experimental approaches to s process branchings n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Experimental approaches to s-process branchings PowerPoint Presentation
Download Presentation
Experimental approaches to s-process branchings

Loading in 2 Seconds...

play fullscreen
1 / 16

Experimental approaches to s-process branchings - PowerPoint PPT Presentation


  • 72 Views
  • Uploaded on

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.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Experimental approaches to s-process branchings' - cian


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
experimental approaches to s process branchings

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 branched

s-process path

~ t1/2-1(T)

s-process path – branched

A

A+1

~ scapturefn

s-process path

what s needed
What’s needed?
  • Reaction rates
  • Half-lives
connection between theory and experiment

Classical s-process

Modern

s-process

models

(AGB stars)

95Zr

93Zr

Classical s-process

93Zr

new n-facility

sample production

DANCE @ LANL

DANCE @ LANL

Connection between theory and experiment
n @ radioctive isotopes

1.

neutrons

neutrons

sample

2.

Ge

Ge

prompt g-rays

g-rays

(n,γ) @ radioctive isotopes

Activation technique - DELAYED

( AX(n,g)A+1X(b-)A+1Y )

PROMPTg-detection

(4p - scintillators)

 TOF experiments

 sensitivity to background

 very high sensitivity (~ µg)

 only average neutron energies

 only if A+1X is “reasonable“ radioactive

sample

activation method
Activation-Method

AX(n,g)A+1X

reaction detected via A+1X(b-) A+1Y

decay

Au

copper

proton beam

Determination of neutron flux via

197Au(n,g)198Au

neutron cone

lithium

AX

Neutron source:

7Li(p,n)7Be

experiment vs previous estimates
Experiment vs. previous estimates

<s> = 22.6 + 2.4 mb

MACS (mb)

kT (keV)

d etector for a dvanced n eutron c apture e xperiments

g-Detector:

  • 160 BaF2 crystals
  • 4 different shapes
  • Ri=17 cm, Ra=32 cm
  • 7 cm 6LiH inside
  • eg 90 %
  • ecasc 98 %

neutrons:

  • spallation source
  • thermal .. 500 keV
  • 20 m flight path
  • 3 105 n/s/cm2/decade

sample

t1/2 > 100 d

m ~ 1 mg

Detector for Advanced Neutron Capture Experiments

collimated

neutrons

beam

34 cm

»Nuclear Astrophysics with Neutron Facilities and LANL and RIA«

151 sm combining to decoupled branching regions

155

156

153

0.7 a

152

154

Received

funding

151

152

13 a

153

154

9 a

155

4.8 a

151

93 a

152

This year

151Sm combining to decoupled branching regions

Gd

Eu

148

150

149

Sm

148

5.4 d

147

2.6 a

149

50 h

Pm

Branch

Point

stable

s-only

148

146

147

10 d

Nd

a specific example branchpoint 154 eu
A specific example: branchpoint 154Eu

Branching ratio: f=  / ( + n)

-decay rate:  = (ln 2) / t1/2

n-capture rate: n =n vT Nn

f(154Eu) ~ 154Gd/152Gd

0 5 mg of 151 sm t 1 2 100 yr with dance
0.5 mg of 151Sm (t1/2 = 100 yr) with DANCE

Multiplicity & Energy cuts allow optimization of the signal/background

ratio

Q = 8.2 MeV

Esum (MeV)

what could be done in the future
What could be done in the future
  • Optimize neutron source
    • Increased source brightness
  • Improved sample production
    • FAIR, RIA, ISOLDE
  • NCAP
    • Short flight path
    • 7Li(p,n)
    • intense proton source
  • n-TOF2
    • 20 m flight path
    • 20 GeV protons, spallation
  • DANCE upgrade
    • 10 m flight path
    • 0.8 MeV protons, spallation
summary
Summary
  • (n,g) data on radioactive isotopes are extremely important for modern astrophysics
  • s-process branching analysis allows knowledge about stellar convections
  • DANCE contributes in the half live time range above a few hundred days
  • some important isotopes can be measured now, more will have to wait for future facilities
  • 152Eu, 154Eu, 153Gd is planned and funded