Paper  Title  Page 

MOPD55  A Field Emission and Secondary Emission Model in OPAL  207 


Dark current and multipacting phenomena, have been observed in accelerator structures, and are usually harmful to the equipment and the beam quality. These effects need to be suppressed to guarantee stable operation. Large scale simulations can be used to understand the origin and develop cures of these phenomena. We extend OPAL, a parallel framework for charged particle optics in accelerator structures and beam lines with the necessary physics to simulate multipacting phenomena. We add a FowlerNordheim field emission model and secondary emission model, as well as 3D boundary geometry handling capabilities to OPAL. These capabilities allows us to evaluate dark current and multipacting in highgradient linac structures and in RF cavities of high intensity Cyclotrons. The electric field in present accelerator structures is high enough, such that space charge effects in the FowlerNordheim model can not be neglect. First a ChildLangmuir model is added to phenomenologically model space charge limited field emission. In a second step a space charge solver capable of handling complicated boundary geometries will be implemented to make our field emission model more selfconsistent. 

MOPD56  Simulations for the SNS Linac  211 


The review of the simulations tools used for the Spallation Neutron Source (SNS) linac tuning and beam dynamics studies is presented. The usage and comparison of the different approaches like singleparticle, envelope, particleincell and codes for particular tasks is discussed. The used codes include Parmila, Impact, Track, XAL online model, and a linac model based on the pyORBIT ring code. The future code development for SNS linac is suggested. 

TUO2A01  Accelerated Particle Tracking Using GPULib  286 


A 4D version of BNL's thin element spin tracking code SPINK* with limited elements has been successfully ported to a C++/GPU platform using GPULib**. This prototype used only quadrupoles, simple snakes, dipoles and drifts. It achieved an 80 fold speed up over serial CPU version of the code when pushing 100,000 particles. We present the approach used to track spin and orbit degrees of freedom of polarized proton beams simultaneously. We also present recent results of prototyping a generalpurpose particle tracking on GPUs, discussing our CUDA implementation of maps for singleparticle dynamics in the Argonne National Lab's accelerator code Elegant***. *A.Luccio,"Spin tracking in RHIC code SPINK," Proc. of Adriatico Res Conf (1995) 



TUO2A02  An Effective Space Charge Solver for DYNAMION Code  290 


An effective analytical and semianalytical method for internal electrical field calculations was proposed for ellipsoidal shaped beam as well as for a beam of arbitrary longitudinal shape with an elliptical transverse cross section. This method combines acceptable accuracy with a high speed of computation. The existing version of the DYNAMION code uses the particleparticle method to calculate the electrical field, which needs a significant time for computation. A semianalytical algorithm of electrical field calculation was introduced into DYNAMION code. It allows much faster beam dynamics simulations than the old one (above 5·10^{3} particles). The DYNAMION parameter "macroparticle size" was investigated in connection with the new space charge algorithm. The beam dynamics simulations were performed through the 1st Alvarez tank of the UNILAC using the original and the new method. The RMS emittance growth as a benchmark parameter shows sufficient agreement between both solvers. 



TUO2A03  Challenges in Simulating MW Beams in Cyclotrons  295 


The 1.3 MW of beam power delivered by the PSI 590 MeV Ring Cyclotron together with stringent requirements regarding the controlled and uncontrolled beam losses poses great challenges with respect to predictive simulations. A new particle matter interaction model in OPAL is taking into account energy loss, multiple Coulomb scattering and large angle Rutherford scattering. This model together with the 3D space charge will significantly increase the predictive capabilities of OPAL. We describe a large scale simulation effort, which leads to a better quantitative understanding of the existing PSI high power proton cyclotron facility. The initial condition for the PSI Ring simulations is obtained from a new time structure measurements and the many profile monitors available in the 72 MeV injection line. A large turn separation and narrow beam size at the extraction turn is obtained. We show that OPAL can precise predict the radial beam pattern at extraction with large dynamic range (34 orders of magnitude). The described capabilities are mandatory in the design and operation of the next generation high power proton drivers. 



WEO2C01  BeamBeam Simulations Challenges for Future ElectronIon Collider eRHIC  516 


The future electronion collider eRHIC  under design at BNL  will collide the electron beam accelerated in an energy recovery linacs with protons or ions circulating in the accelerator ring. This linacring collisions bring up a number of unique features in beambeam interactions. For indepth studies of the beambeam effects and resulting the luminosity limitations, we developed a dedicated simulation code. We researched the effects of the mismatch, the disruption and the pinching on the electron beam. Relevant dynamics of the proton beam including the kink instability in combination with incoherent beambeam effects was also explored in detail. In this talk we will describe the main features of our simulation code and will present the most important simulations results. 



WEO2C02  Computational Challenges for BeamBeam Simulations for RHIC  521 


In this article we will review the computational challenges in the beambeam simulation for the polarized proton run of the Relativistic Heavy Ion Collider (RHIC). The difficulties in our multiparticle and million turn tracking to simulate the proton beam lifetime and proton beam emittance growth due to headon beambeam interaction and headon beambeam compensation are presented and discussed. Soultions to obtain meaning physics results from these trackings are proposed and tested. In the end we will report the progress in the benchmarking of the RHIC operational proton beam lifetime. 



WEO2C04  Simulation of Spacecharge Effects in the Proposed CERN PS  524 


A new proton synchrotron, the PS2, was proposed to replace the current proton synchrotron at CERN for the LHC injector upgrade. Nonlinear space charge effects could cause significant beam emittance growth and particle losses and limit the performance of the PS2. In this paper, we report on simulation studies of the potential spacecharge effects at the PS2 using threedimensional selfconsistent macroparticle tracking. We will discuss the impact of spacecharge effects on the beam emittance growth, especially due to synchrobetatron coupling, aperture sizes, initial painted distribution, and RF ramping schemes. The computational model used in the simulation will also be discussed. 



WEO2C05  Wake Functions for Laminated Magnets and Applications for Fermilab Booster Synchrotron  529 


The Fermilab Booster beam is exposed to magnet laminations, resulting in impedance effects much larger than resistive wall effects in a beam pipe. We present a calculation of wake functions in laminated magnets, which show large values at distances of the order of a few meters, but decrease quickly to zero beyond that. Therefore, strong inbunch and nearestbunch effects are present. We show realistic Synergia simulations of the Booster using these wake functions and spacecharge solvers appropriate for the various geometries of the constituent elements of the machine. The simulation of tune shifts is in good agreement with experimental data. We find that wake fields in the Booster magnet laminations strongly increase beam emittance and have the potential to cause significant beam loss. 



WEO2C06  A New Paradigm for Modeling, Simulation, and Analysis of Intense Beams  534 


Currently when the effects of space charge on a beam line are calculated the problem is solved using a particle in cell method of advancing a large number of macroparticles. If quantities such as space charge induced tune shifts are desired it is difficult to determine which of the many variables that make up the beam is the cause. The new method presented here adds the effects of space charge to a nonlinear transfer map, this allows us to use normal form methods to directly measure quantities like the tune. This was done using the code COSY Infinity which makes use of differential algebras, which allow the direct calculation of how the tune depends on the beam current. The method involves finding the high order statistical moments of the particles, determining the distribution function, and finally the potential. In order to advance the particles as accurately as possible a fast multipole method algorithm is used. In this talk we present the new methods and how they allow us to follow the time evolution of an intense beam and extract its nonlinear dynamics. We will also discuss how these methods can improve the design and operation of current and future high intensity facilities. 

