25 Oct 2022



ISIS' dedicated high-pressure powder diffraction instrument

The PEARL instrument (CAD rendering), showing the 90 degree and low angle detector banks.
​​​​​​​​​​A CAD rendering of the PEARL diffractometer showing the 90o and low-angle detectors ​


The application of 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. Measurements can also be performed under simultaneous high/low temperature conditions. Full technical information can be found here, and information on the available sample environment can be found here. To discuss a proposal for PEARL, please contact an instrument scientist here​.​


Until the 1990’s, high-pressure neutron diffraction studies were limited to the 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 ~18 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 ~£1m upgrade, 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.

Science Areas.

A full list of PEARL publications can be found on ePubs.

  • Studies of pressure-induced structural changes and phase transitions within inorganic systems.
  • Effects of pressure on bonding within small-molecule systems, including pharmaceutical-type systems, explosives and fundamental materials (ices, elements etc).
  • Studies of mineral systems under simultaneous high-pressure and high-temperature conditions, with applications to geos​cience.
  • Pressure-induced changes to the local structure of amorphous and crystalline materials.
  • 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

    Instrument links: PEARL Dashboard

    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