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

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

  • 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?

  • 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)

  • 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


Nuclear data needs for r process calculations

Meyer and Wang (2007)


Production of 4 he from n p t 9 10 8

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


Production of 4 he from n p t 9 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


Nuclear data needs for r process calculations

Meyer and Wang (2007)


Details of the final r process abundances

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

Reference calculation


Neutron capture cross sections

Neutron-capture cross sections


Beta decay rates

Beta-decay rates


Spins and partition functions

Spins and Partition Functions


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?

  • 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

  • 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

  • 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

  • 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

<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)

<!--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

<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

<!-- 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

  • <!– 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

<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

  • 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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