Nuclear data for astrophysics

Nuclear data for astrophysics

ELSEVIER Nuclear Physics A7 18 (2003) 339c-346~ wwwelsevier.com/locate/npe Nuclear Michael data for astrophysics S. Smith” a Physics Division, Oa...

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ELSEVIER

Nuclear Physics A7 18 (2003) 339c-346~ wwwelsevier.com/locate/npe

Nuclear Michael

data for astrophysics S. Smith”

a Physics Division,

Oak Ridge

National

Laboratory,

Oak Ridge,

TN, 37831-6354,

USA

In order to address important astrophysics problems such as the origin of the chemical elements, the inner workings of our Sun, and the evolution of stars, crucial nuclear datasets are needed. Recent evaluation and dissemination efforts have produced a number of such datasets, many of which are online and readily available to the research community. Current international efforts in this field are, unfortunately, insufficient to keep pace with the latest nuclear physics measurements and model calculations. A dedicated effort is required to update and expand existing datasets. I discuss several strategies and new initiatives that would ensure a more effective utilization of nuclear data in astrophysics. These include launching a new web site www.nucastrodata.org to aid in locating available nuclear data sets, and an interactive online plotting program with an easy-to-use graphical user interface to over 8000 reaction rates. An enhanced effort in this field could be maintained by formalizing the position of a Nuclear Astrophysics Data Coordinator.

1. Motivation

for

Nuclear

Astrophysics

Data

Activities

Nuclear astrophysics research addresses some of the most fundamental questions in nature: What are the origins of the elements that make up our bodies and our world? How did the sun, the stars, and the galaxy form, and how do they evolve? There is an intimate connection between nuclear physics and studies of these fascinating astrophysical phenomena. A diverse set of nuclear data is required to model the composition changes and energy release in astrophysical environments ranging from the Big Bang to the inner workings of our own Sun to exploding stars. Measurements and theoretical descriptions of microscopic nuclear physics phenomena provide the foundation for the sophisticated models of macroscopic astrophysical systems. These models are today challenged by incredibly detailed observations from ground-based (e.g., Keck [I], SUBARU [Z]) and space-based (e.g., CHANDRA X-ray Observatory [3]. Hubble Space Telescope [4]) devices that give us an u~~parallelecl view of the Cosmos. We t,ruly live in a golden age of astr0physica.l observations. However, our ability to decipher these observations requires, in many instances, more extensive and precise nuclear data than ever before. This symposium featured many examples of this cosmic sensitivity to nuclear physics [5], including: ‘2C~(cr,y)‘s0, which impacts the abundances produced in supernova explosions, the ratio of C to 0 after core He burning, and the subsequent evolution of massive stars; 7Be(p,y)sB, which helps determine the nature of the neutriuo oscillations; ‘*F(p,~)‘~0, w h’ICh ce 1 ,t ermines . the synthesis of ‘sF nuclei in novae: “O(c~,p)~~iI~. which impacts the hot CNO breakout in stellar rsplo0375-9474/03/$ - see front matter 0 2003 Published by Elsevier Science B.V doi:lO.l016/S0375-9474(03)00736-X

34oc

MS. Smith/Nuclear

Physics A718 (2003) 339c-346~

L3(:(fw)~~o~ WI II‘c ,h influences the production of neutrons for t.he s-process in red to impacts heavy element abundance anomalies in metegiant stars; arid s’I
sions;

2. Nuclear

ture

Data

AstrophysiA information,

Needs

models a.ncl

in Astrophysics

require an enormous the particular clat,a

range, nuclei involved) quantities are needed

varies greatly ? For reactions,

determine thermonuclear energy. Astrophysical cause they vary much

reaction S-factors more slowly

to be extrapolated to energies data needs involving react.ions neutrinos [9] have been recently

with the

a.mount required

the astrophysical phenomena required information includes

rates and a processed with energy below which induced by written.

Nuclear structure data is invaluable stellar energy generation. and nuclear includes: masses, decay lifetimes and

of nuclear reaction and nuclear (e.g., reaction type, relevant studied cross

strucenergy

[6]. What sections to

Q-values to determine releases of nuclear cross section ~ are also extremely useful hethan cross sections, enabling cross sections

they have been charged particles

to determine reaction pathways. branching ratios,

measured. [‘i]; by

Further neutrons

the

rates of unmeasured Some of the relevant pa.i-ameters of resonances

details [S], and

of by

reactions, information (energies,

spins, parities, widths) above particle capture thresholds, separation energies near the driplines, alpha-nucleus potentials? level densities, and optical model parameters. Some specific nuclear structure data needs are addressed elsewhere in these proceedings, and general data needs for astrophysics have been reviewed recently [lo].

3. Nuclear

Astrophysics

Willy Fowler and information tailored

Data

collabo
Activities

were the in astrophysics

and

first

Resources

to produce simulations

estensive [II]. ‘rhe

grown into an international effort, as the variety, simulations has increased over the last 35 years. of the importance of the nuclear astrophysics impressive array of resoiirces have been produced

sophist,ication, There is now au data work that and, iii many

13.4). Laboratory evaluations, and

nuclear measurements, data clissrn~ination

modeling, activities

nuclear astrophysics area.s is describrtl

clat ascts. Some in the sllbsrctions

3.1.

rluclear are all vital

of these resources to follo\v.

and detail international he initiated cases, put

nuclear for the

and

sets of nuclear physics work he initiated has

rtceut

of astrophysics recognition [12], and online (Section

an

clat,a compilations and production of important progress

in each

of these

Measurements

The

availabilit!;

of braills

oprnents

in

urlstable of nuclei

isotopes that. that previollsly

at radioactive cesses [l/I]. sureiiit~iits

nuclear

t)eain

‘I’kse

facilitic,s

rtncrgirs

bparris

iiuclri enable

is our the

of the direct

drive stellar explosions [I31 , a\ nrll coultl o111y be est irllatecl by tlleory

:I no tl ler nr’\v at lo\v

of ratlioxtivf~

physics.

vista

niost

as mapping or systematics.

arc air-eatly changing 0111’ untlerstautling iii esperiilic,iltal nuclear ast,rophysics

ritiliziirg

tll<, trcmeiitlorls

t,ackgrouIltt

exciting

measurement

recent

clevel-

of react,ioiis out,

of astrophysical iilvolvcs malting r~tliictions

on

the propert,ies i\Ieasurelnent,s

iii uiltlergrouiitl

promca-

MS. Smith/Nuclear

Moratories reaction energies

cross found

[ 151 or via coincitlcnce section has for the in t.he core of our

teclluiqlles first, Sun

For

example,

been directly an untlergrouncl The current [I:J.l’i],

it solar

therlllonuclcal

measured at the estrmlely accelerat,or facility [iii], status of nuclear measurements

and

this

proceedings

contains

low and

sonic

of

Modeling

Since needed cosmos. trapolate which to modeling predictions

it

is impossible

for

astrophysics They not only

to

measure

simulations, provide

all

the

nuclear

reactions

nuclear models essential unmeasured

play

and

a crucial information,

structure

inforiliation

role in studies hut a.re used

of to

the es-

measurement,s to new energy regimes as well as to provide a framework with understand laboratory results. Significant advances have been made in riucleal in recent years, with a IKW focus on global nlicroscopic models t,hat ~a.11 deliver with accuracies rivaling those of phenomenological ~notl~ls tuned for a spc-

cific mass range of and reactions

[IS]. There involving

have been a nlmk~er of impressive calculations of properties thousands of nuclei, including references [IS -201 and others It is crucial to benchmark these global calculations with

discussed in this symposium. experimental measurements wherever important in this regard, as they are nuclear lanclsca,pe.

3.3.

[JG].

t inle with

more such studies are pla.nnetl in the future. for astrophysics has been recently reviewed the lat,est work in the field.

3.2.

341c

Physics A718 (2003) 339c-346c

Compilations

Compilations tory measurements

aud and

possible. enabling

Radioactive the exploration

beam facilities of uncharted

are especialI! parts of tile

Evaluations

evaluations and theoretical

are

the first calculations

crucial into

steps clatasets

towards incorporating for astrophysics

laborasimula.tions.

Compilations involve collecting all available information on, for example, a particular reaction or nucleus; literature searches play an important role here. Evalliat,ions are one of the most labor-intensive of all nuclear data activities. New evaluations ml& he initiated t,o combine the lote.d and cwwnt results to get a truly btsl result for the quantities of interest. This tra~polations. new evaluat,ions

often involves combining disparate datasets and performing necessary cx(Recent successful nuclear data evaluation projects for ast,rophysics include: of S6 important chargccl-particle rextions front the NAC’IIF: collahora-

tion in Europe [21]; a new large collection of neutron-inclllcecl reaction rvalllations [%‘I; a new collection of 56 charge&particle reaction rate evaluations for st,ahk a.ntl protonrich unstable isot,opes in the mass 20 - 40 region [zY]; and evaluatioris of a rtllrnber of crucial

cha.rged-particle

scrihctl bc~low. for astrophysics

induced

however, cannot,

rffor!

s.

3.4.

Dissemination

the keep

It is not enough to perform culations antl then to compile ttisl~ribr~tttl t,o Ihc comlnuriity into

their

calculations

models. will

M:it.hout not

be lltilizetl

reaction

cllrrcnt up Ivith

rates

Ilialll)oIver t,hc pace

and

nuclear

tlrvolecl to of ~vorltlwitle

decays

date-of-t.lle-art nuclear nieasurements and rvaluat,e this irlforlJlatior1. Nuclear in fornlats that astrophysics researchers this

step. to

help

the

results

solve

t,hr

of very

the

[23].

conipila~iolls measure1llent.s

latest astrophysical

i\s arltl

will

he tle-

eva.lilatiolls aud lllodcting

or ttieolrt~ical calMa Illust a.lso tx> can directly insert

mCastirements puzzlr~

or

riiodcl

t.ltat

Inot,i-

342~

M.S. Smith/Nuclear

Physics A718 (2003) 339c-346~

vated their generation. Dissemina,tion work provides another crucial link between nuclear physics activities and astrophysics modeling. The modern mechanism for rapid, user-friendly information distribution is electronic dissemination via the World Wide Web (WWW). S’g I ni fi cants strides have been made in nuclear astrophysics data dissemination in the pa.st six years: researchers can now search, browse, display, and down1oa.d data sets specialized for nuclear astrophysics studies (e.g., reaction rates), as well as those for general nuclear physics research, from the WWW. The first website dedicated to disseminating nuclear data relevant for astrophysics [25] was launched in 1996, and now there are sites at numerous institutes around the world ~ including ORNL [26], LANL [‘ST], ULB [2S], LLNL [29], Ba.sel [30], KFI< [31], IAS [32], and Cambridge [33]. Many of these sites feature datasets developed at the host institute and links to other datasets of interest. 4. Brewing

Crisis

In spite of the impressive collection of online resources cited above: there are a number of reasons why the current effort in nuclear astrophysics data is insufficient to meet the needs of the research community. First, the subcritical manpower in this area simply cannot keep up with the worldwide pace of nuclear measurements and modeling efforts. There are, for example, numerous published reaction rates based on experimental measurements made in the last decade that have never been compiled or evaluated. Second, many of the specialized astrophysical datasets (e.g., [21,22]) are not folded into the existing large reaction rate libraries, and are therefore not widely utilized in astrophysics simulations. This is a terrible waste of resources, and one that is growing worse as more up-to-date information from recent nuclear measurements is not accessible to astrophysicists. Third, many very valuable clatasets lack a user-friendly interface or a data format appropriate for astrophysics models, req$ring significant,effort by researchers to use the data. Fourth, there is little coordination and communidation between groups working in this area. Researchers often create their own sets of nuclear data culled from scattered data collections of their choosing, making it extremely difficult to compare results from different groups, or to update popular simulation codes. This confusion is exemplified by REACLIB [34], a widely-used collection of approximately SO00 thermonuclear reaction rates. REACLIB is becoming a standard rate library used by numerous research groups around the world to simulate a wide variety of astrophysical phenomena. The last full update and public release of REACLIB was, however, in 1991, and there are currently numerous versions of this library in use (e.g., [23,33-371). B ecause each of these versions is updated from the last public release in a different way, it is very difficult, and possibly misleading to compare results from simulations using these libraries. Another serious problem: there is no mechanism whereby nlistakes in REACXIB r&es call be communicatecl to REACLIB users. This dataset also lacks a friendly interfacr, and there are many important ra.te collections that have not yet been incorporated into this library. Significant progress was realized in other fields (e.g.> reactor physics in t,he U.S. in the 1970s) when standardized sets of data were widely available to resea,rchers (e.g.. the Fusion Evaluated Nuclear Data Library or FENDL [3S]), a 11owing the model codes to be decoupled from the input data. Some ast,rophysicists will always prefer to use propriet,ary

M.S. Smith/Nuclear data

sets,

and

no one

dataset

can

Physics A718 (2003) 339c-346~

sat)isfy

a.ll astrophysics

simulation

343c needs.

However,

a set

of freely available, regularly updated. communal datasets would lead to a st,andardization that would help advance the field and would encomage the development and improvement of the input datasets themselves in a synergist,ic way. For example, REACLIB has evolved from and

a tool developed for use its utility for astrophysics

proactive

measures

5. Future

are First

top

5.1.

needed

and

to

improve

foremost,

priorities

for

Compilations

expansion

and

Evaluations

current

in this

Working Group some of which are needed for

[43]

5.2.

Astrophysics

Data

manpower for this and evaluation

work efforts

A Nuclear

Since

no

one

field

are

e exploiting communities

some

astrophysics

data

is needed

the significant overlap between [41]. For example, members of

entity

can

on nuclei to focus astrophysics

stages in stars [8]. A partial mass less than

[7], and neutronlist of evaluation 40 needed to supin the Caughlan and are now out at the proton-

from 0 to Si that generate on evaluation projects that discussed in Section 3.1.

neutrons support

Coordinator

(or

primarily t.akr the establishment

should)

[40.44] search

duties would be dissemination The dissemination duties of nuclear

the the

important for There are many charged-particle

is so limited, it is important to coordinate plans in order to share expertise and

should by

listing

for

described.

(CSEWG) [42] evaluate reactions are also critical for astrophysics. astrophysics research, including

field, coordination he greatly facilitated whose core participation.

data

astrophysics

beam facilit,ies; approximately 80 reactions w h’ ICI1 were not, upclated by NACRE [21] compilations of nuclear structure information

and (cu, n) reactions It is especially important in experimental nuclear

WWW

in nuclear

in nuclear

for quiescent and explosive burning for the synthesis of heavy elements reactions on radioactiv? isotopes with

and neutron-driplines; for the s-process. the frontier areas

Because the wide compilation

situation

manpower

likely requir astrophysics

port new work at radioactive and Fowler 1985 collection of dat,e by 14 years; enhanced

a central

resource, taking

evaluation effort is required if accurate, up-to-date nuclear in a timely fashion for astrophysical studies. While most have been produced by nuclear astrophysics researchers, an

effort will most data and nuclear

reactions reactions includes:

plica.tions.

a tremendous community could be ensured by

efforts in measurements and nuclear modeling. This endorsed in reports from meetings of the International as well as by an Aclvisory Group for Long Term Nuclear International Atomic Energy Agency. Below. some of

a new

Cross Section Evaluation a variety of applications, important datasets that induced induced projects

the

dedicated

An expanded, dedicated datasets are to be produced evaluation efforts to date expanded nuclear

to future

now.

to keep pace with the international recommendation has been recently Nuclear Data Committee [39,40], Data Development [7,12], of the the

researchers for the

Strategies

Strategies studies.

by a few research

astrophysics

control

the

international

efforts

t,he form of enhanced communication. of a Nuclear Astrophysics Data ant1 communication, as wrll would include: ma.intaining tlata.sets

(see

Section

ri.3);

avoid

worltltl11-

in this

This Coordillator

can

as active reupdating

and

modifying

exist,-

MS. Smith/Nuclear

344c

ing tla.tasets of tlatasets phies: error

for compatibility via the creation checking, plotting

woultl include: publicizing or currently in progress;

with ast.rophysical of indices, search tools, and other

nuclear establish

list; publicizing relevant scientific important nuclear reactions and interests in the nuclear national data activities of kchnical expertise

5.3.

data project.s that are a nuc1ea.r astrophysics

establishing for further

and study:

recently email

completed distribution

maintaining a priority list of helping t,o build on common

&da. and nuclear astrophysics communities; and promoting intersuch as cooperative research progra.ms, symposia, and exchange and computer codes. It is crucial that. the Coordinator be actively

with. needs

and be sited the Coordinator

Also, of the

at a location is a mrmher

by being a data user community.

user

with

himself.

an active research group of the research community the

Coordinator

will

truly

Dissemination

The

development

of

essential nation

to ensure initiativc>s

5.3.1.

New

Website

new

and

web-ba.secl

utilization below.

Nuclear

t,ools

of the

Astrophysics

site

has features

been launched an extensive

valuable

5.3.2. Much is posted loading,

resource

New

for

Interactive

of the

existing

in the form progralnming.

cal user

interface

data..

data Two

viewers

new

is

dissem-

Data

astrophysics

of tables, plotting)

to the

V’’ lewable add new

Rate for

rates

of over

corporate around

Viewer

nuclear

which usually to visualize.

ttlrough rates aild

from

research.

Reaction informat,ion

independent datasets

astrophysics studies. This site helps users publicize then1 to the research community. and does not compete with any esisting support, this website will grow int,o a

astrophysics require i\‘hile

reaction rates [26,X]. no site has a user-friendly, the largest reaction rate databases. To address heen developed which provides au easy-k-use. library [N]. parameters,

as interactive

nuclear

with support from set of links t,o nuclear

the world (over 60 so far) important for nuclear navigate through these datasets, as well as to The site is independent of auy host, institution nuclear astrophysics d;tt,a sit,e. With community very

such

latest

of information posted online [25-331, t,here has been little synergy nuclear astrophysics data websites, and there is no site which links dotasets relevant for astrophysics studies. To rectify this situation,

www.nucastrodata.org This

sites

for

the wealth the existing available ~zuclenr-

sources.

web

a widespread are discussed

Despite between all

cocks; and improving the user interface capabilities, graphical interfaces, bibliograenhancements. The communication duties

astrophysics and maintain meetings; properties

involved in a.strophysics resea.rch, [39]. This will help ensure that tha.t he will int,erface he able to fulfill the

Physics A718 (2003) 339c-346~

SO00

interactive this need. interactive,

nuc1ea.r

a web browser, plol, them, arid

studies

posted

a number of steps some sites feature

plotting package a. new visualization I’Iat,form-indepentlellt.

reactions ilsc’rs creatr

on

in the

carI

plot

“rate

through a point-an&click graphical user interface bad S uc h visua .. 1’iza t’ ion t 00 1.s \\If’ll mos ,t l’kI e 1y Ime c I e\c i I opcd for websites in conlillg J’ears.

widely-used

multiple

the

U;WW

by the user (downpre-made plot,s of

rates.

that tool

accesses [35] has graphi-

REt-\(‘LIB access

ra.te

vs. temperature“ t,ables all on t Ike c.ha.rt, of the Iluclitlcs. IlIaIIy uuclear astrophysics tla.ta

MS. Smith/Nuclear

Physics A718 (2003) 339c-346~

345c

6. Summary Nuclear physics informat.ion is crucial for the u~~tlerstanclir~g of many phenomena ill astrophysics. There is a wealth of IIIICIF‘X astrophysics data already online. Dctlicatctl effort is nettled, however, to ensure that these da.tasets are upda.tetl to illcluclc the latest experimental and theoretical work, autl t,o ensure that the limited maupowc’r in the ficltl works in a coordinated fashion. It is int,ernationally recognized that the current effort, in this area must be enhanced. A number of strategies to improve the utilization of nuclear data for astrophysics studies llave been identified, and some new init,iatives - a web site www.nucastrodata.org and a. new interactive reaction rate plott,ing program. are already helping to reach these goals. Community support for these autl similar cff’orts is essential to ensure that Willy Fowler’s legacy in nuclear data for astrophysics will continue t,o flourish in support of frontier xsearch in nuclear astrophysics. 7. Acknowledgment ORNL is managed by UT-Battellc, LLC, for the U.S. Department of Energy uncle1 contract DE-AC05-OOOR22725. The author thanks R.A. Meyer and D.W. Bartlayan f’o~ useful comments. REFERENCES 1. 2. 3. -1. i ‘. 6. 7. S. 9. 10.

Il. 12. 13. 14.

1.5. 16.

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unpublished (1995); http://www.plly.orlll.gov/astrophysics/data/task/taskforce-report.html ht.t~~://wmw.~~~~clc.bnl.gov/Nmclar~e/csewg/

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et al., private

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W.A.

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al., Nuclear

htt~p://ie.lbl.gov/whitepaper.htn~l 4.5. E. Lingerfelt et al., Bull.

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(2000).

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and