-confined regions along the magnetic field (B). In the "ramp" region, the measured parallel electric field forms a nearly-monotonic potential ramp that is localized to ~ 10 Debye lengths along B. The ramp is moving parallel to B at the ion acoustic speed (vs) and in the same direction as the accelerated electrons. On the high-potential side of the ramp, in the "beam" region, an unstable electron beam is seen for roughly another 10 Debye lengths along B. The electron beam is rapidly stabilized by intense electrostatic waves and nonlinear structures interpreted as electron phase-space holes. The "wave" region is physically separated from the ramp by the beam region. Numerical simulations reproduce a similar ramp structure, beam region, electrostatic turbulence region and plasma characteristics as seen in the observations. These results suggest that large double layers can account for the parallel electric field in the downward current region and that intense electrostatic turbulence rapidly stabilizes the accelerated electron distributions. These results also demonstrate that parallel electric fields are directly associated with the generation of large-amplitude electron phase-space holes and plasma waves.

A model to determine the initial phase space of a clinical electron beam from measured beam data

2000 ◽  
Vol 46 (2) ◽  
pp. 269-286 ◽  
Author(s):  
J J Janssen ◽  
E W Korevaar ◽  
L J van Battum ◽  
P R M Storchi ◽  
H Huizenga
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Initial Phase

scholarly journals Hrem Of General And Twist Grain Boundaries

1999 ◽  
Vol 5 (S2) ◽  
pp. 108-109
Author(s):  
K. L. Merkle ◽  
L. J. Thompson
Keyword(s):  
Thin Film ◽  
Electron Beam ◽  
Phase Space ◽  
Grain Boundaries ◽  
Scale Structure ◽  
Zone Axis ◽  
Low Energy ◽  
Atomic Scale ◽  
Dimensional Phase Space ◽  
Scale Structures

The observation of atomic-scale structures of grain boundaries (GBs) via axial illumination HREM has been largely restricted to tilt GBs, due to the requirement that the electron beam be parallel to a low-index zone axis on both sides of the interface. This condition can be fulfilled for all tilt GBs with misorientation about a low-index direction. The information obtained through HREM studies in many materials has brought important insights concerning the atomic-scale structure of such boundaries. However, it is well known that tilt GBs occupy only an infinitesimally small fraction of the 5-dimensional phase space which describes the macroscopic geometry of all GBs. Therefore, although tilt GBs are very important due to their low energy, it would be usefulto also study twist GBs and general GBs that contain twist and tilt components.We have prepared thin-film Au samples by an epitaxy technique in which (01l) and (001) grains are grown side by side.

Phase space distribution of an electron beam emerging from Compton/Thomson back-scattering by an intense laser pulse

2013 ◽  
Vol 101 (1) ◽  
pp. 10008 ◽  
Author(s):  
V. Petrillo ◽  
I. Chaikovska ◽  
C. Ronsivalle ◽  
A. R. Rossi ◽  
L. Serafini ◽  
...  
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Laser Pulse ◽  
Intense Laser ◽  
Space Distribution ◽  
Intense Laser Pulse ◽  
Phase Space Distribution ◽  
Back Scattering

scholarly journals Brightness of synchrotron radiation from undulators and bending magnets

2015 ◽  
Vol 22 (2) ◽  
pp. 288-316 ◽  
Author(s):  
Gianluca Geloni ◽  
Vitali Kocharyan ◽  
Evgeni Saldin
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Synchrotron Radiation ◽  
Wigner Distribution ◽  
Geometrical Optics ◽  
Single Electron ◽  
Beam Divergence ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Beam Size

The maximum of the Wigner distribution (WD) of synchrotron radiation (SR) fields is considered as a possible definition of SR source brightness. Such a figure of merit was originally introduced in the SR community by Kim [(1986),Nucl. Instrum. Methods Phys. Res. A,246, 71–76]. The brightness defined in this way is always positive and, in the geometrical optics limit, can be interpreted as the maximum density of photon flux in phase space. For undulator and bending magnet radiation from a single electron, the WD function can be explicitly calculated. In the case of an electron beam with a finite emittance the brightness is given by the maximum of the convolution of a single electron WD function and the probability distribution of the electrons in phase space. In the particular case when both electron beam size and electron beam divergence dominate over the diffraction size and the diffraction angle, one can use a geometrical optics approach. However, there are intermediate regimes when only the electron beam size or the electron beam divergence dominate. In these asymptotic cases the geometrical optics approach is still applicable, and the brightness definition used here yields back once more to the maximum photon flux density in phase space. In these intermediate regimes a significant numerical disagreement is found between exact calculations and the approximation for undulator brightness currently used in the literature. The WD formalism is extended to a satisfactory theory for the brightness of a bending magnet. It is found that in the intermediate regimes the usually accepted approximation for bending magnet brightness turns out to be inconsistent even parametrically.

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