27/Mar./03CHEP03 @UCSD1 Development of an Interface for Using EGS4 Physics Processes in Geant4 K.Murakami (KEK) [email protected] 27/Mar./2003 2003

27/Mar./03 CHEP03 @UCSD 1

Development of an Interface for Development of an Interface for Using EGS4 Physics Processes Using EGS4 Physics Processes

in Geant4in Geant4

K.Murakami (KEK)K.Murakami (KEK)[email protected]@kek.jp

27/Mar./200327/Mar./20032003 Conference for Computing in High Energy and Nuclear 2003 Conference for Computing in High Energy and Nuclear

Physics (CHEP03) @UCSDPhysics (CHEP03) @UCSD


OutlineOutline

I.I. IntroductionIntroduction

II.II. System AnalysisSystem Analysis

III.III. ImplementationImplementation

IV.IV. Status and SummaryStatus and Summary


I. IntroductionI. Introduction


IntroductionIntroduction

By means of this interface,By means of this interface, EGS4 users can share Geant4 powerful EGS4 users can share Geant4 powerful

resources, such as geometry description, resources, such as geometry description, tracking etc.tracking etc.

A common environment for comparison testsA common environment for comparison tests between EGS4 and Geant4 especially in users’ between EGS4 and Geant4 especially in users’ realistic application level.realistic application level.

Geant4 has rich flexibility and expansibility for Geant4 has rich flexibility and expansibility for adding physics processes, in addition to its adding physics processes, in addition to its powerful geometry description.powerful geometry description.

It is not easy to describe complicated/realistic It is not easy to describe complicated/realistic geometry for EGS4 users. geometry for EGS4 users.

Taking advantage of the capabilities of Geant4 as Taking advantage of the capabilities of Geant4 as a framework, we developed an a framework, we developed an interfaceinterface for using for using EGS4 EGS4 as a module of physics processas a module of physics process in Geant4. in Geant4.


Co-WorkersCo-Workers

Persons involved Persons involved K.Murakami (KEK, K.Murakami (KEK, [email protected]@kek.jp)) K.Amako (KEK)K.Amako (KEK) H.Hirayama (KEK)H.Hirayama (KEK) Y.Namito (KEK)Y.Namito (KEK) T.Sasaki (KEK)T.Sasaki (KEK) M.Asai (SLAC)M.Asai (SLAC) T.Koi (SLAC)T.Koi (SLAC)


II. System AnalysisII. System Analysis


Analysis of EGS4 SystemAnalysis of EGS4 System- in terms of difference from Geant4-- in terms of difference from Geant4-

We first carried out analysis of the EGS4 system in terms of We first carried out analysis of the EGS4 system in terms of difference from Geant4.difference from Geant4.

Our policyOur policy is that we should care for is that we should care for NOT to changeNOT to change algorithms algorithms and prescriptionsand prescriptions which are used in the EGS4 system. which are used in the EGS4 system.

Issue-1Issue-1: : A way of calculation of step size and process selectionA way of calculation of step size and process selection

In Geant4In Geant4, , each processeach process has its own fate in terms of has its own fate in terms of NILNIL ( (N of Interaction N of Interaction LengthLength). Then, a process having minimum fate will occur.). Then, a process having minimum fate will occur.

In EGS4In EGS4, the next step size is calculated based on , the next step size is calculated based on the total cross section the total cross section of a particle. Then, which process will occur is chosen at the rate of of a particle. Then, which process will occur is chosen at the rate of branching fraction of a process.branching fraction of a process.

In principle, these work in the same manner. Good!!In principle, these work in the same manner. Good!! We implement the EGS physics processes as We implement the EGS physics processes as singlesingle Geant4 processes for Geant4 processes for

electron/photon respectively.electron/photon respectively.


Analysis of EGS4 System (Cont’d)Analysis of EGS4 System (Cont’d)

Issue-2Issue-2: : Scheme of describing material informationScheme of describing material information In Geant4In Geant4,,

Material information has only properties of material itself (atomic number/mass, density, Material information has only properties of material itself (atomic number/mass, density, composition...)composition...)

Cross section tables are calculated at initialization time.Cross section tables are calculated at initialization time. In EGS4,In EGS4,

Users have to prepare a material (Users have to prepare a material (cross sectioncross section) file by executing ) file by executing PEGSPEGS, which is an external , which is an external program, preceding to execution of a EGS4 program.program, preceding to execution of a EGS4 program.

Additional information related to “processes” (cutoff, parameters/coefficients of formulas) are Additional information related to “processes” (cutoff, parameters/coefficients of formulas) are described as material.described as material.

We manage material information We manage material information in terms of both of Geant4 and EGS4.in terms of both of Geant4 and EGS4. Users have to Users have to execute execute PEGSPEGS externallyexternally and our interface manages material information and our interface manages material information

listed in a PEGS output file. listed in a PEGS output file. A mapping table A mapping table between G4 materials and EGS4 materials is prepared.between G4 materials and EGS4 materials is prepared.

Issue-3Issue-3: : Cutoff schemeCutoff scheme In Geant4In Geant4, ,

There is There is no cutoffno cutoff energy. Particles basically will be transported until they have zero kinetic energy. Particles basically will be transported until they have zero kinetic energy.energy.

An idea of An idea of production cut production cut is introduced to avoid infrared divergence.is introduced to avoid infrared divergence. In EGS4In EGS4, ,

An idea of cutoff energy is applied. Particles below cutoff energy will be discarded. An idea of cutoff energy is applied. Particles below cutoff energy will be discarded.

According to our policy, we don’t disturb the EGS4 treatments According to our policy, we don’t disturb the EGS4 treatments in order to obtain the in order to obtain the same outputsame output as obtained by EGS4 itself. as obtained by EGS4 itself.

Each material has its own cutoff energy for electron/photonEach material has its own cutoff energy for electron/photon..


Table of Components Table of Components – Which package is used –– Which package is used –

Control FrameworkControl Framework : :EGS4EGS4 Geant4Geant4 TrackingTracking : : EGS4EGS4 Geant4Geant4 GeometryGeometry : : EGS4EGS4 Geant4Geant4 MaterialsMaterials : : EGS4EGS4 Geant4Geant4 Cross Section TableCross Section Table::EGS4EGS4 Geant4Geant4

(PEGS)(PEGS) Physics ProcessPhysics Process : : EGS4EGS4 Geant4Geant4 Cutoff SchemeCutoff Scheme : : EGS4EGS4 Geant4Geant4


III. Implementation III. Implementation


Functional MappingFunctional MappingGeant4 Class

tracking manager

stepping managersingle process for electronsingle process for photon

GPIL() (GetPhysicalInteractionLength)calculating the next interaction point

DoIt()describing a reaction

G4 geometryG4 transportation (as a process)

reused as-iswrapped with FORTRAN-C++ interface

EGS4 Flow

SHOWER (tracking controller)

ELECTOR PHOTON

(controller for stepping and process invocation)

HOWFAR (geometry and navigation, user code)

each Physics Process COMPTBREMS...

EGS4 subroutines


How It WorksHow It Works

In the EGS4 worldIn the EGS4 world, a single , a single virtualvirtual volume with volume with no dimensions no dimensions (transportation is a G4 job)(transportation is a G4 job) empty medium empty medium (dynamically updated)(dynamically updated)

is prepared.is prepared.

At tracking timeAt tracking time,,1.1. Medium information of the EGS4 volume is updated at every step Medium information of the EGS4 volume is updated at every step

though though the material map the material map from G4 to EGS4.from G4 to EGS4.2.2. Kinematical information in the EGS4 stack is updated from G4 track Kinematical information in the EGS4 stack is updated from G4 track 3.3. A EGS4 process is invoked.A EGS4 process is invoked.4.4. The stack information of EGS4 is evacuated to a G4 particle-change.The stack information of EGS4 is evacuated to a G4 particle-change.

A virtual volume with• no dimensions• empty media

g4mate

g4-egsmaterial map

egsmate

g4track

egs stack

g4change

egs stack

egs stack

evacuation

update

update


Material DescriptionMaterial Description

G4Material

EGS MaterialPEGS Material

Geant4 World

EGS4 World

There are There are threethree classes describing materials: classes describing materials: PEGS Material:PEGS Material:

It describes materials defined in a PEGS output.It describes materials defined in a PEGS output.

EGS Material:EGS Material: It has a It has a PEGSMaterialPEGSMaterial.. In addition, it has information, such asIn addition, it has information, such as

user cutoffs, user density, user flags, ...user cutoffs, user density, user flags, ...

G4 Material:G4 Material: A A G4MaterialG4Material is related to a is related to a EGSMaterialEGSMaterial by users by users at initialization timeat initialization time.. A A G4MaterialG4Material is translated to a is translated to a EGSMaterial EGSMaterial through through the mapthe map at tracking timat tracking tim

e.e.

G4-EGS Material Map


Process List Currently CoveredProcess List Currently Covered

Photon processesPhoton processes

Rayleigh scatteringRayleigh scattering pair productionpair production photo-electric effectphoto-electric effect w/ subsequent fluorescencew/ subsequent fluorescence Compton scatteringCompton scattering

Electron processesElectron processes

multiple scatteringmultiple scattering momentum flip only.momentum flip only. lateral displacement is not included. lateral displacement is not included. PRESTA is not included.PRESTA is not included. continuous energy losscontinuous energy loss BremsstrahlungBremsstrahlung Møller scattering (e-)Møller scattering (e-) BhaBha(e+)BhaBha(e+) positron annihilation (e+)positron annihilation (e+) (in-flight / at-rest)(in-flight / at-rest)

As the first target, we started with interfacing with a plain EGS4 (distributed as a KEK version).


View from Users’ SideView from Users’ Side User Physics List:User Physics List:

An alternative EM-physics list is provided as a modular “Physics List” for EM w/ EAn alternative EM-physics list is provided as a modular “Physics List” for EM w/ EGS4 processes.GS4 processes.

User Detector Construction (Geometry):User Detector Construction (Geometry): Users don’t have to modify any existing Geant4 geometry codes.Users don’t have to modify any existing Geant4 geometry codes. Users make assignment of a Geant4 material to a EGS4 material by hands.Users make assignment of a Geant4 material to a EGS4 material by hands.

Cross Section Table:Cross Section Table: Users have to execute Users have to execute PEGS PEGS externally.externally.

define PEGS materials in PEGS input files.define PEGS materials in PEGS input files. execute PEGS to generate a cross section file (so-called PEGS output).execute PEGS to generate a cross section file (so-called PEGS output).

All operations can be performed via G4 command line interface All operations can be performed via G4 command line interface interactivelyinteractively.. assigning G4Material to EGSMaterialassigning G4Material to EGSMaterial setting users parameterssetting users parameters initialization, ...initialization, ...


IV. Status and SummaryIV. Status and Summary


5 electrons with 5 electrons with EEkk=50 MeV=50 MeV into a slab geometry composed of sev into a slab geometry composed of several materials. (w/ cutoff eral materials. (w/ cutoff EEkk=10 keV=10 keV))

red: electrongreen: photon

Sample Event DisplaySample Event Display


BenchmarksBenchmarks Development environmentDevelopment environment

Linux (SuSE / RedHat / ...)Linux (SuSE / RedHat / ...) gcc/g77 ver. 3.2 (2.95.2/3)gcc/g77 ver. 3.2 (2.95.2/3) Geant4 ver.5.0 (patch01)Geant4 ver.5.0 (patch01) EGS4 (distributed as a KEK version)EGS4 (distributed as a KEK version)

RobustnessRobustness several-M events in a simple geometry were successfulseveral-M events in a simple geometry were successful

ly generated without crush.ly generated without crush.

Detail benchmark tests were just started.Detail benchmark tests were just started.


Current Status and PlansCurrent Status and Plans

First implementation was finished.First implementation was finished.

Detail system check and benchmark tests are Detail system check and benchmark tests are started as the next target.started as the next target.

We have plans of comparisons;We have plans of comparisons; between EGS4 itself and the EGS4-G4 interface.between EGS4 itself and the EGS4-G4 interface. between G4 and EGS4(w/ the interface) on common between G4 and EGS4(w/ the interface) on common

geometries.geometries.

Technical study for treating Technical study for treating PRESTAPRESTA is planned for is planned for more precise simulation.more precise simulation. The treatment of The treatment of multiple scatteringmultiple scattering is closely coupled is closely coupled

with geometry (boundary).with geometry (boundary).


SummarySummary We have successfully developed the first We have successfully developed the first

version of an interface between EGS4 and version of an interface between EGS4 and Geant4 based on OO-approach. Geant4 based on OO-approach.

This work is a proof of flexibility and This work is a proof of flexibility and expansibility of the Geant4 framework.expansibility of the Geant4 framework.

By means of this interface, EGS4 users will By means of this interface, EGS4 users will be able to share Geant4 powerful resources, be able to share Geant4 powerful resources, such as geometry description, tracking etc.such as geometry description, tracking etc.

Further detail benchmarks are on going.Further detail benchmarks are on going.

Documents

27/Mar./03CHEP03 @UCSD1 Development of an Interface for Using EGS4 Physics Processes in Geant4 K.Murakami (KEK) [email protected] 27/Mar./2003 2003