Seiji Tasaki

Multilayer neutron polarizing mirrors working under a low external magnetic field less than 100 gausses

Abstract We have developed multilayer neutron polarizing mirrors which are controlled under an external magnetic field less than 100 gausses. Multilayers of Permalloy-Ge and Fe-Ge have been evaporated on Si wafers in the magnetic field of about 130 gausses parallel to the surface of the wafer. The polarizing efficiencies of Fe-Ge and Permalloy-Ge multilayer mirrors were 95% and 91% respectively under a low external magnetic field of 80 gausses. Under a very low external field of 50 gausses, the polarizing efficiency was 90% in case of Permalloy-Ge. A neutron pulse was obtained by applying a pulsed magnetic field of about 50 gausses parallel to the Permalloy-Ge polarizing mirror. The pulse rise time is the order of 100μs in the present pulsed magnetic devices.

Cold neutron spin interferometry and its application to modified spin echo methods

Abstract We propose three kinds of modified neutron spin echo methods using cold neutron spin interferometry, which is based on the coherent superposition principle of the neutron spin. Two kinds of the modified methods are based on a novel quantum precession of neutron spin by multilayer spin splitters and another method on time dependent spin interferometry using RF flippers. The performances of the last type are discussed and the firmer two methods are described in other proceedings.

Development of a neutron spin echo spectrometer using four sequential reflection of multilayer spin splitters

Abstract We propose two types of modified neutron spin echo (NSE) spectrometer using the quantum precession caused by multilayer spin splitters. The first spectrometer is constructed by replacing the precession magnet with a pair of two spin splitters. The new NSE spectrometer requires much less volume and magnetic field compared to the conventional NSE spectrometer. The second spectrometer is designed to measure the small angle scattering from a plane sample. The principle and performances of the two types of the modified methods are discussed.

Quantum beat experiments and their applications using cold neutron spin interferometer

Abstract We have carried out quantum beat experiments using cold neutron spin interferometers installed at KURRI and JAERI. Quantum beat profiles (time-dependent interference fringe) with frequencies from 20 μHz to 34 kHz were observed, which correspond to energy difference 8.271 × 10−20and 1.406 × 10−10eV. Delayed choice experiment using quantum beat are proposed as an application.

DEVELOPMENT OF COLD NEUTRON PULSER FOR DELAYED CHOICE EXPERIMENT

Abstract The delayed choice experiment was done using the cold neutron spin interferometer of Jamin type arrangement which is installed at the JRR-3M of JAERI. “A multilayer polarizing cold neutron mirror placed in the pulsed magnetic field” is called a multilayer cold neutron pulser, or, in short, a cold neutron pulser. The switching function of the cold neutron pulser was used for producing the condition of whether or not the magnetic mirror is placed for the polarized neutron. It was shown that the cold neutron pulser is applicable to a cold neutron optical switch for the delayed choice experiment.

A COMPACT NOVEL SPIN-ECHO SPECTROMETER USING QUANTUM PRECESSION

Abstract We propose and make a preliminary experiment of a novel compact spin-echo spectrometer using composite mirrors causing quantum precession of neutron spin. The quantum precession requires less magnetic field (∼10 G) and less volume comparing Larmor precession. The spin-echo signal of the experiment (number of precession = 117) gives polarization of about 0.18. The new spectrometer has a possibility of 10 5 precession.

NEUTRON SPIN ECHO OPTICS THROUGH MAGNETIC MULTILAYER SYSTEMS

Abstract Larmor precession of neutrons due to dynamical diffraction effect through magnetic multilayer of permalloy45 (Fe 55 Ni 45 :55 A)-titanium (Ti:54 A) 15 bilayers has been observed using a forward diffraction (transmission) neu echo technique. The observed transmission probabilities of ↑ and ↓ spin neutrons are well reproduced by a calculated ↑ and ↓ spin wave functions of neutron through one-dimensional periodic potential of rectangular type for each spin direction. The shift of Larmor precession oscillates sinusoidally in the rocking curve of the transmitted beams around a magnetic Bragg condition, which is also well reproduced by the calculated phase difference of ↑ and ↓ spin neutron wave functions based on one-dimensional Schrodinger equation.

Observation of quasibound states of neutron in Fabry-Perot magnetic thin-film resonator using Larmor precession

Abstract Authors have measured Larmor precession angles of neutron spin transmitted through magnetized permalloy45(PA)-germanium(Ge)-PA and PAGePAGePA Fabry-Perot magnetic thin-film resonators at various incident angles above and below the critical angle of total reflection. The Larmor precession angles due to the Fabry-Perot resonator show sinusoidal oscillation as a function of the incident angles, which corresponds to quasibond states of the Fabry-Perot resonator for ↑ spin. The oscillation is well reproduced by the theoretical phase difference of ↑ and ↓ spin neutron wave functions based on one-dimensional Schrodinger equation.