16 Oct 2008



Pearl - dedicated to high-pressure powder diffraction.

​​​​​​A schematic drawing of the upgraded Pearl diffractometer showing the 90 degrees and low angle detectors ​

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.




Science Areas.

  • 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.

Technical Details.

  • 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.

Instrument Paper.

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), 493-511

The paper is available here

Sample Environment.

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 software.


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 diffraction studies.

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.

Instrument links: 

Contact information for Pearl instrument​

Location and contact information for the Pearl beamline

Use telephone extension number 6791 when on RAL site.

RoomPEARL cabin
Telephone01235  446791