Experimental approaches to s-process branchings René Reifarth Los Alamos National Laboratory Astrophysics and Nuclear Structure International Workshop XXXIV on Gross Properties of Nuclei and Nuclear Excitations Hirschegg, Kleinwalsertal, Austria, January 15 - 21, 2006
Experimental approaches to s-process branchings. René Reifarth Los Alamos National Laboratory. Astrophysics and Nuclear Structure International Workshop XXXIV on Gross Properties of Nuclei and Nuclear Excitations Hirschegg, Kleinwalsertal, Austria, January 15 - 21, 2006. s -process path. - PowerPoint PPT Presentation
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Experimental approaches to s-process branchings
René ReifarthLos Alamos National Laboratory
Astrophysics and Nuclear StructureInternational Workshop XXXIV on
Gross Properties of Nuclei and Nuclear ExcitationsHirschegg, Kleinwalsertal, Austria, January 15 - 21, 2006
s-process path – branched
A A+1s-process path
~ t1/2-1(T)
~ capturens-process path
nA
A TFN
N
, 1
Presolar grains: Left-overs from stellar events
(E. Zinner, WUSTL)
What’s needed?
• Reaction rates
• Half-lives
50 100 150 200Energy keV2
4
6
8
10
12Neutrons
kTT
E
kT
E
kT
E E E
E E
v
v
e d
e d
2 0
0
DANCE @ LANL
Classical s-process
93Zr95Zr
Modern s-process models
(AGB stars)
new n-facility sample production
93Zr
DANCE @ LANL
Classical s-process
Connection between theory and experiment
(n,γ) @ radioctive isotopes
TOF experiments
sensitivity to background very high sensitivity (~ µg)
only average neutron energies only if A+1X is “reasonable“ radioactive
neutronssample
prompt-rays Ge Ge2.
1. neutrons
sample
-rays
PROMPT -detection(4 - scintillators)
Activation technique - DELAYED
( AX(n,)A+1X()A+1Y )
Activation-Method
Determination of neutron flux via 197Au(n,)198Au
Neutron source: 7Li(p,n)7Be
AX(n,)A+1Xreaction detected via
A+1X(-) A+1Y decay
lithium
copper
proton beamneutron cone
AX
Au
Experiment vs. previous estimates
<> = 22.6 + 2.4 mb M
AC
S (
mb)
kT (keV)
LANSCE @ LANL
• 160 BaF2 crystals• 4 different shapes• Ri=17 cm, Ra=32 cm• 7 cm 6LiH inside • 90 % • casc 98 %