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Status of 54 Fe and 56 Fe(n, g ) analysis Giuseppe Giubrone Instituto de Fisica Corpuscular

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Status of 54Fe and 56Fe(n,g) analysis

Giuseppe Giubrone

Instituto de Fisica Corpuscular

Valencia

n_ToF Analysis meeting, CERN 2011

Outline

- Experimental details
- Energy and width calibration
- Polynomial WF
- Neutron fluence and Resolution Function
- SAMMY analysis
- Neutron Sensitivity
- Summary

G.Giubrone n_TOF Analysis meeting 2011, CERN

Experimental Details

- In 2009 @ nToF started a campaign to measure isotopes with a relevant interest in astrophysics.
- In 2009 the measurement was made for the 56Fe isotope
- In 2010 the measurement was made for 54Fe isotope and the new lead target allows the use of borated water moderator to reduce beam g-rays scattered background.
- The measurements for the 56Fe and 54Fe were performed using two deuterated benzene(C6D6) scintillation detectors with a low neutron sensitivity.

Experimental setup for 54Fe (2010)

Borated water moderator

Experimental setup for 56Fe (2009)

Water moderator

Experimental Details

- The two setups had different geometries and different detectors:
- 2009 – two K6D6 detectors
- 2010 – One K6D6 and one St. Gobain/Bicron commercial detector (Al housing, smaller volume).

G.Giubrone n_TOF Analysis meeting 2011, CERN

Experimental Details

Samples

2009

2010

Isotopic Analysis

Experimental Details

Data Reduction

- We call data reduction the transformation of the registered
- number of counts into yield.

Yield: Fraction of neutronbeam wich undergoes a capture reaction in the sample

G.Giubrone n_TOF Analysis meeting 2011, CERN

ENERGY AND WIDTH CALIBRATION

- A calibration is needed because the weighting function is obtained from a MC simulation as function of deposited energy.
- The C6D6 detectors were calibrated using three different radioactive sources:
- 137Cs with g=662 keV
- 88Y with g =0.898 keV and 1.4MeV
- Am/Be source with g=4.4MeV

- Linear energy calibration with the pulse height: E= a0+a1*Amplitude.

G.Giubrone n_TOF Analysis meeting 2011, CERN

ENERGY AND WIDTH CALIBRATION

- Quadratic width calibration withs2=b0E+b1E2The instrumental resolution was found different for each detector.56Fe b0=3.277keV and b1=2.859keV for det#1 b0=3.270187keV and b1=4.6016keV for det#2
- 54Fe
- b0=6.01496keV and b1=9.7422keV for K6D6 b0=1.74132keV and b1=0 for Bicron

G.Giubrone n_TOF Analisys meeting 2011, CERN

ENERGY AND WIDTH CALIBRATION

2010

#2 2010

G.Giubrone n_TOF Analysis meeting 2011, CERN

ENERGY AND WIDTH CALIBRATION

- During the 2009 measurement which lasted from August 20 till September 23,the gain of the detectors was drifting
- The total measurement period was divided in six periods with a constant energy calibration:

To check the calibration we have recalibrate all calibration runs,choosen as reference the last calibration runs:

88Y source

G.Giubrone n_TOF Analysis meeting 2011,CERN

ENERGY AND WIDTH CALIBRATION

- During the 2010measurement which lasted from July 13 (after the final setup) till July 30, the gain of the detectors was stable.

The total measurement period was divided in six periods with a constant energy calibration

BICRON

K6D6

Am/Be

Am/Be

ENERGY AND WIDTH CALIBRATION

BICRON

K6D6

Experimental spectrum

Simulated spectrum

Experimental spectrum

Simulated spectrum

G.Giubrone n_TOF Analysis meeting 2011,CERN

Polynomial weighting function

Geometrical setup defined in the GEANT4 simulations

The geometries have been modeled in high detail: detectors, samples, supports....

Experimental setup for 56Fe

Experimental setup for 54Fe

Polynomial weighting function

- Monoenergetic gamma-rays were MC simulated using the Geant 4 code and a detailed geometrical description of the setup.
- To simulate a gamma-ray we assumed that the beam has a gaussian profile (based on MicroMegas result 100keV-1MeV)
- We also took into account the exponential depth profile. Only relevant for the 4.9eV Au reference resonance (λ= 0.001cm)

G.Giubrone n_TOF Analisys meeting 2011, CERN

Polynomial Weighting Function

- A set of 34 monoenergetic gamma-rays with energies 0.05, 0.1, 0.15, 0.2, ...2, 2.5, 3, ….8 MeV were simulated. For each energy 5 e+6 photons were simulated.

To verify the correctness of the shape of the WF we calculate the ratio:

Simulated response

Weighting function

Plolynomial Weighting Function

2009 and 2010 WF

G.Giubrone n_TOF Analysis meeting 2011, CERN

Data reduction statistics and parameters

56Fe

54Fe

To process the data we applied well defined software threshold of 300 keV (low energy cut) ,9MeV(56Fe) and12MeV(54Fe)(high energy cut).

G.Giubrone n_TOF Analysis meeting 2011,CERN

Data reduction statistics and parameters

Det#1 vs Det#2

56 Fe

54 Fe

Data reduction statistics and parameters

56 Fe

DET#1

DET#2

54 Fe

BICRON

FZK

54 Fe

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

The total weighted spectrum has to converted into yield using the relation:

- However due to the deep holes in the flux distribution we decided to analyze whenever is possible the weighted spectrum with a single normalization factor (calculated at the neutron resonance energy)
- For the flux we are using the MCNPX simulation with 100bpd from M. Calviani (with spline interpolation)

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

Flux

Raw Spectra

Weighted Spectra

56Fe

Flux

Raw Spectra

Weighted Spectra

54Fe

Sammy Analysis

- As Resolution Function we have taken provisionally the RPI parametrization of the old target RF done by the Bari group

Sammy Analysis

Normalization of neutron flux was obtained with saturated resonace method

Normalization= 0.649

(~ beam-interception-factor)

197Au

Preliminary

FIT

ToF calibration with Gold and Iron resonance:

Flight path in 2010 =184m

This spectrum was obtained from the En in the ROOT data file.

We have re processed the data using ToF

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

In this first analysis I take into all resonances tabulated in ENDF and

Suchkorushkin library

Sukhoruchkin

ENDF

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

Examples of s and p wave

ENDF

Sukhoruchkin

n_ToF

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

Sukhoruchkin

n_ToF

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

2=1.279

“”A slight improvement in the fit is obteined when a second resonance is added, thus might be a doublet”

2=1.215

G.Giubrone n_TOF Analysis meeting 2011, CERN

Sammy Analysis

Some Fit

Sammy Analysis

First Results

(*) Present in the previous last but not in the last Suchoruchkin compilation

(**) Probably a doublet

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

In average, n_TOF is in better agreement with Suckhoruchkin than with ENDF

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

G.Giubrone n_TOF Analysis meeting 2011,CERN

Sammy Analysis

Zoom in y

"No clear dependence of Gn/Gg versus the resonance energy, thus no neutron sensitivity effect noticeable".

G.Giubrone n_TOF Analysis meeting 2011,CERN

Neutron Sensitivity

- The neutron sensitivity for the experimental setup used for 54Fe and 57Fe will be analized by detalaited MC simulation using Geant4 4.9.3version
- A preliminary result was obtained using the new neutron library developed by D. Cano and E. Mendoza from CIEMAT.

10X10e+6 events

- Energy and width calibrations as a function of run number were obtained. A first round of consistency checks has been done, but new detailed check is necessary
- The weighting functions have been obtained with realistic MC simulations and taking into account the real shape of the neutron beam profile.
- The ToF/Energy preliminary calibration done.
- To proceed with the analysis (extract the yield), a good shape of the neutron flux is necessary for both H2O and borated H2O moderator. For this first analysis a shape of the flux provided by Calviani is used.
- A preliminary analysis of the 2010 54Fe(n,g) measurement
- (with borated water moderator) has been completed

Summary

G.Giubrone n_TOF Analysis meeting 2011,CERN

Summary

- The Resolution Function from the old target (at least in Bari RPI parameterization) seems (nearly) adequate also for the new target
- Statistics seems limited: only a careful, complete analysis will tell us how much improvement on existing resonance parameters will be obtained
- Resonance analysis for few resonances was performed using SAMMY
- Neutron sensitivity for FZK and BICRON detector is under study using a new neutron library implemented for GEANT4.

G.Giubrone n_TOF Analysis meeting 2011,CERN

57Fe Status

359 keV(3.36% 58Fe)

230 keV (3.36% 58Fe)

G.Giubrone n_TOF Analysis meeting 2011,CERN

57Fe(1-10keV)

57Fe(10-100keV)

To solve the problem due to some point with a standard deviation more than ±2 we made a rebinning in the region before and after the

resonance energy