Development of π and π/2 flippers for a neutron spin echo spectrometer

Abstract

For a time-of-flight neutron spin echo (TOF-NSE) spectrometer at a pulsed spallation neutron source, we previously designed new-type π and π/2 flippers which operate with steady current for a white neutron beam. The new-type spin flippers consist of a modified current sheet and Helmholtz coils. Performance tests of the new-type flippers with the modified current sheet made newly were carried out using ISSP-NSE at C2–2 port of JRR-3M in JAERI (Tokai). We replaced all of the Mezei-type π and π/2 flippers with the new-type ones and observed the NSE signal of neutrons scattered elastically from a stacked graphite sheet (grafoil). As the π flipper of iNSE (relocated ISSP–NSE), the new-type π flipper is installed and runs well. We also carried out performance tests of a tiny TOF-NSE machine with the new-type π and π/2 flippers using a pulsed white neutron beam at polarized neutron reflectometer of Neutron Science Laboratory, High Energy Accelerator Research Organization and we observed the TOF-NSE signal pattern, which gave direct evidence that the flippers worked for a pulsed white neutron beam. The new-type π and π/2 flipper operated well without tuning independently of the neutron wavelength. The operation is very easy, that is, one has to tune only the correction field from Helmholtz coils for a given precession field.

Keywords:

• Spin flipper
• Neutron spin echo
• Polarized neutron
• Time-of-flight

Acknowledgements

These experiments at JRR-3 were done under the approval of the Neutron Scattering Program Advisory Committee. One of the authors (T. T.) was financially supported by the Grant-in-Aid for Scientific Research (No. 09640466, No. 13440119 and No. 16540289) from the Japanese Ministry of Education, Science, Sports and Culture, and H. S. was also supported by the REIMEI Research Resources of Japan Atomic Energy Research Institute.

Notes

^‡‡Present address: IMSS, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan.

^¶¶Present address: Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai 319-1195, Japan.

Additional information

Notes on contributors

Norifumi L. Yamada

‡‡ ‡‡Present address: IMSS, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan.

Masayasu Takeda

¶¶ ¶¶Present address: Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai 319-1195, Japan.