Transcript Present-day high-intensity and high-resolution neutron

Present-day high-intensity and high-resolution neutron
diffraction and neutron scattering under high pressure
(introductory lecture)
Anatoly M. Balagurov, Frank Laboratory of Neutron Physics, Dubna, Russia
1. Introduction
2. General questions of neutron scattering
2.1. Neutron elastic scattering as Fourier transformation
2.2. Neutron interactions and modes of experiments
2.3. Neutrons vs. x-Rays & Synchrotron light
3. Neutron spectrometers: new capabilities
3.1. Steady state and pulsed neutron sources
3.2. λ = const vs. “white” beam
4. Neutron scattering under high pressure
4.1. High pressure: cells and range
5. Examples of studies (powder diffraction)
6. Prospects of neutron scattering under high pressure
Sapphire anvil high pressure cell for neutron
scattering experiments.
Рmax ≈ 7 GPa
(48 mm, h=164 mm)
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Neutron scattering for structure and dynamics
We want to know where atoms (molecules)
are situated and how they interact!
Inelastic neutron scattering
↓
Atomic (molecular) dynamics (motion)
↓
Atomic (molecular) interactions
Elastic scattering (diffraction)
↓
Atomic (molecular) positions
↓
Structure (shape, configuration)
Energy transfer (meV)
12.4
24.8
37.2
49.6
62.0
74.4
86.8
99.2
111.6 124.0
300
Eu
280
Ni(OH)2
Eu
260
Mg(OH)2
240
→
GDOS (a.u.)
220
→
A1g
Eg
200
Eu+Eg
180
Eg
A2u
160
140
a
120
Eu
100
60
H
O
b
Eg
A1g
Eg
80
Ni
c
Eu
Acoustic modes
40
20
A2u
0
100
200
300
400
500
600
700
800
900
1000
-1
Energy transfer (cm )
Crystal structure of Sr3YCo4O10.5
Lattice dynamics of Ni-hydroxide, Ni(OH)2
2
How neutrons interact with matter
Scattering
Inelastic
Atomic and magnetic
dynamics, diffuse motion
Nuclear
Crystal structure at
atomic, nano-levels
Absorption
Elastic
Neutron imaging
Incoherent
Coherent
Magnetic
Magnetic structure at
atomic, nano-levels
Elastic and inelastic neutron scattering
Momentum transfer
Energy transfer (Е0 ≈ 0.025 eV)
Always takes place
to atom,
ΔЕ/Е0 ~ 1, “inelastic”
to collective mode,
ΔЕ/Е0 ~ 1, “inelastic”
to crystal,
ΔЕ/Е0 ~ 10-24 (ΔE = 0)
“elastic scattering”
Ei = Ef
|ki| = |kf|
4
Neutron scattering at ILL, Grenoble
3 Axis (4.5)
HR - TOF (7)
Nuclear Physics (5)
Powders – Liquids (3)
SAS - Reflectometry (4)
Single Crystals (3)
Proposals: 59% elastic scattering, 35% inelastic scattering, 6% nuclear physics.
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Neutron space and time domain
S(Q, ω) ~ ∫∫ei(Qr – ωt) G(r, t)drdt
(L. van Hove, 1954 г.)
Scattering law
↕
Fourier transform
Correlation function
l ~ 2π/Q, τ ~ 2π/ω
For elastic scattering:
ΔQ = (10-3 – 50) Å-1
Δl = (0.1 – 6·103) Å
Elastic scattering as Fourier transform of a structure
Intensity of scattered waves
I(q) ~ |f(q)|2
Amplitude of a wave function
I(q) ~ ∫ eiqr G(r)dr
f(q) ~ ∫ eiqr b(r)dr
G(r) ~ ∫ e-iqr I(q)dq
b(r) ~ ∫ e-iqr f(q)dq
Pair correlation function
Scattering-length density
G(r) = ∫ b(u) b(u + r) du
b(r) / G(r) - object
f(q) / I(q) - image
Real space
Reciprocal space
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Cross-section:
Fourier synthesis of
HgBa2CuO4+δ structure
Cu
0 ≤ x = y ≤ 1,
0 ≤ z ≤ 0.5
Cu
Hg
O1
Ba
O1
O1
Cu
Ba
Hg
O3
O2
Hg
O3
HgBa2CuO4+δ structure:
the О3 position is partially
filled, n(O3) = δ = 0.12.
[010]
O3
Difference synthesis.
Cross-section:
0 ≤ x ≤ 1,
0 ≤ y ≤ 1,
z=0
[100]
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Diffraction limit

b(r) ~ e-iqr f(q)dq
0
Q
b(r) ~  e-iqr f(q)dq,
Q = qmax
0
lс ≈ 2π/Q ≥ λmin/2 – diffraction limit
As a rule:
for diffraction
for SANS
In practice: for interatomic distances
for lattice parameters
for radius of gyration
λmin ≈ 1 Å, i.e. lc ≈ 0.5 Ǻ,
Q ≈ 0.5 Å-1, i.e. lc ≈ 20 Ǻ.
σ ~ 0.002 Å,
σ ~ 0.0001 Å,
σ ~ 0.2 Å.
Diffraction limit is overcome owing to:
- periodicity of a structure,
- parametric description of an object.
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Important peculiarities of thermal neutron interaction
with matter
1) b (coherent scattering length) does not depend on  (thermal factors)
2) no regularity in b dependence on atomic number
light atoms in presence of heavy atoms: H-O, Mn-O, U-H, …
neighbours discrimination: O-N, Co-Fe, … )
3) no regularity in b dependence on nuclear mass (isotope contrasting)
bH = 0.37
bFe-56 = 1.01
bD = 0.67
bFe-57 = 0.23
4) b can be < 0 (“zero” matrix without coherent scattering from container)
5) strong magnetic scattering (magnetic structure)
6) small absorption (high penetration)
Neutron sources for condensed matter studies
I. Continuous neutron sources
W = 10 – 100 MW
Const in time
VVR-M, Russia
IR-8, Russia,
ILL, France
LLB, France
BENSC, Germany
FRM II, Germany
BNC, Hungary
NPI, Czechia
NIST, USA
ORNL, USA
…
SINQ, Switzerland
II. Pulsed neutron sources
Short pulse
II-a. SPS
W = 0.01 – 1 MW
Pulsed in time
Δt0 ≈ (15 – 100) μs
ISIS, UK
LANSCE, USA
SNS, USA
KENS, Japan
J-SNS, Japan
Long pulse
II-b. LPS
W = 2 – 5 MW
Pulsed in time
Δt0 ≈ (300 – 1000) μs
IBR-2M, Russia
ESS, Europe
LANSCE (new)
???
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Steady state reactor / Pulsed neutron source
I()
1
"White" (Maxwellian)
distribution
0.1
max
min
0.01
0.001
0
1
2
3
, Å
4
5
6
Monochromatic incident beam:
Polychromatic incident beam:
λ = const ≈ 1.4 Å, Δλ/λ ≈ 0.01,
Source: W = (10 – 100) MW = const,
λmin ≤ λ ≤ λmax, Δλ ≈ 5 Ǻ,
Source: W = (0.01 – 2) MW, pulsed,
Scan over time of flight (TOF),
Scan over scattering angle,
Wide angle range is needed.
Fixed angle geometry – higher
pressure is possible.
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TOF diffractometer at LPS or CNS type source
Neutron pulse after fast
chopper Δt0 ≈ (20 – 50) μs
Fermi chopper
with 2 slit
packages
21.79 m
22.5 m
23.5 m
29.9 m
6 Disc
choppers
49.6 m
73.4 m
Δd/d ≈ 0.001 for back scattering
Magnet (25 T)
EXED instrument at
BENSC
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Neutron diffractometer:
the most important parameters for structural studies
• Flux at the sample position
• Resolution
• Solid angle of detector
• d-spacing interval
• Background level
• …
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Intensity / Counting rate
I ≈ Φ0 · S · (Ω/4π) · δ [n/s]
Φ0 – integrated neutron flux at a sample
S – effective sample cross-section
Ω – solid angle of detector system
~ 107 n/cm2/s
1 cm2 → 1 mm2
~ 1 sr
δ – probability of scattering
~ 0.1 → 0.01
I ≈ 105 n/s → 102 n/s
D20, ILL:
DN-2, IBR-2:
GEM, ISIS:
Ω ≈ 1 sr
Ω ≈ 1 sr
Ω ≈ 4 sr
It is not so important how many neutrons
strike a sample; much more important how
many scattered neutrons we can collect.
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Neutron detectors. New generation.
GEM at ISIS, UK
DRACULA at ILL, France
TOF diffractometer
ZnS/6Li detector, Ωdet ≈ 3.86 sr
λ = const diffractometer
Linear-wire, 3He PSD, Ωdet ≥ 1 sr
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Resolution of λ=const and TOF powder diffractometers
0.01
TOF_Resolut-3
d/d
0.008
HRPT
0.006
0.004
0.002
HRFD
HRPD
0
0
1
2
3
4
5
6
7
8
d, Å
HRPT: λ = const diffractometer
at SINQ neutron source (SINQ, PSI).
Resolution functions of:
HRFD (RTOF, IBR-2),
HRPD (TOF, ISIS),
HRPT (λ = const, SINQ).
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NAC standard (Na2Al2Ca3F14) on TOF and λ0 diffractometers
λ = const diffractometer
Time-of-Flight diffractometer
nac-6000-2_4
HRFD
NAC
nac-hrpt-2_4
Intensity
Normalized intensity
HRPT
NAC, =1.886 Å
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
d, Å
HRFD (IBR-2): 2θ0 = 152,
wavelength range = 1.2 – 7.2 Å.
2.4
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
d, Å
HRPT (SINQ): λ0 = 1.886 Å, range
of scattering angles = 10 - 165.
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High-pressure cells for neutron scattering
Piston-cylinder cell
Single-crystal anvil cell
Pmax = 7 GPa (sapphire)
Pmax = 30 GPa (diamond)
T = 0.1 – 300 K
Vs = 0.5 – 5 mm3
Paris – Edinburgh press
Pmax = 1 GPa
Pmax = 3 GPa (with support)
T = 2 – 300 K
Vs = 100 – 500 mm3
Pmax = 10 GPa (WC)
Pmax = 30 GPa (diamond)
T = 90 – 1000 K
Vs = 30 – 100 mm3
Single crystal anvil cells
1200
Интенсивность, усл. ед.
Geometry of the diffraction experiment
with single crystal anvil cell.
kC
10 K
290 K
5 ГПа
2.3 ГПа
800
k2/3
0 ГПа
3
400
4
5
k2/3
6
5 ГПа
0 ГПа
0
1
2
3
4
5
6
d, (Å)
Single crystal anvil cells are used at:
- DISC, Kurchatov Institute (1983)
- DN-12, FLNP, JINR (1994)
- G6.1 “Micro”, LLB (1995)
- GEM, ISIS (2002)
-…
DN-12 diffractometer, IBR-2 reactor.
Neutron
diffraction
patterns
of
La0.33Ca0.67MnO3 at P = 0 and 5 GPa and
T = 290 and 10 K (insert). Sample volume
is around 2 mm3. Exposure time is 24 h.
At high pressure and low temperature a
complex AFM state is observed.
HP cell at the DN-12 diffractometer, IBR-2 reactor, Dubna
Sapphire anvil cell
3He
ring detector
Close-cycle refrigerator
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“Kurchatov-LLB” single crystal anvil
cells of Igor Goncharenko
Neutron Scattering at High Pressures I
October 5 – 7, 1994, Dubna, Russia.
Igor Goncharenko
02.06.1965 – 04.11.2007
(diving accident in the Red Sea)
Compact “Kurchatov-LLB” high-pressure
cells for low-temperature neutron diffraction
"Igor Goncharenko: a pioneer in high-pressure
neutron diffraction“ High Pressure Research (2008)
Diffractometer G6.1 MICRO at the LLB (Saclay)
GdAs measured at
T = 1.4 K and
P = 8.5, 30, 43 GPa
with G6.1.
PRB 64 (2001).
Focusing system and Kurchatov – LLB
pressure cell on specialized high-pressure
G6.1 with sapphire or diamond anvil cells
allows neutron diffraction experiments at:
pressures as high as 50 GPa,
temperatures down to 0.1 K,
applied magnetic fields up to 7.5 T.
diffractometer G6.1 (LLB, Saclay)
I.N. Goncharenko (2004) “Neutron diffraction
experiments in diamond and sapphire anvil cells”
High Press. Res. 24, 193
“Toroid” or “Paris – Edinburgh” cell
HRPT, SINQ:
NiO
P = 0 – 9.5 GPa
T = 300 K
λ = 1.5 Ǻ
Vs = 100 mm3
t = 4 hours
nuclear
magnetic
Cd
Steel
Toroid cells are used at:
- POLARIS (PEARL), ISIS (1992)
- HIPD, LANSCE (1994)
- DN-12, FLNP, JINR (2002)
- HRPT, SINQ (2005)
- ...
“Toroid type high-pressure device: history and prospects”
L.G. Khvostantsev et al., High Pressure Research (2004)
WC
BN
TiZr
Sample
Toroid (Paris – Edinburgh) cell
with radial collimator at HRPT (SINQ, PSI)
Sample
Cryostat walls, etc
2θ
Radial
collimator
Detector
Mesoscopic phase separation in complex magnetic oxides and
giant oxygen isotope effect
Charge-localized
AFM insulating
matrix
Metallic state
FM-M
clusters
(La0.25Pr0.75)0.7Ca0.3MnO3
Insulating state
Metal – Insulator percolation phase transition
(Nd,Tb)0.55Sr0.45MnO3 with 16O and 18O isotopes at HRPT
150
150
PD-O16
FM + AFM
100
AFM
50
40
0
0.45
5.9 GPa
FM + AFM
0
0.4
(Nd,Tb)0.55Sr0.45Mn18O
Normalized intensity
FM
TC & TN, K
AFM
FM + AFM
TC & TN, K
Re1-xSrxMn18O
100
50
nts-18_1-6
PD-O16
Re1-xSrxMn16O
60
80
100
120
Scattering angle, deg.
0.5
0.4
0.45
x
0.5
x
Phase diagram for Re1-xSrxMnO3
NTS-16-18_Vol
with 16O and 18O isotopes
Vc, Å3
225
220
Cell volume of (Nd,Tb)0.55Sr0.45MnO3
with 16O and 18O isotopes as the
function of external pressure
18
16
O
O
215
0
1
2
3
4
P, GPa
5
6
7
8
Neutron diffraction patterns of
(Nd,Tb)0.55Sr0.45MnO3,
measured at P = 0 и 5.9 GPa
(T = 290 K) with VX Paris–
Edinburgh press at HRPT
(SINQ, PSI) with λ = 1.886 Ǻ
Pulsed reactors in Frank Lab of Neutron Physics, Dubna
1961 – 1968
IBR-1 (1 – 6 kW)
Fuel
PuO2
Power:
1969 – 1980
- average
IBR-30 (15 kW)
- pulsed
2 MW
1500 MW
Frequency
1981 – 1983
IBR-2 (100 – 1000 kW)
1984 – 2006
IBR-2 (1500 – 2000 kW)
2007 – 2010
IBR-2 reconstruction
2010 – 2030
IBR-2M (2000 kW)
5 s-1
Pulse width 350 μs
Active core and movable
reflector
Neutron spectrometers on the IBR-2M reactor (JINR, Dubna)
Diffraction (6):
HRFD, DN-2, SKAT, EPSILON,
FSD, DN-6 (30 GPa, 0.1 mm3)
SANS (2):
YuMO, SANS-C
Reflectometry (3):
REMUR, REFLEX, GRAINS
Inelastic scattering (2):
NERA, DIN
13 spectrometers (5 new)
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DN-6 – diffractometer for micro-samples
Chopper
Neutron guide
Actual state:
Sample
Ring-shape detectors
Resolution: optimal for high-pressure studies
Intensity: one of the best in the world
Pressure: up to 7 GPa with sapphire anvils
Will be:
Intensity: 25 times better than now
Pressure: 30 - 40 GPa with diamond or mussonite anvils
Ring-shape multi-element
ZnS(Ag)/6LiF detector
1. Cold source
2. Detector array
3. Neutron guide
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Neutron powder diffraction. Where are we going on?
Proposals for the third generation pulsed neutron sources (1990)
Realized:

Structure complexity  100 parameters
 50

Scattering Law
total pattern decomposition
yes

Speed:
reversible
t  5 s
(2 – 5) s
irreversible
ts  10 s
(0.5 – 10) s
ultimate
ts  0.005 s
0.003 s

d-range:
0.3  dhkl  30 Å
0.2 – 60 Å

Small sample size:
Vs  1 mm3
0.1 mm3

Highest pressure:
10 GPa
>30 GPa
Third generation pulsed neutron sources:
SNS (USA), J-PARC (Japan), IBR-2M (Russia), ESS (Europe), …
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Lecture is finished. Any questions?
May I ask you?
Yes, sure.
I did not understand when it would be
possible to realize neutron scattering
experiments at 1000 GPa.
I am sorry, but it is not a question, it is
a statement.
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