Neutron capture cross sections of 70,72,73,74,76Ge at n_TOF EAR-1

C. Lederer, Goethe University Frankfurt

J. Andrzejewski, M. Barbagallo, E. Chiaveri, C. Domingo-Pardo, R. Dressler, P. Ferreira, I.F. Goncalves, C. Guerrero, F. Gunsing, F. Käppeler, J.Neuhausen, C. Massimi, J. Perkowski, R. Reifarth, D. Schumann, G. Tagliente, J.L. Tain, P.

Vaz, A. Wallner, C. Weiß, and the n_TOF Collaboration

23rd October 2013INTC Meeting,CERN

1

INTC-P-381

Nucleosynthesis above Fe

Fe

Ni

Zn

Ge

Se

r-process (

~50%)

s-process (~ 50% of abundances)

Neutron number

rp, p-process (~1%)

Prot

on n

umbe

r

October 23, 2013 Claudia Lederer INTC Meeting, CERN

s process

Fe

Ni

Zn

Ge

Se

s-process

Neutron number

Prot

on n

umbe

r

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Nuclear Physics Input:• b decay half lives• <s>…. Maxwellian Averaged Cross Section MACS

nnn

nnnnkT dEkTEE

dEkTEEE

)/exp(

)/exp()(2 s

s

nnn

nnnnkT dEkTEE

dEkTEEE

)/exp(

)/exp()(2 s

s

s process

Fe

Ni

Zn

Ge

Se

s-process

Neutron number

Prot

on n

umbe

r

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Nuclear Physics Input:• b decay half lives• <s>…. Maxwellian Averaged Cross Section MACS

kT=8 – 90 keV

s process

October 23, 2013 Claudia Lederer INTC Meeting, CERN

s process

October 23, 2013 Claudia Lederer INTC Meeting, CERN

72Ge(n,g)x2

Mass Number

Rel.

Abun

danc

e Ch

ange

Motivation

Neutron capture cross sections of Ge crucial for• understanding elemental abundances from Ge to Sr• Low background experiments: - GERDA (neutrinoless double b decay of 76Ge) - Dark matter experiments, e.g. CDMS-II (Ge detectors)

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Available Data

72Ge(n,g)

Good et al (1966): Gn for En<40 keV

Maletski et al (1968): Gn for En<30 keVGg for En<4 keV

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Available Data

72Ge(n,g)

Good et al (1966): Gn for En<40 keV

Maletski et al (1968): Gn for En<30 keVGg for En<4 keV

74Ge(n,g)

Good et al (1966): Gn for En<22 keV

Maletski et al (1968): Gn for En<60 keVGg for En<3 keV

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Experimental Setup

• n_TOF EAR-1 – high neutron energy resolution, high neutron flux • C6D6 Detection system – low neutron sensitivity• Samples: enriched GeO2 pellets from ISOFLEX prepared at PSI, cylindrical form, 2 cm diameter

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Countrate Estimate

73Ge 74Ge

72Ge70Ge

Countrate Estimate

73Ge 74Ge

72Ge70Ge

76Ge

Beam Time Request

• n_TOF EAR-1 – high neutron energy resolution, high neutron flux • C6D6 Detection system – low neutron sensitivity• Samples: enriched GeO2 pellets from ISOFLEX prepared at PSI, cylindrical form, 2 cm diameter

• split measurement over 2 experimental campaigns

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Summary

• (n,g) cross sections on Ge isotopes are crucial for understanding s process nucleosynthesis and are important for estimating backgrounds in dark matter and double b decay experiments• Few experimental data on Ge in the keV neutron energy region

Goal:• measure cross section and analyze resonances from thermal up to about 200 keV• MACSs from 10-100 keV with uncertainties <5%

Measurement:• enriched GeO2 samples of 2 g• Measurement at n_TOF EAR-1 - high neutron energy resolution, high neutron flux• C6D6 capture setup - low neutron sensitivity

• 12x1018 protons on target, split over 2 experimental campaigns

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Additional Slides

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Experimental Data

70Ge(n,g)

Good et al (1966): Gn for En<40 keV

Maletski et al (1968): Gn for En<30 keVGg for En<4.5 keV

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Experimental Data

73Ge(n,g)

Maletski et al (1968): Gn for En<9 keVGg for En<2 keV

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Experimental Data

76Ge(n,g)

Good et al (1966): Gn for En<30 keV

Maletski et al (1968): Gn for En<50 keVGg for En<5 keV

October 23, 2013 Claudia Lederer INTC Meeting, CERN

Neutron scattering

October 23, 2013 Claudia Lederer INTC Meeting, CERN