Chopper Systems

Neutron choppers are devices designed to periodically interrupt the neutron beam for a well-defined duration. They act as a sort of neutron switch and can individually or in groups be configured to perform a number of functions to condition neutron beams for scientific uses.

Choppers Research & Development

Mechanical integration, controls integration and the development of the T0 chopper for ESS.

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Workshops & Facilities

ESS maintains a number of facilities for R&D, including workshops in Lund, test beamlines in Germany and Norway, and a thin films coating facility in Linköping.

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To define company standards and requirements for all the neutron chopper systems that will be installed at the facility.

Undertake instrument-specific but widely applicable technology development activities, such as the T0 chopper for ESS.

Undertake critical technology development in chopper control systems at ESS and chopper mechanical integration at ESS.

Collaborate with the European-wide community of chopper experts in the field of high-speed chopper systems.

Organisation of support facilities and activities to operate and maintain neutron chopper systems at ESS.

Support instrument teams by providing quality assurance and validation functions on chopper systems.

Support and advise instrument teams during the definition and procurement of neutron chopper systems, utilising existing technology and vendors whenever possible.

Coordinate the procurement of choppers in conjunction with ESS partners and vendors.

Chopper systems are expected to be present on nearly all of the instruments foreseen for ESS.

1935-2015: 80 years of neutron choppers


The pulse structuring and wavelength band selection functions of neutron chopper systems are central to the operation of instruments at all neutron science facilities. At ESS, chopper systems design will be critical to unlocking the full potential of the facility's unique long-pulse source. High performance systems will be required in order to access as much as possible of the long pulse, simultaneously increasing the flux available and permitting access to the large dynamical range of the pulse. This is part of what will make ESS neutron scattering instruments unique.

However, purely neutronic-oriented criteria are not the only ones on which chopper systems are crucial for the overall performance of an instrument at ESS. During the specification, design and implementation of these complex systems it is also of utmost importance to consider the serviceability, maintainability and accessibility of the individual systems and units in order to ensure the highest instrument availability achievable.

Neutron choppers requirements at ESS

Instruments at ESS will require choppers to perform all the classical functions encountered at other facilities, and, in addition, a number of new challenges to exploit the benefits of the source's long pulse.

  • Functions such as pulse shaping, pulse suppression, course and narrow bandwidth selection, and background noise reduction will be required, and a number of system architectures and unit configurations, or ‘types’, are envisaged.
  • Several different strategies to fully exploit both high peak intensity and the dynamic range of the long-pulse structure are being considered in instrument concepts.
  • The implementation of strategies such as frame rate multiplication and advanced guide systems is under study and seem set to ‘push the envelope’ of current systems' performance. 

Based on the reference instrument suite currently available and historical data from other spallation sources, a preliminary estimation of the ESS requirements has been established.