3,932 research outputs found
Relativistic particle motion of a charge including the radiation reaction
The problem of the electromagnetic radiation of an accelerated charged particle is one of the
most controversial issues in Physics since the beginning of the last century representing one of
the most popular unsolved problems of the Modern Physics. Different equations of motion for
a point charge including the electromagnetic radiation emitted have been proposed throughout
history, but all these expressions show some limitations. An equation based on the principle of
conservation of energy is proposed for the ultra-relativistic motion. Different examples are
analyzed showing that the energy lost by the charge agrees with the relativistic generalization
of the Larmor formula. This proposed equation has been compared with the Landau-Lifshitz
equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula.
Finally, it is discussed a possible variation of the typical relativistic particle integrators (e.g. Boris,
Vay or Higuera-Cary methods) in order to include the radiation reaction
Numerical study of dark current dynamics in a high-gradient backward travelling wave accelerating cavity using the electromagnetic simulation software CST studio.
High-Gradient accelerating cavities are one of the main research lines in the development of
compact linear colliders. However, the operation of such cavities is currently limited by nonlinear
effects that are intensified at high electric fields, such as dark currents and radiation
emission or RF breakdowns.
A new normal-conducting High-Gradient S-band Backward Travelling Wave accelerating
cavity for medical application (v=0.38c) designed and constructed at Conseil Européen pour la
Recherche NuclĂ©aire (CERN) is being tested at Instituto de FĂsica Corpuscular (IFIC) High Power
RF Laboratory. The objective consists of studying its viability in the development of compact
linear accelerators for hadrontherapy treatments in hospitals.
Due to the high surface electric field in the cavity, electrons are emitted following Fowler-
Nordheim equation, also known as dark currents. The emission and dynamic of these
electrons are of fundamental importance on different phenomena such as RF Breakdowns or
radiation dose emission.
In this work, 3D electromagnetic numerical simulations have been performed using the
computer simulation technology software CST Studio Suite. Then, the resulting EM field maps
are used to study the emission and electron dynamics inside the cavity. The simulation results
are compared with experimental data and first conclusions discussed
Novel reaction force for ultra-relativistic dynamics of a classical point charge
The problem of the electromagnetic radiation of an accelerated charged
particle is one of the most controversial issues in Physics since the beginning
of the last century, representing one of the most popular unsolved problems of
the Modern Physics. Different equations of motion have been proposed throughout
history for a point charge including the electromagnetic radiation emitted, but
all these expressions show some limitations. An equation based on the principle
of conservation of energy is proposed in this work for the ultra-relativistic
motion. Different examples are analyzed showing that the energy lost by the
charge agrees with the Li\'enard formula. This proposed equation has been
compared with the Landau-Lifshitz equation obtaining a good agreement in the
range of application of the Landau-Lifshitz formula.Comment: 9 pages, 10 figure
Effect of reactive ion beam etching on the photoluminescence of CdTe epitaxial layers
We demonstrated the effect of reactive ion beam etching (RIBE) process on the PL properties of CdTe/sapphire metal organic vapor phase epitaxy layers. At optimum conditions, the RIBE attack does not make significant morphological changes but it results in an increase of the concentration of acceptor impurities. This was revealed by an increase of the overall photoluminescence (PL) intensity and, simultaneously, a decrease of the PL decay time, more important on the low energy side of PL spectrum due to the recombination of carriers in acceptor [email protected]
Study of the RF pulse heating phenomenon in high gradient accelerating devices by means of analytical approximations
The main objective of this work is to present a
simple method, based on analytical expressions, for obtaining
a quick approximation of the temperature rise due to the Joule
effect inside the metallic walls of an RF accelerating device. This
proposal relies on solving the 1D heat-transfer equation for a
thick wall, where the heat sources inside the wall are the ohmic
losses produced by the RF electromagnetic fields penetrating
the metal with finite electrical conductivity. Furthermore, it is
discussed how the theoretical expressions of this method can be
applied to obtain an approximation to the temperature increase
in realistic 3D RF accelerating structures, taking as an example
the cavity of an RF electron gun. These theoretical results have
been benchmarked with numerical simulations carried out with
commercial finite-element method codes, finding good agreement
among them
Two-dimensional simulation of the electron transport in a photomultiplier tube
Photomultiplier tubes are widely used in experimental physics because they convert small light
signals into a measurable electric current. Although their working principle is well known, it is
very difficult to find simulations of the electron transport in these devices. For this reason, the
electron transport in the Hamamatsu R13408-100 photomultiplier tube has been simulated in
2D. The software SUPERFISH is used for calculating the electrostatic fields and the Boris method
for the effective electron dynamics. The secondary electron emission in the dynodes is
implemented using an effective electron model and the modified Vaughan’s model. Some
figures of merit for photomultiplier tubes (e.g. the gain, the electron transit time or the transit
time spread) in function of the supply voltage and an external magnetic field have been studied
obtaining a good qualitative accordance with the Hamamatsu datasheet. In further studies, we
are going to compare our simulations with experimental measurements
Status of Diamond Detector Development for Beam Halo Investigation at ATF2
Work supported by Chinese Scholarship Council - THPME092, ISBN 978-3-95450-132-8International audienceWe are developing a diamond detector for beam halo and Compton spectrum diagnostics after the interaction point (IP) of ATF2, a low energy (1.3 GeV) prototype of the final focus system for ILC and CLIC linear collider projects. Tests of a 500 ÎĽm thick sCVD diamond detector with a dimension of 4.5 mmĂ—4.5 mm have been carried out with radioactive sources and with electron beam from PHIL low energy (<10 MeV) photo-injector at LAL. The tests at PHIL were done with different beam intensities in air, just after the exit window at the end of the beam line, to test the response of the diamond detector and the readout electronics. We have successfully detected signals from single electrons, using a 40 dB amplifier, and from an electron beam of 108 electrons, using a 24 dB attenuator. A diamond sensor with 4 strips has been designed and fabricated for installation in the vacuum chambers of ATF2 and PHIL, with the aim to scan both the beam halo (with 2 strips of 1.5 mmĂ—4 mm) and the beam core (with 2 strips of 0.1 mmĂ—4 mm) transverse distributions
Spectra of Coherent Smith-Purcell Radiation Observed from Short Electron Bunches: Numerical and Experimental Studies
MOPWA056 - ISBN978-3-95450-122-9International audienceThere is a significant interest in the development of compact particle accelerators within research areas including X-ray and THz (T-ray) sources of radiation, particle physics and medical sciences. To support the progress in these areas, non-invasive, electron beam diagnostics that are capable of measuring a single femtosecond electron bunch are required. At the current stage such beam diagnostics for femtosecond-long electron bunches are still not available. The goal of the work presented is to understand the spectral characteristics of coherent Smith-Purcell radiation to enable its quick and reliable interpretation including the longitudinal profile reconstruction of electron bunches. The research presented comprises results from numerical modelling and experimental studies. Using the numerical data, we discuss the radiated spectra dependence on the electron bunch profile and analyse the results. We also discuss the experimental data and compare it with theoretical predictions
Proposal for Single-Bunch Collimator Wakefield Measurements at SLAC ESTB
Collimator wakefields in the Beam Delivery System (BDS) of future linear
colliders, such as the International Linear Collider (ILC) and the Compact
Linear Collider (CLIC), can be an important source of emittance growth and beam
jitter amplification, consequently degrading the luminosity. Therefore, a
better understanding of collimator wakefield effects is essential to optimise
the collimation systems of future linear colliders in order to minimise
wakefield effects. In the past, measurements of single-bunch collimator
wakefields have been carried out at SLAC with the aim of benchmarking theory,
numerical calculations and experiments. Those studies revealed some
discrepancies between the measurements and the theoretical models. New
experimental tests using available beam test facilities, such as the End
Station A Test Beam (ESTB) at SLAC, would help to improve our understanding on
collimator wakefields. ESTB will provide the perfect test bed to investigate
collimator wakefields for different bunch length conditions, relevant for both
ILC (300 micrometers nominal bunch length) and CLIC (44 micrometers nominal
bunch length) studies. Here we propose to perform new experimental tests of
collimator wakefield effects on electron/positron beams at SLAC ESTB.Comment: 22 pages, 19 figure
Longitudinal Profile Monitor Using Smith-Purcell Radiation: Recent Results from the E-203 Collaboration
TUPC38 - Work supported by seed funding from the John Fell Fund, University of Oxford, Université Paris-Sud, program "Attractivité" and by the ANR under contract ANR-12-JS05-0003-01International audienceWe report on recent measurements made at FACET by the E-203 collaboration to test a longitudinal bunch profile monitor based on Coherent Smith-Purcell radiation. The capacity of this monitor to resolve sub-picosecond bunches will be shown as well as a comparison of profile reconstructed for different beam compression settings. We will also present recent electromagnetic simulations of the interactions between the beam and the grating as well as the expected resolution of such monitor. Comparison between Coherent Smith-Purcell radiation measurement and those made with other techniques will also be discussed. Finally future upgrades of the experiment and steps toward the construction of a single shot longitudinal profile monitor will be presented
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