neutron scattering under extreme conditions at the...
TRANSCRIPT
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
•
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
View at the Sample Position
December 6-7, 2007
Neutron Scattering Sciences Division
Instrument Enclosure
December 6-7, 2007
Neutron Scattering Sciences Division
Instrument Components in
the Field
December 6-7, 2007
Neutron Scattering Sciences Division
Focusing Mirrors: The KB Concept
Two curved neutron super mirrors-
One focusing vertically-
One focusing horizontally
December 6-7, 2007
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
Measuring the Spot Size
109 microns in the Horizontal 111 microns in the Vertical
December 6-7, 2007
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
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
Neutron Scattering Sciences Division
THANK YOU!