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Bragg edge transmission analysis at a medium intensity pulsed neutron source

Javier R. Santisteban- J. Rolando Granada. Laboratorio de F í sica de Neutrones Centro Atómico Bariloche y CONICET. Bragg edge transmission analysis at a medium intensity pulsed neutron source. Japan July 2007. Outline. Past work in this area Bragg edge transmission experiments

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Bragg edge transmission analysis at a medium intensity pulsed neutron source

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  1. Javier R. Santisteban- J. Rolando Granada Laboratorio de Física de Neutrones Centro Atómico Bariloche y CONICET Bragg edge transmission analysis at a medium intensity pulsed neutron source Japan July 2007

  2. Outline 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

  3. Neutron transmission experiments Incident spectrum Pulsed neutron source Transmitted spectrum Sample (r, A) x Detector

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

  5. Neutron transmission of single crystals

  6. Change with crystal orientation Peak positions • The positions of the (hkl)peaks change between 0 and 2dhkl TOF neutron transmission of mosaic crystals, J.R. Santisteban, J. Applied Crystallography (2005) 38, 934-944

  7. lhkl=2dhkl Detector l l • The edge itself corresponds to the peak coming from the crystal planes that are normal to the incident beam Origin of Bragg edges Neutron beam • Bragg edges are due to the contribution of crystallites with all possible orientations

  8. Some applications • Analysis of crystallographic phases • Strain analysis • Microstructure identification Phase analysis Strain Microstructure identification

  9. Precise position and height of Bragg Edges (msec) Time of flight 15400 15500 15600 15700 15800 0.4 (110) edge Fe 0.3 Transmission Experiment 0.2 Difference Instrumental broadening of the edge 0.1 2.00 2.02 2.04 2.06 d spacing (Å) Fit R(l,t) Tr(l) 2dhkl Dd/d = 10-5 Time-of-flight neutron transmission diffraction, J. R. Santisteban, L. Edwards , A. Steuwer, P. J. Withers, J. Appl. Crystall 34 (2001), 289-297.

  10. y Stress TD sTD=-60MPa sLD=-230MPa y LD 2.8669 a Longitudinal direction ^ ) Å m ( 2.8663 LD r e t e m a Unstressed lattice parameter 2.8656 r a a 0 p e c i t 2.8650 t a Transverse direction L m TD 2.8643 0.0 0.2 0.4 0.6 0.8 1.0 2 y sin Strain analysis: the sin2y technique TD Sample Slit Neutrons LD ND Detector 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).

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

  12. Phase transformation evolution

  13. 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.

  14. Overall objectives of CRP 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.

  15. Work already performed (last three months) • 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).

  16. Experiments on Molybdenum Transmission Mo (110) Transmission Mo (211) 8.3 m flight path 1 hour counting time Resolution (Dt/t) ~ 0.005 (Dd/d) uncertainty ~ 0.0005 Right side: 90 counts/msec Left side: 55 counts/msec (screenshots from OpenGenie)

  17. TOF - Wavelength Calibration Molybdenum Bragg edge Indium resonance

  18. Experiments on Graphite • 5cm thick nuclear graphite • Study of total cross section along different directions • Bragg edges least-squares fits • Optimization of counting times Trans Graphite (0002) Lattice parameters c=(6.7427±0.0004)Å (from 0002 edge) a=(2.3784±0.0004)Å (from 10-10 edge) We want to do experiments faster, for systematic materials science studies

  19. First-year workplan 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/

  20. Second-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.

  21. END OF PROJECT RESULTS 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.

  22. 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

  23. 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) 255-258.

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