TOTAL CROSS-SECTION MEASUREMENTS AND RESONANCE PARAMETER ANNYLISIS OF 169 TM BELOW 100 EV ICTP, Trieste, Italy 2010/05/14 Presentation in the Workshop.

TOTAL CROSS-SECTION MEASUREMENTS AND RESONANCE PARAMETER ANNYLISIS OF 169TM

BELOW 100 EV

ICTP, Trieste, Italy

2010/05/14

Presentation inthe Workshop on Nuclear Data

Wenming Wang

2

This presentation is split into the following sections:

1 Introduction

2 Experimental Arrangements

3 Data Processing and Analysis

4 Conclusion

Contents

Presentation in ICTP 　 10/05/14

3

The neutron resonance phenomenon is very common, which is of great importance in nuclear engineering and research.

An Example of Neutron Resonance (Natural Tungsten, From EXFOR)

1 Introduction

Resolved region

Resolved region

Unresolved region

Unresolved region


4

The full flow of resonance parameter (RP) analysis usually contains the following three steps, that is data acquisition, data evaluation and data benchmark.

Data Acquisition

RP Generation and Evaluation

Data Benchmark Testing

1 Introduction

white-light neutron source

– Electron Linear Accelerator and bremsstrahlung

– Spallation neutron source

Using n-TOF method etc to get trans, cap, tot, fission… spectrum

Using RP analysis tools(SAMMY, Atlas…) or codes to generate neutron RP

According to the experimental environment, correct the exp data, including resolution and Doppler broadening , background correction etc.

Using different series of data for evaluation

Generate the formatted(ENDF) data sheet

Comparing with the result of resonance integral experiment.

Using the benchmark settings and MCNP code for simulation and testing

If the result is not good enough, the flow should return to step II

1

2

3


5

The commonly used tools for RP analysis are SAMMY, REFIT, etc. , which are applied for nuclei with different weights and energy range.

Details Sketch

Energy

Unresolved

EDA

RUC

SAMMY

REFIT

GNASH

EMPIRE…

EDA

RUC

SAMMY

REFIT

…

Resolved

Light

Heavy

Nuclei Weight

EDA(LANL) and RUC(Prof. Chen.) are both R-matrix calculating codes, which can be used for light nuclei in full energy range.

Gnash and Empire ( so do other codes such as UNF and Talys) are theoretical calculating codes for nuclear reaction, which can be use in fast region.

SAMMY(ORNL) is a multi-level R-matrix fitting codes using bayesian equations, which is used for the analysis of 169Tm data.

1 Introduction


6


1 Introduction



4 Conclusion

Contents


7

Time of flight method was widely applied in high-resolution trans measurement, which uses time signals corresponding to energy and trans ratio to get x-s.

Principle of TOF methods

L

t0 t1tn

Neutron Detector

][sec][

][3.72

2

12

2 eVt

mLvmE

nnn

vi



8

100 MeV LINAC

Water moderator

Target room

Ta target

HV

Ta -target

LINAC

BC702

STOP

START

AMP

5.4

m12. 0

6 m

1.8

m2.

9 m

START

Turbo-MCS

SCA

BMPI

STOP

SCContrl

TSCA

TTL/NIM

MEM116k

TimeEncoder

CAMAC Part

EG&G Ortec Part

Gate &Delay

Generator

RFTrigger

SampleChanger

Concrete

PbH3BO3

Iron TAC

Delay

PSA

Gate &Delay

Generator

DecimalCounter

TTL/NIM

DetectorNumberEncoder

Sample changer

Detector

Sample Changer

The 169Tm trans experiment was done in PNF, which was build in 1999, with four main components: Linac, target system, experimental hall, and data acquisition system.



9

PNF can be used for neutron trans measurement, with an acceptable energy resolution below 100 eV, whose details can be seen elsewhere**.

Pohang Neutron Facility (PNF) Key Components

RF gun to produce electrons

Electron Linear Accelerator (65 MeV)

Water-cooled Ta-Target to produce white neutrons through bremsstrahlung

– The calculated neutron yield can be above 1012 n/kW.s

Time of flight(TOF) experimental hall

– TOF experimental Hall with a flight path of 12.06m

– Automatic sample changer

Data acquisition system

– CAMAC and NIM module


**G N Kim, et al. J Kor. Phys. Soc. 43, 479 (2003)


10

Two Tm templates were used during this experiment, whose physical properties are as follows, as well as that of the notch filters.

Tm Templates

Notch Filter Templates


Sample Purity(%) Thickness(mm) Diameter(mm) Density(g/cm3)

169Tm 99.95% 1.41 64 9.32

169Tm 99.95% 0.41 64 9.32

Sample Purity(%) Size(cm2) Thickness(mm) Density(g/cm3)

Cobalt 99.9 10 * 10 0.5 8.90

Indium 99.99 10 * 10 0.2 7.31

Cadmium 99.99 10 * 10 0.5 8.65


11


1 Introduction



4 Conclusion

Contents


12

The energy calibration and background measurement were performed with notch filter methods, containing Co,Ta,In, Gd, with determined standard resonance below 100eV.

The Background Spectrum



13

The energy calibration fitting is as follows, during which the dead time correction factor and flight path can be deduced.

Energy Calibration Fitting

Co,132eVCo,132eV

In,9.04eVIn,9.04eV

In,3.85eVIn,3.85eV

In,1.457eV

In,1.457eV

2

0

72.3 [ ][ ]

( ) [ ]

L mE eV

I I W s



14

After calibration and background measurements, two Tm templates were measured simultaneously, normalized with PICO record.


Normalised Tm Data after De-background Experimental Details

Exposure order: 　 Thick 　　Thin 　 Open 　　　　　　 Thick ….

Exposure Time: totally 80h, 5min for each position every cycle.

Total counts: over 9k

Normalization with PICO record, which has almost direct proportion with the incident neutron flux.:

Re-shielding was carried out with olefin to eliminate the small defect at the edge of Tm templates.

( ) ( )

( ) ( )i i

i i

I E kB ET

O E mB E


15

After the background correction and normalization, we can get the transmission spectrum of Tm, which can be directly used for SAMMY analysis.


Calculated Tm Trans Spectrum Details and Discussion

The energy region with acceptable energy resolution is below 100 eV

The sample templates is not thin enough, which leads to a black resonance at 3.9eV, increasing the uncertainty of fitting.

( ) ( )

( ) ( )i i

i i

I E kB ET

O E mB E

2

0

72.3 [ ][ ]

( ) [ ]

L mE eV

I I W s


16

The total X-S spectrum can easily be deduced by trans spectrum, with a good agreement with the experimental data before**.


Total X-S spectrum Details and Description

The unusual data point has been eliminated before calculation

The X-S has been averaged over energy

The Mughabghab data are the re-construction curve from the recommended parameters from Mughabghab.

1( ) ln ( )

jj

i iN

E T E

( )( )

f

i

f

i

E

Eeff E

E

E EdEE

EdE

**W M Wang, et al. CPC(HEP & NP), 34(2), 1-5 (2010)


17

The total uncertainty is consisted of two parts: the statistic uncertainty and systemic uncertainty.

Uncertainty of X-S

Uncertainty Analysis (simple)

Factors on Energy Resolution

Taking all factors into consideration, the total uncertainty of XS should be < 5%

3 169Tm共振能区中子全截面测量

Statistic error propagation：

Statistic uncertainty is around 4%

Systemic uncertainty

— from de-back (around 2%）

— from sample thickness measurement(around 2%）

— Others (less than1% )

Systemic uncertainty is less than 3%

Through the relationship between flight time and energy, the energy resolution should be correlated to that of the flight path:

Thus the factors on energy resolution should be as follows:

Uncertainty from flight path fitting

Uncertainty from dead(zero) time correction

Others (like the position of detectors)

Total energy resolution around 100 eV is 3.6%**

2 2 21( ) ( ) ( )

T k m kI mOI O B

NT N kI B mO B kI B

/ 2 /E E t t

** G N Kim, et al. Nucl Instr and Meth A, 485 458-467 (2002)


18

Using SAMMY** code, the trans spectrum can be fitted property, with the Mughabghab parameters as start values and calculated correction factors as input.

SAMMY Fitting Results


** N M Larson. Updated Users’ Guide for Sammy: Multilevel R-matrix Fits to Neutron Data Using Bayes’ Equations (2003)


19

The resonance parameters can be get through SAMMY fitting, whose results are of a little difference from that of Mughabghab.

Parameters Comparison


Discriptions

The energy range is from 0.1 to 100 eV.

This two series of parameters are a little bit different.

Atlas is just the data recommended by Mughabghab.

The parameters in red are of big uncertainties for black resonance or go far beyond the average capture width.

The determination of capture width need more solid support of the capture measurements.

E(eV) 2gГn(meV) Гγ(meV)Atlas Present Atlas Present Atlas Present

-20.13 -20.16 358±42 86.37 173±21

3.906±0.001 （ 3.93） 11.2±0.3 （ 17） 102.4±1.2

（ 131）

14.32±0.01 14.41±0.03 4.56±0.06 5.4±0.5 97.1±2.0 160±15

17.42±0.01 17.51±0.02 2.87±0.03 3.8±0.5 81.4±3.0 107±12

28.9±0.1 28.9±0.1 0.31±0.03 0.42±0.04 95±20 93±20

34.79±0.05 34.86±0.06 8.8±0.5 14.1±1.0 86±3 113±20

37.51±0.05 37.47±0.05 0.69±0.07 0.8±0.1 （ 5.0）

44.79±0.05 44.87±0.06 5.2±0.3 7.0±1.0 93±5 97±8

50.58±0.10 50.7±0.3 8.1±0.8 12.0±2.0 79±5 74±5

59.07±0.10 58.5±0.3 15.0±0.9 25±3.0 84±5 66±6

62.97±0.10 62.9±0.2 1.5±0.2 1.2±0.5 78±15 76±15

65.75±0.10 65.90±0.2 56.5±1.5 71±5 83±4 97±15

83.18±0.10 83.53±0.3 11.3±0.6 15±1 85±5 83±10

94.1±0.1 94.6±0.3 48±5 58±8 （ 4.9）95.4±0.1 95.6±0.3 1.9±0.2 3.5±1.0 71±20 71±15


20


1 Introduction



4 Conclusion

Contents


21

Taking all experimental data available into consideration, the RP of 169Tm below 100 eV may be determined as follows. ( still under discussion)

Recommended RP

3 Conclusion and Discussion

Basis of Recommendation

J parameters are from the polarization measurement of Alfimenkov in JNR in 1982

E and Г parameters are determined mainly on 4 series of data including present one

— Mughabghab’s parameters

— 1973, Tellies, et al, on SACLAY

— 1999, Danon, et al, on RPI

— Present one, on PNF

Гγ from Mughabghab

RP at 3.9eV from Danon

Others from present results

J E(eV) 2gГn(meV) Гγ(meV)

1 -20.13 358 86.37

1 3.906±0.001 11.2±0.3 102.4±1.2

0 14.36±0.04 4.9±0.3 97.1±2.00 17.47±0.05 3.34±0.4 81.4±3.0

1 28.9±0.1 0.42±0.04 95±20

1 34.86±0.06 14.1±1.0 86±3

1 37.47±0.05 0.8±0.1

1 44.87±0.06 7.0±1.0 93±5

1 50.7±0.3 12.0±2.0 79±51 58.5±0.3 25±3.0 84±51 62.9±0.2 1.2±0.5 78±150 65.90±0.20 71±5 83±41 83.53±0.30 15±1 85±51 94.6±0.3 58±8

0 95.6±0.3 3.5±1.0 71±20


TOTAL CROSS-SECTION MEASUREMENTS AND RESONANCE PARAMETER ANNYLISIS OF 169 TM BELOW 100 EV ICTP, Trieste, Italy 2010/05/14 Presentation in the Workshop.

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