bragg edge transmission analysis at a medium intensity pulsed neutron source javier r. santisteban-...
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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.