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A Large Beam High Efficiency Radio Frequency Neutron Spin Flipper



Wangchun Chen, Ross W. Erwin, Peter Tsai, Md. T. Hassan, Nancy Hadad, Charles F. Majkrzak


A design for a radio-frequency (RF) neutron spin flipper obtained from magneto-static and neutron spin transport simulations is presented. The RF flipper constructed from this design provides a flipping probability of 0.999 or better for a beam size 6 cm wide and 15 cm high and a wavelength band between 0.4 nm and 0.6 nm. Three permanent magnet compression guide field sections with air gaps provide a large cross-sectional area linear field gradient along the beam propagation direction. An RF oscillator based on coupling the resonant coil of a Hartley oscillator to the excitation coil was developed which provides a higher current, and thereby a larger RF amplitude, as compared to a conventional RF power amplifier. Two opaque 3He neutron spin filters were employed to measure the flipping probability of the flipper with very high precision. A spatially uniform flipping probability of 0.9995(2) or higher was measured over the large cross-sectional area neutron guide. This RF neutron spin flipper will be employed in a polychromatic beam reflectometer at the National Institute of Standards and Technology Center for Neutron Research. This design can be applied to other polarized neutron instruments or applications requiring a very high continuous flipping probability of the neutron spin for a large cross-sectional area beam.
Review of Scientific Instruments


radio-frequency neutron spin flipper, opaque3He spin filter, flipping probability, magneto-static simulation, polarized-beam transport using Schrodinger-Pauli


Chen, W. , Erwin, R. , Tsai, P. , Hassan, M. , Hadad, N. and Majkrzak, C. (2021), A Large Beam High Efficiency Radio Frequency Neutron Spin Flipper, Review of Scientific Instruments (Accessed March 4, 2024)
Created June 20, 2021, Updated November 29, 2022