International audienceRecent updates to the status of the BDSIM particle tracking code are presented. In particular, we describe eﬀorts to combine the secondary particle generation of BDSIM with the wakeﬁeld calculations of Placet in order to quantify backgrounds from col- limating elements in the beam delivery system of the International Linear Collider. Further recent updates to BDSIM are also introduced

A. Blair, G.

Agapov, I.

Dadoun, O.

Latina, A.

P. Malton, S.

Malton, S P

Blair, G A

Agapov, I

Latina, A

Dadoun, O

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Update on the Status of BDSIM

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Update on the Status of BDSIMS. P. Malton, G. A. Blair, I. Agapov, A. Latina, O. DadounTo cite this version:S. P. Malton, G. A. Blair, I. Agapov, A. Latina, O. Dadoun. Update on the Status of BDSIM.A. Frey ; S. Riemann. Linear Collider Workshop 2007: LCWS2007 and ILC2007, May 2007,Hamburg, Germany. Desy, 2, pp.835-837, 2008. <in2p3-00310255>HAL Id: in2p3-00310255http://hal.in2p3.fr/in2p3-00310255Submitted on 8 Aug 2008HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.Update on the Status of BDSIMS. P. Malton1∗, G. A. Blair1, I. Agapov2, A. Latina2, O. Dadoun3 †1- John Adams Institute/Royal Holloway University of LondonEgham, Surrey - UK2- CERNGeneva - Switzerland3- Laboratoire de l’Acce´le´rateur Line´aireOrsay, Paris - FranceRecent updates to the status of the BDSIM particle tracking code are presented. Inparticular, we describe efforts to combine the secondary particle generation of BDSIMwith the wakefield calculations of Placet in order to quantify backgrounds from col-limating elements in the beam delivery system of the International Linear Collider.Further recent updates to BDSIM are also introduced.1 IntroductionBDSIM [1] is an extension to the Geant4 [2] toolkit. It combines accelerator style particletracking with Geant4 Runge-Kutta based tracking. Beamline elements are implementedthrough C++ classes, each with an associated stepper function which implements the parti-cle transportation inside this element. The full Geant4 physics processes are available, andnon-Geant processes can be added as separate C++ classes. The motivation is to permit fasttracking within the beampipe, while being able to generate backgrounds from beam/materialinteractions.2 WakefieldsAs a single-particle tracking code, BDSIM does not take account of intra-particle effects suchas wakefield generation in collimating elements. In order to correctly model the backgroundsinduced by wakefield kicks, some method is required to interface BDSIM with another codethat is capable of performing the necessary calculations.Placet [3] is a multi-particle tracking code which simulates the dynamics of the beamin the presence of wakefields. Particle bunches are divided into slices longitudinally and theinduced wakefield of each slice is applied to all those which follow. In cases where particlesare near to the beampipe aperture, the wakefield kick may be sufficient to cause these parti-cles to interact with the beampipe material. BDSIM is capable of generating the secondaryparticles in this situation, while Placet is not.∗malton@pp.rhul.ac.uk†Work supported in part by the STFC LC-ABD Collaboration, the British Council, and by the Commis-sion of European Communities under the 6th Framework Programme Structuring the European ResearchArea, contract number RIDS-011899LCWS/ILC20072.1 BDSIMBDSIM is a single-particle tracking code; wakefields are a multi-particle effect. Calculationof the wakefield kicks requires a description of the full bunch at the appropriate location. Inorder to generate this, a sensitive volume is introduced prior to the element, which transfersparticles from the urgent stack to the postpone stack. This pauses the tracking of eachparticle in turn at this location. When the requested number of particles has been trackedup to this point, the clean up routine passes the bunch description to Placet through atemporary fifo. BDSIM then listens on the same fifo, waiting for Placet to return thedistribution of particles from after the collimator. Tracking continues in BDSIM from theend of the previous run.2.2 PlacetAs a multi-particle code, Placet has a full description of the bunch at each point of tracking.Routines were added to insert a new bunch description at a given location, in this case atthe entrance to a collimating element, and also to output the bunch description.2.3 TrackingThe implementation described above simply calls Placet to perform tracking in wakefieldregions. However the purpose of this interface is to quantify the backgrounds caused bynear-wall particles which are kicked into the beampipe by wakefield effects. This requiresthat the tracking be done by BDSIM. Ideally, BDSIM will use the bunch description re-turned by Placet to calculate the wakefield kicks ∆x′ = x′after collimator − x′before collimator(and similarly for ∆y′) and apply these at the centre of the collimator logical volume.The process currently requires that equivalent decks are available in both Placet andgmad. The CLIC deck (dated 28/11/05) has been used so far as a test system. However,as tracking in Placet is only relevant in the collimating elements, it should be possible togenerate the same results with only the collimating elements in the Placet input file.3 Further DevelopmentsArbitrary materials definitions can now be placed in the gmad file to generate materials thatare not already included in BDSIM using the material command like this:CarbonDioxide : material, density=1e-14, components={"C","O"},componentsWeights{1,2}Chemical elements which have not been previously defined may also be included using theatom keyword:ytterbium : atom, Z=70, A=174, symbol="Yb"Currently this allows for the inclusion of materials in which every molecule is identical. Fur-ther refinements will allow the user to specify a mixture of materials by fractional weight.This will generate a more accurate description of common accelerator (tunnel) materialsLCWS/ILC2007such as soil and concrete.The BDSIM installation has now been updated to make use of gcc4.0, CLHEP2.0.x.x andGeant4.9.0. Numerous bugfixes have also been included.4 Future updatesBDSIM is continually evolving. A short list of the updates intended for inclusion in futurereleases includes:• The integration of the OpenScientist framework [4] to allow interactive pan and zoomfunctionality in the visualisation.• Design of realistic magnet element geometries to be built by default. This wouldreplace the current default cylindrical elements.• Support for a GDML/XML input format, such as LCDD [5] complementary to thegmad and Mokka/SQL formats.• Polarisation tracking is supported in later versions of Geant4. This facility should beutilised by BDSIM.• Further output data options, such as energy deposition by element. This would includedosimetry/activation.5 ConclusionsThe implementation of data transfer between the single- and multi-particle codes has beencompleted. This in effect calls Placet to track through wakefield regions during BDSIMtracking; further refinements will use the bunch description from Placet to calculate thewakefield kicks so that they can be applied in BDSIM and near-wall particles will interactwith the beampipe material. Updated Materials input from gmad file. The current develop-ment version can be obtained from CVS at http://cvs.pp.rhul.ac.uk/cvsweb.cgi/BDSIM.The next major release, version 0.4, is expected by the end of October.References[1] I. Agapov et al., BDSIM - Beamline Simulation Toolkit Based on Geant4, EuroTev-Report-2006-035(2006).[2] Geant4 Users’ Guide,http://geant4.web.cern.ch/geant4/[3] Daniel Schulte, The Tracking Code Placet, Users’ Manual, (2000)[4] G. Barrand, OpenScientist. Status of the Project, Proceedings of CHEP04, Interlaken, Switzerland(2004)[5] LCDD Homepagehttp://lcsim.org/software/lcdd/[6] Slides:http://ilcagenda.linearcollider.org/contributionDisplay.py?contribId=221&sessionId=67&confId=1296LCWS/ILC2007

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