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G4NuclideTable

Koi, Tatsumi

EPP SLAC National Accelerator Laboratory

Geant4 Radioactive decay mini workshop

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Background

In development of multi-treading library, we had a request to

construct all particles at initialization phase

To satisfy the request, we needed to have a full list of

nuclide which may be produced in simulation.

• The list should not depend any individual model

• Locating in particle category was a natural solution

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Basic Design

Contents of the table should be sufficient to construct

particle object

• A, Z, Level energy, Mean life, spin, Magnetic moment

“Decay table” is a property of particle object, but we decided

that the table should not provide it and this is left to each

model

• Model has a freedom to create final states

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Data source

We decided to use single snapshot of ENSDF library (2012

August) as the source of NuclideTable, PhotoEvaporation

and Radioactive decay data set.

• If the library were perfect, then we should not have

inconsistency in levels among the table and models.

• But it turned out it is not true

ENDF library is alternative

• But it only have data for mean life grater than 1mili second

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G4NuclideTable

G4NuclideTable

• was introduced in Geant4 V10 to provide properties of nuclide states.

• The excitation energy and decay times of each state are listed in this table.

• The spin and dipole magnetic moment are also given for some states.

Source of the data

• The source of data in this table is ENSDF of August 2012

• 24,359 states were extracted from the source

• ground states and excited states having half-lives longer than 1 nanosecond were implemented in the source code of the

class.

• The total number of hard-coded states, 6807

• The full set of 24,359 states is contained in a data file. G4NuclideTable accesses the data file pointed to by the

environment variable "G4ENSDFSTATEDATA".

Isomer levels

• G4NuclideTable provides an integer that represents the isomer level of each state.

• Due to PDG code limitations, only level numbers from 0 to 9 are allowed. All ground states have a level number of 0,

lowest energy state isomers have level number 1, next lowest have level number 2, and so on. This continues up to level

8. All excited states above this will have level number 9. This numbering scheme is used only for the preloaded states.

• In general the isomer level number for certain excited states depends on the half-life threshold for preloaded states.

• All excited states dynamically generated within the event loop will have 9 as its isomer level.

Adding states

• Users are able to add states to the table with specific values of excitation energy, decay constant, spin and dipole

magnetic moment.

• This should be done at initialization time and then user-defined states will be preloaded. However they always have an

isomer level of 9 and neglect the numbering of isomer levels of other states.

http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForToolkitDeveloper/html/ch03s03.html#sect.ExtdFuncParticles.NuclideTable

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Discussion

G4NuclideTable is in “particle” category

• Followed design of the category

In most case, access to the table will happen through

ParticleTable interfaces

• This sometime costs a lot- Trigger construction of particle object

• Interface is not sufficient or convenient- Limited number of public interfaces

• Method are required which provide information (like energy

level) without triggering object construction

• We are happy to have request to add public interface

Please avoid to make duplicated table, instead use the new

interfaces we will provide