Sample Environment of the SNAP Instrument

Spallation Neutrons and Pressure Diffractometer

SNAP | BL-3 | SNS

Sample Environment of the SNAP Instrument

SNAP Pressure Equipment

Pressure media and markers: for the Paris-Edinburgh press we routinely use liquid pressure media, deuterated methanol:ethanol (4:1 by volume), deuterated pentanes, fluorinated liquids or deuterated glycerol. For sample pressure determination, Pb is routinely used as a pressure marker (internal calibrant) with a variable PT equation-of-state available. Other internal standards such as NaBr/NaCl/NaF and MgO among others are available. For clamp cells, fluroinated oils are preferred. In the DAC we typically gas load using Ar gas as a medium, and use ruby fluoresence for pressure determination.

Diamond Anvil Cells: the DAC system routinely operates to 30 GPa with a sample volume of 0.2 mm³, measurable from 7 to 300 K, suitable for powders and single-crystals. Given this very small sample volume, these measurements still require higher symmetry systems, consisting of strong scattering elements or well aligned crystals. In some cases, from very simple, strong scattering systems, we have reached 94 GPa on a sample volume 0.04 mm³. Pressure control and measurement via ruby spectroscopy is all done in-situ. If you have an idea for a DAC experiment, we strongly encourage you to discuss it with an instrument team member in advance.

The table below can be used to provide approximate measurement ranges for the SNAP equipment. The instrument staff welcomes any technical questions about the feasibility of your experimental ideas.

Equipment	Max. Pressure (GPa)	Temperature range (K)	Approx. Sample size (mm³)	d-spacing range (Å)	Scattering angles (°)	Notes
Diamond anvil cell	40	10-350	0.05	0.7-5 Å	80-100° 2Θ, +/- 22° vertical	Contact the instrument team. Powder or single crystal.
Paris-Edinburgh press, single-toroidal anvils	10	85-350	70	0.8-16 Å	26-142° 2Θ, +/- 7° vertical	cBN anvils, clean signal. Powder or single crystal.
Paris-Edinburgh press, double-toroidal anvils	20	85-350	35	0.7-16 Å	26-142° 2Θ, +/- 7° vertical	Bragg peaks from polycrystalline diamond anvils above 6 GPa. Powder or single crystal.
Versimax anvil cell	8	2-350		0.7-16 Å	26-142° 2Θ, +/- 22° vertical	Single crystal samples only.
Clamp Cell	2	2-350	150	0.7-16 Å	26-142° 2Θ, +/- 22° vertical	Parasitic scatter from cell (NiCrAl/Al or BeCu). Powder or single crystal.
Gas cell (Al)	0.6	2-350	700	0.7-16 Å	26-142° 2Θ, +/- 22° vertical	Parasitic scatter from cell (Al). Powder or single crystal.
Gas cell (TiZr null-scattering alloy)	0.2	2-350	340	0.7-16 Å	26-142° 2Θ, +/- 22° vertical	No Bragg peaks, incoherent background (TiZr). Powder or single crystal.

Sample Mass Calculator

	Bulk Modulus (GPa)	Density (g/cm³)	Volume (mm³)	Sample Mass Needed (mg)
Custom Values
NaCl	24.4	2.17	87.1	171.888
MnO	148.0	5.37	87.1	354.256
V	160.0	6.00	87.1	388.104
CoO	180.0	6.44	87.1	402.766
Bi	31.0	9.78	87.1	767.770

Sample Geometry

Click below for illustration of sample shapes for use in the Paris-Edinburgh press	Volume (mm³)
Double-toroid, encapsulated	30
Double-toroid, non-encapsulated	40
Single-toroid, encapsulated	60
Single-toroid, non-encapsulated	88

If you see NaN in the "Sample Mass Needed (mg)" field, then one of your entries probably contains non-numeric data or is not a valid number, for example, entering 3.9.0 (double decimal points).