In this section
PEARL
Extreme pressures exert profound changes in material properties - examples include: the performance of functional oxides; bioavailability in pharmaceuticals; sensitivity of energetic materials; and the structures of minerals and ices found on Earth, and other planetary bodies. PEARL is the dedicated instrument at ISIS for studying these effects by measuring crystal structures under high pressures.
Instrument scientists
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Technical information
Pearl is a medium-resolution, high flux instrument located in ISIS Target Station 1, viewing the methane moderator. The instrument consists of nine transverse detector modules, three backscattering detectors and two forward-scattering detectors. A summary of technical specifications and measurement capabilities are presented below, but it is essential that users discuss any proposed experiment with the instrument scientists.
Instrument characteristics
| Time-of-flight range (µs) | 1500 – 19900 | 20300 – 38800 |
| Wavelength range (Å) | 0.43 – 5.8 | 5.9 – 11.3 |
| Primary flight path (m) | 12.8 | |
Transverse detector
| Secondary flight path (m) | 0.8 | |
| d-spacing range (Å) | 0.4 – 4.1 | 4.2 – 8.0 |
| Δd/d | 0.64 | |
| 2θ (°) | 81.2 – 98.8 | |
Longitudinal detectors
| Secondary flight path (m) | 1.2 | |
| d-spacing range (Å) | 0.4 – 12.5 | |
| 2θ (°) | 20.0 – 60.0 | 100.0 – 160.0 |
Related resources
Pressure experiments
Several variants of the Paris-Edinburgh press are available – the accessible pressure and temperature ranges depend on several factors, not all listed here. Please discuss your experiment requirements with an instrument scientist.
Accessible pressures
Generally, this is dependent on the choice of anvil (listed in order of increasing neutron attenuation):
- Zirconia-toughened alumina: ~ 6G Pa
- Single-toroid sintered diamond: ~ 12 GPa
- Double-toroid sintered diamond: ~ 25 GPa*
- Tungsten carbide: ~ 10 GPa
*in discussion with instrument scientists.
Please note
Pressure measurement is usually performed via inclusion of a contaminant material with a known equation of state.
- Pressure markers available: Pb, MgO, NaCl, NaF, CaF2
To apply a hydrostatic pressure (to avoid strain broadening), it is necessary to include a pressure-transmitting medium (perdeuterated where necessary. These are:
- 4:1 methanol:ethanol (v/v) – hydrostatic limit 10.5 GPa
- 1:1 pentane:isopentane (v/v) – hydrostatic limit 5 GPa
- Fluorinert – hydrostatic limit ~ 2 GPa
In discussion with instrument scientists, it is possible to use gas as a pressure transmitting medium.
- Argon – quasi-hydrostatic to ~ 15 GPa
- Helium – hydrostatic to ~ 25 GPa, quasi-hydrostatic > 25 GPa
Temperature range
- Variable-temperature insert press: 120 – 480 K
- Creche tank press: 80 – 350 K
- High-temperature resistive heating: 300 – 1400 K**
- VX1 CCR press: ~ 10 K***
**requires tungsten carbide anvils
***limited to ~ 3 GPa
Other sample environments
Cryogenic sample loading is possible using the creche tank press.
A gas-loading device enables compressed gas loading at 2 kbar into the sample space. This includes H2/D2.
Recent publications
Instrument reference
All publications and datasets based on experiments using Pearl should cite that the data is collected by DOI: 10.5286/isis.instrument.5194. Experiment DOIs follow the format 10.5286/ISIS.E.RBXXXXXXX, where XXXXXXX is the 7-digit experiment (RB) number and these can be viewed via the Data Gateway.