Bragg edge transmission analysis at a medium intensity pulsed neutron source

Javier R. Santisteban- J. Rolando Granada

Laboratorio de Física de Neutrones

Centro Atómico Bariloche y CONICET

Japan

July 2007

Past work in this area

Bragg edge transmission experiments

Some applications at spallation sources

CRP Tasks

Implementation at a low-medium intensity source

Bragg edge analysis software

Outline

Pulsed neutronsource

5000 10000 15000 20000

0

10000

20000

30000

40000

Cou

nts

TOF (sec)

Incidentspectrum

Sample (, A)

5000 10000 15000 20000

0

10000

20000

30000

40000

50000

Cou

nts

TOF (sec)

Transmittedspectrum

x

AII exp)( 0

x

nxI

I

0

ln

Detector

Neutron transmission experiments

Neutron Transmission of Copper

0.5 1.0 1.5 2.0 2.5 3.0 3.50.2

0.3

0.4

0.5

0.6

0.7

Neutron wavelength (Å)

Tra

nsm

issi

on

2.0 2.5 3.0 3.5 4.0 4.5

20

25

30

35

40

45

50

Tra

nsm

issi

on

Neutron wavelength (Å)

2.0 2.5 3.0 3.5 4.0 4.5

0.25

0.30

0.35

0.40

Tra

nsm

issi

on

Neutron wavelength (Å)

(111)(200)

(220)(311)

1 2 3 4 5 60.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Tra

nsm

issi

on

Neutron wavelength (Å)

Single crystal

Large-grained

Small grain Random

Small grain Textured

Neutron transmission of single crystals

1.0 1.5 2.0 2.5 3.00

10

20

30

40

50

Neutron wavelength (Å)

Transmitted beam

Direct beam

C

ou

nts

/Å (

a.u

.)

1.0 1.5 2.0 2.5 3.00.0

0.2

0.4

0.6

Bragg-reflected peaks

Absorbed

Scattered (TDS)

1 -

Tra

nsm

issi

on

Neutron wavelength (Å)

S a m p le

N e u tro n s

T D

L DN D

(1 0 0 )

(0 0 -1 )

(0 1 0 )

• The positions of the (hkl) peaks change between 0 and 2dhkl

Peak positions

Change with crystal orientation

sin2 hklhkl d

TOF neutron transmission of mosaic crystals, J.R. Santisteban, J. Applied Crystallography (2005) 38, 934-944

Origin of Bragg edges

Neutronbeam Detector

hkldhkl

•The edge itself corresponds to the peak coming from the crystal planes that are normal to the incident beam

•Bragg edges are due to the contribution of crystallites with all possible orientations

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.06

8

10

12

14

16

18

20(3

10)

(220

)

(211

)

(200

)

(110

)

Tot

al c

ross

sec

tion

(bar

ns)

Neutron wavelength (Å)

Fe powder

Neutrons

Stra ind irection

x

y

z

Strain va lues

350-400 300-350

400-450 450-500

A bove 500

250-300 200-250 150-200 100-150 100-150

50-100 0-50

-50 -0 -100 -50

B e low -100

y (m

m)

x (m m )5 10 15

-20

-15

-10

-5

0

0

5

10

15

20

0.85

1.00

1.15

1.30

1.45

1.60

Fe thickness (mm)

0.85

1.00

1.15

1.30

1.45

1.60

Fe thickness (mm)

0.85

1.00

1.15

1.30

1.45

1.60

Fe thickness (mm)

StrainPhase analysis Microstructure identification

• Analysis of crystallographic phases

• Strain analysis

• Microstructure identification

Some applications

2.00 2.02 2.04 2.06

0.1

0.2

0.3

0.4

15400 15500 15600 15700 15800

Experiment

(110) edge Fe

Tra

nsm

issi

on

Time of flight sec

d spacing (Å)

Precise position and height of Bragg Edges

Fit Difference

tdtRTrIttItr

0 0 ,

2dhkl

Tr()

R(t)

Instrumental broadening of the edge

d/d =

Time-of-flight neutron transmission diffraction, J. R. Santisteban, L. Edwards , A. Steuwer, P. J. Withers, J. Appl. Crystall 34 (2001), 289-297.

Detector

LD

TD

ND

Sample

Neutrons

Slit

Transverse directionm

TD

TD

0.02.8643

2.8650

2.8656

2.8663

2.8669

20.2 0.4 0.6 0.8 1.0

La

ttic

e p

ara

me

ter

(Å)

sin

LD

Longitudinal direction

m

LD

a

a 0

TDLD mmaa

10

Unstressed lattice parameter

0

,, 1 a

mE LDTDTDLD

Stress

TD=-60MPaLD=-230MPa

Strain analysis: the sin2 technique

In-situ Stress Determination by Pulsed Neutron Transmission, A. Steuwer, J. R. Santisteban, P. J. Withers, L. Edwards and M. E. Fitzpatrick, Journal of Applied Crystallography. 36, 1159-1168 (2003).

Phase analysis in EN24 steel

neutrons

sample

air blower

Austenization furnace(830oC)

transformation furnace(380oC)

detector

sample guide output

sample guide input

Phase transformation evolution

10 100 1000 10000

0

20

40

60

80

100

Pha

se v

olum

e (%

)

Time (seconds)

3.5 4.0 4.5 5.08

10

12

14

16

18

20

(111) -Fe

(110) -Fe

(200) -Fe

5 sec 3.4 min 7.7 min 23.9 min

Tot

al c

ross

sec

tion

(bar

ns)

Neutron wavelength (Å)

0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

(311

) (211

)

(220

)

(200

)

(200

)

(110

) (111

)

=59.7% =40.3%

Tra

nsm

issi

on (

a.u)

d-spacing (Å)

Experiment Rietveld fit Difference

BetMan: a Rietveld analysis software

A Rietveld-Approach for the Analysis of Neutron Time-Of-Flight Transmission Data, Sven Vogel, Ph D. Thesis (2000) Kiel University, Germany.

1- To implement the technique of Bragg edge neutron transmission analysis at a medium-intensity pulsed neutron source (the 25 MeV LINAC at the Centro Atómico Bariloche).

2- The development and maintenance of a free computer code for least-squares analysis of Bragg edge transmission experiments, oriented towards medium intensity neutron sources.

Overall objectives of CRP

1- Bragg-edge experiments on the present transmission beamline at the Bariloche LINAC

– Experiments on Molybdenum, for reference and calibration.

– Experiments on graphite as part of a broader research program.

2- Implementation of the Open Genie data analysis system on the Bariloche transmission beamline.

3- Derivation of optimum counting times for given Incident Beam and Background rates for a sample with an estimated transmission (J. Blostein).

Work already performed (last three months)

Experiments on Molybdenum

Transmission Mo (110)

Transmission Mo (211)

8.3 m flight path1 hour counting timeResolution (t/t) ~ 0.005d/d) uncertainty ~ 0.0005Right side: 90 counts/secLeft side: 55 counts/sec(screenshots from OpenGenie)

TOF - Wavelength Calibration

0 1 2 3 4 5

0

2000

4000

6000

8000

10000Flight path= (832.9±0.5) cm

Param Value ErrorA 0.64703 3.59802B 2105.27 1.39747-------------------------------------------R=1SD=1.36

TO

F (s

ec)

Neutron wavelength (A)

MolybdenumBragg edge

Indium resonance

Experiments on Graphite

Trans Graphite (0002)

Lattice parametersc=(6.7427±0.0004)Å (from 0002 edge)a=(2.3784±0.0004)Å (from 10-10 edge)

•5cm thick nuclear graphite•Study of total cross section along different directions•Bragg edges least-squares fits•Optimization of counting times

We want to do experiments faster, for systematic materials science studies

1- Visit of Dr Santisteban to Los Alamos (September), to receive the BetMan software from Dr. Vogel.

2- Fabrication of the new cold neutron source for the Bariloche LINAC (higher flux).

3- Implementation of independent Data acquisition electronics for the transmission beamline, using NIM modules+ software already available.

4- Optimization of detection system, in order to reduce counting times (higher resolution).

5- Publication of “Neutron Transmission webpage”, focused on transmission on the thermal range: http://www.cab.cnea.gov.ar/~nyr/neutron_trans_page/

First-year workplan

1- Visit of Dr Vogel to Bariloche, to work on the BetMan program (documentation, distribution, etc).

2- Strain analysis demonstration experiments on stressed steel specimens.

3 -Phase analysis demonstration experiments on CuZn specimens.

3- Evaluate of the performance of different moderators (slab, grilled, cold) for phase and strain analysis, respectively.

Second-year workplan

1 – An optimized Bragg edge transmission beamline for phase and strain analysis at the LINAC pulsed neutron source of Neutron Physics Laboratory, Centro Atomico Bariloche, Argentina. This beamline should include a rotation stage for strain analysis experiments.

2 – A user-friendly and documented computing program for prediction and least-squares analysis of the neutron spectra transmitted by crystalline materials.

3 – A freely-distributable version of this program, designed to be installed on other Bragg edge transmission facilities.

END OF PROJECT RESULTS

Characterization of Ancient Bronze

2.5 3.0 3.5 4.0 4.5

40

50

60

70

80

Celtic handle

Cast bronze1-T

rans

mis

sion

(%

)

Neutron wavelength (Å)

2.5 3.0 3.5 4.0 4.540

50

60

70

Hardened +annealed bronze

Vilanovan necklace

1-T

r an

smis

sion

(%

)

Neutron wavelength (Å)

As-cast ingotAs-cast ingot

Large crystals

Non-destructive investigation of Picenum Bronze artefacts using neutron diffraction, S. Siano,et al, Archaeometry 48 (2006) 77-96

Position sensitive Bragg edge analysis

Neutrons

Stra ind irection

x

y

z

Strain va lues

350-400 300-350

400-450 450-500

A bove 500

250-300 200-250 150-200 100-150 100-150

50-100 0-50

-50 -0 -100 -50

B e low -100

y (m

m)

x (m m )5 10 15

-20

-15

-10

-5

0

0

5

10

15

20

Note: it requires really long counting times

Strain imaging by Bragg edge neutron transmission, J.R. Santisteban et al, Nucl. Instr. Methods A 481 (2002) 255-258.