ICAP 2006 - List of Keywords (emittance)

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emittance

Paper	Title	Other Keywords	Page
MOMPMP02	Computational Needs for the ILC	luminosity, simulation, damping, feedback	7
	D. Schulte CERN, Geneva K. Kubo KEK, Ibaraki
	Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme, contract number RIDS-011899. The ILC requires detailed studies of the beam transport and of individual components of the transport system. The main challenges are the generation and preservation of the low emittance beams, the protection of the machine from excessive beam loss and the provision of good experimental conditions. The studies of these effects leads to specifications for the different accelerator components and hence can significantly impact the cost.
	Slides

MOA2IS03	Towards the Description of Long Term Self Consistent Effects in Space Charge Induced Resonance Trapping	beam-losses, simulation, space-charge, resonance	65
	G. Franchetti, I. Hofmann GSI, Darmstadt S. Machida CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
	In recent studies the effect of the space charge induced trapping has been shown relevant for long term storage of bunches. There the mechanism of emittance growth and beam loss have been studied for frozen bunch particle distribution. However, when beam loss or halo density are large enough, this approximation have to be reconsidered. We present here a first study on the effect of self consistency in frozen models as intermediate step towards fully 2.5 and 3D simulations.
	Slides

TUPPP10	Design and Modeling of Field-Emitter Arrays for a High Brilliance Electron Source	electron, cathode, simulation, space-charge	114
	M. Dehler PSI, Villigen
	The realization of compact Angstrom wave length free electron lasers depends critically on the brilliance of their electron sources. Field emitters are attractive given their small emission surface and subsequent high current density. The low emittance gun project (LEG) at PSI focuses on developing suitable field emitter arrays (FEA) with a dual gate structure emitting a total current of 5.5A out of a diameter of 500 microns with an emittance in the order of 50 nm rad. Simulations show for idealized emitters that despite micron scale variations of the charge density a low emittance can be obtained by putting the FEA in a pulsed DC diode at 250 MV/m. The challenge lies in modelling all real world effects in the individual field emitter and assembling these into a global emission model. Field emission is often labeled as a cold emission process, nevertheless quantum physical effects lead to a base line energy spread of an order of 150 meV FWHM for the emitted electrons. Replenishing the conduction band with electrons from deep layers gives a further increase in the momentum spread. For the metallic field emitter used, surface roughness has an important influence on the emission properties. It typically gives an additional field enhancement factor of 2.5 to 3 resulting in lower required gate voltages. Additionally we have a detrimental effect on the transverse momentum spread. Work is in progress on obtaining numerical estimates for these effects using among other things measurements using secondary electron microscopy. Further more, the extraction and focusing gates both both give rise to nonlinear defocusing and focusing forces, which have to be minimized by a careful geometric optimization. Combining all these effects gives a reliable parametrization of the individual emitters, which together with a stochastic spatial distribution of emitter properties is used in the global emission model.

TUPPP23	Numerical Minimization of Longitudinal Emittance in Linac Structures	controls, linac, target, acceleration	124
	S. Lange, M. Clemens, L. O. Fichte Helmut-Schmidt-University, Hamburg M. Dohlus, T. Limberg DESY, Hamburg
	Relativistic electron bunches in linear colliders are characterized by 6D phase spaces. In most linear accelerators, the longitudinal phase space distribution does not interact significantly with the transverse distributions. This assumption allows the use of a 2D design model of the longitudinal phase space. The design of linear colliders is typically based on manipulations in the longitudinal phase space. The two dimensional single bunch tracking code LiTrack (Bane/Emma 2005) allows to simulate bunch-compression up to 3rd order and RF acceleration with wake fields. This code is implemented in Matlab with a graphic user interface front end. In order to improve the ability to simulate a two-stage bunch compression system, which consist of a RF accelerating section, a higher harmonic RF section and a dipole magnet chicane, an extension to the LiTrack code is proposed. An analytical model of this two-stage bunch compression system is defined using the energy and the momentum derivatives up to 3rd order of the system. As a consequence, the energy of the system can now be specified directly, for the simulation criteria the peak current and the symmetry of the charge distributions and be specified via parameters. This extended model allows the definition of bunches with an arbitrary energy, phase space correlation, longitudinal emittance, charge distribution and resulting peak current. A minimal longitudinal emittance is generally considered as a quality factor of the bunch, where the bunch energy, peak current and a symmetric charge distribution are represented as constraints. Under these conditions, a constrained optimization problem is defined to minimize the longitudinal emittance with a predetermined bunch-energy and peak-current with respect to the charge distribution symmetry. For the solution of this problem, LiTrack is extended with a optimization solver based on a SQP formulation to find an optimal bunch corresponding to the newly introduced constraints.

TUPPP26	A Time-Adaptive Mesh Approach for the Self-Consistent Simulation of Particle Beams	simulation, gun, cathode, vacuum	132
	S. Schnepp, E. Gjonaj, T. Weiland TEMF, Darmstadt
	Funding: This work was partially funded by HGF (VH-FZ-005) and DESY Hamburg. In many applications the self-consistent simulation of charged particle beams is necessary. Especially, in low-energetic sections such as injectors the interaction between particles and fields considering all effects has to be taken into account. Well-known programs like the MAFIA TS modules typically use the Particle-In-Cell (PIC) method for beam dynamics simulations. Since they use a fixed computational grid which has to resolve the bunch adequately, they suffer from enormous memory consumption. Therefore and especially in the 3D case, only rather short sections can be simulated. This may be avoided using adaptive mesh refinement techniques (AMR). Since their application in Finite-Difference methods in time-domain is critical concerning instabilities, usually problem-matched but static meshes are used. In this paper a code working on the basis of a fully dynamic Cartesian grid is presented allowing for simulations capturing both, a high spatial resolution in the vicinity of the bunch and the possibility of simulating structures up to a length of several meters. The code is tested and validated using the RF electron gun of the Photoinjector Test Facility at DESY Zeuthen (PITZ) as an example. The evolution of various beam parameters along the gun is compared with the results obtained by different beam dynamics programs.

WEMPMP01	Computational Needs for XFELS	undulator, electron, simulation, space-charge	164
	M. Dohlus DESY, Hamburg
	X-ray Free Electron Lasers (FEL) make use of the principle of Self-Amplified-Spontaneous-Emission (SASE) where electron bunches interact in an undulator with their own co-propagating radiation. They do not require optical resonators and their frequency is therefore not limited by material properties as the reflectivity of mirrors. The performance of X-ray SASE FELs depends exponentially on the beam quality of the electron bunch. Therefore effects in the beamline before the undulator are as important as particle-field interactions of the FEL-SASE process. Critical components are the low emittance electron source, accelerating sections, the bunch compression system and the undulator. Due to the high peak currents and small beam dimensions space charge (SC) effects have to be considered up to energies in the GeV range. Coherent synchrotron radiation (CSR) drives not only the FEL but is also emitted in dispersive sections as bunch compressors. SC, CSR, and wake fields affect significantly longitudinal beam parameters (peak current, correlated and uncorrelated energy spread) and the transverse emittance. Start-to-end simulations use a sequence of various tracking codes (with or without SC, CSR and wake fields) and FEL programs. Usually the particle or phase space information has to be carefully converted for each transition from one tool to another. Parameter studies need many simulations of the complete system or a part of it and beyond that, calculations with several random seeds are necessary to consider the stochastic nature of SASE-FEL process.
	Slides

WEMPMP03	Parallel Higher-Order Finite Element Method for Accurate Field Computations in Wakefield and PIC Simulations	gun, simulation, space-charge, plasma	176
	A. E. Candel, A. C. Kabel, K. Ko, L. Lee, Z. Li, C.-K. Ng, E. E. Prudencio, G. L. Schussman, R. Uplenchwar SLAC, Menlo Park, California
	Funding: Work supported by US DOE contract DE-AC002-76SF00515 Under the US DOE SciDAC project, SLAC has developed a suite of 3D (2D) Parallel Higher-order Finite Element (FE) codes, T3P (T2P) and PIC3P (PIC2P), aimed at accurate, large-scale simulation of wakefields and particle-field interactions in RF cavities of complex shape. The codes are built on the FE infrastructure that supports SLAC’s frequency domain codes, Omega3P and S3P, to utilize conformal tetrahedral (triangular) meshes, higher-order basis functions and quadratic geometry approximation. For time integration, they adopt an unconditionally stable implicit scheme. PIC3P (PIC2P) extends T3P (T2P) to treat charged particle dynamics self-consistently using the PIC approach, the first such implementation on the FE grid. Examples from applications to the ILC, LCLS and other accelerators will be presented to compare the accuracy and computational efficiency of these codes versus their counterparts using structured grids.
	Slides

WEPPP03	Recent Improvements of PLACET	simulation, ground-motion, collider, linac	188
	A. Latina, L. Neukermans, G. Rumolo, D. Schulte CERN, Geneva P. Eliasson Uppsala University, Uppsala
	The tracking code PLACET simulates beam transport and orbit correction in linear colliders from the damping ring to the interaction point and beyond. It is a fully programmable and modular software, thanks to a Tcl interface and external modules based on shared libraries. Recent improvements of the code are presented, including the possibility to simulate bunch compressors and to use parallel computer systems.

WEPPP07	Phase Space Tomography Diagnostics at the PITZ Facility	simulation, diagnostics, electron, quadrupole	194
	G. Asova, S. Khodyachykh, M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen P. Castro, F. Loehl DESY, Hamburg
	Funding: This work has partly been supported by the European Community, contract 011935 (EUROFEL) A high phase-space density of the electron beam is obligatory for the successful operation of a Self Amplified Spontaneous Emission - Free Elector Laser (SASE-FEL). Detailed knowledge of the phase-space density distribution is thus very important for characterizing the performance of the used electron sources. The Photo Injector Test Facility at DESY in Zeuthen (PITZ) is built to develop, operate and optimize electron sources for FELs. Currently a tomography module for PITZ is under design as part of the ongoing upgrade of the facility. This contribution studies the performance of the tomography module. Errors in the beam size measurements and their contribution to the calculated emittance will be studied using simulated data. As a practical application the Maximum Entropy Algorithm (MENT) will be used to reconstruct the data generated by an ASTRA simulation.

WEPPP08	Computation of transfer maps from magnetic field data in large aspect-ratio apertures	wiggler, damping, dynamic-aperture, linear-collider	198
	C. E. Mitchell, A. Dragt University of Maryland, College Park, Maryland
	Simulations indicate that the dynamic aperture of the proposed ILC Damping Rings is dictated primarily by the nonlinear properties of their wiggler transfer maps. Wiggler transfer maps in turn depend sensitively on fringe-field and high-multipole effects. Therefore it is important to have a detailed and realistic model of the interior magnetic field, including knowledge of high spatial derivatives. Modeling of these derivatives is made difficult by the presence of numerical noise. We describe how such information can be extracted reliably from 3-dimensional field data on a grid as provided, for example, by various 3-dimensional finite element field codes (OPERA-3d) available from Vector Fields. The key ingredients are the use of surface data and the smoothing property of the inverse Laplacian operator. We describe the advantages of fitting on an elliptic cylindrical surface surrounding the beam, as well as extensions to more general domain geometries useful for magnetic elements with large saggitta.

WEPPP10	Implementation of the DYNAMION Code to the End-To-End Beam Dynamics Simulations for the GSI Proton and Heavy Ion Linear Accelerators	rfq, simulation, linac, ion	201
	S. Yaramyshev, W. Barth, L. A. Dahl, L. Groening, B. Schlitt GSI, Darmstadt
	The advanced multi-particle code DYNAMION is sufficient to calculate beam dynamics in linear accelerators and transport lines under space charge conditions with high accuracy. Special features like the consideration of field measurements, misalignment and fabrication errors, and data from the real topology of RFQ electrodes, drift tubes, quadrupole lenses lead to reliable results of the beam dynamics simulations. End-to-end simulations for the whole linac (from ion source extraction to the synchrotron entrance) allow for the investigation and optimization of the overall machine performance as well as for the calculation of the expected impact of different upgrade measures, proposed to improve beam brilliance. Recently the DYNAMION code is applied to investigate the beam dynamics for the different GSI-linacs: the heavy ion high current UNILAC, the high current proton linac for the future Facility for Antiproton and Ion Research at Darmstadt (FAIR), and the light ion accelerator for the cancer therapy (HICAT), to be commissioned in Heidelberg (Germany) in the near future. Recent results of the beam dynamics simulations by means of the DYNAMION code are presented. The proposed upgrade measures as well as tuning and optimization of the linacs are discussed.

WEPPP11	Comparison of the Beam Dynamics Designs for the FAIR High Current Proton LINAC-RFQ	rfq, proton, linac, simulation	205
	S. Yaramyshev, W. Barth, L. A. Dahl, L. Groening GSI, Darmstadt A. P. Durkin MRTI RAS, Moscow S. Minaev ITEP, Moscow A. Schempp IAP, Frankfurt-am-Main
	The antiproton physics program for future Facility for Antiproton and Ion Research (FAIR) at Darmstadt is based on a rate of 7·10¹⁰ cooled antiprotons per hour. To provide sufficient primary proton intensities a new proton linac is planned. The proposed linac comprises an Electron Cyclotron Resonance (ECR) proton source, a Radio Frequency Quadrupole (RFQ), and Crossed-bar H-cavities (CH). Its operation frequency of 352 MHz allows for an efficient acceleration to up to 70 MeV using normal conducting CH-DTLs. The beam pulses with a length of 32 mks, a current of 70 mA, and total transverse emittances of 7 mkm will allow to fill the existing GSI synchrotron SIS 18 within one multi-turn-injection up to its space charge limit of 7·10¹² protons. Conceptual RFQ designs for two different RFQ types are proposed simultaneously: an RFQ of 4-rod type from the University Frankfurt and a 4 windows type RFQ from Institute for Theoretical and Experimental Physics (ITEP) and Moscow Radio-Technical Institute (MRTI). Studies of the beam dynamics in both RFQs has been done with the versatile multi-particle code DYNAMION. The topology of the RFQ tanks and electrodes is used "as to be fabricated" to provide for the realistic calculations of the external electrical field. The simulations are done under space charge conditions and including influence of the possible misalignments and errors of the fabrication. Simulated results for both designs will be discussed, as well as pros and cons. A comparison of the DYNAMION results with the simulations done by means of the PARMTEQM and LIDOS (dedicated codes for an RFQ design) is presented.

WEPPP21	Efficient Time Integration for Beam Dynamics Simulations Based on the Moment Method	simulation, beam-transport, space-charge, multipole	224
	W. Ackermann, T. Weiland TEMF, Darmstadt
	Funding: This work was partially funded by EUROFEL (RIDS-011935) and DESY Hamburg. The moment method model has been proven to be a valuable tool for numerical simulations of a charged particle beam transport both in accelerator design studies and in optimization of the operating parameters for an already existing beam line. On the basis of the Vlasov equation which describes a collision-less kinetic approach, the time evolution of such integral quantities like the mean or rms dimensions, the mean or rms kinetic momenta, and the total energy or energy spread for a bunched beam can be described by a set of first order non-autonomous ordinary differential equations. Application of a proper time integrator to such a system of ordinary differential equations enables then to determine the time evolution of all involved ensemble parameter under consistent initial conditions. From the vast amount of available time integration methods different versions have to be implemented and evaluated to select a proper algorithm. The computational efficiency in terms of effort and accuracy serves as a selection criterion. Among possible candidates of suited time integrators for the given set of moment equations are the explicit Runge-Kutta methods, the implicit theta methods, and the linear implicit Rosenbrock methods. Various algorithms have been implemented and tested under real-world conditions. In the paper the evaluation process is documented.

WESEPP01	CST's Commercial Beam-Physics Codes	simulation, controls, impedance, electromagnetic-fields	228
	U. Becker CST, Darmstadt
	During the past decades Particle Accelerators have grown to higher and higher complexity and cost, so that a careful analysis and understanding of the machines' behaviour becomes more and more important. CST offers userfriendly numerical simulation tools for the accurate analysis of electromagnetic fields in combination with charged particles, including basic thermal analysis. The CST STUDIO SUITE code family is the direct successor of the code MAFIA, combining the numerical accuracy of the Finite Integration Theory and Perfect Boundary Approximation within an intuitive, easy-to-use CAD environment. Automatic Parameter Sweeping and Optimization are available to achieve and control the design goals. In this paper various solver modules of CST PARTICLE STUDIO, CST EM STUDIO and CST MICROWAVE STUDIO will be presented along accelerator-relevant examples, such as: Cavity design using eigenmode solver including calculation of losses, Q-factors, shunt impedance and thermal analysis. Coupler Design, including external Q-factor Wakefield Simulation, including resistive wall effects, also realized for beams slower than speed of light dispersion diagram for the analysis of periodic structures design of guns, including beam emittance studies study of secondary emission processes and dark current effects in accelerating structures.

WESEPP03	High-Order Algorithms for Simulation of Laser Wakefield Accelerators	simulation, laser, electron	230
	D. L. Bruhwiler, J. R. Cary, D. A. Dimitrov, P. Messmer Tech-X, Boulder, Colorado E. Esarey, C. G.R. Geddes LBNL, Berkeley, California E. Kashdan Brown University, Providence, Rhode Island
	Funding: This work is funded by the US DOE Office of Science, Office of High Energy Physics, including use of NERSC. Electromagnetic particle-in-cell (PIC) simulations of laser wakefield accelerator (LWFA) experiments have shown great success recently, qualitatively capturing many exciting features, like the production of ~1 GeV electron beams with significant charge, moderate energy spread and remarkably small emittance. Such simulations require large clusters or supercomputers for full-scale 3D runs, and all state-of-the art codes are using similar algorithms, with 2nd-order accuracy in space and time. Very high grid resolution and, hence, a very large number of time steps are required to obtain converged results. We present preliminary results from the implementation and testing of 4th-order algorithms, which hold promise for dramatically improving the accuracy of future LWFA simulations.

WEA1MP02	Analysis of Measured Transverse Beam Echoes in RHIC	quadrupole, octupole, betatron, dipole	234
	S. Sorge, O. Boine-Frankenheim GSI, Darmstadt W. Fischer BNL, Upton, Long Island, New York
	Funding: Work supported by EU design study (contract 515873-DIRACsecondary-Beams) The transverse echo amplitudes observed in RHIC will be analysed using particle tracking codes together with different kinetic intrabeam scattering models. We discuss the different diffusion rates observed in proton and heavy ion beams.
	Slides

WEA1MP03	Computing Methods in FFAG Accelerators Design	factory, magnet-design, optics, proton	238
	F. Meot CEA, Gif-sur-Yvette
	There has recently been a regain of interest of Fixed Field Alternating Gradient (FFAG) accelerators, the use of which use is now envisaged in various domains, from the fast acceleration of muon beams in the Neutrino Factory, to high average intensity medical beams, via proton and other electron driver applications. The capability of computer codes to model the FFAG type of accelerator and to perform precision tracking is a concern, in design stages, from both point of views of optics and of magnet design. The difficulties come mainly from, (i) the reference orbit moving with energy, in relation with the large momentum bite in these machines, (ii) the presence of possibly very strong sources of non-linearities, as fields and kinematical effects, (iii) the necessity of exploring large amplitude motion inherent to the capacity of FFAGs to accelerate very large emittances. These questions, the way they are addressed, and the methods/codes in use nowadays to perform FFAG studies will be reviewed. This will be illustrated with contemporary problems, drawn from the Neutrino Factory, medical application of FFAGs, etc.
	Slides

THM1MP02	Parallel Particle-In-Cell (OIC) Codes	simulation, electron, diagnostics, laser	290
	F. Wolfheimer, E. Gjonaj, T. Weiland TEMF, Darmstadt
	Funding: This work has been partially supported by DESY Hamburg. Particle-In-Cell (PIC) simulations are commonly used in the field of computational accelerator physics for modelling the interaction of electromagnetic fields and charged particle beams in complex accelerator geometries. However, the practicability of the method for real world simulations, is often limited by the huge size of accelerator devices and by the large number of computational particles needed for obtaining accurate simulation results. Thus, the parallelization of the computations becomes necessary to permit the solution of such problems in a reasonable time. Different algorithms allowing for an efficient parallel simulation by preserving an equal distribution of the computational workload on the processes while minimizing the interprocess communication are presented. This includes some already known approaches based on a domain decomposition technique as well as novel schemes. The performance of the algorithms is studied in different computational environments with simulation examples including a full 3D simulation of the PITZ-Injector []. A. Oppelt et al Status and First Results from the Upgraded PITZ Facility, Proc. FEL 2005
	Slides

THM2IS03	CST's Commercial Beam-Physics Codes	simulation, controls, impedance, electromagnetic-fields	308
	U. Becker CST, Darmstadt
	During the past decades Particle Accelerators have grown to higher and higher complexity and cost, so that a careful analysis and understanding of the machines' behaviour becomes more and more important. CST offers userfriendly numerical simulation tools for the accurate analysis of electromagnetic fields in combination with charged particles, including basic thermal analysis. The CST STUDIO SUITE code family is the direct successor of the code MAFIA, combining the numerical accuracy of the Finite Integration Theory and Perfect Boundary Approximation within an intuitive, easy-to-use CAD environment. Automatic Parameter Sweeping and Optimization are available to achieve and control the design goals. In this paper various solver modules of CST PARTICLE STUDIO, CST EM STUDIO and CST MICROWAVE STUDIO will be presented along accelerator-relevant examples, such as: Cavity design using eigenmode solver including calculation of losses, Q-factors, shunt impedance and thermal analysis. Coupler Design, including external Q-factor Wakefield Simulation, including resistive wall effects, also realized for beams slower than speed of light dispersion diagram for the analysis of periodic structures design of guns, including beam emittance studies study of secondary emission processes and dark current effects in accelerating structures.
	Slides

THMPMP02	Adaptive 2-D Vlasov Simulation of Particle Beams	simulation, heavy-ion, focusing, lattice	310
	E. Sonnendrucker, M. Gutnic, O. Hoenen, G. Latu, M. Mehrenberger, E. Violard IRMA, Strasbourg
	In order to address the noise problems occuring in Particle-In-Cell (PIC) simulations of intense particle beams, we have been investigating numerical methods based on the solution of the Vlasov equation on a grid of phase-space. However, especially for high intensity beam simulations in periodic or alternating gradient focusing fields, where particles are localized in phase space, adaptive strategies are required to get computationally efficient codes based on this method. To this aim, we have been developing fully adaptive techniques based on interpolating wavelets where the computational grid is changed at each time step according to the variations of the distribution function of the particles. Up to now we only had an adaptive axisymmetric code. In this talk, we are going to present a new adaptive code solving the paraxial Vlasov equation on the full 4D transverse phase space, which can handle real two-dimensional problems like alternating gradient focusing. In order to develop this code efficiently, we introduce a hierarchical sparse data structure, which enabled us not only to reduce considerably the computation time but also the required memory. All computations and diagnostics are performed on the sparse data structure so that the complexity becomes proportional to the number of points needed to describe the particle distribution function.
	Slides