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Updated: Oct 29, 2025
10:24
Neutron Radiography and Computed Tomography of Biological Systems at the Oak Ridge National Laboratory's High Flux Isotope Reactor
Published on: May 7, 2021
2.5K
A large beam high efficiency radio frequency neutron spin flipper
1NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
The Review of Scientific Instruments
|July 10, 2021
Summary
A new radio frequency neutron spin flipper design achieves over 99.9% spin flipping probability for large neutron beams. This advanced design enhances polarized neutron research capabilities at facilities like the National Institute of Standards and Technology.
Area of Science:
- Neutron optics
- Condensed matter physics
- Materials science
Background:
- Polarized neutrons are crucial for materials research.
- High-precision neutron spin manipulation is essential for advanced experiments.
- Existing neutron spin flippers face limitations in efficiency and beam size.
Purpose of the Study:
- To present a novel radio frequency (RF) neutron spin flipper design.
- To achieve a high and uniform neutron spin flipping probability over a large beam area.
- To improve the performance of polarized neutron instruments.
Main Methods:
- Magneto-static and neutron spin transport simulations were used for design optimization.
- A custom RF oscillator was developed for enhanced RF amplitude.
- Permanent magnet guide field sections created a linear field gradient.
- Helium-3 neutron spin filters precisely measured flipping probability.
Main Results:
- The RF neutron spin flipper achieved a flipping probability of 0.999 or better.
- A spatially uniform flipping probability of 0.9995(2) was measured across a large beam cross-section.
- The design accommodates a beam size of 6 cm x 15 cm and a wavelength band of 0.4–0.6 nm.
Conclusions:
- The developed RF neutron spin flipper design meets stringent performance requirements.
- This technology will be implemented in a polychromatic beam reflectometer.
- The design is adaptable for various polarized neutron applications requiring high flipping efficiency.
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