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Nuclear Data Needs for r-Process Calculations. Bradley Meyer Clemson University. Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998). An appropriate astrophysical model of events significant for nucleosynthesis . (“Appropriate” does not necessarily = “correct”!)

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Nuclear data needs for r process calculations

Nuclear Data Needs for r-Process Calculations

Bradley Meyer

Clemson University


Four requirements for meaningful measurements for astrophysics the et al 1998
Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998)

  • An appropriate astrophysical model of events significant for nucleosynthesis . (“Appropriate” does not necessarily = “correct”!)

  • An observable from the nucleosynthesis process, usually an abundance result that is either known or measurable.

  • The dependency of the value of the observable on the value of a nuclear cross section.

  • An experimental strategy for measuring that cross section, or at least of using measurable data to better calculate it.


R process observables
R-Process Observables Astrophysics (The et al. 1998)

  • Production of heavy elements:

    • Neutron-to-seed ratio (~100)

    • Dependent on nuclear reactions at T9 > 4

  • Details of final abundance distribution

    • Peaks

    • Freezeout abundances—smoothing

    • Dependent on nuclear reactions for T9<3


Appropriate model which regime
Appropriate Model? Which regime? Astrophysics (The et al. 1998)

  • Low-entropy r-process

  • High-entropy r-process

  • High-entropy, fast expansion r-process


Production of heavy nuclei in the first place n s 100
Production of heavy nuclei in the first place (n/s~100) Astrophysics (The et al. 1998)

  • Depends on weak interaction physics—electron capture rates, neutrino-nucleus interaction rates

  • Quasi-equilibrium: nuclear masses and partition functions

  • Three-body reaction rates (α+α+α12C, α+α+n9Be and 9Be+α12C+n

  • Charged-particle reactions on proton-rich isotopes for the high-entropy, fast expansion regime


Meyer and Wang (2007) Astrophysics (The et al. 1998)


Production of 4 he from n p t 9 10 8
Production of Astrophysics (The et al. 1998)4He from n, p (T9 = 10 – 8)


Production of 4 he from n p t 9 8
Production of Astrophysics (The et al. 1998)4He from n, p (T9 < 8)

Too few heavy nucleineutrons and protons don’t assemble into

alpha particles and heavier speciesmany free neutrons and protons

around to bombard the few heavy nuclei present


Meyer and Wang (2007) Astrophysics (The et al. 1998)


Details of the final r process abundances
Details of the Final R-Process Abundances Astrophysics (The et al. 1998)

  • Depends on:

    • Nuclear masses

    • Neutron-capture cross sections

    • Beta-decay rates

    • Spins and partition functions

    • Fission yields


Reference calculation
Reference calculation Astrophysics (The et al. 1998)


Neutron capture cross sections
Neutron-capture cross sections Astrophysics (The et al. 1998)


Beta decay rates
Beta-decay rates Astrophysics (The et al. 1998)


Spins and partition functions
Spins and Partition Functions Astrophysics (The et al. 1998)


Four requirements for meaningful measurements for astrophysics the et al 19981
Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998)

  • An appropriate astrophysical model of events significant for nucleosynthesis . (“Appropriate” does not necessarily = “correct”!)

  • An observable from the nucleosynthesis process, usually an abundance result that is either known or measurable.

  • The dependency of the value of the observable on the value of a nuclear cross section or other nuclear property.

  • An experimental strategy for measuring that cross section, or at least of using measurable data to better calculate it.


What is libnucnet
What is libnucnet? Astrophysics (The et al. 1998)

  • A C toolkit for storing and managing nuclear reaction network.

  • Built on top of libxml (the gnome XML parser and toolkit) and gsl (the GNU scientific library).

  • Released under the GNU General Public License.


History of libnucnet
History of libnucnet Astrophysics (The et al. 1998)

  • Original goal—online nucleosynthesis tool

  • Problem—input over the web

  • Solution—XML (eXtensible Markup Language)

  • Libxml as input and output

  • Libxml has powerful built-in data structures (lists, hashes, trees, etc.)—build new nucleosynthesis code on top of libxml

  • Hashes provide easy access to data—particularly useful for experimentalists


Features of libnucnet
Features of libnucnet Astrophysics (The et al. 1998)

  • Intrinsically 3-d

  • Easily handles arbitrary nuclear network (bbn to r-process), including (any number of) isomeric states

  • Reactions are handled the way humans think about them: “c12 + he4  o16 + gamma” or “o15  n15 + positron + neutrino_e”

  • Hierarchically structured

  • Naturally uses xml as input (allows for schemas, stylesheets, xpath selection, etc.)

  • Read and validate data across the web

  • Allows for user-supplied screening and NSE correction factor functions.


Structure of libnucnet
Structure of libnucnet Astrophysics (The et al. 1998)

  • Libnucnet__Nuc.c/h: a collection of nuclei

    • Libnucnet__Species: a species

    • Libnucnet__Nuc: a collection of species

  • Libnucnet__Reac.c/h: a collection of nuclear reactions

    • Libnucnet__Reaction: a reaction

    • Libnucnet__Reac: a collection of reactions

  • Libnucnet.c/h: a network and a collection of zones

    • Libnucnet__Net: a Libnucnet__Nuc + Libnucnet__Reac

    • Libnucnet__Zone: a physical zone

    • Libnucnet: a network plus a collection of zones


Xml data for the nuclear collection
XML Data for the nuclear collection Astrophysics (The et al. 1998)

<nuclear_data>

<!--n-->

<nuclide>

<z>0</z>

<a>1</a>

<source>Tuli (2000)</source>

<mass>8.071</mass>

<spin>0.5</spin>

<partf_table>

<point>

<t9>0.01</t9>

<log10_partf>0</log10_partf>

</point>

<point>

<t9>0.15</t9>

<log10_partf>0</log10_partf>

</point>

</partf_table>

</nuclide>

</nuclear_data>


Xml data for the nuclear collection with states
XML Data for the nuclear collection (with states) Astrophysics (The et al. 1998)

<!--al26-->

<nuclide>

<z>13</z>

<a>26</a>

<states>

<state id="g">

<source>Tuli (2000) + Gupta and Meyer (2001)</source>

<mass>-12.21</mass>

<spin>5</spin>

<partf_table>

...

</partf_table>

</state>

<state id="m">

<source>Tuli (2000) + Gupta and Meyer (2001)</source>

<mass>-11.982</mass>

<spin>0</spin>

<partf_table>

,,,

</partf_table>

</state>

</states>

</nuclide>


Xml data for reactions a rate table
XML Data for Reactions—a rate table Astrophysics (The et al. 1998)

<reaction_data>

<!-- h1 + n to h2 + gamma -->

<reaction>

<source>Smith et al. (1993)</source>

<reactant>h1</reactant><reactant>n</reactant>

<product>h2</product><product>gamma</product>

<rate_table>

<point>

<t9>0.001</t9>

<rate>4.6168E+04</rate>

<sef>1.000</sef>

</point>

</rate_table>

</reaction>

….

</reaction_data>


Xml data for reactions a single rate
XML Data for Reactions—a single rate Astrophysics (The et al. 1998)

<!-- o19 to f19 + electron + anti-neutrino_e -->

<reaction>

<source>Nuclear Data tables</source>

<reactant>o19</reactant>

<product>f19</product>

<product>electron</product>

<product>anti-neutrino_e</product>

<single_rate>1.6251e-01</single_rate>

</reaction>


Xml data for reactions a non smoker fit
XML Data for Reactions—a non-smoker fit Astrophysics (The et al. 1998)

  • <!– ne15 + n to ne16 + gamma ->

  • <reaction>

  • <source>ADNDT (2001) 75, 1 (non-smoker)</source>

  • <reactant>ne15</reactant> <reactant>n</reactant>

  • <product>ne16</product> <product>gamma</product>

  • <non_smoker_fit>

  • <Zt> 10</Zt>

  • <At> 15</At>

  • <Zf> 10</Zf>

  • <Af> 16</Af>

  • <Q> 8.071000</Q>

  • <spint> 0.0000</spint>

  • <spinf> 0.0000</spinf>

  • <TlowHf>-1.0000</TlowHf>

  • <Tlowfit> 0.0100</Tlowfit>

  • <acc> 1.900000e-06</acc>

  • <a1> 6.225343e+00</a1>

  • <a2> 1.023384e-02</a2>

  • <a3>-1.272184e+00</a3>

  • <a4> 3.920127e+00</a4>

  • <a5>-1.966720e-01</a5>

  • <a6> 1.394263e-02</a6>

  • <a7>-1.389816e+00</a7>

  • <a8> 2.983430e+01</a8>

  • </non_smoker_fit>

  • </reaction>


Zone data
Zone data Astrophysics (The et al. 1998)

<initial_mass_fractions>

<multiple_zones>

<zone label1="x1" label2="y1" label3="z1">

<nuclide>

<z>0</z>

<a>1</a>

<x>0.5</x>

</nuclide>

<nuclide>

<z>1</z>

<a>1</a>

<x>0.5</x>

</nuclide>

</zone>

</multiple_zones>

</initial_mass_fractions>


Where we re headed
Where we’re headed Astrophysics (The et al. 1998)

  • Release of libnucnet 0.3 imminent

  • Put network code based on libnucnet on line this fall

  • My research with libnucnet

    • Study nuclear network equilibria (NSE, QSE, etc.)

    • Build a multi-zone Galactic chemical evolution network on top of libnucnet.


Four requirements for meaningful measurements for astrophysics the et al 19982
Four Requirements for Meaningful Measurements for Astrophysics (The et al. 1998)

  • An appropriate astrophysical model of events significant for nucleosynthesis . (“Appropriate” does not necessarily = “correct”!)

  • An observable from the nucleosynthesis process, usually an abundance result that is either known or measurable.

  • The dependency of the value of the observable on the value of a nuclear cross section or other nuclear property.

  • An experimental strategy for measuring that cross section, or at least of using measurable data to better calculate it.


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