user requirements document

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User Requirements Document

Title: General Purpose Source Particle Module for GEANT4/SPARSET

Project reference: UoS-rep-07

Prepared by: Colin Ferguson

Signature:

Date: 24/02/00

Authorised by: Jon Lockley

Signature:

Issued by:Sector/location/telephone/fax:

Physics and Astronomy DepartmentUniversity of SouthamptonHighfield, SouthamptonTel: 023 80 59 3916 Fax: 023 80 59 3910

Abstract

The user requirements are described for a General Source Particle Module for use with Geant4. Thismodule represents an important requirement for any space radiation simulation toolkit, since thespacecraft primary particle environment can be complex, varying as a function of energy, physicaldistribution and angular distribution.


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Record of changes

This is a controlled document. Additional copies are obtained through the issuing authority. In theevent of copying locally, including electronically, mark each document Uncontrolled Copy. Fullissues and page amendments are identified on this page. Forward proposals for change in writing tothe issuing authority.

Issue Date Detail of changes0.a0.b1.01.1

22 January 199929 July 199931 August 199924 February 2000

Draft releaseUpdated following initial reviewUpdatedUpdated


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Table of contents

1 INTRODUCTION ......................................................................................................... 4

1.1 Contractual...................................................................................................................................................4

1.2 Purpose of the Document..............................................................................................................................4

1.3 Scope of the Software.................................................................................. .................................................4

1.4 Definitions.....................................................................................................................................................4

1.5 References ....................................................................................................................................................4

2 GENERAL DESCRIPTION .......................................................................................... 6

2.1 Product Perspective......................................................................................................................................6

2.2 General capabilities .....................................................................................................................................62.2.1 Definition of source particle type (UR1) ................................................................................................62.2.2 Definition of source position distribution (UR2) ....................................................................................62.2.3 Definition of source angular direction (UR3).........................................................................................62.2.4 Definition of energy (UR4)....................................................................................................................62.2.5 Use of particles generated by a previous simulation (UR5) ....................................................................62.2.6 Source particle biasing (UR6)................................................................................................................6

2.3 General constraints ......................................................................................................................................7

2.4 User characteristics......................................................................................................................................7

2.5 Operational environment .............................................................................................................................7

3 SPECIFIC REQUIREMENTS....................................................................................... 8

3.1 Definition of source particle type (UR1)...................................................................................................... 8

3.2 Definition of source position distribution (UR2)..........................................................................................8

3.3 Definition of source angular distribution (UR3)..........................................................................................8

3.4 Definition of energy (UR4)...........................................................................................................................9

3.5 Use of particles generated by a previous simulation (UR5).........................................................................9

3.6 Source particle biasing (UR6)..................................................................... .................................................9


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1 Introduction

1.1 Contractual

This document has been issued by DERA Space Department for ESA/ESTEC under contract

12115/96/NL/JG, Work Order No. 3 (ESA Technology Research Programme, Space Environmentand Effects Major Axis). This report describes work undertaken in Work Package 6.1 Radiationtransport physics modelled requirements and review. Specifically, this report describes the userrequirements and architectural design covering new software to be used by European spacecraftengineers and widely distributed in ESA.

1.2 Purpose of the Document

This document describes the user requirements of a General Source Particle Module (GSPM) for aSpacecraft Radiation Shielding and Effects Toolkit (SPARSET), based on the radiation transportcode Geant4. These requirements will be used to specify the software requirements and architecturaldesign in the Software Specification Document.

1.3 Scope of the Software

The GSPM software is only intended for use with the CERN Geant4 code for Monte Carlo, high-energy particle transport. Specifically, this software shall be developed for Geant4.0.1 orGeant4.1.0, if the latter is released before October 1999. When compiled and linked into the Geant4toolkit, the code will allow the generation of source particles with little or no C++ coding, butproviding the user with an environment sample from almost any source distribution.

1.4 Definitions

Geant4 version 4 of the CERN GEANT code for Monte Carlo simulation of high-energy,fundamental particle transport simulation.

GPSM General Source Particle Module

CERN Conseil Europeen pour la Recherche Nuclaire

DERA Defence Evaluation and Research Agency

ESA European Space Agency

OO object-oriented

SPARSET Spacecraft Radiation Shielding and Effects Toolkit

URD User Requirements Document

1.5 References

[1] The CERN Geant4 Collaboration provides a significant amount of references information:http://wwwinfo.cern.ch/asd/geant/geant4.html

From this Web page, access can be obtained to User Documentation:


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[2] User Guide for Application Developers:http://wwwinfo.cern.ch/asd/geant4/G4UsersDocuments/UsersGuides/ForApplicationDeveloper/html/index.html

[3] User Guide for Toolkit Developers:http://wwwinfo.cern.ch/asd/geant4/G4UsersDocuments/UsersGuides/ForToolkitDeveloper/html/index.html

[4] The Physics Reference manual:http://wwwinfo.cern.ch/asd/geant4/G4UsersDocuments/UsersGuides/PhysicsReferenceManual/html/index.html

[5] The Software Reference manual provides information on the public methods to the Geant4classes: http://geant4.kek.jp/../cgi-bin/G4GenDoc.csh?flag=1

[6] The parent project reference is the proposed Evaluation and Development of ShieldingToolsfor Spacecraft, DERA/CIS/CIS2/7/36/4/1. This parent project is itself defined in Work Order contract 12115/96/NL/JG, file reference DERA/CIS/CIS2/7/36/4/1/1 as modified bythe minutes of meetings (DERA/CIS/CIS2/7/36/4/1/3).


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2 General Description

2.1 Product Perspective

Geant4 provides a comprehensive toolkit for the simulation of fundamental particle transport, and

the basis of a general Spacecraft Radiation Shielding and Effects Toolkit. However, since Geant4was initially developed for terrestrial high-energy physics (HEP), the source particle description isoften straight-forward (typically unidirectional and mono-energetic) and therefore definition of thesource has been left to the user to program. For a SPARSET, the user may wish to apply Geant4 toa variety of scenarios where the incident particles are uni- or omni-directional, and exist within aspectrum rather than just as a mono-energetic source. Furthermore, the base-level user will beexpected to apply the SPARSET without code modification. The General Source Particle Module isintended to extend the functionality of Geant4 to permit definition of an arbitrary source withoutcoding.

2.2 General capabilities

The software shall allow the following operations in normal usage. The headings used for the listingof these operations are also used in section 3 for the classification of detailed user requirements.

2.2.1 Definition of source particle type (UR1)

The user shall be able to specify any particle type that may be defined as a source in Geant4.

2.2.2 Definition of source position distribution (UR2)

The user shall be able to specify the position of a source (if a point), or sample the position over a

simple surface or within a simple volume.

2.2.3 Definition of source angular direction (UR3)

The user shall be able to specify the direction of the source with respect to a user-defined directionor the normal to the surface source.

2.2.4 Definition of energy (UR4)

The user shall be able to specify the energy of the particle either as monoenergetic or as a spectrumin energy, or momentum.

2.2.5 Use of particles generated by a previous simulation (UR5)

The user shall be able to use particles generated by a previous run to specify the source for thecurrent run. Data transfer shall be through object persistency, with particles on the OODB that meetuser specified criteria (species, energy, position, direction, and time) being propagated.

2.2.6 Source particle biasing (UR6)

The user shall be able to apply one or more biasing schemes to the sample distributions toconcentrate the simulation in the phase space where the most effects are expected, e.g. to bias a

cosmic ray spectrum to simulate more high-energy particles since these give rise to greater numbersof secondaries.


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2.3 General constraints

The GSPM shall be capable of operation with Geant4. The modules to implement this algorithmshould be consistent with existing methods of defining source particles, e.g. by using a derived classof the G4ParticleGun class. It should also be possible to use this module by appropriateprogramming, or the Geant4 User Interface. The sampling processes used to define the sourceparticles should not give rise to significant increase in overall simulation time.

2.4 User characteristics

In the first instance, the user is expected to be a scientist or engineer involved studying the effects of radiation on spacecraft at complete system, sub-system or component level. Although it is expectedthat the GSPM may be used by other members of the Geant4 user community, the requirements of the GSPM are primarily driven by those expected to use Geant4 for space applications.

The GSPM should be capable of being used and controlled without the user having to write aprogram that specifies the source distribution (using the Geant4 User Interface).

2.5 Operational environment

The target machine for GSPM will be Sun SPARC running Solaris 2.7 or Intel x86 (IBM compatiblePCs) running Linux.


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3 Specific Requirements

3.1 Definition of source particle type (UR1)

UR ID Description of Requirement

UR 1.1 The user shall be able to specify any source particle that may be specified byG4ParticleGun class.

UR 1.2 The particles shall include nuclei ( e.g. to treat radioactive decay).

UR 1.3 The user shall be able to specify the charge state of ions.

UR 1.4 For nuclei, the user shall be able to specify the excitation energy.

UR 1.5 The user shall be able to specify only one source particle species, unlessparticles are being read from an OODB from a previous run (see UR5).

3.2 Definition of source position distribution (UR2)


UR 2.1 The user shall be able to specify the Cartesian co-ordinates of a point fromwhich the source particles emanate.

UR 2.2 The user shall be able to specify a simple planar area source (circle, ellipse,square, rectangle) from which source particles emanate, with criteria forsource starting in specific volumes of the geometry.

UR 2.3 The user shall be able to specify a surface source based on simple volumes(sphere, ellipsoid, cylinder, right parallelepiped) from which surface sourceparticles emanate, with criteria for the source starting in specific volumes ofthe geometry.

UR 2.4 The user shall be able to specify a simple volume source (sphere, ellipsoid,cylinder, right parallelepiped) in which source particle emanate, with user-defined criteria for the source starting at specific volumes.

3.3 Definition of source angular distribution (UR3)

Isotropic flux is assumed to mean the flux originating from 2 as seen at a unit sphere in the centre.The cosine-law distribution describes the flux originating from 2 as seen at a plane.


UR 3.1 The user shall be able to specify the angular distribution with respect to auser-defined co-ordinate system, or with respect to the surface normal.

UR 3.2 The user-defined co-ordinate system, if specified, is identified by two (non-parallel) Cartesian vectors.

UR 3.3 The angular distribution may be isotropic, cosine-law, based on a user-defined distribution in , or a user-defined distribution in both and (thisincludes planar wave sources).

UR 3.4 The user shall be able to define the angular extent of the source in minimum

and maximum and with respect to the user-defined co-ordinate system, or(if using a surface or planar source) minimum and maximum with respect tothe surface normal.


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3.4 Definition of Energy


UR 4.1 The user shall be able to specify the energy of the source as mono-energeticor a spectrum.UR 4.2 If the particle energy is a spectrum, the user shall be able to choose pre-

defined functions such as linear, power-law, exponential, bremsstrahlung,black body and cosmic diffuse X-/ -ray spectrum. The user shall also be ableto define a distribution via a histogram or a set of arbitrary points.

UR 4.3 The user shall be able to specify either the particle energy or energyspectrum, or the particle momentum or momentum spectrum. It shall also bepossible for the user to enter a differential energy per nucleon spectrum.

UR 4.4 It shall be possible to define either a differential or integral spectrum by a setof arbitrary points.

UR 4.5 When using arbitrary points, the user shall specify point-wise linear,exponential, logarithmic or cubic splines fit to the point-wise data provided.

UR 4.6 The user shall be able to specify a stationary source (mono-energetic, withenergy=0) e.g. to simulate decaying radionuclei.

3.5 Use of particles generated by a previous simulation (UR5)


UR 5.1 The user shall be able to specify a OODB file, generated from a previousexecution of the code, to define the particle source (species, excitation state,

position, velocity vector, energy, and statistical weight).UR 5.2 The user shall be able to identify ranges in the particle attributes (state) so

that the particles selected from the OODB meet desired criteria in terms of:species, excitation state, position, velocity vector, energy and products of aparticular interaction.

UR 5.3 The user shall have be able to modify the start position of the selectedparticle, e.g. to sample cascade products of nuclear interactions in thinmaterials.

3.6 Source particle biasing (UR6)


UR 6.1 The user shall be able to bias the position sampling distribution based on auser-provided histogram.

UR 6.2 The user shall be able to bias the angular sampling distribution based on auser-provided histogram.

UR 6.3 The user shall be able to bias the energy/momentum sampling distributionbased on a user-provided histogram.