نتایج جستجو برای: electron beam effect

تعداد نتایج: 1989434  

Journal: :Microscopy and Microanalysis 2015

2009
G. D. Ruano

We report measurements of secondary electron emission (SEE) induced by electron and ion bombardment on porous silicon (PS). We found that electron induced emission is strongly reduced by ion bombardment, and that this reduction is reversible. The reduction effect is large even for ion fluxes much lower compared to that of the electron beam. We attribute this effect to changes in the charge dist...

Journal: :iranian journal of medical physics 0
mohammad taghi bahreyni toossi professor, medical physics research center, bu-ali research institute, mashhad university of medical sciences, mashhad, iran mehdi momen nezhad ph.d., linear accelerator dept., imam reza hospital, mashhad university of medical sciences, mashhad, iran seyed mohammad hashemi m.sc., medical physics research center, mashhad university of medical sciences, mashhad, iran

introduction: in recent decades, several monte carlo codes have been introduced for research and medical applications. these methods provide both accurate and detailed calculation of particle transport from linear accelerators. the main drawback of monte carlo techniques is the extremely long computing time that is required in order to obtain a dose distribution with good statistical accuracy. ...

2008
W. Fischer U. Dorda J.-P. Koutchouk G. Sterbini F. Zimmermann

Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the...

2001
M. G. Kim C. D. Park E. S. Park T.-Y. Lee

Like other third generation light sources, main contributions to the be am lifetime of the Pohang Light Source come from the beam-gas scattering and the Touschek effect. The beam-gas scattering lifetime is measured with extremely low stored current in the long train of bunches. By investigating the vertical gap dependence of the beam-gas scattering lifetime, it i possible to decompose the beam-...

2000
S. Falabella

Using an induction linac, ETA-II, we are studying the interaction of a 2 kA, 6 MeV electron beam focused to a <2 mm diameter spot on high-Z foils. A focus shift was noticed when changing from 5 mil to 40 mil tantalum foil targets. This shift was subsequently attributed to the effect of a substantial fraction of the incident electron beam backscattering from the target, reducing the net beam cur...

Journal: :Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada 2004
John Cumings A Zettl M R McCartney

During in situ transmission electron microscopy (TEM) field emission experiments, carbon nanotubes are observed to strongly diffract the imaging TEM electron beam. We demonstrate that this effect is identical to that of a standard electrostatic biprism. We also demonstrate that the nanotube biprism can be used to capture electron-holographic information.

ژورنال: سنجش و ایمنی پرتو 2019

In an electron curtain accelerator, when the electron beam passes through the titanium exit window of the accelerator chamber, X-ray photons are produced as a negative by-product of retarding accelerated electrons. Controlling the produced X-ray photons to avoid their detrimental effects or in fact, proper shielding of the accelerator is an important issue that has to be considered in the use o...

Objective: The aim of this study is to evaluate the effect of tissue composition on dose distribution in electron beam radiotherapy.Methods: A Siemens Primus linear accelerator and a phantom were simulated using MCNPX Monte Carlo code. In a homogeneous cylindrical phantom, six types of soft tissue and three types of tissue-equivalent materials were investigated. The tissues included muscle (ske...

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