[PPT] - Neutron time-of-flight measurements and transmission measurements PowerPoint Presentation

SLIDE 1

The European Commission’s science and knowledge service

Joint Research Centre

Neutron time-of-flight measurements and transmission measurements

Peter Schillebeeckx

Workshop on the Evaluation of Nuclear Reaction Data for Applications 2 – 13 October 2017 ICTP, Trieste, Italy

SLIDE 2

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σtot σn,n σn,γ σn,f

Cross section / barn Neutron energy / eV

σtot = σn,n + σn,γ + σn,f +

Neutron induced reaction cross sections

238U+n

Mono-energetic neutrons (cp,n) reactions

Van de Graaff GELINA

White neutron source + Time-of-flight (TOF)

2 - 13 October, 2017, ICTP Trieste

SLIDE 3

7Li(p,n)7Be

En: 0 - 5.3 MeV T(p,n)3He En: 0 - 6.2 MeV D(d,n)3He En: 1.8 - 10.1 MeV T(d,n)4He En: 12.1 - 24.1 MeV quasi mono-energetic neutrons produced via nuclear reactions

e.g. T(d,n)4He

d n α α α α d n α α α α

Mono-energetic neutron beams by (cp,n) reactions

2 - 13 October, 2017, ICTP Trieste

SLIDE 4

Mono-energetic neutron beams by (cp,n) reactions

2 - 13 October, 2017, ICTP Trieste

SLIDE 5

1.0E+06 1.0E+07 1.0E+08 1.0E+09 5 10 15 20

Neutron energy / MeV Neutron yield (n/sr.µC)

7Li(p,n)7Be, Ep= 0-7 MeV, 0o

T(p,n)3He, Ep=0-7 MeV, 0o D(d,n)3He, solid target, Ed=0-7 MeV, 0o D(d,n)3He, gas target, Ed=0-7 MeV, 0o T(d,n)4He, Ep = 1 MeV, 0 -150o T(d,n)4He, Ep=0-7 MeV, 0o

Mono-energetic neutron beams by (cp,n) reactions

2 - 13 October, 2017, ICTP Trieste

SLIDE 6

FLIGHT PATHS SOUTH FLIGHT PATHS NORD ELECTRON LINAC TARGET HALL

Pulsed white neutron source

(10 meV < En < 20 MeV)

Neutron energy : time – of – flight (TOF)
Multi-user facility: 10 flight paths (10 m – 400 m)
Measurement stations with special equipment:

− Total cross section measurements − Reaction cross section measurements

Time-of flight facility GELINA

7

2 - 13 October, 2017, ICTP Trieste

SLIDE 7

GELINA : neutron production

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(dϕ/dlnE) / (cm

2 s
1)

Neutron energy / eV

Fast Moderated MCNP MCNP Exp. Exp.

GELINA 30m 800 Hz

Neutron production:

Bremsstrahlung in U-target
( γ , n) and ( γ , f ) in U-target
Low energy part enhanced by moderator

(water in Be-canning)

NEUTRON MODERATOR ELECTRON BEAMLINE EXIT NEUTRON TARGET NEUTRON FLIGHT PATHS

2 - 13 October, 2017, ICTP Trieste

SLIDE 8

Characteristics of neutron source

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(dφ/dE) / ( 1 / eV s cm

2 )

Energy / eV

Experiment MCNP (at 12 m)

Isotropic emission
Moderated Spectrum

Maxwellian + 1/E

2 n

L 1 ) L ( ∝ ϕ

2 - 13 October, 2017, ICTP Trieste

SLIDE 9

TOF - measurements

t L v =

Target- moderator assembly Detector Sample

L

pulsed e- - beam

T0 Ts t ≈ (T

s – T0)

v

2 2

mv 2 1 ) 1 ( mc E ≅ − γ = ⇒

2 - 13 October, 2017, ICTP Trieste

SLIDE 10

TOF - measurements

Evacuated tube

Neutron detector

2 - 13 October, 2017, ICTP Trieste

T0

Experiment MCNP (at 12 m)

s

T T −

Ts

Event Time 1 4000 ns 2 50000 ns 3 750000 ns 4 500 ns . . . .

SLIDE 11

TOF - measurements

Evacuated tube

Neutron detector

2 - 13 October, 2017, ICTP Trieste

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Counts / (1/ns) Time-of-flight / ns

Event Time 1 4000 ns 2 50000 ns 3 750000 ns 4 500 ns . . . .

Experiment MCNP (at 12 m)

ϕ ε =

ut

C

SLIDE 12

TOF - measurements

Evacuated tube

Neutron detector

2 - 13 October, 2017, ICTP Trieste

Experiment MCNP (at 12 m)

Sample

ϕ ε = T Cin

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Counts / (1/ns) Time-of-flight / ns

SLIDE 13

TOF - measurements

t L v =

Target- moderator assembly Detector Sample

L

pulsed e- - beam

T0 Ts t ≈ (T

s – T0)

v

2 2

mv 2 1 ) 1 ( mc E ≅ − γ = ⇒

2 - 13 October, 2017, ICTP Trieste

SLIDE 14

TOF - measurements

Target- moderator assembly Detector Sample

L

pulsed e- - beam

T0 v3 Ts

v t = tm – ( tt + td )

2 - 13 October, 2017, ICTP Trieste

t L v =

tm = (T

s – T0)

tt td

SLIDE 15

TOF - measurements

L

Ts T0

v t = tm – ( tt +td )

2 2 2 2

L L t t v v ∆ + ∆ = ∆

2 - 13 October, 2017, ICTP Trieste

t L v = ) 1 ( mc E

2

− γ = v v ) 1 ( E E ∆ γ γ + = ∆

2

mv 2 1 E ≅ v v 2 E E ∆ ≅ ∆ s / m 10 x 8 . 13 v

3

≅

2

t L 298 . 72 E       ≅ E : eV t : µs L : m ⇒ 1 eV neutron : ⇒ γ-ray : s / m 300 s / m 10 x 3 c

8

µ ≅ ≅

SLIDE 16

Response of TOF-spectrometer

2 - 13 October, 2017, ICTP Trieste

L

v v ∆

2 2 2 2

L L t t v v ∆ + ∆ = ∆ t L v =

2 2 2

L t v L 1 v v ∆ + ∆ = ∆

L

Ts T0

v t = tm – ( tt +td )

SLIDE 17

∆

∆ ∆ ∆L (∼ ∼ ∼ ∼ 1 mm)

∆

∆ ∆ ∆t

− Initial burst width

∆T0

− Time jitter detector & electronics

∆Ts

− Neutron transport in target - moderator

∆tt

− Neutron transport in detector

∆td

Response of TOF-spectrometer

2 - 13 October, 2017, ICTP Trieste

tm = (T

s – T0)

2 2 2 2

L L t t v v ∆ + ∆ = ∆ t L v =

L

v

Ts T0

t = tm – ( tt +td )

SLIDE 18

Probability distribution of tt : GELINA

2 - 13 October, 2017, ICTP Trieste

dt dL ) E , ) t ( L ( ' R ) E , t ( R

t t

=

Transformation of variables : Lt = v tt

₋

Lt : equivalent distance

₋

v : neutron velocity when leaving the moderator

₋

tt : time difference between neutron creation and moment it leaves the moderator

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0.01 - 0.02 eV 1 - 2 eV 1 - 2 keV 100 - 125 keV

R(tt,E) Time, tt / µs

x 10

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SLIDE 19

Probability distribution of Lt : GELINA

2 - 13 October, 2017, ICTP Trieste

Transformation of variables : Lt = v tt

₋

Lt : equivalent distance

₋

v : neutron velocity when leaving the moderator

₋

tt : time difference between neutron creation and moment it leaves the moderator

5 10 15 20 25 0.0 0.1 0.2 0.3 0.4

2 4 6 8 10 0.0 0.1 0.2 0.3 0.4

1 - 5 eV

1 - 5 eV 100 - 500 eV 1000 - 2000 eV 6000 - 8000 eV 10000 - 20000 eV 60000 - 80000 eV

Probability desinsity Distance / cm

2 cm

dt dL ) E , ) t ( L ( ' R ) E , t ( R

t t

=

Equivalent distance, Lt / cm

SLIDE 20

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1 - 5 eV 100 - 500 eV 1000 - 2000 eV 6000 - 8000 eV 10000 - 20000 eV 60000 - 80000 eV

Probability desinsity Distance / cm

Probability distribution of Lt : GELINA

2 - 13 October, 2017, ICTP Trieste

Equivalent distance, Lt / cm

dt dL ) E , ) t ( L ( ' R ) E , t ( R

t t

=

Between 0.5 eV and 1000 eV: χ2

R’(Lt,En) dominated by χ2 due to moderation process and almost independent of En

Below 0.5 eV : χ2 + storage
Above 1000 keV : more complex

SLIDE 21

Probability distribution of Lt : GELINA

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Monte Carlo REFIT (adjusted to exp.)

Probability Density

Delay distance / m

Equivalent distance, Lt / m

2 - 13 October, 2017, ICTP Trieste

SLIDE 22

P(tt, E) : photonuclear

2.57 2.58 2.59 0.0 0.4 0.8 1.2 1.6 2.0

GELINA 40 m

R(tt,E) (L / tm) / (m/µs)

En = 35 keV 2 - 13 October, 2017, ICTP Trieste

Resolution : ∆L (FWHM) GELINA : 2 cm ∆L (FWHM) = 2 cm ⇒ about half of the moderator thickness

GELINA : 40 m

En = 35 keV

SLIDE 23

P(tt, E) : photonuclear

2.57 2.58 2.59 0.0 0.4 0.8 1.2 1.6 2.0

GELINA 40 m ORNL 40 m

R(tt,E) (L / tm) / (m/µs)

En = 35 keV 2 - 13 October, 2017, ICTP Trieste

Resolution : ∆L (FWHM) GELINA : 2 cm ORELA : 2 cm

GELINA : 40 m ORELA : 40 m

En = 35 keV

SLIDE 24

P(tt, E) : photonuclear ⇔ spallation reactions

2.57 2.58 2.59 0.0 0.4 0.8 1.2 1.6 2.0

GELINA 40 m ORNL 40 m nTOF 180 m

R(tt,E) (L / tm) / (m/µs)

En = 35 keV

Dimensions : 80 × 80 × 60 cm3 Pure Lead : 4 t H2O moderator : 5 cm Al-window : 1.6 mm Al-container : 140 l

2 - 13 October, 2017, ICTP Trieste

Resolution : ∆L (FWHM) GELINA : 2 cm ORELA : 2 cm nTOF : 10 cm

GELINA : 40 m ORELA : 40 m nTOF : 180 m

En = 35 keV

SLIDE 25

P(tt, E) : photonuclear ⇔ spallation reactions

2.57 2.58 2.59 0.0 0.4 0.8 1.2 1.6 2.0

GELINA 40 m ORNL 40 m nTOF 180 m

R(tt,E) (L / tm) / (m/µs)

En = 35 keV

2.54 2.56 2.58 2.60 0.0 0.2 0.4 0.6 0.8 1.0 1.2

GELINA 23 m ISIS 23 m JPARC 23 m

R(tt,E) (L / tm) / (m/µs)

En = 35 keV

Resolution : ∆L (FWHM) ISIS (INES) : 5 cm J-PARC (MLF/ANNRI) : 13 cm Strongly depend on target/moderator configuration (coupled/decoupled)

2 - 13 October, 2017, ICTP Trieste

GELINA : 40 m ORELA : 40 m nTOF : 180 m

Resolution : ∆L (FWHM) GELINA : 2 cm ORELA : 2 cm nTOF : 10 cm En = 35 keV En = 35 keV

GELINA : 23 m ISIS : 23 m JPARC : 23 m

SLIDE 26

∆

∆ ∆ ∆L (∼ ∼ ∼ ∼ 1 mm)

∆

∆ ∆ ∆t

− Initial burst width

∆T0

− Time jitter detector & electronics

∆Ts

− Neutron transport in target - moderator

∆tt

− Neutron transport in detector

∆td

Response of TOF-spectrometer

L

Ts T0

v t = tm – ( tt +td )

2 - 13 October, 2017, ICTP Trieste

tm = (T

s – T0)

2 2 2 2

L L t t v v ∆ + ∆ = ∆ t L v =

SLIDE 27

Initial burst (T0)

Single burst : mostly normal (Gaussian) distribution

− GELINA : ∆T0 = 1 ns (FWHM) − ORELA : ∆T0 = 4 ns (FWHM) − nTOF : ∆T0 = 10 ns (FWHM)

Double pulse structure :

− ISIS − J-PARC

2 - 13 October, 2017, ICTP Trieste

100 200 300 400 500 600 500 1000 1500

Exp Fit

Counts (1/ns) Time-of-flight (ns)

FWHM = 65 ns

∆P = 320 ns

SLIDE 28

Response GELINA (12.5 m) < - > ISIS (22.8 m)

2 - 13 October, 2017, ICTP Trieste

2000 4000 6000 100 1000 10000 Counts / (1/µs) Neutron energy (eV)

GELINA (12.5 m) ISIS (22.8 m)

100 200 300 400 500 600 500 1000 1500

Exp Fit

Counts (1/ns) Time-of-flight (ns)

FWHM = 65 ns

∆P = 320 ns

Double pulsed proton beam also at J-PARC Double pulsed proton beam

SLIDE 29

TOF : resolution components

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∆ ∆ ∆ ∆L = 2 cm ∆ ∆ ∆ ∆T = 0 ∆ ∆ ∆ ∆T = 100 ns ∆ ∆ ∆ ∆T = 10 ns ∆ ∆ ∆ ∆T = 1 ns ∆L = 2 cm ∆L = 2 cm

∆E / E

Energy / keV

L = 30 m

Neutron energy / eV

2 - 13 October, 2017, ICTP Trieste

v v 2 E E ∆ ≅ ∆

2 2 2

L t v L 1 v v ∆ + ∆ = ∆

∆L = 0 cm ∆L = 2 cm

∆L = 2 cm ∆t = 0

SLIDE 30

197Au(n,γ) at L = 12 m and 30 m

58 60 62 0.0 0.2 0.4 0.6 0.8 1.0

12 m ∆R ~ 200 meV 30 m ∆R ~ 80 meV

Yield Neutron Energy (eV)

Γ ~ 120 meV ∆ ∆ ∆ ∆D ~ 300 meV

610 620 630 640 650 0.00 0.02 0.04 0.06 0.08 0.10

12 m ∆

∆ ∆ ∆R ~ 2020 meV

30 m ∆R ~ 840 meV

Γ ~ 120 meV ∆D ~ 940 meV

Yield Neutron Energy (eV)

2 - 13 October, 2017, ICTP Trieste

2 2

t t L L 2 E E       ∆ +       ∆ ≅ ∆

n X B D

m / m T k E 4 = ∆

D

2 ln 2 FWHM ∆ =

SLIDE 31

Velocity from TOF

Neutron fluence rate
Resolution

TOF – measurements at GELINA

(n,γ γ γ γ) (n,tot) (n,f) and (n,cp) (n,n’γ γ γ γ) (n,n)

2 2 2

L t v L 1 v v ∆ + ∆ = ∆

2

L 1 ) L ( ∝ ϕ t L v =

2 - 13 October, 2017, ICTP Trieste

Moderated Fast

⇒ L ⇒ L

SLIDE 32

Resonance parameters

Determination of resonance parameters is a complex process and requires a set of

complementary data

Combine reaction cross section measurements on thin samples with transmission

measurements on samples with different thicknesses

2 - 13 October, 2017, ICTP Trieste

SLIDE 33

Transmission measurements

Basic principles
Background measurements (black resonance filters)
Resolved resonance region
Unresolved resonance region

2 - 13 October, 2017, ICTP Trieste

SLIDE 34

Cross section measurements

Transmission

T : transmission Fraction of the neutron beam traversing the sample without any interaction

tot

n

e T

σ −

≅

2 - 13 October, 2017, ICTP Trieste

SLIDE 35

TOF-cross section measurements

.

Ts T0

t L v T T t

s

= − =

Evacuated tube

Neutron detector

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Counts / (1/ns) Time-of-flight / ns

L : distance between target and detector t : time-of-flight

2 - 13 October, 2017, ICTP Trieste

ϕ ε =

ut

C

SLIDE 36

Sample

.

Ts T0

t L v T T t

s

= − =

Evacuated tube

L : distance between target and detector t : time-of-flight

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Counts / (1/ns) Time-of-flight / ns 241Am

Neutron detector

TOF-cross section measurements

2 - 13 October, 2017, ICTP Trieste

ϕ ε = T Cin

SLIDE 37

Transmission measurements

Transmission

Incoming neutron flux cancels
Detection efficiency cancels

Cin Cout

2 - 13 October, 2017, ICTP Trieste

ut

in exp

C C T =

SLIDE 38

tot

n

ut

in exp

e C C T

σ −

∝ =

Transmission measurements

Transmission

Incoming neutron flux cancels
Detection efficiency cancels

⇒ Direct relation between Texp and σtot

Cin Cout

2 - 13 October, 2017, ICTP Trieste

SLIDE 39

Transmission : principle

2 - 13 October, 2017, ICTP Trieste

Target e- PMT

6Li

Target e- PMT

6Li

(1) All detected neutrons passed through the sample (2) Neutrons scattered in the target do not reach detector (3) Sample perpendicular to parallel neutron beam ⇒ Good transmission geometry (collimation) (4) Homogeneous target (no spatial distribution of n)

tot

n

ut

in exp

e C C T

σ −

∝ =

SLIDE 40

(1) All detected neutrons passed through the sample (2) Neutrons scattered in the target do not reach detector (3) Sample perpendicular to parallel neutron beam ⇒ Good transmission geometry (collimation) (4) Homogeneous target (no spatial distribution of n)

2 - 13 October, 2017, ICTP Trieste

Transmission measurements

tot

n

ut

in exp

e C C T

σ −

∝ =

SLIDE 41

Transmission station at GELINA

Neutron target + moderators Sample changer

6Li detector

Castle

2 - 13 October, 2017, ICTP Trieste

SLIDE 42

Transmission : principle

2 - 13 October, 2017, ICTP Trieste

Detectors Low energy : 6Li(n,t)α Li-glass High energy : H(n,n)H Plastic scintillator

tot

n

ut

in exp

e C C T

σ −

∝ =

SLIDE 43

Lithium-glass scintillator : energy deposition

6Li(n,t)α

Scintillator + PMT

500 1000 1500 2000 10000 20000 30000 40000

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6Li(n,α)t Eα = 2.73 MeV and Et = 2.73 MeV

Counts Amplitude

2 - 13 October, 2017, ICTP Trieste

SLIDE 44

Lithium-glass scintillator : resolution

0.0 0.5 1.0 1.5 2.0 2.5 0.0 0.2 0.4 0.6 0.8 1.0

MCNP

R(Ld,E) Equivalent distance, Ld / cm

En=10 eV

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6Li(n,t)α

Scintillator + PMT

2 - 13 October, 2017, ICTP Trieste

SLIDE 45

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Cout

Time - of - flight / ns Response / (1/ ns)

Transmission : sample-out

2 - 13 October, 2017, ICTP Trieste

Sample - out

Na 2.85 keV Co 132 eV

Detector

− NE912 Li-glass scintillator, 95% enriched in 6Li diameter : 101.1 mm thickness : 6.35 mm − at 49.34 m from neutron source

SLIDE 46

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Cin

Time - of - flight / ns Response / (1/ ns)

Transmission : sample-in

2 - 13 October, 2017, ICTP Trieste Na 2.85 keV Co 132 eV

Sample - in

Sample

− Au metal foil 50 mm x 50 mm x 3 mm 1.757 (0.004) 10-2 at/b − at 23.78 m from neutron source

Detector

− NE912 Li-glass scintillator, 95% enriched in 6Li diameter : 101.1 mm thickness : 6.35 mm − at 49.34 m from neutron source

SLIDE 47

Background: black resonance technique

2 - 13 October, 2017, ICTP Trieste

Black resonance filter

strong resonance at Er
removes all neutrons at TOF

corresponding to Er ⇒ Remaining counts are due to background

e T

tot

n

≈ =

σ −

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Cin Bin

Time - of - flight / ns Response / (1/ ns)

Na 2.85 keV Co 132 eV

Sample - in

SLIDE 48

Background: black resonance technique

B(t) = B0

Bo

time independent From measurement with no beam

2 - 13 October, 2017, ICTP Trieste

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Cin Bin

Time - of - flight / ns Response / (1/ ns)

Sample - in

SLIDE 49

Background: black resonance technique

B(t) = B0 + Bγ(t)

Bo

time independent

Bγ(t)

1H(n, γ)

Eγ = 2.2 MeV b1e-λ1t Shape from measurement with thick poly-ethylene filter in the beam to remove neutrons

2 - 13 October, 2017, ICTP Trieste

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Cin Bin

Time - of - flight / ns Response / (1/ ns)

Sample - in

SLIDE 50

Background: black resonance technique

B(t) = B0 + Bγ(t) + Bn(t)

Bo

time independent

Bγ(t)

1H(n, γ)

Eγ = 2.2 MeV b1e-λ1t

Bn(t)

scattered neutrons b2e-λ2t Shape from measurement with Pb-filter + black resonance filters

2 - 13 October, 2017, ICTP Trieste

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Time - of - flight / ns Response / (1/ ns)

Sample - in

SLIDE 51

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Cout Bout

Time - of - flight / ns Response / (1/ ns)

Background: black resonance technique

Na 2.85 keV Co 132 eV Na 2.85 keV Co 132 eV

Background influenced by sample ⇒ use of fixed background filters to adjust b1 and b2

t 2 t 1

2 1

e b e b b B

λ − λ −

+ + =

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Cin Bin Bout

Time - of - flight / ns Response / (1/ ns)

Sample - out Sample - in

2 - 13 October, 2017, ICTP Trieste

SLIDE 52

TOF-spectra ⇒ Texp

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Time - of - flight / ns Response / (1/ ns)

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Cout Bout

Time - of - flight / ns Response / (1/ ns)

ut
ut

in in exp

B K C B K C N T − − =

Sample - out Sample - in Sample - in

K = 1.00 ± 0.03

Na 2.85 keV

2 - 13 October, 2017, ICTP Trieste

Factor K introduces a correlated uncertainty due to the background model

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0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

SLIDE 53

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Transmission

Time-of-flight / ns

TOF-spectra ⇒ Texp

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Time - of - flight / ns Response / (1/ ns)

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Time - of - flight / ns Response / (1/ ns)

ut
ut

in in exp

B K C B K C N T − − =

Sample - out Sample - in Sample - in

K = 1.00 ± 0.03 N = 1.0000 ± 0.0025

Na 2.85 keV

2 - 13 October, 2017, ICTP Trieste

Factor N introduces a correlated uncertainty due to the normalisation

SLIDE 54

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Transmission

Time-of-flight / ns

TOF-spectra ⇒ Texp

10

3

10

4

10

5

10

6

10

7

10

6

10

5

10

4

10

3

Cin Bin

Time - of - flight / ns Response / (1/ ns)

10

3

10

4

10

5

10

6

10

7

10

6

10

5

10

4

10

3

Cout Bout

Time - of - flight / ns Response / (1/ ns)

ut
ut

in in exp

B K C B K C N T − − =

Sample - out Sample - in Sample - in

K = 1.00 ± 0.03 N = 1.0000 ± 0.0025

Na 2.85 keV

Repeated measurements of sample-in and sample-out cycles to avoid impact of:

Electronic drifts
Variations in beam intensity

2 - 13 October, 2017, ICTP Trieste

SLIDE 55

10

3

10

4

10

5

10

6

0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

TOF-spectra ⇒ Texp

10

3

10

4

10

5

10

6

10

7

10

6

10

5

10

4

10

3

Cin Bin

Time - of - flight / ns Response / (1/ ns)

10

3

10

4

10

5

10

6

10

7

10

6

10

5

10

4

10

3

Cout Bout

Time - of - flight / ns Response / (1/ ns)

ut
ut

in in exp

B K C B K C N T − − =

Sample - out Sample - in

% 3 K uK ≈ % 25 . N uN ≈

Sample - in

Na 2.85 keV

2 - 13 October, 2017, ICTP Trieste

SLIDE 56

20 40 60 80 100 120 0.7 0.8 0.9 1.0 Texp Neutron energy / keV Transmission

100000 200000 300000 400000 0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

Resonance Region D > Γ

Resolved Resonance Region ∆R < D
Unresolved Resonance Region ∆R > D

Resonance region

2 - 13 October, 2017, ICTP Trieste

10

3

10

4

10

5

10

6

0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

SLIDE 57

Data analysis

2 - 13 October, 2017, ICTP Trieste

20 40 60 80 100 120 0.7 0.8 0.9 1.0 Texp Neutron energy / keV Transmission

100000 200000 300000 400000 0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

88 90 92 94 5 10 15 Cross Section / barn Neutron Energy / eV

σ

σ σ σγ

γ γ γ

Eo

Γ Γ Γ Γ

D

Resonance Region D > Γ

Resolved Resonance Region ∆

∆ ∆ ∆R < D

Unresolved Resonance Region ∆R > D

SLIDE 58

dE e ) E , t ( R ) t ( T

) E ( n M

tot

σ −

∫

=

Transmission data : 241Am + n

2 - 13 October, 2017, ICTP Trieste

1000 2000 3000 4000 5000 0.0 0.2 0.4 0.6 0.8 1.0

Texp

Transmission Time-of-flight / µs

Determine resonance parameters from a GLSQ fit to the experimental data

( ) ( )

M exp 1 T T M exp 2

T T V T T ) RP (

exp

− − = χ

−

R(tm,E) : response of TOF-spectrometer σtot : total cross section n : areal number density total number of atoms per unit area

% 25 . T u

exp T exp <

ut
ut

in in exp

B C B C T − − =

SLIDE 59

( ) ( )

M exp 1 T T M exp 2

T T V T T ) RP (

exp

− − = χ

−

Determine resonance parameters from a GLSQ fit to the experimental data Resonance shape analysis (RSA) with REFIT dE e ) E , t ( R ) t ( T

) E ( n M

tot

σ −

∫

=

R(tm,E) : response of TOF-spectrometer σtot : total cross section n : areal number density total number of atoms per unit area

% 25 . T u

exp T exp <

1000 2000 3000 4000 5000 0.0 0.2 0.4 0.6 0.8 1.0

Texp TM

Transmission Time-of-flight / µs

Transmission data : 241Am + n

2 - 13 October, 2017, ICTP Trieste

ut
ut

in in exp

B C B C T − − =

SLIDE 60

1000 2000 3000 4000 5000 0.0 0.2 0.4 0.6 0.8 1.0

Texp TM

Transmission Time-of-flight / µs

Transmission data : 241Am + n

2 - 13 October, 2017, ICTP Trieste

Determine resonance parameters from a GLSQ fit to the experimental data Resonance shape analysis (RSA) with REFIT

241Am : Iπ =5/2- l = 0 from shape

∆D ∼ 25 meV and ∆R ∼ 2.5 meV (L = 25 m) Uncertainties only due to counting statistics

⇒absolute measurement ⇒no reference to any other cross section Energy /eV

J g

gΓn/meV Γγ/meV 0.306

3 7/12

0.0373 ± 0.0002 41.6 ± 0.4 0.574

2 5/12

0.0629 ± 0.0004 42.1 ± 0.6 1.271

3 7/12

0.2176 ± 0.0023 41.7 ± 0.8

SLIDE 61

4.9 eV resonance for 197Au+n

2 - 13 October, 2017, ICTP Trieste

0.0 0.2 0.4 0.6 0.8 1.0

Texp TM,REFIT

Transmission 4.0 4.5 5.0 5.5 6.0 0.0 0.2 0.4 0.6 0.8 1.0

Texp TM,REFIT

Transmission Neutron Energy / eV

10 µm 50 µm

Γn = ( 15.06 ± 0.08) meV Γγ = (121.7 ± 1.3 ) meV

⇒

Γn = ( 14.66 ± 0.30) meV Γγ = (124.8 ± 3.7 ) meV Resonance shape analysis with REFIT

l = 0 from shape, spin J = 2 from fit with capture data

∆D ∼ 80 meV and ∆R ∼ 5 meV (L = 50 m)

⇒

197Au : Iπ = 3/2+

Uncertainties only due to counting statistics

SLIDE 62

60 64 68 72 0.4 0.6 0.8 1.0

Measurement FIT

Transmission Neutron Energy / keV

206Pb + n

R = 9.55 (0.02) fm Interference

Determination of scattering radius

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

( ) ( ) ( )

2 2 2 R n R n n n 2 2 R n n 2 n n tot

R 4 g ) 2 ( E E R ) E E ( k 4 g ) 2 ( E E k g E π + Γ + − − Γ π + Γ + − Γ Γ π = σ

2 - 13 October, 2017, ICTP Trieste

206Pb : L = 25 m

l l l l = 0 from shape

SLIDE 63

25000 25500 26000 0.2 0.4 0.6 0.8 1.0

t=3.00 x 10-2 at/b

Measurement FIT

Trasnmission Neutron Energy / eV 0.2 0.4 0.6 0.8 1.0

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

Trasnmission

Determination of statistical factor

25000 25500 26000 0.2 0.4 0.6 0.8 1.0

t=3.00 x 10-2 at/b

Measurement FIT

Trasnmission Neutron Energy / eV 0.2 0.4 0.6 0.8 1.0

Measurement FIT

Trasnmission

t = 1.60 x 10-2 at/b

) 1 I 2 ( 2 1 J 2 g + + =

206Pb (Iπ = 0+) + n

l = 1 from shape J = 1/2 g = 1

95 .

2

= ν χ

J = 3/2 g = 2

25 . 2

2

= ν χ

2 - 13 October, 2017, ICTP Trieste

⇒ J = 1/2 ⇒ g = 1

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

SLIDE 64

2.5 2.6 2.7 2.8

4

4 Residuals 0.4 0.6 0.8 1.0

Γ Γ Γ Γn = 2.00 meV Γ Γ Γ Γγ

γ γ γ = 25.0 meV

Transmission

T = 77 K

Γ Γ Γ Γn = 1.46 meV Γ Γ Γ Γγ

γ γ γ = 36.5 meV

REFIT : homogeneous sample

PuO2 powder mixed with carbon powder

Neutron energy / eV

Peak cross section underestimated Width overestimated

242Pu

Γn underestimated Γγ

verestimated

) E ( n tot

tot

e ) , n , E ( T

σ −

= σ

Homogeneous sample

dE ) n , , E ( T ) E , t ( R ) t ( T

tot M

σ =∫

SLIDE 65

REFIT : sample inhomogeneities

Neutron energy / eV

PuO2 powder mixed with carbon powder

2.5 2.6 2.7 2.8

4

4 Residuals 0.4 0.6 0.8 1.0

Γ Γ Γ Γn = 2.00 meV Γ Γ Γ Γγ

γ γ γ = 25.0 meV

Transmission

T = 77 K

Γ Γ Γ Γn = 1.90 meV Γ Γ Γ Γγ

γ γ γ = 25.0 meV

See Becker et al.

Account for particle size distribution

2 2 2

s 2 ) 2 / s x (ln 2 e

s 2 x 1 ) x ( p

+ −

π =

dE ,...) n , , E ( T ) E , t ( R ) t ( T

tot M

σ =∫

∫

+ − = σ

∑ σ − h ' n x h tot

f dx ) x ( p e ) f 1 ( ...) n , , E ( T

k k , tot k

h k k

f n ' n =

SLIDE 66

20 40 60 80 100 120 0.7 0.8 0.9 1.0 Texp Neutron energy / keV Transmission

100000 200000 300000 400000 0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

Resonance region

2 - 13 October, 2017, ICTP Trieste

Resonance Region D > Γ

Resolved Resonance Region ∆R < D
Unresolved Resonance Region ∆

∆ ∆ ∆R > D

10

3

10

4

10

5

10

6

0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

SLIDE 67

20000 40000 60000 0.0 0.2 0.4 0.6 0.8 1.0

Time - of - flight / ns Transmission

Unresolved Resonance Region

Unresolved resonance region

2 - 13 October, 2017, ICTP Trieste

10

3

10

4

10

5

10

6

0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

SLIDE 68

20 40 60 80 100 120 0.7 0.8 0.9 1.0 Texp Neutron energy / keV Transmission

Unresolved Resonance Region

From average Texp to average σtot

2 - 13 October, 2017, ICTP Trieste

10

3

10

4

10

5

10

6

0.0 0.2 0.4 0.6 0.8 1.0

Transmission

Time-of-flight / ns

<T

exp>

SLIDE 69

> < − ≠ > σ <

exp tot

T ln n 1

From average Texp to average σtot

2 - 13 October, 2017, ICTP Trieste

tot

n

e T

σ −

=         + σ + = > < = > <

> σ < − σ −

... ) var( 2 n 1 e e T

tot 2 n n

tot tot

> σ < −

≠ > <

tot

n

e T

SLIDE 70

tot

n

e T

σ −

=

T exp tot

F T ln n 1 > < − = > σ < ... ) var( 2 n 1 e e F

tot 2 n n T

tot tot

+ σ + = > < =

> σ < − σ −

From average Texp to average σtot

2 - 13 October, 2017, ICTP Trieste

        + σ + = > < = > <

> σ < − σ −

... ) var( 2 n 1 e e T

tot 2 n n

tot tot

> σ < − σ −

≠ > < = > <

tot tot

n n

e e T

20 40 60 80 100 1.00 1.02 1.04 1.06

MCNP / NJOY SESH

Neutron energy / keV FT

SLIDE 71

20 40 60 80 100 10 15 20 25 Neutron energy / keV

σtot / b

From average Texp to average σtot

2 - 13 October, 2017, ICTP Trieste

<σtot> / b T exp tot

F T ln n 1 > < − = > σ < ... ) var( 2 n 1 e e F

tot 2 n n T

tot tot

+ σ + = > < =

> σ < − σ −

> < − = > σ <

exp tot

T ln n 1

SLIDE 72

20 40 60 80 100 10 15 20 25 Neutron energy / keV

σtot / b

T

exp tot

F T ln n 1 − = σ

From average Texp to average σtot

2 - 13 October, 2017, ICTP Trieste

<σtot> / b T exp tot

F T ln n 1 > < − = > σ < ... ) var( 2 n 1 e e F

tot 2 n n T

tot tot

+ σ + = > < =

> σ < − σ −

> < − = > σ <

exp tot

T ln n 1

T

exp tot

F T ln n 1 > < − = > σ <

SLIDE 73

Parameterisation by average parameters

2 - 13 October, 2017, ICTP Trieste

20 40 60 80 100 10 15 20 25

GELINA Purtov et al. Poenitz et al. Evaluation (HF + WF)

Neutron energy / keV

σtot / b

[ ]

) 2 cos( T 1 1 g k 2

c c c 2 c c

ψ − − π >= σ <

<σtot> / b

<σtot> = f(R,Sl=0,1,2)

E ) 1 2 ( ) g ( S

N 1 j j n

∆ + Γ =

∑

=

l

l l

l l l , n c c n n

P a k eV 1 / E 1 Γ = Γ

SLIDE 74

Parameterisation by average parameters

2 - 13 October, 2017, ICTP Trieste

20 40 60 80 100 10 15 20 25

GELINA Purtov et al. Poenitz et al. Evaluation (HF + WF)

Neutron energy / keV

σtot / b

20 40 60 80 100 20 40 60 80 100

l = 0 l = 1 l = 2

100 x σtot,l / σtot Neutron energy / keV

<σtot> / b

100 x <σtot,l> / <σtot>

<σtot> = f(R,Sl=0,1,2)

E ) 1 2 ( ) g ( S

N 1 j j n

∆ + Γ =

∑

=

l

l l

l l l , n c c n n

P a k eV 1 / E 1 Γ = Γ

SLIDE 75

Parameterisation by average parameters

2 - 13 October, 2017, ICTP Trieste

20 40 60 80 100 10 15 20 25

GELINA Purtov et al. Poenitz et al. Evaluation (HF + WF)

Neutron energy / keV

σtot / b

20 40 60 80 100 10

4

10

3

10

2

10

1

10 10

1

S1 S2 R ' S0

(δσtot/σtot)/ (δθ/θ) Neutron energy / keV

<σtot> / b

(δ<σtot>/<σtot>) / (δθ/θ)

<σtot> = f(R,Sl=0,1,2)

E ) 1 2 ( ) g ( S

N 1 j j n

∆ + Γ =

∑

=

l

l l

l l l , n c c n n

P a k eV 1 / E 1 Γ = Γ

SLIDE 76

Parameterisation by average parameters

2 - 13 October, 2017, ICTP Trieste

20 40 60 80 100 10 15 20 25

GELINA Purtov et al. Poenitz et al. Evaluation (HF + WF)

Neutron energy / keV

σtot / b

Correlation matrix R / fm 9.12 ± 0.09 1

0.43

S0 / 10-4 1.93 ± 0.03

0.43

1 S1 / 10-5 5.64 S2 / 10-4 3.48 from OM

Average parameters are essential for self-shielding calculations ENDF file in URR:

Average resonance parameters

: required

Average point wise cross section : optional

<σtot> / b

<σtot> = f(R,Sl=0,1,2)

E ) 1 2 ( ) g ( S

N 1 j j n

∆ + Γ =

∑

=

l

l l

l l l , n c c n n

P a k eV 1 / E 1 Γ = Γ

SLIDE 77

"Experimental Neutron Resonance Spectroscopy", by J. Harvey

ISBN-13: 978-0123298508

"Evaluation and Analysis of Nuclear Resonance Data", by F.H. Fröhner

https://www.oecd-nea.org/dbdata/nds_jefreports/jefreport-18/jeff18.pdf

"Determination of Resonance Parameters and their Covariances from Neutron Induced Reaction

Cross Section Data", Schillebeeckx et al. Nuclear Data Sheets 113 (2012) 3054 – 3100.

"Results of total cross section measurements for 197Au in the neutron energy region from 4 to

108 keV", Sirakov et al. European Physics Journal A 49 (2013) 144.

"Measurement of the direct particle transport through stochastic media using neutron

resonance transmission analysis", Becker et al. European Physics Journal Plus 129 (2014) 58.

"Neutron Resonance Spectroscopy for the Characterisation of Materials and Objects",

Schillebeeckx et al. JRC Science and Policy Reports, Report EUR 26848 (2014).

Literature

2 - 13 October, 2017, ICTP Trieste