Nuclear data needs for r process calculations
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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

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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”!)

  • 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

  • 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?

  • 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)

  • 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)


Production of 4He from n, p (T9 = 10 – 8)


Production of 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)


Details of the Final R-Process Abundances

  • Depends on:

    • Nuclear masses

    • Neutron-capture cross sections

    • Beta-decay rates

    • Spins and partition functions

    • Fission yields


Reference calculation


Neutron-capture cross sections


Beta-decay rates


Spins and Partition Functions


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?

  • 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

  • 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

  • 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

  • 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

<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)

<!--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

<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

<!-- 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

  • <!– 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

<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

  • 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. 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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