COMPRES Fifth Annual Meeting

• Identify and broaden the EAR neutron Identify and broaden the EAR neutron scattering community in the U.S.scattering community in the U.S.

• Stimulate and promote the use of Stimulate and promote the use of neutron scattering in the Earth neutron scattering in the Earth Sciences.Sciences.

• Support educational activities Support educational activities • Identify needs of the community, Identify needs of the community,

including future requirements for including future requirements for instrumentation and sourcesinstrumentation and sources

COMPRES Neutron Initiative:COMPRES Neutron Initiative:

COMPRES Fourth Annual Meeting

• Financial assistance tFinancial assistance to carry out neutron scattering experiments and/or to participate in workshops and conferences on neutron scattering

• H. Sitepu: design and carry out high-H. Sitepu: design and carry out high-P,T neutron experiments P,T neutron experiments

• Build user community by assisting Build user community by assisting members of community with members of community with experimentsexperiments

• Community informed about upcoming Community informed about upcoming neutron workshops, conferences, neutron workshops, conferences, deadlines for proposals, etc.deadlines for proposals, etc.

• Education materials available on Education materials available on www.vt.edu/compreswww.vt.edu/compres

COMPRES Neutron Initiative:COMPRES Neutron Initiative:

sitepu@vt.edusitepu@vt.edu

COMPRES Fourth Annual Meeting

• “High-pressure neutron diffraction study of AlOOD” (ISIS) - C. Vanpeteghem, H. Sitepu (VT) and E. Ohtani, S. Asami

• “Feasibility high pressure study of lithium aluminum deuteride [LiAlD4] and calcite [CaCO3]” using a PE cell on HIPD at LANSCE – H. Sitepu, A. Llobet Megias, and Y. Zhao

• “Investigation of Mg-Al site disorder in shocked MgAl2O4 spinel using neutron diffraction“ (ISIS) O. Tschauner (UNLV), H. Sitepu (VT), P. Asimow and T.J. Ahrens (Cal Tech).

• “Quantitative texture analysis of deformed natural quartz vein from the Torridon area of NW Scotland using neutron diffraction” (FRM-II) R.D. Law (VT), H. Sitepu (VT) and Prof. H.-G. Brokmeier (Tech. Univ. Clausthal).

• “Compressibility of layered molybdite (MoO3) powders determine from neutron diffraction studies at high pressure” (LLB) H. Sitepu (VT) and Dr. I. Goncharenko (LLB).

Recent projects:Recent projects:

Neutron Initiative in Compres II?Neutron Initiative in Compres II?

• Travel support will continue – to be administered by COMPRES Central

• Form high-pressure neutron “task-force” made up members of the COMPRES community, experienced neutron researchers and representatives from neutron facilities(i) form high-pressure neutron network for exchange of information between high-pressure neutron facilities within the United States (LANSCE, IPNS, HIFR, SNS) and from around the world (ISIS, ILL, J-PARC) (ii) identify community needs and nurture infrastructure development projects and / or grand challenges as(iii) target, where appropriate, additional resources through which to leverage COMPRES funds

New projects such as . . . • Temperature measurement using neutron reasonance

spectroscopy (synergy with high P-T calibration effort)

• Software development for on-line / off-line evaluation and processing of data (synergy with CEAD)

M. Dove, Y. Le Godec, S.A.T. Redfern, W.G. Marshall, H.J. Stone, M.G. Tucker,

High P-T cells for community?

• Paris-Edinburgh cell

• Modified P-E cell with belt design (Dobson, 2005)

• Panoramic cell • or ???

200 m

m

MSA Short Course:NEUTRON SCATTERING IN

EARTH SCIENCES

• December 7th and 8th, 2006 http://www.minsocam.org/msa/sc/

Temperature measurement by radiography

Incoming neutron

beam

Sample in two sections

Thin foil

Transmitted neutron beam

Detector

WavelengthTra

nsm

itte

d inte

nsi

ty

NeutronAbsorptionresonance

Effect of temperature

Wavelength

Tra

nsm

itte

d inte

nsi

ty

Width of resonance line can be used to calibrate temperature

Width of resonance line increases with temperature due to Doppler effect

1.1

1.0

0.9

0.8

0.7

0.6

0.5

No

rma

lise

d t

ran

smis

sio

n

94x10-3

9290888684Neutron wavelength (Å)

181Ta 10.36eV resonanceRoom temperature

181Ta 10.36eV resonance1400°C

1.1

1.0

0.9

0.8

0.7

0.6

0.5

No

rma

lise

d t

ran

smis

sio

n

94x10-3

9290888684Neutron wavelength (Å)

1.0

0.8

0.6

0.4

0.2

0.0

Norm

alis

ed tra

nsm

issio

n

0.180.160.140.120.100.080.060.04Neutron wavelength (Å)

Doppler Broadening of Absorption Resonances: 181Ta (early data)

Measured neutron resonance lineshape

EdEETrEREEPEI )()()()()(

))(exp()( EETr tot

EdEESEE BWtot

)()()(

Pulse sourcefunction

Detected signal:

Area density ofabsorbing nuclei

Detector efficiency

Instrumentresolution function

Energy transfer function(the Doppler broadening function)

Breit-Wigner lineshape

Transmitted signal:

Total cross-section:

Example resonance absorption specta

• The resonance lineshape for a stationary nuclei is well described by

the single-level Breit-Wigner equation

• Must account for the thermal motion of the nuclei in the lab frame (energy transfer function)

– For a free gas or classical solid assume a Maxwellian distribution of velocities

– For weak lattice binding can treat as a free gas replacing T by Teff

Doppler Broadening of Absorption Resonances - Theory

r(E)2gJnr

(E E r )2 ( 12)

2

S(E)1

exp (E En )

2 2

4mMEr kT

(mM )2where

kTeff 1

2d coth h

2kT

g( )

kTeff 1

2hE coth

hE2kT

For an Einstein solid: