Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
YSU, Yerevan, Armenia
SLAC, Menlo Park, California, USA
We present and discuss the properties of coherent electromagnetic fields of a very short, ultra-relativistic bunch, which travels in a rectangular vacuum under the influence of a bending force of a magnet. The analysis is based on the results of a direct numerical solution of Maxwell’s equations together with Newton's equations. We use a new dispersion-free time-domain algorithm which employs a more efficient use of finite element mesh techniques and hence produces self-consistent and stable solutions for very short bunches. We investigate the fine structure of the CSR fields. We also discuss coherent edge radiation. We present a clear picture of the field using the electric field lines constructed from the numerical solutions. This approach should be useful in the study of existing and future concepts of particle accelerators and ultrafast coherent light sources, where high peak currents and very short bunches are envisioned.
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
HZB, Berlin, Germany
Energy Recovery Linacs (ERLs) being the most promising candidates for next-generation light sources put very high demands on preservation of beam brightness and reduction of beam losses. Thus, it is mandatory to avoid the impact of ionized residual gas considered as a source for instabilities in accelerators. Recently, we have presented simulations for the clearing of ionized residual gas with electrodes performed with an upgraded version of software package MOEVE PIC Tracking [1] which is being currently further developed to model the interaction of the ions with the electron beam in presence of external electromagnetic potentials such as the field of clearing electrodes. The tracking code allows for studies on clearing times for electrodes with different voltage as well as detailed studies of the behavior of the ions in the environment of the electrodes. In this paper we take further steps to study possible designs of clearing electrodes. Especially, we will consider the influence of different gas mixtures on clearing times and possible configurations for the clearing electrodes. We use parameters planned for BERLinPro as an example for our studies.
[1] G. Pöplau, A. Meseck, U. van Rienen, Simulation of the Behavior of Ionized Residual Gas in the Field of Electrodes, IPAC 2012, New Orleans.
HZB, Berlin, Germany
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
Energy Recovery Linacs (ERLs) are the most promising candidates for next-generation light sources now under active development. An optimal performance of these machines requires the preservation of the high beam brightness generated in the injector. For this, the impact of the ionized residual gas on the beam has to be avoided as it causes instabilities and emittance growth. Obviously, the vacuum chamber has to be cleared out of ions but as the potential of the electron beam attracts the ions, it is not enough to install vacuum pumps. One measure for ion clearing are gaps in the bunch train long enough that the ions have time to escape the force of the bunch potential. In this paper, we present numerical studies of the behavior of an ion cloud that interacts with a bunch train. Especially, we consider different distributions for the particles in the bunch, different fill patterns and several mixtures of ions in the residual gas. The simulations are performed with the package MOEVE PIC Tracking. The presented numerical investigations take into account the parameters of the ERL BERLinPro with the objective to deduce appropriate measures for the design and operation of BERLinPro.
Saint-Petersburg State University, Saint-Petersburg, Russia
We analyze radiation of a small bunch crossing a boundary between two dielectrics in a cylindrical waveguide. The total energy of radiation was studied earlier for such problem but dynamics of an energy loss as well as a field structure was not investigated. Meanwhile these questions are of essential interest for the wakefield acceleration technique and for new methods of generation of microwave radiation. Our research is based on original approach used previously for the case of the vacuum-plasma boundary*. The principal difference of presented work consists in generation of Cherenkov radiation in dielectric and so-called Cherenkov-transition radiation in vacuum. Algorithms of computations for the field and the energy loss are founded upon certain transformations of integration path. Comparison of analytical results with numerical ones shows a good coincidence. We consider two instances in detail: the bunch is flying from vacuum into dielectric and from dielectric into vacuum. In both cases we compare the energy losses by transition radiation and by Cherenkov one. Our investigation shows, for example, that energy loss can be negative at certain segments of the bunch trajectory.
* T.Yu. Alekhina and A.V. Tyukhtin, Phys. Rev. E. 83, 066401 (2011)
CERN, Geneva, Switzerland
EPFL, Lausanne, Switzerland