The application of high pressure can
induce dramatic changes in the physical properties of materials. The PEARL
diffractometer is optimised for studies of the structural changes that occur
under high pressure. If necessary, measurements can also be performed under
simultaneous high/low temperature conditions.
- Powder diffraction studies at pressures up to around 7, 10 or 20 GPa using the Paris-Edinburgh (PE) press, depending on the press configuration (please discuss experiment requirements with instrument scientists for advice).
- Studies of pressure-induced phase transitions within inorganic systems.
- Effects of pressure on bonding within small-molecule systems, including pharmaceutical-type systems, explosives and fundamental ices.
- Studies of mineral systems under simultaneous high-pressure and high-temperature conditions.
- Pressure-induced changes to the local structure of amorphous materials.
- Beamline : S9 on TS-I.
- Moderator : Poisoned liquid CH4 at 100 K.
- Incident Flightpath : Evacuated flight tubes. L1=12.8 m.
- Incident Beam Collimation : Adjustable jaws to change beam size at sample (5×5 mm standard) and Δd/d resolution.
- Choppers : None.
- Normal Operating Frequency : 50 Hz.
- Detector Banks : 81.2o<2θ<98.8o (L2=0.8 m, 0.5<d(Å)<4.1, Δd/d~0.65%) optimised for the geometry of the PE press. Additional 'longitudinal' detector banks cover 100o<2θ<160o and 20o<2θ<60o to give access to data at higher resolution and to higher d-spacings, respectively.
- Detector Technology : ZnS scintillator.
Please use the following citation to reference PEARL:
C. L. Bull, N. P. Funnell, M. G. Tucker, S. Hull, D. J. Francis
and W. G. Marshall, High
Press. Res., 2016, 36(4),
The paper is available here
The design of PEARL is optimised for
the PE press and its variable-temperature variants. Alternative sample
environments may be possible – please discuss with beamline scientists.
Control of data acquisition and sample
environment on PEARL uses the PC-based SECI software, whilst normalisation and
correction of the powder diffraction data uses routines within the MANTID
Until the 1990’s, high-pressure neutron
diffraction studies were confined to the rather limited pressure range 0-3 GPa.
However, the development of the Paris-Edinburgh (PE) press at ISIS extended
this range up to ~10 GPa using ISIS supplied tungsten carbide anvils, or up to
~23 GPa when using sintered diamond anvils. Following the initial development
of the PE press on Polaris, funding was provided by the EPSRC’s Instrument
Development Fund to construct the dedicated high pressure facility PEARL on
TS-I. The instrument was commissioned in the mid-1990s, with the installation
of a large array of detectors at scattering angles around ±90o and
the development of a suite of PE presses whose design is complementary
to the scattering geometry of the diffractometer. These quickly
established PEARL as a world-leading facility for high-pressure neutron powder
In mid-2012, PEARL resumed user
operation following a major upgrade (around £1M), funded by the Consejo
Superior de Investigaciones Cientificas (CSIC) in Spain. This project involved
the construction of new detector modules at scattering angles close to 90o,
at backscattering and at low angles, plus the installation of improved
collimation of the incident neutron beam. As part of a complementary ISIS-led
programme of developments to the PE press, anvils using Zirconia-Toughened
Alumina (ZTA) as a replacement for the conventional tungsten carbide have
recently been introduced. These exploit the improved transmission properties of
ZTA—namely their transparency to neutrons—leading to significant improvements
in data quality, especially at long d-spacings.
A number of development projects are
currently in progress, to provide improved data quality through new anvil
designs and materials, expand the experimentally accessible region of
pressure-temperature space accessible and establish a suite of offline facilities
to complement the results obtained by neutron diffraction.
Contact information for Pearl instrument
Location and contact information for the Pearl beamline
Use telephone extension number 6791 when on RAL site.
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