BIFROST-An indirect geometry cold neutron spectrometer at the European Spallation Source

Area of Science:

• Neutron scattering
• Materials science
• Spectroscopy

Background:

• Neutron time-of-flight spectrometers are crucial for materials research.
• Existing instruments face limitations in flux and energy resolution.
• The European Spallation Source (ESS) requires advanced instrumentation for its high-intensity neutron beams.

Purpose of the Study:

• To present the design and performance simulations of BIFROST, a novel neutron spectrometer.
• To highlight BIFROST's capabilities in terms of neutron flux and energy resolution.
• To demonstrate BIFROST's suitability for specific research areas like quantum magnetism and superconductivity.

Main Methods:

• Detailed design and performance simulations of the BIFROST instrument.
• Utilizing a multiplexing indirect time-of-flight technique.
• Employing a fast pulse-shaping chopper for primary spectrometer flexibility.
• Incorporating prismatic analyzers in the secondary spectrometer.

Main Results:

• BIFROST achieves a neutron bandwidth of Δλ = 1.74 Å.
• Polychromatic flux reaches 6 × 10^9 n/s/cm², with relative energy resolution of 3.5% at 5 meV.
• Adjustable energy resolution down to 0.2% (at 12 meV) and secondary spectrometer resolution of 0.02-0.05 meV.
• The instrument is optimized for small samples (< 1 cm³) and extreme environment studies.

Conclusions:

• BIFROST offers unprecedented neutron flux and adjustable energy resolution.
• The spectrometer's design significantly increases measurement efficiency compared to current instruments.
• BIFROST is poised to advance research in quantum magnetism, unconventional superconductivity, and functional materials.