workshop on nuclear reaction data for advanced reactor technologies – trieste, 19 – 30 may,...

Workshop on Nuclear Reaction Data for Advanced Reactor Technologies – Trieste, 19 – 30 May, 2008, P. Schillebeeckx 1

[email protected]

Joint Research Centre (JRC)IRMM - Institute for Reference Materials and Measurements

Geel - Belgiumhttp://irmm.jrc.ec.europa.eu/

http://www.jrc.ec.europa.eu/

Neutron Induced

Cross Section Measurements

Workshop on Nuclear Reaction Data for Advanced Reactor Technologies

Trieste, Italy, 19 – 30 May 2008

2Workshop on Nuclear Reaction Data for Advanced Reactor Technologies – Trieste, 19 – 30 May, 2008, P. Schillebeeckx

Importance of neutron induced reactions for reactor operation

• Nuclear fuelU, Pu, Th (n,f), (n,), …

• Fission products (“neutron poisoning”)103Rh, 135Xe, 135Cs, 149Sm (n,)

• Structural materialsFe, Cr, Ni

n,xn

n,3n

n,3n

233Th

232Th

231Th

230Th 230Pa

231Pa

232Pa

233Pa

234Pa 234U

233U

232U

n,f

n,2n n,e.g. Th-U cycle

Safety + Economics


Cross section data

Integral data

Theory EvaluationEvaluatedData File

Industry

Microscopicdata

Research Laboratories

RegulatoryBodies

Benchmark measurements


Neutron induced reactions

• Neutron induced reactionsn + X Y + r

• Various reaction channelsn + X X + n (n,n) elastic scattering n

Y + (n,) capture Y1 + Y2 (n, f) fission f

Y + p (n,p) p

...

• Probability for a reaction (n,r) to occur:Partial cross section: r

• Total cross sectiontot = r = n + + f + p + …


Cross section

• A cross section has the dimension of an area.

• The unit of a cross section is taken as: 1 barn, 1 b = 10-24 cm2.

• Reaction rate for a neutron beam on a target (thin layer) :

n : neutron flux

NA : Avogadro constant

NX : number of nuclei

MX : molar mass of nucleus X

m(X) : mass of X

in most cases the number of nuclei per unit area are required (these will be denoted by n)

10-2 100 102 104 10610-4

10-2

100

102

104

59Co(n,)

(n)

/ bar

n

Neutron Energy / eV

)X(mM

NN

X

AX nXNR


Resonance structure

A cross section as a function of En

shows a resonant structure, which can be described by a Breit-Wigner shape :

with

natural line width (FWHM)

ER resonance energy

22Rn

tot)2(EE

1~

133 134 135

0

4000

8000

t

R

ER

t /

bar

n

Neutron Energy / eV

o tot

tot /

ba

rn


Cross sections : energy dependent

238U(n,tot) = 238U(n,n) + 238U(n,) tot = n +

• Resonance Region : D >

Resolved Resonance Region : R < D

Unresolved Resonance Region : R > D

• High Energy Region : D < 10-2 100 102 104 10610-2

102

106

88 90 92 940

5

10

15

Eo

D

Cro

ss-s

ectio

n / b

arn

Energy / eV

t

n

tot

ER


Parameterisation of neutron cross sections by nuclear reaction theory

• Ensures consistency between partial and total cross sections

• Ensures consistency between cross section data in different energy regions

• Prevents the use and recommendation of unphysical data

• Reliable calculations of Doppler broadened reaction cross sections

• Permits inter - and extrapolation into regions were no experimental data are available

• Permits prediction of reaction cross sections for isotopes not directly accessible to experiments



• Thermal : R - Matrix

• RRR : R - Matrix (SLBW, Reich-Moore)

• URR : Statistical Models (Hauser – Feshbach + WF)

• High : Optical Model, precompound, direct reactions, …



URRStatistical Models

Res. Par.ERj , n,j , ,j , Jj , R

High EnergyOptical Models

Thermal

RRRR-Matrix

Level Statistics + RD0 , So , < >

)E,,g(f RjjnjJth

Average Par.Do,1 , So,1 , < >, R

Exp. Data

Exp. DataExp. Data

Exp. Data


Neutron energy spectrum

10-2 100 102 104 106 1080.0

0.1

0.2

0.3

(d n

/ d

lnE

n)

/ (c

m-2 s

-1)

fast thermal

Neutron Energy / eV

Reactor ADS : Ep = 600 MeV

10-2 100 102 104 106 1080.0

0.1

0.2

0.3

0.4

(d n

/ d

lnE

n)

/ (c

m-2 s

-1)

ADS-spectrum for Ep = 600 MeV

Neutron Energy / eV


Importance of resonance structure

3.7 3.8 3.9 4.0 4.1 4.20.0000

0.0002

Tra

nsm

issi

on

Neutron Energy / MeV

Transmission (dFe = 40 cm)

0

2

4

6

8

tot

/ b

arn

IRMM 1993 ENDF/ B-VI

natFe + nGELINA


Resonances : compound nucleus reactions

n + X C* Y + rEntrance channel Compound nucleus Exit channel


• Two step process

(1) Formation of compound nucleus C*

(2) Decay of compound nucleus Pr

• Partial cross section

Bohr’s hypothesis : compound nucleus reactionResonance part of cross section

22

Rn

n2n

Jn*C)2(EEk

gE

,...)f,,nr(r

r

,...)f,,nr(P rr

r*Cr P

AX

-Sn

En

A+1X

c*

E*

AX +n

nn* E

1A

ASE


nJ2

R

o gk

4

133 134 135

0

4000

8000

Eo

n

o

n

n /

bar

n

Neutron Energy / eV133 134 135

0

4000

8000

Eo

o

/

bar

n

Neutron Energy / eV

ER = 134 eVn = 0.093 eV = 0.106 eVJ = 1-

= 0gJ = 3/4

133 134 135

0

4000

8000

t

o

Eo

t /

ba

rn

Neutron Energy / eV

e.g. 109Ag s-wave at ER = 134 eV(ER, n, , J

(), )

tot

tot

/ bar

n

ER

ER

ER


Compound nucleus reactions

• No capture without scattering

• Relative contribution of n and to tot may be different

• Boundaries of the resonance region differ

• Not only resonances (see 58Fe + n)

10-2 100 102 10410-3

10-1

101

103

105

t

n

Cro

ss s

ectio

n /

barn

Neutron Energy / eV

197Au + n

10-2 100 102 104 10610-4

10-2

100

102

104

t

n

Cro

ss s

ectio

n /

barn

Neutron Energy / eV

56Fe + n

tot

tot


SLBW for low energy s-wave(n,n) and (n,)

• (n,)

• (n,n)

• Total

22

Rn

n2n

Jn)2(EEk

gE

2J22

Rn

Rnn

nJ22

Rn

nn2n

Jnn R4g)2(EE

R)EE(

k

4g

)2(EEkgE

2J22

Rn

Rnn

nJ22

Rn

n2n

Jntot R4g)2(EE

R)EE(

k

4g

)2(EEkgE

n

)1I2(2

1J2gJ

fmA23.1R 31

(ER, n, , J(), )


Interference term s-wave <---> p-wave ( > 0)

3.350 3.355 3.360 3.3650

400

800

1200

Neutron Energy / keV

p-waveE

0 = 3357.1 eV

n = 0.240 eV

= 0.087 eV

tot

/ ba

rn

64 66 68

0

10

20

30

40


tot

/ ba

rn

E0 = 65.954 keV

n = 93.0 eV

= 1.3 eV

s-wave

(ER, n, , J(), )

n

22n

J22Rn

nnRn2n

J22on

nn2n

Jntot sink

4g

)2(EE

)2sin()EE(

k

2g

)2(EE

)2cos(

kgE


Ideal experiment

• In ideal conditions, without any instrumental resolution broadening, we can determine o/ and from one experiment.

and n o = f(gJ, n, )

However,

• Due to instrumental limitations and Doppler effect it is in most cases impossible to determine and o/

• Due to the instrumental limitations the effective experimental observable is :the area of a resonance

133 134 135

0

4000

8000

Eo

o

/

ba

rn

Neutron Energy / eV

ER


3340 3350 3360 3370

0

20

40

60


0.0

0.2

0.4

0.6

0.8

1.0

Experimental observables

• Transmission

• Capture

nJthick,t ngA

n

Jthin, ngA

nJthin,t ngA

n is the number of nuclei per unit area

Neutron energy / eV

Rae et al., Nucl. Phys. 5 (1958) 89F. Fröhner et al., ND1966, p. 55

totneT


Capture + Transmission

n n

Ideally : combine thin capture measurements with transmission measurements on samples with different thicknesses

n

JngA nJgn Jgn• Capture

nJgn thick,tA nJgn

thin,tA nJgn • Transmission nJgn

Rae et al., Nucl. Phys. 5 (1958) 89F. Fröhner et al., ND1966, p. 55

more sensitive to small resonances


Example: 109Ag s-wave at 5.2 eV

n / meV

gn = 3/4 gn = 1/4

12.7 38.0

I = 1/2-, i = 1/2 , and = 0 J = 0- or J = 1-

gJ = 1/4 or gJ = 3/4

nJ2n

2

thin,t ngk

2A

n / meV

/ meV gn = 3/4 gn = 1/4

50 37.8 113.5

100 18.9 56.7

150 12.6 37.8

200 9.5 28.4

300 6.3 18.9

400 4.7 14.2

nJn

thick,t ngk

2A

Thin Sample Transmission

n = 1.39 10-5 at/bAt,thin = 0.106 eV

Thick Sample Transmission

n = 4.74 10-4 at/bAt,thick = 1.039 eV

gJ = 3/4 gJ = 1/4 gJ = 3/4 gJ = 1/4

Rae et al., Nucl. Phys. 5 (1958) 89

(gJ n 9.5 meV , 150 meV, =0)


Resonance Area Analysis e.g. 109Ag 5.2 eV

0 100 200 300 400 5000

10

20

c2

min = 3.2

At,thin

At,thick

A A

n

g = 3/4

n /

meV

/ meV

ER = 5.2 eV, n = 12.7 (0.23) meV , = 149.0 (7.8) meV, gJ = 3/4

0 100 200 300 400 5000

25

50g = 1/4

c2

min = 75

At,thin

At,thick

A A

n

n /

meV

/ meV

gJ = 3/4 gJ = 1/4gJ = 3/4

Rae et al., Nucl. Phys. 5 (1958) 89

(ER, n, , J(), )


10-2 100 10210-2

100

102

104

106

109Ag(n,)

EO = 5.2 eV

th = 91 b

s-wave p-wave

/

bar

n

Neutron Energy / eV

Neutron widths-wave <----> p-wave ( > 0)

n depends on En : due to the centrifugal-barrier penetrability, which depends on the angular momentum quantum number of the incoming neutron and En

(penetration probability depends on )

• s-wave ( = 0)

• p-wave ( = 1)

cross section at 0.025 eV (Thermal)

eV1

E)E( n0

nnn

22n

22nn1

nnnak1

ak

eV1

E)E(

N

1j2

Rj

rjonjJ2

6thr

E

g

A

1A10.099.4

22

Rn

n2n

Jn)2(EEk

gE


th and contribution of s-wave resonances

•

• Additional contribution from bound states (negative resonances)

N

1j2

Rj

jonjJ

2

A

A6th0E

th

E

g

m

1m10.099.4

10-3 10-1 10110-2

100

102

104

106 , total

for Er = 1 eV

for Er = - 1 eV

(n,)

/ bar

n

Neutron Energy / eV

AX

-Sn A+1X

c*

E*

AX +n


Determination of resonance parameters

• SLBW and Resonance Area Analysis– Instructive– Principles remain valid !

• Resonance Shape Analysis (RSA)

(R- Matrix : theory)

– Extension of RRR– Direct treatment of broadening effects (Resolution & Doppler)– Direct treatment of multiple scattering effects (capture data)– Reduction of uncertainties

– SAMMY ( N. Larson) S. Marrone– REFIT ( M. Moxon) Summer School on Neutron Resonance Analysis

2- 6 June 2008, IRMM Geel


TOF - measurements

• Introduction

• TOF - measurements

– TOF-principle– Neutron production– Resolution– Experimental observables

• Transmission experiments

• Examples


Cross section measurements

• Thermal– Reactor– TOF-facilities

• Resolved Resonance Region– TOF-facilities (photonuclear reactions, spallation sources)

• Unresolved Resonance Region– TOF-facilities– VdG + TOF– Filtered beams (+ TOF)– Activation

• High Energy Region– TOF-facilities (spallation sources)– Activation– VdG (< 20 MeV)– Cyclotron

N. Colonna


TOF - measurements

• Photonuclear reactions– GELINA (n,tot) + (n,), (n,f), (n,p), (n,)– ORELA (n,tot) + (n,), (n,f), (n,p), (n,)– RPI (+ filtered) (n,tot) + (n,), (n,f), (n,n)– POHANG (KAERI) (n,tot)– KURRI (n,tot) + (n,)

• Spallation sources (N. Colonna)– n_TOF (n,), (n,f)– LANSCE (n,tot) + (n,), (n,f)


• Velocity from TOF

• Resolution L

• Neutron flux L

TOF - measurements

nn t

Lv

2

2

2n

2n

n

n

L

L

t

t

v

v

2n L

1)L(

1

)c/v(1

1cmE

2n

2nn

150

MeV

LIN

AC Sample

Flight pathUdepl.

fn’

tot

tn

Lvn


TOF-facility : GELINA

• Time-of-flight facility

• Pulsed white neutron source (5 meV < En < 20 MeV)

• Multi-user facility with 10 flight paths (10 m - 400 m)

• The measurement stations have special equipment to perform:

– Total cross section measurements– Partial cross section measurements

Pulse Width : 1ns

Frequency : 50 – 800 Hz

Average Current : 4.7 – 75 A

Neutron intensity : 1.6 1012 – 2.5 1013 n/s


GELINA : neutron production

NEUTRONMODERATOR

ELECTRONBEAMLINE EXIT

NEUTRONTARGET

NEUTRONFLIGHT PATHS

• e- accelerated to Ee-,max ≈ 140 MeV

• (e-, ) Bremsstrahlung in U-target

(rotating & cooled with liquied Hg)

• ( , n) , ( , f ) in U-target

• Low energy neutrons by water

moderator in Be-canning


Compression Magnet

140 MeV

80 MeV

10 ns 1 ns

100 A

10 A

E

qc

2B

qc

E

B

1

eq;pcE;q

pB

2

compressed pulse length ~ 1 ns

E = 60 MeV = 10 ns


GELINA : neutron production

SHIELDING for MODERATED SPECTRUM

SHIELDING for FAST SPECTRUM

10-2 100 102 104 106102

103

104

105 GELINA 30 m 800 Hz

Exp. Mod. Fast

MCNP Mod. Fast

dn/

dlnE

n /

(cm

-2 s

-1)

Neutron Energy / eV

Flaska et al.,NIM A , 531, 394 (2004)


ORELA : neutron production

10-3 10-2 10-1 100 101 102 103 104 105 106 107 108105

106

107

108

109

1010

1011

OR

EL

A F

lux

n/s

ec/s

r/kW

Cap

abili

ties

Neutron Energy (eV)


Resolution

T

– Initial burst width

– Time jitter of detector

– Electronics

L

– Neutron transport in target and moderator

– Neutron transport in the detector or sample

2

2

2

2

n

n

L

L

T

T

v

v

Detector

L0

Resolution

L = L0 + L’m

En

e- beam

L’m

R(L’m)


Resolution: Monte Carlo simulations

-5 0 5 10 1510-4

10-3

10-2

10-1

100E

n = 10000 - 30000 eV

Distance / cm

-5 0 5 10 1510-4

10-3

10-2

10-1

100

MCNP (PhD M. Flaska) Coceva

En = 100 - 1000 eV

Distance / cm-5 0 5 10 15

10-4

10-3

10-2

10-1

100 En = 1 - 10 eV

Res

pons

e /

(1/

cm)

Distance / cm

Flaska et al.,NIM A , 531, 394 (2004)


Resolution : experimental verification

3.34 3.35 3.36 3.370

20

40206Pb(n,)

C

aptu

re Y

ield

/ B

arn

FWHM

= 3.89 eV

R = 3.25 eV

D = 2.24 eV

t = 0.34 eV


Exp RSA (REFIT) Resolution (Coceva)

34.1 34.2 34.3 34.40

1

256Fe(n,)

FWHM

= 42.88 eV

R = 42.29 eV

D = 6.84 eV

t = 1.96 eV

Exp. RSA (REFIT) Resolution (Coceva)



Direct spectrumModerated spectrum

(n,) NIM, A577 (2007) 626

(n,tot) NP A 773, 173 (2006)

(n,f) and (n,cp) NSE 156, 211 (2007)

(n,n’) NP A 786, 1 (2007)

Measurement Stations



Reaction Measurements Transmission

Detector

Detector

totneT rrrrr AYC


Transmission

• Incoming flux cancels

• Detection efficiency cancels

• Good geometry

Direct relation between T and tot

Reaction

r Neutron fluence rate

r Detection efficiency

• Ar Effective area

• Yr Reaction Yield

Beam fraction undergoing (n,r)

Complex relation between Cr and Yr

Yr related to r

totn

out

in eC

CT rrrrr AYC



Reaction yield : thin Sample

• Thin sample, no scattering only self-shielding

Yr = f(r , tot)

• Infinitely thin sample

Direct Relation : Yr <--> r

t

rnr )e1(Y tr

rrt

rσnthin,r n

σ

σe1Y tr

n

x

n(x)


n nn’

nn’

n’’

Yo Y1 Y2

j

jYY

tot

n

n

)e1(nY

tot

2

22

n

A2

nA

nn

'n sin

m

mcos

mm

mEE

Correction for self-shielding and multiple scattering requires

tot & n

Reaction yield : thick sample


Transmission experiments

• Introduction

• TOF – measurements


– Principle– Experimental set-up– Facilities– Data reduction

• Applications


Transmission : principle

– All detected neutrons have traversed the material– Neutrons scattered in the target do not reach the detector

Homogeneous sample

Importance of collimation (good geometry!)

totneT

sample detector


Neutron DetectorLithium-glas scintillator

• Neutrons interact with lithium via 6Li(n,)t

• The charged particles create fluorescence

in the scintillator material

• The light is reflected to the entrance

window of the photomultiplier

• The light is transformed into electrons in

a photocathode

• The electron signal is amplified in the

photo-multiplier tube

6Li(n,t) Scintillator + Photomultiplier


Transmission detector

Time Resolution

6Li(n,t) Scintillator + Photomultiplier

0 1 2 3 410-3

10-2

10-1

100

101

Res

pons

e / (

1/cm

)

MCNP REFIT

En = 10 eV

Distance / cm


Transmission: experimental set-up

Sample & Background Filters Detector

Kopecky and Brusegan, Nucl. Phys. A 773 (2006) 173Borella et al., Phys. Rev. C 76 (2007) 014605

Low energy : 6Li(n,t) Li-glassHigh energy : H(n,n)H Plastic scintillator

Detector stations at GELINAModerated : at 30 m, 50 m, (100 m, 200 m)Fast : at 400 m


Transmission

103 104 105 10610-2

10-1

100

101

102

103

Total BKG fit BKG points

SAMPLE OUT

Re

spo

nse

/ (1

/ns)

TOF / ns

103 104 105 10610-2

10-1

100

101

102

103

Total BKG fit BKG points

SAMPLE IN

Re

spon

se /

(1/n

s)

TOF / ns

0 20000 40000 60000 800000.0

0.2

0.4

0.6

0.8

1.0

Tra

nsm

issi

on

Neutron Energy / eV

'out

'out

'in

'in

BC

BCT


Transmission

Sample out

(1) Dead time correction

(2) Background subtraction

'out

'out

'in

'in

TexpBC

BCNT

n)E(

nnTnexp dEe)E,T(R)T(T ntot

Sample in

(1) Dead time correction

(2) Background subtraction

RRRResonance shape analysis

URRCorrection for resonance structure

...)var2

n1(ee tot

2nn tottot

totnexp eT


Resonance analysis : 241Am

0.1 1 10

-4

0

4

Res

idua

ls

Neutron Energy / eV

0.0

0.5

1.0

Exp. REFIT

Tra

nsm

issi

on


ORELA : transmission + capture

Guber et al., Phys. Rev C 65 (2002) 058801

35,37Cl + n

Transmission- at 20, 80 and 200 m- 6Li-glass scintillator

Capture- at 40 m- C6D6-detectors

Measurements on over 180 nuclides: ORELA measurements have contributed to ~80% of U.S. Evaluated Nuclear Data File (ENDF/B) evaluations


RPI : transmission + capture

Transmission- at 15, 25 and 100 m- 6Li-glass scintillator

Capture- at 30 m- 16 segment NaI(Tl)-scintillator

Drindak et al., Nucl. Sci. Eng. 154 (2006) 294

Leinweber et al.,Nucl. Sci. Eng. 134 (2000) 50

Nb


POHANG : transmission

Transmission- at 10 m- 6Li-glass scintillator (1.5 cm thick)

Lee et al., Radiat. Meas. 35 (2002) 321


LANSCE : transmission in high energy region

Transmission- at 38 m- plastic scintillator (1.27 cm thick)

Abfalterer et al., Phys. Rev. 63 C (2001) 044608


Applications

• Introduction

• TOF – measurements


• Applications

– Doppler– Thermal region– RRR & URR– High energy region


Doppler measurements

Temperatures from 10 K - 300 K

19 20 21 220.7

0.8

0.9

1

Temperature 15K 300K

Tra

nsm

issi

on F

acto

r

Neutron Energy / eV

240Pu : target thickness = 8.7 10-5 at/b

ER = 22.45 eV


Optimise the U - Pu fuel cycle

More accurate nuclear data are needed for:

1) Tendency to operate conventional nuclear power plants at increased fuel burn-up

2) Fuel cycles based on reprocessed fuel(closed fuel cycle)

3) Spent fuel storages (ORNL – RADWASTE)

M. Salvatores, ND2002, J. Sci. & Techn. 2 (2002) p. 4F. Storrer et al., ND2002, J. Sci. & Techn. 2 (2002) p. 1357NEA High Priority List, March 2001

< 2-3%

1 & 2 : Collaboration with CEA Saclay (F)

3 : Collaboration with ORNL (US)

Nuclide Priority Level

Storrer et al.

Burnup

Salvatores

Reprocessing 103Rh 1 133Cs 1 155Gd 1 147Sm 1 149Sm 1 152Sm 1 143Nd 2 1 145Nd 1 153Eu 2 1 155Eu 1


103Rh: Thermal region

(n,) at 25.3 meV

WF : 142.0 (1.5) b

1.0 % normalization

0.5 % uncorrelated

Counts : 143.3 b

0.01 0.1 1 1010-3

10-2

10-1

100 Experiment REFIT

Cap

ture

Yie

ld

Neutron Energy / eV

Transmission: 50 m 100 Hz Capture : 15 m 40 Hz

n = 3.35 10-4 at/b

n = 1.87 10-3 at/b

ER = 1.260 eV

n = 0.464 meV

= 156.0 meV

gJ = 3/4D 35 meVR < 5 meV


55Mn Transmission measurements at 50 m

10000 20000 30000 40000 50000

-4

4

Re

sid

ua

ls

Neutron Energy / eV

0.2

0.4

0.6

0.8

1.0

Tra

nsm

issi

on

10000 20000 30000 40000 50000

-4

0

4

Sputtering target n = 1.92 10-2R

esi

ud

als

0.2

0.4

0.6

0.8

1.0

Tra

nm

smis

sio

n

Mn powder n = 9.94 10-3

100 1000 10000

-4

4

Res

idua

ls

Neutron Energy / eV

0.2

0.4

0.6

0.8

1.0

Exp. REFIT

Mn + S powder n = 1.53 10-3

Tra

nsm

issi

on

100 1000 10000

-4

0

4

Res

iuda

ls

0.2

0.4

0.6

0.8

1.0

Tra

nmsm

issi

on

Mn + S powder n = 4.35 10-4


IAEA CRP: Thorium – Uranium Fuel Cycle

Resonance parameters (RRR & URR) for 232Th + n

Facility Measurement

Type

Flight Path

Length

Target Thickness

at/b

ORELA Transmission 180 m 1.68 10-4 14.00 10-4 38.70 10-4 193.1 10-4

GELINA Transmission 50 m 8.00 10-4 34.0 10-4 61.0 10-4

GELINA Capture 15 m 15.8 10-4 60 m 34.0 10-4

n-TOF Capture 200 m 41.0 10-4


232Th Resolved Resonance Region

Simultaneous analysis of

transmission and capture

• Determine R

• Determine

• Determine n

• Verify gJ

Examples

0.0

0.5

1.0

Cap

ture

Yie

ld

0 200 400 600 800 10000.0

0.5

1.0

Tra

nsm

issi

on

Energy / eV


Scattering radius : transmission with thick sample

R’ = 8.9 fm R’ = 9.5 fm

Neutron Energy / eV Neutron Energy / eV

200.0199.0 199.0 200.0

Tra

nsm

iss

ion

Interferencepotres

2J22

Rn

Rnn

nJ22

Rn

n2n

Jntot R4g)2(EE

R)EE(

k

4g

)2(EEkgE

232Th + n


Statistical factor : simultaneous analysis of capture and transmission data

7.22

c

Neutron Energy / eV Neutron Energy / eV

Cap

ture

Yie

ld

Cap

ture

Yie

ldT

ran

smis

sio

n

Tra

nsm

iss

ion

gJ = 2gJ = 1 2.1

2

c

200.0199.0 200.0199.0232Th + n


Average radiation width from capture datawith REFIT

0 250 5000.0

0.1

0.2

Cap

ture

Yie

ld

Neutron Energy / eV

ORELA (Transmission) : <> = 25.10 (0.40) meV

IRMM (Capture) : <> = 25.12 (0.06) meV

232Th(n,)


Evaluation in URR and high energy region

0 50 100 15010

15

20

25 Capote Iwasaki et al. Poenitz et al. Uttley et al. Vertebnyj et al. Kobayashi et al. Grigor'ev et al.

< n

,tot>

/ b

arn


0 50 100 15060

70

80

90

100

This work Capote

(< n>E

1/2 )

/

(bar

n eV

1/2 ) Macklin and Winters

Kobayashi et al. Aerts et al. Borella et al. Average


Sirakov et al., Annals of Nuclear Energy, accepted 2008Capote et al., Phys. Rev. C 72 (2005) 064610Soukhovitskii et al., Phys. Rev. C 72 (2005) 024604


10-3 10-1 101 103 105 10710-5

10-3

10-1

101

103

t

Cro

ss s

ectio

n / b

Neutron Energy / eV

206Pb + n : new evaluation in RRR

Thermalneutronenergy

BNC

RRR

GELINA


60 64 68 720.5

0.6

0.7

0.8

0.9 Measurement FIT

Tra

nsm

issi

on


Scattering radius from transmission of s-wave at 66 keV

R = 9.55 (0.02) fm

R = 9.46 (0.15) fm (Mughabghab)

Interferencepotres

2J22

Rn

Rnn

nJ22

Rn

n2n

Jntot R4g)2(EE

R)EE(

k

4g

)2(EEkgE

Borella et al., Phys. Rev. C 76 (2007) 014605

206Pb+n


Determination of statistical factor gJ

thin <--> thick transmission

95.01g2

J c

25000 25500 260000.2

0.4

0.6

0.8

1.0t=3.00 x 10-2 at/b Measurement

FIT

Tra

snm

issi

on

Neutron Energy / eV

0.2

0.4

0.6

0.8

1.0 Measurement FIT

Tra

snm

issi

on

t = 1.60 x 10-2 at/b

25000 25500 260000.2

0.4

0.6

0.8

1.0t=3.00 x 10-2 at/b Measurement

FIT

Tra

snm

issi

on

Neutron Energy / eV

0.2

0.4

0.6

0.8

1.0t = 1.60 x 10-2 at/b Measurement

FIT

Tra

snm

issi

on

25.22g2

J c

nJthin,t ngA

nJthick,t ngA

)1I2(2

1J2gJ

206Pb+n


Final RSA results: 206Pb+n

• 304 resonances observed

• 221 resonances in evaluated files

• R = 9.54 (0.02) fm

• En, n from transmission < 80 keV : IRMM data (Borella et al.)> 80 keV : ORELA data (Horen et al.)

• E0, up to 620 keV (Borella et al.)(before up to 200 keV )

• fE1 and fM1 from unfolding of C6D6 spectra

1E-5

1E-3

0.1

Yie

ld

Capture

Horen et al., Phys. Rev. C 24 (1981) 1961, C20 (1979) 478Borella et al., Phys. Rev. C 76 (2007) 014605Rochman and Koning, Nucl. Instr. Meth. A (2008), doi:10.1016/j.nima.2008.02.003

0 20000 40000 60000 800000.0

0.2

0.4

0.6

0.8

1.0

Transmission

Tra

nsm

issi

on

Neutron Energy / eV


High energy region + Optical Model

LANSCEFinlay et al., Phys. Rev. C 47 (1993) 237Abfalterer et al., Phys. Rev. C 63 (2001) 044608


Total cross section + Optical model

Deb et al., Phys. Rev. Lett. 86 (2001) 3248


Importance of transmission data

• Easiest and most accurate measurement

• No need for a standard cross section !

• Resonance region– parity assignment– thick & thin measurements result in (gJ, n) and R (scattering radius)– partial cross section data complementary to transmission for << n

– normalization of capture data (n<< )

tot data are a prerequisite to good partial cross section analysis(Fröhner, JEF Report 18)

– self-shielding and multiple scattering corrections– neutron sensitivity of the detectors

• Total cross section + optical model (predictive power)

• High resolution transmission data for shielding calculations

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