AGILE is a program that works in the IBM-PC, MS-Windows environment and is dedicated to the interactive design of alternating-gradient lattices for synchrotrons and transfer lines. The program was originally intended as a teaching tool, but has been used mostly for professional design work and is subject to continuous development. It contains original algorithms for coupling, scattering and eddy currents, and some slightly unusual algorithms for off-axis orbits and space charge. There are also additional features such as engineering design aids, calculators for relativistic and synchrotron radiation parameters, expert routines for optimising slow extraction, fitting and matching, and the internal storage of constants for over 1000 stable and quasi-stable charged particles. The program is object-oriented and fully integrated into the Windows environment - it is not a shell. Apart from office work, AGILE is ideal for home use, design workshops and when travelling. It is particularly suited to practical problems in small and medium-sized rings and transfer lines. Operation is largely intuitive and supported by an on-line help facility

Bryant, P J

Bryant, P

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AGILE, a tool for interactive lattice design

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHCERN – PS DIVISIONCERN-PS-2000-036 (DR)AGILE, A TOOL FOR INTERACTIVE LATTICE DESIGNP. BryantAbstractAGILE is a program that works in the IBM-PC, MS-Windows environment and is dedicated to theinteractive design of alternating-gradient lattices for synchrotrons and transfer lines.  The programwas originally intended as a teaching tool, but has been used mostly for professional design workand is subject to continuous development.  It contains original algorithms for coupling, scatteringand eddy currents, and some slightly unusual algorithms for off-axis orbits and space charge.  Thereare also additional features such as engineering design aids, calculators for relativistic andsynchrotron radiation parameters, expert routines for optimising slow extraction, fitting andmatching, and the internal storage of constants for over 1000 stable and quasi-stable chargedparticles.  The program is object-oriented and fully integrated into the Windows environment - it isnot a shell.  Apart from office work, AGILE is ideal for home use, design workshops and whentravelling.  It is particularly suited to practical problems in small and medium-sized rings andtransfer lines.  Operation is largely intuitive and supported by an on-line help facility.7th European Particle Accelerator Conference, 26th-30th June 2000, Vienna, AustriaAlso available on WWW, http://preprints.cern.chGeneva, Switzerland17 July 2000AGILE, A TOOL FOR INTERACTIVE LATTICE DESIGNP.J. Bryant, CERN, Geneva, SwitzerlandAbstractAGILE is a program that works in the IBM-PC, MS-Windows environment and is dedicated to the interactivedesign of alternating-gradient lattices for synchrotrons andtransfer lines.  The program was originally intended as ateaching tool, but has been used mostly for professionaldesign work and is subject to continuous development.  Itcontains original algorithms for coupling, scattering andeddy currents, and some slightly unusual algorithms foroff-axis orbits and space charge.  There are also additionalfeatures such as engineering design aids, calculators forrelativistic and synchrotron radiation parameters, expertroutines for optimising slow extraction, fitting andmatching, and the internal storage of constants for over1000 stable and quasi-stable charged particles.  Theprogram is object-oriented and fully integrated into theWindows environment - it is not a shell.  Apart fromoffice work, AGILE is ideal for home use, designworkshops and when travelling.  It is particularly suited topractical problems in small and medium-sized rings andtransfer lines.  Operation is largely intuitive and supportedby an on-line help facility.1  INTRODUCTIONThe original aim of the AGILE program was to providea simple tool for teaching accelerator lattice design.  TheIBM-PC, MS-Windows environment was adopted sincealmost all sectors of society, both private andprofessional, have experience of this computing platform.This creates confidence in new users and makes many ofthe basic operations, such as searching help files,automatic.  The universal use of the IBM PC means thatthe user can get access to facilities at almost any time andplace.  As the program developed, it was used more andmore for professional design work and workshops, but itssimplicity, portability, rapid interactive interface andbuilt-in graphics have remained its key advantages.AGILE uses a database in global memory that serves amaster program running a number of application objectsand their windows.  The windows form a logical ‘starstructure’ with the Main Window at the centre.  The MainWindow performs basic tasks as well as acting as agateway to the other windows that are dedicated tospecific purposes such as lattice editing, ring calculations,transfer line calculations, numerical matching, analyticmatching and so on.  The current version handles up to5000 elements.2  COMPUTATIONAL FACILITIES2.1  Basic facilitiesThe program is centred around the calculation of thelinear lattice functions on orbits with up to ±4%momentum deviation.  The philosophy for off-axis beamsis to find the orbit by dipole tracking in the hard-edgedmagnet model.  The geometry of the track and the modelare then used to create a new hard-edge model that iscentred on the track.  Thus, an off-axis beam in aquadrupole becomes an on-axis beam in a dipole.  Thefocusing is then calculated using first-order matrices inthe new lattice.  This avoids expansions using second-order matrices, which are especially sensitive aroundedge-angles.  In principle, the precision is the same for allorbits whatever the momentum deviation.  The program iscurrently limited to ±4% momentum error, until animproved geometric tracking routine can be installed.  Thelinear lattice functions are complemented by a number oflinear calculations such as orbit bumps, closed-orbitcorrection, envelopes and so on.  For tracking, resonanceexcitation and other non-linear functions, the programtakes into account normal and skew multi-poles up todecapole, and solenoids.Graphs can be plotted directly on the Windows defaultprinter, or exported as postscript files.  Similarly,numerical results can be printed directly or exported infiles with standard spreadsheet format.  A useful feature isthat rows, columns and arbitrary rectangular blocks innumerical displays can be highlighted and copied to theWindows clipboard.  Input files can also be created for theMAD program [1].2.2  AnimationsThe beam can be represented by a particle distribution,or by envelopes, together with the vacuum chamber walland can be visualised in a dynamic way as the observertravels around a ring or down a transfer line.  Spacecharge can be included, loss plots can be made along thelattice and, in transfer lines, scatterers can be placed in thebeam path.  There is also an expert routine for multi-turninjection.  When large numbers of turns are to beconsidered, it is quicker to use phase-space maps thatshow how the beam evolves when viewed at one specifiedposition in a ring.  One application of phase-space maps isan expert routine for the design of third-integer, slow-extraction schemes.  In this case, the routine shows thesearch for unstable orbits and the plotting of the phase-space separatrices as an animated display (see Fig. 1).Figure 1:  Final screen display from routine foroptimisation slow extraction2.3  Interactive lattice designThe interactive design of a lattice is supported by fittingand matching routines.  The former optimise geometry,set tunes, set chromaticities and set the driving terms ofcoupling resonances.  The latter includes severalanalytical matching routines based on thin-lens modules(one doublet, three triplet and two quadruplet routines) aswell as numerical matching by minimisation.  Theprogress of numerical matching can be watched on-line asthe graphical representation of the lattice parameterschanges (see Fig. 2).Figure 2:  Screen display during numerical matching[Processed to give a b/w line image]2.4  Space chargeSpace charge can be treated in three ways.  Firstly,incoherent and coherent space charge can be included inthe Twiss optics, but these two space-charge regimes canonly exist separately.  Numerical matching and fitting canalso be carried out with the incoherent space chargeapplied when on central orbit.  The program automaticallyinhibits those calculations that are not appropriate for thetype of space charge being used.  The third method forcalculating space charge is by tracking particledistributions with direct particle-particle forces, whichallows all non-linearities, scattering and coupling to beincluded.  This is an experimental routine that is beingdeveloped to investigate self-space-charge forces at MeVenergies and images are not included (see Fig. 3).Typically the routine could be applied to a multi-turninjection scheme.  For space-charge calculations, theprogram stores parameters for over 1000 particle speciesthat include most stable or quasi-stable ions and exoticparticles.Figure 3:  Screen display of three bunches injected withspace charge after losses on the vacuum chamber[Processed to give a b/w line image]2.5  CouplingThe tracking of single particles and distributionsincludes solenoids and all skew elements up to decapolein rings and transfer lines.  In rings, the linear couplingcan be treated either with the sigma matrix formalism thatgives beam sizes, the Teng-Edwards formalism thatderives the normal modes, or as a perturbation to thelinear lattice by evaluating the driving terms of the sumand difference, second-order coupling resonances.  Thereare several routines for designing coupling compensationschemes that are based on a very recent theory concerningresonance families [2].  Solenoids can also be given endplates with slots rather than round beam holes.  In transferlines, only the sigma matrix formalism is used.One extra feature is the calculation of sections oftransfer lines that rotate on their axis.  This is  basically acoupling problem and has been included for thecalculation of gantries and rotators in medical facilities.2.6  ‘Distorted’ orbitsIn some cases, it is necessary to take into accountperturbations in the lattice functions on orbits that arestrongly distorted.  For this condition, the program createsa special lattice for the ‘distorted’ orbit.  An example,could be an injection or extraction orbit that passes closeto the edge of the aperture and then crosses to the axis.  Inthis case, the special lattice section can be added to thetransfer line in the normal way, so that the beam can betracked right up to the central orbit of the ring.2.7  KicksDipole kicks, quadrupole kicks and skew quadrupolekicks can be created randomly or systematically toestimate the effects of errors.  Statistics for up to 1000randomly-generated ‘machines’ can be produced forseveral different types of errors.2.8  DesignCalculators are included for relativistic parameters,synchrotron radiation parameters and lattice parameters,and specialised design aids are included for magnets,water-cooled coils and the field distortion due to eddycurrents in laminations, end-plates and vacuum chambers[3].2.9  ScatteringOne of the more unique features of the program is thetreatment of scatterers.  Scatterers can be introduced intotransfer lines for all the beam particles available in theprogram, except electrons, H– ions and H2+ ions.  Theprogram can treat the scattering data in two ways.  Thefirst method modifies the Twiss functions to calculatebeam envelopes with the scattering included [4].  Thebeam envelopes, beam emittances, average momentumloss, increase in momentum spread and transmissionefficiency are tabulated along the whole lattice.  It is alsopossible to use the thickness of the scatterers as amatching variable and to match the beam parameters andbeam sizes (or emittances) in the numerical matchingroutine.  The second method for treating scattering is totrack particle distributions.  The principal scattering effectis multiple coulomb scattering, but nuclear elasticscattering can be added for protons when in the trackingmode.3  SOME PROGRAM DETAILSThe program, its help file and some example latticescan be down-loaded fromhttp://bryant.home.cern.ch/bryant/It is suggested that a directory named WINAGILE becreated and the program file (WINAGILE.EXE), its helpfile (WINAGILE.HLP) and example lattice files (*.LAT)be placed in that directory.  The program can be started inall the standard ways, including by double clicking on alattice file, providing Windows has been made aware ofthe association.  Please note that with Windows NT, theprogram and all its files MUST be in the same folder.The opening screen is the ‘Main Window’, which initiallycontains a short welcome message.  In the menu bar, clickthe 'File Menu', which among several possibilities offers‘New’ for creating a new lattice and 'Open' for findingexisting lattice files.  Assuming that a lattice file exists,this can be loaded and its data will appear in the ‘MainWindow’. If, by chance, the lattice file is incomplete, orunchecked, the program will prompt you to click ‘Edit’and to correct the problem.  Now click on the 'CalculationMenu' and choose what you would like to do with thelattice.  If ‘Ring’ or ‘Line’ is chosen, then  the programcalculates the matrices, the geometry and the Twissfunctions, either with periodicity imposed (a ring ormatched section) or with initial conditions (a line).  TheRing or Line Window will now be shown and furthercalculation options will be made available.  The Help Filecontains details of element definitions, sign conventions,etc.  If you would like to do something specific, you mayfind an account of the steps in a "How To..." topic.  Toexit click the Exit button near the top left of the display.Many of the commands have standard keyboardshortcuts.  In ‘spreadsheet’ displays, the mouse can beused to select single cells, sets of lines, sets of rows orarbitrary blocks of data for copying to the Windows clipboard.  Double clicking the left-hand button activates dataentry and variable selection in the appropriate Windows.Double clicking the right-hand button in the MatchWindow selects link variables.  In ‘graph windows’ theright-hand button is used to stop animated displays(except in one case that has a dedicated button).  Fulldetails can be found in the Help.4  SUMMARYAGILE has proven to be a convenient tool that iscomplementary to the older command-line, batch-jobprograms that are customarily used for accelerator design.Users have found that the interactive style allows them tofollow ideas quickly and the graphical interface helps therapid appraisal of results.  New routines have been addedto the program steadily over more than a decade, whichhas resulted in a code that can tackle a wide range ofproblems, some of them unique.  This process willcontinue and the intention is to equip AGILE with radio-frequency cavities in the near future.REFERENCES[1] H. Grote, F. Iselin, The MAD program, Users’Reference Manual, CERN/SL/90-13 (AP), (1990).[2] G. De Ninno, D. Fanelli, Resonance families andtheir action on betatron motion, Phys. Rev. SpecialTopics – Accelerator Beams, Vol. 3, 000000, (2000).[3] P.J. Bryant, Basic theory for magnetic measurements,CERN 92-05, (Sept., 1992), pp65-69.[4] A. Maier, Thick scatterers seen through the Twissfunctions, CERN/PS 98-061 (DI).

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