Y. Otake

The neutron reflectometer (C3-1-2) at the JRR-3M reactor at JAERI

Abstract A neutron reflectometer has been installed at the cold neutron guide tube (C3-1-2) of the JRR-3M reactor at JAERI. Incident neutrons for the reflectometer have a long wavelength of 12.6 A, with a wavelength resolution of 3.2%. The reflectometer has the advantage of a large reflection angle which is appropriate for studies of low- q and off-specular phenomena. The neutron intensity reduction due to the long wavelength is substantially compensated by the relatively coarse beam divergence and wavelength resolution. The reflectometer is mounted in vertical geometry to yield a beam of 3 × 40 mm 2 and is applicable to measurements of mirror systems formed on flat substrates. Applications of the reflectometer to neutron optics and polymer studies are demonstrated and discussed.

Multilayer mirror interferometer for very cold neutrons

Abstract The feasibility of a very cold neutron interferometer using multilayer mirrors is discussed. This device is a kind of Mach-Zehnder interferometer known in classical optics, using multilayer neutron monochromator mirror as optical elements. These mirrors consist of thin layers deposited on a very flat silicon multilayer substrate. Spacings of the multilayer are available in the range from 80 to 500 A. We discuss the characteristics of the mirror, the accuracy with which the mirror positions must be adjusted to their position and the perfection of the mirror including the present status of our development. Applications to physics are listed.

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 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.

Evaluation of a multilayer mirror as an optical element of an interferometer using a double diffractometer with channel-cut perfect crystals

The large lattice spacing of multilayer mirrors (d > 50 A) enables us to construct interferometers for long wavelengths and good beam separation. We measured the spread in angular divergence of the Bragg reflected beam from the Ni/Ti multilayer mirror evaporated on a specially well-polished Si substrate using a double diffractometer with channel-cut Si perfect crystal for cold neutrons (λ = 4.7 A). The angular divergence of the reflected beam is less than 5 μrad. This multilayer satisfies the requirement for the neutron optical elements in such interferometers.

Experimental research into the effects of interface roughness in multilayers on neutron reflection and transmission

Abstract The effects of interface roughness for several multilayers are evaluated from measurements of neutron reflectivity and transmissivity as a function of momentum transfer, together with the profiles of the reflected and transmitted neutron beams. The multilayers are fabricated by vacuum evaporation onto polished Si substrates, whose roughness is measured with another optical technique. The multilayer samples are: (1) Ni/Ti with a period of 100 A, and 100 layers evaporated on a rough Si substrate, (2) a Ge/Ti multilayer with 36 layers and a 200 A period evaporated on sample 1, (3) a Ni/Ti multilayer with 52 layers and a 100 A period on a smooth Si substrate, and (4) a V/Ti multilayer with 8 layers and a 400 A period on a smooth Si substrate. The neutron measurements are carried out using a reflectometer at JRR-3M at JAERI. The reflectometer is a θ — 2θ scanning-type using a 12.6 A neutron beam. The comparison between the experimental neutron reflectivity with that calculated using a one-dimensional optical method with a modified optical potential is also discussed.

The cold neutron multilayer phase-spin echo interference experiment with mechanical alloying samples to investigate the state transition which derives decoherence

Abstract It has not been solved theoretically and experimentally how to explain the process which derives decoherence from coherent state though certain interactions between a quantum system such as a neutron and mesoscopic system, which consists of many particles. It is still an open question how to explicate decoherence and the quantum process through the quantum mechanical measurement process. In the last few decades this subject has become more important and discussed in various fields. Many quantum mechanical measurement theories derive decoherence from coherent state without experimental verification. Theoretically, it seems already clear that a kind of fluctuation of the mesoscopic system derives decoherence. We have done interference experiments to study this phenomena using spin interferometer for cold neutron inserting such a mechanical alloying (MA) samples as Ni25Ti75 of different alloying time. We chose such samples as Ni and Ti so that the total potential becomes zero but the fluctuation of weighted structure factor remains. We study this system to find the phenomena decreasing the coherence of wave function after once it improves in a diffuse scattering component.

MEASUREMENT OF TRANSVERSE COHERENT SEPARATION OF SPIN PRECESSING NEUTRON USING SPIN SPLITTERS

Abstract The authors have carried out measurement of a maximum length of transverse coherent separation by means of spin precessing neutrons and spin splitters. We have measured the spin precession when the transverse separation is up to 4.0xa0μm using a spin interferometer in MINE in JAERI. We interpreted that the loss of the visibility of the spin interference is caused from less overlap of coherent probability distribution of ↑ and ↓ spin neutron waves. Furthermore we have installed a neutron spin interferometer at ULS in JAERI in order to research the existence of an intrinsic maximum coherent separation. The results shows the feasibility of the measurement of the coherent separation with a well monochromatic beam.

Neutron reflectivity of 6LiTi multilayer with a Ni reflector applied to UCN detector

Abstract The neutron reflectivity of a 6 Li Ti multilayer mirror with a Ni reflector at the base has been measured using a time-of-flight spectrometer and a reflectometer. The results show that the reflectivities rise to 0.5 at 560 A, which corresponds to the Ni critical wavelength, decrease to 0.2 with increasing neutron wavelength, and then rise towards unity at about 800 A. This implies that neutrons in wavelength region between 560 A and 800 A penetrate through the 6 Li Ti multilayer and are absorbed by 6 Li. The application of the 6 Li Ti multilayer to a neutron converter for an ultracold neutron detector is discussed.

Performance tests of multilayer interferometer for very cold neutrons

Abstract A multilayer-mirror interferometer for very cold neutrons has been in progress for five years. This interferometer is analogous to a classical Mach -Zehnder interferometer using multilayer mirrors as optical elements. The conditions required for the multilayer interferometer are presented, including mirror perfection and mirror-position accuracy. Performance tests are discussed such as mirror characteristics, mirror-position adjustments and the interference pattern using neutrons.