neutron scattering under extreme conditions at the...

December 6-7, 2007

Neutron Scattering Sciences Division

Neutron Scattering under Extreme ConditionsNeutron Scattering under Extreme Conditionsat the Spallation Neutron Sourceat the Spallation Neutron Source

Jamie Molaison

Neutron Scattering Sciences DivisionOak Ridge National Laboratory

International Workshop on Synchrotron High PressureMineral Physics and Materials Science

Argonne National Laboratory -

December 6-7, 2007

December 6-7, 2007


Collaboration

•

John Parise

-

Stony Brook University•

H.-k. Mao, R. J. Hemley -

Carnegie Institution of Washington

•

Gene Ice -

Oak Ridge National Laboratory•

Darren Locke, Lars Ehm, Dave Martin -

Stony Brook University•

Ian Swainson, R. Rogge, L. Cranswick

-

NRC CNBC Chalk River

December 6-7, 2007


•

You can work in extreme sample environments (T, P,...) e.g. He cryostat (Shull & Wollan) and penetrate into dense samples

•

Sensitivity to a wide range of properties, both magnetic and structural

•

The magnetic and nuclear cross-sections are comparable, nuclear cross-sections are similar across the periodic table

98-6242 uc/rfg

Neutrons and Neutron Sources

December 6-7, 2007


z

yx

30 32 34 36 38 40 42

0

400

800

1200

1600

Remaining Ice VI

6.41 GPa (1050 bar)5.85 GPa (990 bar)

5.23 GPa (900 bar)4.40 GPa (800 bar)

3.69 GPa (700 bar)2.58 GPa (600 bar)

2.18 GPa (545 bar) Ice VII Ice VI

Ice VI

Inte

nsity

2 theta (degrees)

Ice VI

Ice VII [110] peakof transformed sample

EXAMPLE:

Spin Reorientation in α-Fe2

O3

up to 70 kbar

at room temperature –

C2 (NRC), WAND

magnetic peaks

nuclear peaks

Intensity of (111) peak drops with increasing pressure

Hexagonal structure, vectorsindicate spin directions alongthe c–axis above 70 kbar

Spin vector angle w.r.t

c-axis

EOS and transitionsin ice used to deter. P

70 kbar

December 6-7, 2007


Pressure Ranges and Neutron Scattering

1E-32

1E-22

1E-12

0.01

1E8

1E18

1E28

10-7

10-5

10-3

10-1

101

103

105

107

101

102

103

104

105

Adapted fromN. W. AshcroftE-F School VerennaItaly 2001

Existing PressureDevices

Metallic Hydrogen

P at center of Earth(~350 GPa)

Pressure at greatestocean depth

Atm P at sea level

Vapor P of waterat triple point

P at centerof neutron star

P at centerof white-star

P cosmic microwave BG

non-equilibrium P of hydrogen in intergalactic space

Pre

ssur

e (A

tm)

1 Atm = 1 bar, 10 kbar = 1 GPa100 Gpa = 1 Mbar

Available at Current Neutron Sources

P where H2O freezes at 100oC

Sound at thresholdof pain

Radiation P at Sun

core-mantle boundary(100 GPa)PIA in quartzdensification of silicaPIA in ice

high pressure X'llforms

Chemsitry under pressurehigh pressure (compound/Bio)

December 6-7, 2007


SNAP Pressure Cells

Paris-Edinburgh (P-E) Design Panoramic Design Beijing-Washington Design

Second Gen

First Gen

First GenSecond Gen

Large volume: ~80 mm3 Sample size = 100 µm (linear) to 1 mm3

Large volume: 40-60 mm3

December 6-7, 2007


SNAP Research —

Cell Testing

Densification process glassy water.Tulk, et al. PRL, 97, 2006

Studies of guest cluster geometryin high pressure clathrate

hydrates

CaSiO3

glass up to 90 kbar, x-ray data, L. Ehm, D. Locke, et al.

BaTiO3rhombohedral

↔ orthorhombic ↔ tetragonal ↔ cubic

K.W. Chapman, P.J. Chupas, D. Locke, J.B. Parise 2006 in preparation

Pair Distribution Function

N. C. Hyatt (Sheffield), J. A. Hriljac (Birmingham), et al.

0.0 2.5 5.0 7.5 10.0 12.5 15.0

0

2

4

6

8

3.5 GPa

2.6 GPa

2.0 GPa

Q(S

(Q)-1

)

Q (angstroms^-1)

Xe Hydrate, in situ measurement

1.7 GPa

0 5 10 15 20

0

50

100

150

200

250

I(Q)

Q (angstroms^-1)

Atomic Form Factor

December 6-7, 2007


The Spallation Neutron Source

•

SNS construction finished in 2006, $ 1.4 billion construction cost•

Full power = 1.4 MW. SNS is now producing neutrons at approximately ISIS power levels, plans to increase power.

•

It is a short drive to HFIR, a reactor source with a flux comparable to the ILL

December 6-7, 2007


Target Building and Instrument Layout

Beam Line 2 Backscattering Spectrometer

Beam Line 3High Pressure Diffractometer (SNAP)

Beam Line 4AMagnetism Reflectometer

Beam Line 4BLiquids Reflectometer

Proton Beam

Beam Line 7Engineering Diffractometer(VULCAN)

Beam Line 11APowder Diffractometer

Beam Line 12Single CrystalDiffractometer(TOPAZ)

Beam Line 17Chopper Spectrometer(SEQUOIA)

Beam Line 18Chopper Spectrometer(ARCS)

December 6-7, 2007


SNAP Overview and Status

Support labs & mezzanine Enclosure Ceiling

& Hatch

Stacked Shielding

Beam Stop Instrument Enclosure

Sample Position & Detectors

Flight Tube Assembly

Shutter & Core Vessel Insert

P-I-P Shielding

Choppers & Supports

December 6-7, 2007


View at the Sample Position

December 6-7, 2007


Instrument Enclosure

December 6-7, 2007


Instrument Components in

the Field

December 6-7, 2007


Focusing Mirrors: The KB Concept

Two curved neutron super mirrors-

One focusing vertically-

One focusing horizontally

December 6-7, 2007


Bending is Practical Option for SNAP Mirrors

•

Monolithic figuring–

~$400K not in SNAP budget

•

Differential deposition–

Not right scale for neutron mirrors (too thick)

•

Bending–

Widely used-cost effectiveleaf

spring

mirror

mirror

bending moments

bending moments

bending moments

bending moments

December 6-7, 2007


Micro beams for high pressure neutron scattering

Prototype micro-focusing mirrorsNRU reactor at CRL (NRC)

0

10000

20000

30000

40000

50000

60000

70000

555 560 565 570 575 580 585 590 595 600 605

Signal saturated at 65535

Tulk, Ice, Locke, Xu, Parise, et al. (2004), ORNL, NRC, Stony Brook and Carnegie Institution.

Doubly Focused

Measured spot size ~ 110 x 110 µm

December 6-7, 2007


Measuring the Spot Size

109 microns in the Horizontal 111 microns in the Vertical

December 6-7, 2007


Microdiffraction

from Free-standing Crystal

focused beamunfocused beam

Avg

. pea

k in

t./sc

att.

vol.

(cou

nts/

µm3 )

rotation angle (degrees)

• 300 x 300 x 700 µm irregular forsterite

(Mg2

SiO4

)

single crystal

• Rotated 360o

in 20o

steps about Φ

• Focused run gave 701 reflections, unfocused gave 368 (196 common)

December 6-7, 2007


Pressure cells coupled with mirrors at CNBC-Chalk River

Looks very much like an x-ray hutch at a synchrotron facility

-

utilize sample alignment-

utilize sample HT-LTenvironment techniques

December 6-7, 2007


Microdiffraction

from pressurized sample

•

200 x 500 µm FeO

single crystal in panoramic cell at ~7 GPa

200 µmsample

sample 90 µmbeam

700 µm

December 6-7, 2007


Advanced K-B Mirrors for SNAP

• Nested geometry can be farther from sample

• Theoretical increase of ~2.5 in flux vs. standard K-B geometry

December 6-7, 2007


THANK YOU!

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