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 neutron source Incident spectrum Sample ( , A) Transmitted spectrum x Detector Neutron transmission experiments

Neutron Transmission of Copper Single crystal Large-grained Small grain Random Small grain Textured

Neutron transmission of single crystals

The positions of the (hkl) peaks change between 0 and 2d hkl Peak positions Change with crystal orientation TOF neutron transmission of mosaic crystals, J.R. Santisteban, J. Applied Crystallography (2005) 38,

Origin of Bragg edges Neutron beam Detector hkl  d hkl 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

Strain Phase analysis Microstructure identification Analysis of crystallographic phases Strain analysis Microstructure identification Some applications

Precise position and height of Bragg Edges Fit Difference 2d hkl 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),

Detector LD TD ND Sample Neutrons Slit Transverse direction m TD  L a t t i c e p a r a m e t e r ( Å ) sin  LD Longitudinal direction m  LD  a a 0 Unstressed lattice parameter Stress  TD =-60MPa  LD =-230MPa Strain analysis: the sin 2  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, (2003).

Phase analysis in EN24 steel neutrons sample air blower Austenization furnace (830 o C) transformation furnace (380 o C) detector sample guide output sample guide input

Phase transformation evolution

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 path 1 hour counting time Resolution (  t/t) ~  d/d) uncertainty ~ Right side: 90 counts/  sec Left side: 55 counts/  sec (screenshots from OpenGenie)

TOF - Wavelength Calibration Molybdenum Bragg edge Indium resonance

Experiments on Graphite Trans Graphite (0002) Lattice parameters c =(6.7427±0.0004)Å (from 0002 edge) a =(2.3784±0.0004)Å (from 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: 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 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 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)