1 Mbar

Neutron scattering in the Mbar range?
Challenges, facts and opinions
Stefan Klotz
IMPMC
Université P&M Curie, Paris

1 Mbar = 1000 tn/cm 2 1 Mbar
1 Mbar on 1 cm 3 sample would require
at least 3000 tonnes.
More realistic: 10 000 tn
(mass of Eiffel tower: 7000 tn)

‘5000‘ ton press BGI
(Bayreuth)
‘50000 ‘ ton press Troitsk
(Moscow area)

Outline

A naive approach: cylinder
‘monobloc ‘
‘compound ‘
Ø int
Ø ext
K = Ø ext / Ø int ‘wall ratio’
Y: yield strength

Cylinder: burst pressure

Cylinder: summary

Segmented cylinder
jacket
segments
liner
1 Mbar: K 450; Ø int = 5mm, Ø ext = 2.25 meter !
But: piston holds at most 3 GPa

V max vs P max : Cylinders, belts

Belt devices
Geometry unfavourable
D. Dobson et al., 2005

Bridgman anvils

Bridgman anvils
(flat, profiled, toroidal)

Profiled Bridgman anvils (mostly toroidal * )
Sample: 80 mm 3
10 mm
WC (to 15 GPa)
cBN (to 12 GPa)
TiZr gasket (zero scattering)
Sintered diamond: 30 GPa
V = 30 mm 3
*L.G. Khvostantsev et al., High Temp.-High Press. 9, 637 (1977)

detectors
detectors
Collimation
Incident beam
(polychromatic)
S
Incident beam
(monochromatic)
S
high pressure cell
high-pressure cell
energy-dispersive diffraction
2 = 90°
Pulsed sources
(ISIS, SNS, JPARC)
angle-dispersive diffraction
Continuous sources (ILL, SINQ)

Background: diffraction at 90° (example: PEARL @ISIS)
S. K. et al., Appl. Phys. Lett. 66, 1735 (1995)
Fe 3 O 4
Only visible
reflection
from anvils

Background: angle dispersive diffraction (example: D20 @ILL, HRPT@SINQ)
S. K. et al., Appl. Phys. Lett. 86 031917 (2005)
TiZr gasket: no Bragg peaks
NiO
0 GPa
sample
n
c-BN anvils:
absorb neutrons
NiO
9.5 GPa
No contamination from gasket/anvil

Load frames: capacity 50 - 450 tonnes
A fact: current P-limit is set by anvils
not by the load frame

Diamond anvil cells (DACs)

Besedin et al., 1985; Goncharenko 2005

Diamond
Moissanite
Courtesy C.L. Bull

DACs: Single crystals
Glazkov et al. 1988
D 2
D 2
V=10 -2 mm 3
3 reflections to 31 GPa
38 GPa
5 reflections to 38 GPa
Goncharenko & Loubeyre 2004

DACs: Powders
Goncharenko et al., 2000
But: Eu 3+ , Gd 3+ : m = 7 B !

DACS: Powders
But: ice VII is an extemely strong scatterer!
completely fills the pressure chamber

Multianvil cells

E. Ito, Misasa
Multianvil cells: x-rays

Multianvil cells: neutrons
500 tn
800 tn
PLANET (JPARC)
under construction
BGI (Bayreuth), for FRMII?

Conclusions-Perspectives-Opinions
1. The only currently available technologies for
reaching 1 Mbar are DACs and multianvil cells
2. The impact of DACs will remain very limited as long as the
sample volume is less than 0.1 mm 3
Powders: limited to very strong scatterers
Single crystals: Obtain one! Not enough reflections, time
consuming

3. A serious perspective for 0.1-0.5 mm 3 samples at 1 Mbar are
multianvil cells.
BUT:
Are likely to be restricted to spallation sources
Complex assembly, needs highly specialized team
Very restricted applications: no low T, no excitations, not
transferable to other beamlines.
Most important: Serves only the Earth science community: the
decision is highly political.

Political issues
PLANET
5
0
0
t
n
Earthquakes

Other issues: neighbors: x-rays
In the high P/T buisseness you will always
feel a strong competition with synchrotrons

Ohtani et al. (2001)

Other options?
Focus on high P – low T phenomena
Bet on small versatile devices with opposed anvils geometry
Existing load frames of

Nano-polycrystalline diamond (NPD)
(Irifune, 2001)

Thank you!